Atto 8

Name: Atto 8
Brand: byd

BEV

2024-2025

914Fault Codes

Fault Codes

B1108›
For the BYD Song MAX (2017–2019), DTC B1108 indicates a short circuit in the PM2.5 air quality detection module (dust sensor) or its wiring harness. The sensor uses laser scattering to detect in-cabin and outside PM2.5 concentrations and transmits data to the HVAC ECU via the LIN bus or an analog signal. Short circuit conditions include: 1) Sensor power supply wire (+5V/+12V) shorted to ground 2) Signal wire shorted to power or ground 3) Short circuit in the sensor's internal photoelectric detection circuit This fault prevents the automatic climate control from switching between fresh air and recirculation based on air quality. The system enters fail-safe mode (typically forced recirculation). Severe short-circuit current can destroy the HVAC ECU sampling circuit. The system classifies this as a Level 3 severe fault and restricts vehicle operation to prevent electrical fires or controller damage. For other BYD models (such as the Qin EV, E5, and Song DM), B1108 indicates a driver-side sunload sensor fault, reflecting differences in DTC definitions across models.
Causes
— Water ingress or moisture inside the PM2.5 sensor causes a short circuit on the circuit board (commonly due to condensate leakage from the A/C evaporator housing or vehicle wading).— Sensor wiring harness insulation wears and contacts sharp edges of the body metal frame or air conditioning housing, causing a short to ground (common after dashboard removal and installation if the harness is not correctly routed).— Sensor connector pins bent, backed out, or oxidized due to water ingress, causing a short circuit between the power supply and signal pins.+2 more →
Actions
— Use BYD VDS or a dedicated diagnostic tool to read the DTC freeze frame. Verify the ambient temperature, humidity, and vehicle status when the fault occurred, and determine whether it is a current or history fault.— Remove the PM2.5 sensor located on the right side of the dashboard or the upper part of the A/C unit (on Song MAX models, usually behind the glove box or inside the center console). Visually inspect the connector for water stains, oxidation, or deformed pins.+5 more →
B110811›
This DTC indicates a short circuit in the air conditioning system PM2.5 air quality sensor (rapid detector). Specifically, abnormal continuity exists between the sensor power supply circuit or signal output circuit and body ground or battery positive. This causes the control module (ACU/air conditioning controller) to detect abnormal current or a voltage signal outside the valid range (typically 0V or supply voltage). The PM2.5 sensor monitors internal and external particulate concentrations, providing the data the automatic air conditioning system uses to switch between fresh air and recirculation modes. A short circuit disables the air quality monitoring function. This fault may force the air conditioning system into recirculation protection mode and trigger related thermal management system faults, as the air conditioning system acts as a key actuator in vehicle thermal management. In severe cases, the short circuit current can damage the internal sampling circuit of the air conditioning controller or overheat the wiring harness.
Causes
— PM2.5 sensor internal circuit board short circuit (laser detection module or voltage regulator chip breakdown); common causes include water ingress or component aging.— Damaged sensor wiring harness insulation causing a short to ground or short to power, most commonly at vibration and chafing points such as the firewall pass-through and the edge of the A/C housing.— Short circuit in the air conditioning controller (ACU) internal signal sampling circuit, triggering a false sensor fault.+2 more →
Actions
— Use the BYD VDS diagnostic tool to read complete fault information and freeze frame data, record the ambient temperature and air conditioning operating status at the time of the fault, and check for other B11 series fault codes.— Locate the PM2.5 sensor (on Qin series models, typically located in the air intake duct downstream of the A/C filter/upstream of the blower, or under the passenger dashboard). Inspect the connector for signs of water ingress, pin corrosion, or backed-out pins.+4 more →
B1109›
DTC B1109 indicates an open circuit in the communication line between the air conditioning system PM2.5 air quality sensor (dust concentration sensor) and the air conditioning control unit (AC ECU), or an open circuit within the sensor internal circuitry. Typically located in the air conditioning intake duct, this sensor monitors real-time PM2.5 particle concentration inside and outside the vehicle. It provides data to the automatic air conditioning system for intelligent switching between fresh air and recirculation modes and for controlling the air purification device. During an open circuit fault, the AC ECU cannot receive the air quality signal, triggering the system fail-safe mode. Symptoms typically include failure of the automatic recirculation function, abnormal air purification indicator light operation, or abnormal air quality data displayed on the air conditioning panel. Severe cases may compromise the cabin environment control strategy, but do not directly affect vehicle driving safety.
Causes
— Open internal circuit in the PM2.5 sensor (due to sensor aging, internal component damage, or water ingress corrosion)— Loose sensor wiring harness connector, backed-out pins, corroded terminals, or poor contact (common after dashboard removal/installation or vehicle wading).— Sensor power supply circuit open or blown fuse (B+ power supply or IGN power supply circuit interrupted)+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS or ED400) to read the fault code. Confirm B1109 is an active fault. Record the freeze frame data, clear the fault code, and check for an intermittent fault.— Visually inspect the PM2.5 sensor installation (located near the A/C filter element or inside the right-side instrument panel air duct). Check the sensor connector for looseness, backed-out pins, or water ingress. Check the sensor air inlet for foreign matter blockages.+4 more →
B110913›
DTC B110913 indicates an open signal circuit for the PM2.5 rapid detector (in-cabin air quality sensor). This sensor typically mounts inside the air conditioning system intake duct. It monitors in-cabin PM2.5 concentration in real time and provides data to the automatic air conditioning system for intelligent control of the air purification function. The BYD diagnostic protocol uses sub-code '13' to specifically indicate an open signal circuit. Although this fault theoretically affects a comfort feature, BYD Qin series vehicles classify it as a Level 3 (severe) fault. This classification occurs because the air conditioning system interacts with the battery thermal management system (e.g., monitoring battery cooling intake air quality). The fault can disable the automatic air conditioning mode and prevent the air purification function from operating. In extreme cases, it affects the battery compartment intake air quality assessment, triggering the 'repair immediately' strategy.
Causes
— Internal open circuit or aging failure of the PM2.5 sensor, interrupting signal output.— Loose sensor wiring harness connector, backed-out pin, or corroded/oxidized terminal causing poor contact.— Vibration wears or crushes the wiring harness at the firewall grommet or instrument panel frame, breaking the wire.+2 more →
Actions
— Use VDS2000 or a BYD dedicated diagnostic tool to read the complete fault codes and freeze frame data. Confirm the ambient temperature, vehicle speed, and air conditioning status when the fault occurred. After ruling out intermittent faults, clear the fault codes and perform a road test to verify if the fault recurs.— Remove the front passenger glovebox or A/C filter. Visually inspect the installation status of the PM2.5 sensor (usually marked 'Air Quality Sensor'). Verify the wiring harness connector is fully seated. Inspect the terminals for green oxidation or backed-out pins, and clean with electrical contact cleaner if necessary.+4 more →
B110A›
This DTC indicates interrupted CAN bus communication or abnormal data between the air conditioning control unit (ACU) and the PM2.5 air quality sensor. The PM2.5 sensor monitors particulate concentration inside and outside the vehicle and provides the basis for purification control in the automatic air conditioning system. The ACU triggers this fault if it fails to receive a valid CAN message from the sensor within the specified period (usually 100-500 ms), if message verification fails, or if the signal frame times out. Although this fault does not affect vehicle driving safety, it disables the automatic air purification function. The air conditioning system cannot automatically switch between recirculation and fresh air modes or activate the air purification mode based on air quality. A persistent fault may restrict the thermal management strategy.
Causes
— PM2.5 sensor internal circuit fault or module damage, preventing CAN signal transmission or causing error frame transmission.— Open or short circuit in the sensor power supply circuit (constant B+ or IGN power), or a loose or oxidized ground point causing abnormal power supply.— Open circuit, short circuit, or short to ground/power in the CAN_H and CAN_L wiring, or connector pin back-out or poor contact due to oxidation.+2 more →
Actions
— Use the VDS or ED400 diagnostic tool to read the complete fault codes and freeze frame data. Confirm whether B110A is a current (Active) or history (History) fault. Check for accompanying U-class communication fault codes (such as U0146, U0155).— Visually inspect the PM2.5 sensor (usually located inside the passenger-side dashboard or at the A/C unit air inlet) for physical damage. Check the connector for looseness, oxidation, or water ingress, and inspect the wiring harness for damage.+6 more →
B110A02›
DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.
Causes
— Faulty internal laser scattering module in the PM2.5 sensor or damaged PCB CAN transceiver chip, causing failure to respond to bus requests.— Sensor wiring harness connector (usually located inside the passenger-side dashboard) is loose, has backed-out pins, or has oxidized terminals, causing increased contact resistance (>5Ω) or an intermittent open circuit on CAN-H and CAN-L.— Sensor power supply fault: Blown B+ power supply fuse (constant power or IGN power), excessive circuit voltage drop, or corroded ground points G301/G302 causing reference voltage drift.+2 more →
Actions
— Use a VDS2000 or Launch X-431 diagnostic tool to read complete fault codes and freeze frame data. Record the ambient temperature, IGN voltage, and vehicle speed at the time of the fault. Distinguish between current (Present) and historical (History) faults. If multiple CAN communication fault codes exist, prioritize troubleshooting common network issues.— Remove the front passenger glove box or cabin air filter cover. Locate the PM2.5 sensor (usually a small black square box with an air inlet). Visually inspect the 4-wire connector (BAT+, GND, CAN-H, CAN-L) for oxidation or backed-out pins. Measure the supply voltage at the connector terminals (should be 12V±0.5V; some models use 5V). Ground resistance should be <1Ω.+3 more →
B110B07›
This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.
Causes
— Air pump motor mechanical binding or carbon brush wear: After long-term use, lack of air pump bearing lubrication, a seized impeller, or worn motor carbon brushes prevent startup.— Power supply circuit fault: Blown PM2.5 sensor power supply fuse, poor connector contact, or oxidized or backed-out pins causing insufficient supply voltage to the air pump.— Sensor internal circuit damage: air pump driver chip overheated and burned out, PCB moisture corrosion, or abnormal linkage control logic between the laser and air pump.+2 more →
Actions
— Use the VDS2000/6000 diagnostic tool to read the complete fault code, confirm whether B110B07 is a current or history fault, and record the freeze frame data (ambient temperature, vehicle speed, etc.).— Visually inspect the PM2.5 sensor installation. Confirm the mounting bracket is not loose and the sensor air inlet filter is free of visible blockages.+5 more →
B160C-00›
DTC B160C-00 indicates the SRS (Supplemental Restraint System) control module detects the driver frontal airbag (steering wheel airbag module) igniter (squib) circuit resistance exceeds the calibrated upper limit. Normal BYD Qin series airbag igniter resistance is 2.0-3.0 Ω. The ECU triggers this fault when it detects the resistance continuously exceeds the threshold (typically >5 Ω or an open circuit). This hard fault means the airbag may fail to deploy normally (fail-safe mode) or delay deployment during a collision, severely compromising driver passive safety. Poor contact, wiring oxidation, a partial open circuit, or igniter aging causes the abnormal increase in circuit resistance.
Causes
— Internal open circuit or poor contact in the clock spring (spiral cable): Frequent steering wheel rotation causes the internal flat cable to fatigue and break. This is the most common fault point in the BYD Qin series.— Airbag module connector loose or oxidized: Poor contact at the yellow connector below the steering wheel (usually marked DAB) causes increased contact resistance.— Airbag inflator internal open circuit: Aging of the squib inside the airbag module or a manufacturing defect causes an abnormal increase in internal resistance.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the low-voltage battery negative terminal, and wait at least 3 minutes (to fully discharge the SRS capacitor). Do not measure the airbag circuit directly with a low-impedance multimeter.— Visual inspection: Check the yellow airbag connector (DAB connector) below the steering wheel for looseness, backed-out pins, water ingress, or oxidation. Check the clock spring housing for damage.+6 more →
B110B›
DTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.
Causes
— Worn internal carbon brushes or a seized bearing in the air pump motor prevents rotation or causes excessive startup current, triggering overcurrent protection.— Poor contact, backed-out terminals, or oxidized pins at the PM2.5 sensor wiring harness connector, interrupting the power supply, ground, or PWM control signal.— Damaged MOSFET or filter capacitor on the air pump drive circuit board inside the sensor assembly, causing abnormal drive voltage.+2 more →
Actions
— Use a VDS or Launch diagnostic tool to read the complete fault codes. Confirm the fault is current (Current DTC), check for sub-codes such as B110B07 (air pump mechanical fault), and record the freeze frame data.— Remove the PM2.5 sensor assembly located inside the passenger-side dashboard or near the cabin air filter. Inspect the exterior for damage. Check the connector for looseness, water ingress, or corrosion. Measure and verify normal voltage and waveform at plug terminal 1 (constant B+), terminal 2 (ground GND), and terminal 3 (LIN line or PWM control).+3 more →
B110C›
DTC B110C indicates a functional failure of the internal laser diode in the PM2.5 air quality detection module. The sensor operates on the laser scattering principle. The laser diode emits a 650nm or 780nm laser beam. Airborne particulate matter passing through the detection chamber scatters this light. A photodiode array receives the scattered light and converts it into electrical signals. An algorithm then calculates the PM2.5 mass concentration. Laser diode failure (open circuit, light degradation below threshold, or driver circuit fault) prevents the sensor from establishing the detection optical path. The system continuously outputs abnormal concentration values (typically fixed at 0 μg/m³ or 999 μg/m³). This causes the air conditioning thermal management system to lose automatic air quality closed-loop control, preventing automatic recirculation, negative ion generator linkage, and air purification reminders. This fault does not directly affect drive motor thermal management or power battery cooling. However, the system classifies this as a Level 3 severe fault because the sensor acts as a core environmental sensing component for the air conditioning system. False readings can also force the HVAC module into continuous high-power operation or cause abnormal air flap adjustment. In some models (e.g., Song MAX), the sensor communicates with the air conditioning control unit via the LIN bus. A laser assembly fault can cause abnormal bus sleep current.
Causes
— Laser diode natural aging or thermal breakdown: Prolonged exposure to the high-temperature, high-humidity environment in the air conditioning duct (especially near the evaporator) accelerates optical degradation when the laser diode junction temperature exceeds 60°C, or abnormal drive current burns out the PN junction.— Sensor power supply and ground fault: Poor connection in the B+ power circuit, fuse holder oxidation, or excessive ground resistance (>5Ω) causes the operating point of the laser drive constant-current source to drift, triggering undervoltage protection.— Optical chamber contamination or condensation: Dust accumulation, oil fume deposits, or condensation on the lens assembly inside the detection chamber causes excessive scattered laser background light. The system falsely identifies this as a laser source failure (software logic in some models classifies optical contamination as B110C).+2 more →
Actions
— Freeze frame analysis: Use VDS2000/3000 to read the DTC freeze frame. Record the ambient temperature, air conditioning operating status, and battery voltage when the fault occurred. Determine whether it is an intermittent fault (history code) or a current hard fault.— Power supply and ground verification: Disconnect the PM2.5 sensor 4-pin connector and measure the voltage between PIN1 (constant B+) and PIN2 (GND). Standard value: 12V±0.5V. Measure the resistance between the ground point and the vehicle body. Resistance must be less than 1Ω. Check fuse EF14/IF08 (depending on vehicle configuration).+4 more →
B110C09›
DTC B110C09 indicates a driver-side seat belt pretensioner circuit fault, specifically an open circuit, short to ground, or abnormal resistance (standard resistance 1.8-2.5Ω). This fault relates to the Supplemental Restraint System (SRS). The Airbag Control Unit (ACU) triggers this code upon detecting driver-side pretensioner circuit voltage or resistance outside the specified threshold. The pretensioner is a critical safety device operating in conjunction with the airbag. During a collision, the gas generator tightens the seat belt to eliminate slack between the webbing and the occupant. This fault forces the airbag system into fail-safe mode and continuously illuminates the instrument panel airbag warning light. This condition can prevent the pretensioner from deploying during a collision, significantly increasing occupant injury risk.
Causes
— Internal open circuit or abnormal resistance in the driver-side seat belt pretensioner assembly (e.g., infinite resistance from failing to replace the assembly after accident deployment).— Loose pretensioner wiring harness connector under the seat, oxidized pins, backed-out pins, or poor contact.— Fore-and-aft seat movement chafes the wiring harness sleeve between the floor and seat frame, causing an intermittent open circuit or short to ground.+2 more →
Actions
— Connect the VDS2000/BYD dedicated diagnostic tool, read the fault code to confirm B110C09, and check the live data stream to verify the driver pretensioner resistance is 1.8-2.5Ω.— Check that the yellow wiring harness plug (pretensioner connector) under the driver's seat is fully seated. Inspect the pins for oxidation or deformation. Clean and apply conductive grease if necessary.+5 more →
B121209›
DTC B121209 indicates an abnormality in the PTC (Positive Temperature Coefficient) heater drive control unit, specifically a driver module fault. This fault involves the high-voltage control system. Causes include IGBT power module failure, driver circuit board malfunction, high-voltage interlock (HVIL) failure, or abnormal current/voltage sampling. The PTC heater is a core component for EV cabin heating and battery thermal management. This fault prevents cabin heating and disables battery heating. In low-temperature environments, it degrades battery charge/discharge performance and reduces driving range. When this fault occurs, the BMS or thermal management controller cuts off the PTC high-voltage power supply to protect the system.
Causes
— Internal driver board fault in the PTC controller (high-voltage power distribution box integrated module), such as IGBT power transistor breakdown, gate drive circuit damage, or DC-DC power conversion module failure.— Degraded PTC heater insulation or an internal short circuit causes the drive assembly to detect an overcurrent or insulation fault and set the code.— Poor contact, ablation, or terminal back-out in the high-voltage wiring harness or connectors, especially oxidized or loose PTC high-voltage positive and negative terminals, causing the drive assembly to detect an abnormal voltage drop.+2 more →
Actions
— Use the VDS2000/BYD dedicated diagnostic tool to read all fault codes. Check for related codes such as B121309 (PTC heater assembly fault) and B121111 (temperature sensor fault). Check the PTC operating voltage, current, and temperature values in the freeze frame data.— Visually inspect the PTC controller (usually located near the high-voltage power distribution box in the front compartment) for burning or fluid leakage. Inspect high-voltage wiring harness connectors P33, P34, etc., for looseness, backed-out terminals, or burn damage. Measure the continuity of the high-voltage interlock circuit.+5 more →
B110D›
DTC B110D indicates a failure of the Photoelectric Receiving Module in the in-cabin PM2.5 detection system. In the BYD Song MAX Green Purification System, the PM2.5 sensor operates on the laser scattering principle: a laser diode emits a light beam of a specific wavelength through an air sample, and airborne particles scatter the light. The Photoelectric Receiving Module (usually containing a photodiode or photomultiplier tube) captures the scattered light signal and converts it into an electrical signal. When this module fails, the system cannot accurately detect the in-cabin PM2.5 concentration. This failure disables the automatic air purification function, disrupts the A/C automatic fresh air/recirculation switching function, and may trigger an air quality detection fault on the instrument cluster. Although this fault does not directly affect vehicle power or core thermal management functions, it disables the intelligent A/C purification system and impairs in-cabin air quality management during severe smog conditions.
Causes
— Dust or contamination on the photoelectric sensor optical window: After prolonged use, dust, oil vapor, or condensation adheres to the sensor lens surface. This attenuates the received optical signal or causes abnormal scattering, triggering a module failure warning.— Photoelectric receiver module circuit aging or damage: The photodiode, operational amplifier, or ADC chip degrades or short-circuits due to prolonged operation in high-temperature, high-humidity environments.— Poor contact or corrosion at the wiring harness connector: Vibration and temperature cycling loosen or oxidize the terminals of the PM2.5 sensor plug near the air conditioning duct, interrupting signal transmission.+2 more →
Actions
— Use a BYD dedicated diagnostic tool (VDS or ED400) to read all fault codes. Confirm B110D is a current fault, not a history fault. Check for accompanying communication fault codes (such as codes starting with U).— Remove the PM2.5 sensor assembly from inside the air conditioning duct or dashboard (on Song MAX models, this is usually at the air inlet duct inside the center console). Inspect the photoelectric receiving window for obvious dust contamination or physical damage. Clean the optical window with anhydrous ethanol and an anti-static cloth.+4 more →
B110D09›
DTC B110D09 indicates a failure of the internal photoelectric receiving module in the PM2.5 rapid detector (laser particulate sensor). The sensor operates on the laser scattering principle: a laser diode emits a beam to illuminate an air sample. Suspended particulate matter produces scattered light. The photoelectric receiving module (typically a high-sensitivity photodiode or photomultiplier tube) captures this light and converts it into an electrical signal. The signal processing circuit then calculates the PM2.5 concentration. DTC B110D09 specifically refers to a fault in the module receiving the scattered light. Possible causes include photoelectric component aging or burnout, a signal amplification circuit fault, A/D conversion module damage, or an internal open circuit. This fault prevents the Green Air Purification System from obtaining accurate air quality data, disabling the automatic air purification mode and the A/C automatic fresh air/recirculation switching function. Although this fault typically does not affect the powertrain or driving safety, it disables the thermal management system's environmental adaptive control strategy. The system classifies this fault as severe because abnormal communication between the sensor and the A/C control module can trigger cascading faults.
Causes
— Aging or burnout of the photodiode inside the photoelectric receiver module: Prolonged operation under laser irradiation causes the photoelectric component to degrade or fail completely due to optical fatigue or electrostatic discharge, preventing it from generating a valid photocurrent signal.— Sensor circuit board fault: Overvoltage (vehicle voltage fluctuations), thermal stress, or manufacturing defects damage the signal amplification circuit, filter circuit, or microprocessor chip, preventing photoelectric signal processing.— Wiring harness connector issue: Connectors near the center console or A/C duct interrupt signal transmission due to loosening from vehicle vibration, pin oxidation, moisture ingress (A/C condensate seepage), or excessive contact resistance.+2 more →
Actions
— Use the BYD VDS2000/VDS2100 diagnostic tool to access the air conditioning/thermal management system. Read and record all fault codes and freeze frame data. Confirm only B110D09 or related communication fault codes are present. Check if the PM2.5 real-time data stream displays a fixed, zero, or invalid value.— Locate the PM2.5 sensor (usually inside the center console, behind the glovebox, or at the A/C evaporator air inlet). Inspect the sensor exterior for physical damage, cracks, or signs of water ingress. Check the mounting bracket for looseness.+5 more →
B110E09›
This DTC indicates a functional failure of the temperature and humidity sensing module in the PM2.5 air quality rapid detection system. This module integrates into the PM2.5 detector and monitors ambient air temperature and relative humidity in real time. The system uses these readings to compensate and correct the light-scattering measurement data from the laser particulate sensor, as temperature and humidity changes significantly affect PM2.5 detection accuracy. An abnormal analog signal or digital communication interruption causes this fault. This prevents the air conditioning controller from obtaining accurate ambient temperature and humidity parameters, disabling the automatic air purification, negative ion generator linkage, and air quality display functions. Although the system classifies this as a "severe" fault, it only affects comfort features and does not impact the powertrain or driving safety. The vehicle can travel a short distance to a repair facility.
Causes
— Physical damage to the temperature and humidity sensor element: internal NTC thermistor open/short circuit or humidity-sensing capacitor failure, causing the output signal to fall outside the valid 0.5-4.5V range.— Poor wiring harness connector contact: The sensor plug located in the center of the dashboard or air conditioning intake housing is loose, has backed-out pins, or has oxidized terminals, causing intermittent signal interruption.— Power supply circuit fault: A damaged sensor 5V reference voltage module or excessive ground circuit resistance (>1Ω) causes unstable sensor operating voltage.+2 more →
Actions
— Use the VDS2000/VDS3000 diagnostic tool to read all fault codes. Check for B110E09 and any accompanying B110A02 (CAN fault) or U-series communication faults, and record the ambient temperature value from the freeze frame data.— Remove the center dashboard trim and locate the PM2.5 sensor (usually behind the A/C control panel or inside the center air vent). Check if the wiring harness connector is loose. Measure the voltage between connector pin 1 (power) and pin 3 (ground). Standard value: 5V ± 0.25V.+3 more →
B121013›
This DTC indicates an open circuit in the left heat sink temperature sensor of the thermal management system PTC (Positive Temperature Coefficient) heater. This sensor, typically an NTC (Negative Temperature Coefficient) thermistor, monitors the real-time surface temperature of the PTC ceramic heating element to prevent overheating. The ECU determines an open circuit when it detects a continuously high sensor signal voltage (typically the 5V reference voltage returning without voltage division). This fault triggers a protective shutdown of the PTC heater, resulting in no warm air in the cabin. In extreme cases, if the PTC overheats and the failed sensor cannot provide feedback, it may trigger a high-voltage safety cut-off or risk thermal runaway.
Causes
— Internal open circuit in the temperature sensor: Aging, thermal shock, or mechanical stress fractures the NTC thermistor internally, resulting in infinite resistance.— Wiring harness connector fault: Prolonged high-temperature exposure causes oxidized or recessed pins in the connector near the PTC assembly, or a loose locking tab causes poor contact.— Wiring harness physical damage: The wiring harness in the engine compartment or left side of the front compartment rubs against sharp edges due to vehicle vibration, breaking the signal or ground wire.+2 more →
Actions
— Use VDS to read the complete fault information and freeze frame data, confirm the PTC operating status and ambient temperature when the fault occurred, and check for other thermal management-related fault codes.— Visually inspect the PTC heater left temperature sensor. Check the wiring harness sleeve for damage and the connector for looseness, water ingress, or burn marks.+5 more →
B110F›
DTC B110F indicates an actuator circuit failure in the solenoid valve (switching valve) inside the PM2.5 air quality detection module. This solenoid valve controls the physical switching of the sampling air passage to select the channel for in-cabin or outside air sampling. The air conditioning controller (ACU) triggers this code if it issues a switching command but fails to detect the solenoid valve current feedback or position confirmation signal (such as Hall sensor feedback), or if it detects a coil short or open circuit. This failure prevents the system from accurately comparing the PM2.5 concentration difference between the cabin and outside air, disables Auto Clean mode, and may force the air conditioning system into a protective recirculation mode.
Causes
— Solenoid valve coil burned out or open circuit: Long-term use or voltage fluctuations cause abnormal coil resistance (standard resistance is typically 20-60Ω; deviations exceeding ±10% indicate failure).— Valve core mechanically stuck: Dust, fibers, or oil accumulate in the PM2.5 sampling passage, preventing the solenoid valve armature from returning or causing it to stick during operation. The resulting abnormal current draw triggers the diagnosis.— Wiring harness and connector fault: wear at bends in the internal instrument panel wiring harness, oxidized terminals, terminal back-out, or high temperatures in the HVAC housing deforming the plug, causing an intermittent open circuit.+2 more →
Actions
— Use a VDS1000 or Launch X431 diagnostic tool to read the complete DTCs. Confirm whether the fault is current (Present) or history (History). Record the ambient temperature and A/C operating conditions from the freeze frame data.— Remove the front passenger glove box or PM2.5 sensor module cover (depending on configuration; on the Song MAX, it is usually located above the blower motor or on the side of the HVAC housing). Visually inspect the solenoid valve wiring harness connector for burning or water ingress.+4 more →
B161A-00›
Fault code B161A-00 indicates the front passenger frontal airbag ignition circuit resistance is 0 ohms. This condition signifies a short to ground in the airbag circuit or an internal short circuit within the airbag module. Normal airbag system resistance is typically 2-3 ohms. A 0-ohm resistance allows current to bypass the airbag inflator and flow directly from the positive terminal to ground. Consequently, the Airbag Control Unit (ACU) determines the airbag risks unintended deployment or failure to deploy. The system then illuminates the airbag warning lamp and disables the airbag. Repair procedures for certain BYD models (such as the Qin, Tang, and Song series) may also log this fault code as a Left Front Impact Sensor communication fault or wiring short circuit. Verify the exact definition using the specific model year and SRS software version. Regardless of the definition, this constitutes a critical safety system fault that prevents the airbag system from protecting occupants during a collision.
Causes
— Front passenger airbag igniter internal short circuit (airbag assembly damage causing 0 resistance).— Airbag wiring harness short to body ground (damaged insulation, pinched or chafed harness causing a short circuit between positive and negative terminals)— Water ingress and oxidation in the airbag connector plug (common after car washes or wading, causing a short circuit between pins)+2 more →
Actions
— Safety preparation: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 3 minutes to fully discharge the SRS system capacitor and prevent accidental airbag deployment.— Use the BYD dedicated diagnostic tool (VDS2000 or Launch X431) to read detailed fault codes and freeze frame data. Confirm whether the fault is persistent or intermittent, and record the vehicle status when the fault occurred.+6 more →
B110F09›
DTC B110F09 indicates a High Voltage Interlock Loop (HVIL) fault, contrary to some materials that incorrectly label it as a "PM2.5 rapid tester solenoid valve failure". The HVIL serves as a critical safety protection mechanism on BYD new energy vehicles. The system triggers this code when it detects compromised high-voltage circuit integrity, such as a loose connector, an open wiring harness, or an abnormal service disconnect switch. Upon logging this fault, the BMS immediately opens the high-voltage relays and disables high-voltage power-up to prevent electric shock. As a hard safety fault, it prevents the vehicle from entering READY mode or causes a sudden loss of power while driving.
Causes
— Poor contact, broken locking clip, or oxidized pins at the battery pack low-voltage wiring harness connector (BMS 32-pin connector), causing abnormal resistance in the interlock circuit.— Burnt interlock pins, deformed spring contacts, or water ingress corrosion inside the Manual Service Disconnect (MSD), causing an open circuit.— The fast charging port or high-voltage power distribution box interlock wiring harness rubs against the vehicle body, causing wear. Damaged insulation causes intermittent short circuits or open circuits.+2 more →
Actions
— Use VDS2000 or a dedicated diagnostic tool to read the complete fault codes. Confirm B110F09 and any accompanying high-voltage interlock-related fault codes (such as P1A6000).— Check the Manual Service Disconnect (MSD) installation status. Measure the resistance between the interlock pins (normal: continuity, less than 10 Ω). Replace the MSD assembly if necessary.+6 more →
B121111›
This DTC indicates a short to ground in the PTC (Positive Temperature Coefficient) heater left heat sink temperature sensor signal circuit, or an internal sensor short circuit. BYD Qin series vehicles typically integrate this sensor into the PTC heater assembly to monitor heater core temperature and prevent overheating. During a short circuit, the air conditioning controller detects an abnormally low voltage signal (near 0V) and triggers protection logic to cut PTC power, disabling the heating function. Because the PTC heater draws high operating current (up to tens of amperes), temperature monitoring failure risks overheating or fire. Therefore, the system classifies this as a severe fault (Level 3).
Causes
— PTC temperature sensor wiring harness insulation damaged: High temperatures and vibration in the motor compartment cause the sensor wiring harness to rub against metal body edges, shorting the signal wire to ground.— Internal short circuit in sensor body: NTC thermistor package failure or moisture ingress causes resistance to drop abnormally to nearly 0 Ω.— PTC heater assembly internal fault: Insulation layer breakdown between the heat sink temperature sensor and the PTC ceramic element causes a short circuit.+2 more →
Actions
— Connect the VDS2000 diagnostic tool. Read the complete fault codes and freeze frame data. Confirm the fault frequency (current/history). Check for an accompanying B121013 (open circuit) fault appearing alternately, indicating an intermittent contact issue.— Disconnect the battery negative terminal, wait 5 minutes, then unplug the temperature sensor connector on the PTC heater (usually located near the heater core, 2-pin black plug). Measure the resistance at the sensor terminals: a normal NTC sensor measures 10 kΩ ±5% at 25°C. A reading of 0–10 Ω indicates an internal short circuit in the sensor.+4 more →
B121309›
DTC B121309 indicates a fault in the PTC (Positive Temperature Coefficient) heating assembly. The PTC heater is a core high-voltage component in the electric vehicle thermal management system. Operating at 320V-750V DC, it heats the coolant to provide cabin heating and low-temperature battery pack preheating. Trigger conditions for this DTC include: PTC unit insulation resistance falling below the safety threshold (typically <1MΩ/V); abnormal PTC operating current (overcurrent, open circuit, or short circuit); communication timeout between the PTC controller and the air conditioning controller/thermal management controller (CAN signal lost); abnormal PTC temperature sensor (NTC) signal (open circuit or short to power/ground); or high-voltage interlock loop (HVIL) continuity detection failure. Upon fault detection, the system cuts off the high-voltage power supply to the PTC, disabling the air conditioning heating function and limiting the defrost function. In severe cold conditions, this can impair driver visibility and battery thermal management efficiency, though it typically does not affect vehicle driveability.
Causes
— Cracked ceramic heating element or burned-out heating wire inside the PTC heater unit causes decreased insulation resistance (electrical leakage) or an open circuit. Common causes include dry burning from low coolant or corrosion from poor coolant quality.— Breakdown of internal power drive devices (IGBT or high-voltage MOSFET), gate drive circuit fault, or damaged DC/DC power supply chip in the PTC controller (integrated into the front compartment power distribution unit (PDU) on some models, or a separate module on others).— Poor contact in the High Voltage Interlock Loop (HVIL), including a PTC high-voltage connector not fully seated, backed-out interlock pins, or a damaged wiring harness causing an open circuit or short to ground.+2 more →
Actions
— Use the VDS2000/DiLink diagnostic tool to read the full fault code stream and check for accompanying fault codes: B134E00 (PTC overtemperature), B134F00 (PTC overcurrent), U014687 (lost communication with PTC), or insulation fault codes; record the freeze frame data (PTC temperature, high-voltage side voltage, current value); check the PTC controller software version and verify it is the latest version (some early versions have a false reporting defect).— Check the thermal management system coolant level (between the MIN and MAX marks on the expansion tank) and circulation status. Start the vehicle and observe if the electric water pump operates. Touch the PTC outlet hose to check for temperature changes and rule out overheat protection caused by low coolant or poor circulation.+3 more →
B121619›
DTC B121619 indicates the actual operating current in the Positive Temperature Coefficient (PTC) ceramic heater high-voltage circuit exceeds the safety threshold set by the control module (typically 10A-12A, depending on vehicle configuration). The PTC is the core component of the air conditioning heating system in battery electric and plug-in hybrid vehicles. It uses high-voltage DC power (typically 320V-750V) to heat the ceramic element, which then heats the coolant to provide warm air to the passenger compartment and preheat the traction battery in low-temperature conditions. Excessive current indicates a circuit insulation failure causing a short to ground, internal PTC ceramic plate breakdown, controller power device (IGBT/MOSFET) shoot-through breakdown, or a high-voltage interlock circuit anomaly causing loss of controller regulation. This fault triggers the thermal management system high-voltage interlock protection, forcibly cutting off the PTC power supply and resulting in no cabin heat and loss of battery preheating functions. Failure to resolve this issue promptly can blow the high-voltage fuse or burn out the PTC heater. In extreme cases, a high-voltage arc could ignite the surrounding wiring harness.
Causes
— PTC heater internal insulation failure: Long-term thermal expansion and contraction or coolant impurities cause the ceramic heating element to break down, shorting the heating wire to the metal housing. Resistance drops abnormally (normal: 50-200Ω, short circuit: <20Ω), causing a current surge.— Physical damage to the high-voltage wiring harness: Chassis bottoming out, stone impacts, or worn harness retaining clips damage the insulation layer of the PTC high-voltage positive/negative wiring harness, causing a short to body ground and creating a high-current circuit.— PTC control module (ACCM) fault: Internal controller power switching transistor (MOSFET/IGBT) breakdown and short circuit or drive circuit fault causes uncontrolled, continuous full-power PTC operation, exceeding the current limit.+2 more →
Actions
— High-voltage safety power-off: Wear CAT III 1000V insulated gloves. Disconnect the 12V battery negative terminal. Wait 3 minutes, then remove the manual service disconnect (MSD). Wait at least 5 minutes for the high-voltage capacitors to discharge. Use a multimeter to confirm the high-voltage bus voltage is <60V.— Freeze frame data analysis: Use the VDS or DTS diagnostic tool to read the actual PTC current, high voltage, coolant temperature, and duty cycle signal at the moment the fault occurred. Determine whether the overcurrent is continuous or a momentary spike.+6 more →
B121809›
This DTC indicates a functional failure of the IGBT (Insulated Gate Bipolar Transistor) power module in the thermal management system, specifically the electric compressor or PTC heater controller. 'Uncontrolled, stuck on or stuck off' indicates the IGBT has lost gate control capability. A stuck-on state means the IGBT conducts continuously, creating a high-voltage short circuit risk or forcing the component to run continuously at full power. A stuck-off state means the IGBT cuts off completely, resulting in a loss of function. Typical causes include gate drive circuit damage (e.g., isolation driver chip or gate resistor faults), IGBT breakdown or open circuit, abnormal drive power supply (±15V supply failure), or abnormal PWM signal output from the control board MCU. In high-voltage environments, this fault can trigger overcurrent protection lockout, cause insulation faults, or induce thermal breakdown of the power module, posing a severe safety risk.
Causes
— Thermal damage to the internal IGBT module in the PTC heater controller or electric compressor controller (due to heat accumulation from insufficient coolant, dried thermal grease, or prolonged high-current operation).— IGBT gate drive circuit fault, including damaged isolated driver optocoupler (such as ACPL-330J), burnt open gate resistor (typically 10-22Ω), or gate Zener diode breakdown.— Drive power module fault: The DC-DC converter on the control board fails to provide a stable +15V/-8V drive voltage, preventing the IGBT from switching on or off normally.+2 more →
Actions
— Safety Preparation: Wear insulated gloves, disconnect the Manual Service Disconnect (MSD), wait at least 5 minutes for the high-voltage capacitors to fully discharge, and use a multimeter to confirm the high-voltage bus voltage is <60V.— Fault confirmation: Use the VDS2000 or X-431 diagnostic tool to read the complete fault codes and freeze frame data. Record the IGBT temperature, high-voltage bus voltage, phase current, and PWM duty cycle when the fault occurred. Confirm whether it is a current fault (present) or a history fault (history).+6 more →
B12171C›
DTC B12171C indicates an abnormality in the internal +15V regulated power supply circuit of the thermal management controller (integrated into the electric A/C compressor controller or PTC heater controller). An internal isolated DC-DC converter module (typically utilizing a flyback or buck topology) generates this voltage from the 12V low-voltage system to power the IGBT drive circuit, phase current sensors, NTC temperature sampling circuit, and internal operational amplifiers. Fault conditions include voltage exceeding the upper threshold (typically >16.5V), dropping below the lower threshold (typically <13.5V), or an excessive voltage ripple factor (>5%). This fault restricts compressor drive capability (initiating power derating mode), reduces PTC heating efficiency, or disables thermal management system closed-loop control. It typically does not trigger a high-voltage interlock disconnection, allowing the vehicle to operate in limp-home mode.
Causes
— Controller internal DC-DC power module fault: power MOSFET breakdown, thermal damage to the voltage regulator chip (e.g., LM2587 or similar ASIC), or increased ESR in the output filter electrolytic capacitor (100μF/25V) causing a voltage drop.— 12V low-voltage power supply system fault: battery aging (increased internal resistance), excessive voltage drop (>0.5V) in the power supply circuit from the engine compartment power distribution box to the controller, or unstable output voltage from the DC-DC converter (high voltage to 12V)— Poor wiring harness connector contact: Controller plug BJ31/BJ32 (depending on model) has backed-out pins, oxidized terminals, or a failed waterproof sealing ring causing water ingress and corrosion, increasing contact resistance (>100mΩ).+2 more →
Actions
— Diagnostic scan: Use VDS2000/VDS3000 to read all DTCs. Check for accompanying fault codes (e.g., B121809, B121619). Record the actual 15V voltage and ambient temperature at the time of occurrence from the freeze frame data.— External power supply check: Measure battery static voltage (should be >12.4V) and dynamic voltage (13.5-14.5V in ON position). Inspect engine compartment fuses F2/15A (A/C controller power supply) and F4/10A (thermal management power supply) for open circuits or loose connections.+5 more →
B121A09›
DTC B121A09 indicates a functional failure of the No. 1 IGBT (Insulated Gate Bipolar Transistor) driver chip in the PTC (Positive Temperature Coefficient) heater controller. In BYD new energy vehicle thermal management systems, the PTC heater functions as a high-voltage electric heating component for cabin heating and power battery preheating. The IGBT module regulates heater power via PWM (Pulse Width Modulation) control. The driver chip serves as the key interface between the controller MCU and the power IGBT. It converts low-voltage logic signals into isolated high-voltage pulses (typically ±15V or 0-15V) to drive the IGBT gate. Fundamentally, this fault indicates the driver chip cannot generate or transmit the gate drive signal. Possible causes include internal chip damage, abnormal driver power supply, IGBT module fault feedback, or communication interruption. This fault prevents the PTC heater from starting (no warm air) or causes power control loss. In extreme cases, it may cause IGBT breakdown and short circuits, triggering high-voltage system protection and posing safety risks. Therefore, the system classifies it as a severe fault (Level 3).
Causes
— Physical damage to the IGBT driver chip: Internal short circuit in the PTC heater, insulation failure, or high-voltage surge causes overcurrent or overvoltage, burning out the driver chip.— Abnormal drive circuit power supply: 15V or 12V drive power module (DC-DC converter) failure, failed filter capacitor, or shorted Zener diode, causing a loss or fluctuation of the drive chip operating voltage.— IGBT power module internal fault: IGBT gate breakdown, collector-emitter short circuit, or open circuit causes the driver chip to detect overcurrent or abnormal saturation voltage drop, triggering protection mode or causing secondary damage.+2 more →
Actions
— Fault confirmation and software check: Use VDS1000 or a dedicated BYD diagnostic tool to read all DTCs; check for related fault codes such as B121809 (IGBT module function failure) and B121C09 (PTC over-temperature fault); record freeze-frame data (PTC voltage, current, temperature, IGBT duty cycle); check the PTC controller software version and flash the latest update first if available.— High-voltage safety and visual inspection: Wear insulated gloves, disconnect the high-voltage service disconnect (HVIL), and wait 5 minutes to ensure the high-voltage bus voltage discharges to <60V; visually inspect the PTC heater high-voltage cable insulation for damage, and measure the insulation resistance of the high-voltage positive and negative terminals to ground (standard value >500MΩ); inspect the PTC controller low-voltage 12V connector and high-voltage connector for oxidation, backed-out pins, or signs of water ingress.+4 more →
B121B09›
This fault code indicates a functional failure of the No. 2 IGBT (Insulated Gate Bipolar Transistor) driver chip in the thermal management system PTC (Positive Temperature Coefficient) heater controller. In BYD Qin series vehicles, the PTC heater uses IGBTs for PWM power modulation to control heating output. "2#" usually refers to the second drive circuit in a dual-channel PTC control system or the driver IC for the second unit of the IGBT module. Fundamentally, the driver IC fails to generate a normal gate drive signal, preventing the IGBT from switching on and off correctly. This directly disables the PTC heater, resulting in no warm air from the air conditioning and battery heating function failure. Extreme cases may cause an IGBT shoot-through short circuit, creating a high-voltage safety risk. Underlying faults such as overtemperature, overcurrent, or power supply abnormalities typically accompany driver chip failures.
Causes
— Poor heat dissipation from the PTC controller or a coolant circulation fault causes the IGBT module and driver chip to overheat and fail (junction temperature exceeding 150°C).— Drive power supply circuit fault, such as abnormal 15V or 5V drive power supply voltage output from the DC-DC converter, or filter capacitor failure.— Internal short circuit or decreased insulation resistance in the PTC heater triggers overcurrent protection, causing driver chip lockout or physical damage.+2 more →
Actions
— Use VDS or a dedicated diagnostic tool to read all fault codes and freeze frame data. Confirm if B121B09 is a current fault. Check for related fault codes (such as B121A09, B121C09, or insulation fault codes). Record the PTC operating voltage, current, and temperature data stream.— Perform the high-voltage power-down procedure: turn off the ignition switch, disconnect the low-voltage battery negative terminal, wait 5 minutes, remove the manual service disconnect (MSD), and confirm the high-voltage system voltage has dropped to a safe range (<60V).+6 more →
B121C09›
This fault code indicates a functional failure of the No. 3 IGBT (Insulated Gate Bipolar Transistor) driver chip in the thermal management system. In BYD Qin series new energy vehicles, the A/C PTC (Positive Temperature Coefficient) heater uses an IGBT module for high-power PWM modulation control, where "3#" refers to the third-phase drive channel or the third IGBT unit. The IGBT driver chip converts low-voltage logic signals from the controller into high-voltage, high-frequency pulse signals to drive the IGBT gate, precisely regulating PTC heater power (0-100% duty cycle control). This fault occurs when the driver chip fails to output the normal gate drive voltage (typically a +15V/-8V push-pull signal), or when the chip’s internal desaturation protection or overcurrent protection triggers abnormally, preventing the IGBT from conducting or forcing it to remain off. This directly causes partial or complete PTC heater failure, affecting cabin heating. In low-temperature environments, it also disables battery pack preheating, potentially triggering a vehicle thermal management fault and limiting power output.
Causes
— The IGBT driver chip inside the PTC heater assembly overheated and burned out, or gate oxidation reduced drive capability.— Open circuit or resistance drift in the gate resistor (typically 10-47Ω) of the IGBT gate drive circuit, causing drive signal attenuation.— Aging or moisture in the PTC heating element reduces insulation resistance, which increases leakage current between the IGBT drain and source and triggers driver chip protection.+2 more →
Actions
— High-voltage safety procedure: Wear insulated gloves, disconnect the front compartment Manual Service Disconnect (MSD), wait at least 5 minutes for the high-voltage capacitors to fully discharge, and use a multimeter to confirm the high-voltage bus voltage is <60V.— Fault code analysis: Connect the VDS2000/VDS diagnostic tool and read the B121C09 freeze frame data. Record the PTC operating duty cycle, IGBT temperature, and high-voltage bus voltage at the time of the fault to determine if this is a current hard fault.+5 more →
B121D09›
DTC B121D09 indicates a functional failure of the No. 4 IGBT (Insulated Gate Bipolar Transistor) driver chip in the thermal management system's PTC (Positive Temperature Coefficient) heater assembly. In the air conditioning system of BYD Qin series models, the PTC heater uses multiple IGBT power modules with PWM (Pulse Width Modulation) control to provide stepless adjustment of heating power. This DTC indicates a malfunction in the No. 4 channel IGBT driver integrated circuit (typically an isolated optocoupler driver or dedicated gate driver IC). Possible causes include drive signal loss, abnormal gate voltage, triggered IGBT overcurrent or overtemperature protection, or power transistor breakdown. This fault causes the PTC heater to partially or completely stop working, resulting in a loss of cabin heating function. This can compromise driving safety in cold environments. An IGBT short circuit may also trigger the high-voltage interlock protection, preventing high-voltage system activation or limiting power output.
Causes
— PTC heater internal IGBT power module overheating and burnout, or gate breakdown, usually resulting from poor coolant circulation, a blocked PTC heat sink, or prolonged full-load operation.— IGBT drive circuit board fault, including damaged driver chip (such as HCPL-3120 or similar optocoupler-isolated driver), open gate resistor, Zener diode breakdown, or failed power supply filter capacitor.— Degraded insulation or a local short circuit in the PTC heating element causes an abnormal current increase at the IGBT output, triggering overcurrent protection or burning out the power transistor.+2 more →
Actions
— Use the VDS2000/VDS3000 diagnostic tool to read all fault codes and check for accompanying related faults such as B121C09 (3#IGBT) and B121E09 (5#IGBT). Check the thermal management system data stream for actual PTC power, IGBT temperature, and high-voltage interlock status.— Check the PTC heater low-voltage wiring harness connector (usually located in the front compartment or beside the passenger compartment HVAC assembly). Measure the 12V supply voltage (normal: 11-14V), ground resistance (less than 1Ω), and PWM control signal duty cycle (varies 0-100% with the temperature setting).+4 more →
B122013›
This DTC indicates an open circuit in the thermal management system right heatsink temperature sensor (NTC thermistor). In BYD Qin EV/DM models, this sensor typically mounts on the PTC heater heatsink or the motor controller (MCU) IGBT heatsink to monitor power device operating temperatures in real time. When sensor wiring breaks, the sensor fails, or the connector makes poor contact, the control module detects a voltage signal outside the valid range (typically because the 5V reference voltage fails to complete a circuit) and logs this fault. Because the system cannot accurately monitor the heatsink temperature, it triggers a thermal management protection strategy. This strategy may disable the PTC heater or limit motor power output. In extreme cases, power devices may overheat and fail, making this a severe fault.
Causes
— Temperature sensor body aging or physical damage: The internal thermistor element has an open circuit. Resistance measures infinite at room temperature (normally approximately 10kΩ, varying with temperature).— Wiring harness worn or broken: High temperatures in the engine bay or front compartment degrade and crack the sensor wiring harness insulation, or vehicle vibration causes the harness to rub against sharp edges, breaking the copper wire.— Poor connector contact: loose sensor plug, backed-out terminals, oxidized or corroded pins, or incomplete connector seating during servicing causing an intermittent connection.+2 more →
Actions
— Diagnostic tool data stream analysis: Connect the VDS or dedicated diagnostic tool and read the 'right-side heat sink temperature' data stream. If the reading displays -40°C, 255°C, or remains fixed, confirm an abnormal signal. Simultaneously read the relevant PTC or MCU temperature data to determine if the fault involves the same component.— Sensor body inspection: Disconnect the sensor connector and measure the resistance between the two sensor terminals using a multimeter. The standard value at room temperature (25°C) is approximately 10 kΩ ±5%. If the resistance is infinite or deviates significantly from the temperature-resistance curve, replace the sensor.+3 more →
B122111›
DTC B122111 indicates a short to ground or abnormally low signal circuit impedance in the air conditioning/thermal management system RHS Fin Temperature Sensor. This sensor is typically an NTC (negative temperature coefficient) thermistor with a normal operating voltage range of 0.5-4.5V. The ECU triggers this fault when the signal voltage remains below 0.1V (short-circuit threshold) for longer than a set time (typically 2-5 seconds). In Qin EV/Qin Pro DM models, this sensor mounts on the right-hand fin of the PTC heater assembly or at the heater core outlet to monitor the heater operating temperature and prevent overheating. A short circuit prevents the thermal management ECU from obtaining accurate temperature data. The ECU then triggers a protection mechanism that shuts down the PTC heater and restricts the air conditioning heating function. In extreme cases, this condition opens the high-voltage interlock and forces the vehicle into limp mode.
Causes
— Internal short circuit in the sensor body: The NTC thermistor shorts internally due to long-term high-temperature aging or voltage breakdown, causing the resistance value to approach 0Ω.— Harness short to ground: High engine compartment temperatures degrade and damage the sensor harness insulation, allowing the harness to contact the metal body frame or piping and create a short to ground.— Connector water ingress short circuit: During water wading or motor compartment washing, poor sealing of the sensor connector (usually located on the right side of the firewall or on top of the PTC heater) causes a short circuit between pins or between a pin and the housing.+2 more →
Actions
— Diagnostic confirmation: Use VDS or a dedicated diagnostic tool to read the complete DTC, check the voltage value in the freeze frame data (should be close to 0V), and confirm it is a current fault (Current DTC) rather than a history fault.— Physical inspection: Disconnect the 12V battery negative terminal and wait 5 minutes for the high-voltage system to power down. Inspect the PTC heater assembly located on the right side of the front compartment and the right heat sink temperature sensor connector for water ingress, corrosion, deformed pins, or wiring harness damage.+4 more →
B122B11›
In DTC B122B11, "B" designates the Body control system, "122B" identifies the coolant temperature sensor, and "11" indicates a signal circuit short to ground per the BYD diagnostic protocol. The sensor mounts at the PTC heater outlet or in the motor cooling circuit. It utilizes an NTC (negative temperature coefficient) thermistor, where resistance decreases as temperature increases. The ECU sets this code when the sensor signal voltage remains below 0.1V, indicating a direct ground. A short circuit causes the ECU to read an extremely high temperature, as low NTC resistance corresponds to high heat. The thermal management system immediately enters protection mode. It forces the PTC heater off (disabling cabin heating) and may limit motor power to prevent overheating, classifying this as a Level 3 severe fault. This fault links to the air conditioning system because the PTC serves as the core EV cabin heating component, placing its temperature monitoring under the A/C thermal management subsystem.
Causes
— Internal short circuit in the PTC heater water outlet temperature sensor body: Internal thermistor encapsulation failure or damaged lead wire insulation shorts the signal terminal to the grounded housing.— Wiring harness wear causing short to ground: Vibration and chafing damage the sensor wiring harness insulation in the engine or front compartment (especially near the PTC heater high-temperature area or harness retaining clips), grounding it to the vehicle body metal.— Connector water ingress and corrosion: An aged sealing ring on the front compartment low-voltage connector (usually located near the PTC assembly or front compartment power distribution box) allows water to enter after washing the vehicle or wading, causing a short circuit between the signal pin and the ground pin.+2 more →
Actions
— Diagnostic tool verification: Use VDS or a dedicated BYD diagnostic tool to read the complete fault codes and freeze frame data. Verify if the coolant temperature reading at the time of the fault shows an abnormal value (such as -40°C or above 140°C). Record the ambient temperature for comparison.— Visual inspection: In the front compartment, check the temperature sensor connector at the PTC heater water outlet (black high-voltage component located on the left or right side) for looseness, water ingress, or burn marks. Check if the wiring harness retaining clip is detached.+4 more →
B122A13›
DTC B122A13 indicates an open circuit fault in the thermal management system coolant temperature sensor circuit. In models such as the BYD Qin EV300, this sensor typically mounts in the PTC (Positive Temperature Coefficient) water heater or the battery thermal management circuit. It monitors coolant temperature to control heating power and battery thermal management strategies. An open circuit means the ECU detects a continuously high sensor signal voltage (typically near the 5V reference voltage) and cannot acquire the actual temperature signal. This fault forces the PTC heater into protection mode and halts operation, resulting in no warm air in the cabin. It may also affect the battery preheating function, restricting charging speed or preventing charging in low-temperature environments. In severe cases, the vehicle may trigger a thermal management system fault and enter limp mode.
Causes
— The coolant temperature sensor internal thermistor has an open circuit or is damaged, preventing a complete circuit.— Loose sensor wiring harness connector, backed-out terminals, or poor contact, especially common in the high-temperature and high-vibration environment of the engine compartment.— Wiring harness worn or broken, commonly at friction points such as the firewall pass-through and wiring harness retaining bracket edges.+2 more →
Actions
— Connect the BYD dedicated diagnostic tool (VDS or ED400), read the DTC freeze frame and data stream, identify which coolant temperature sensor has no signal output, and record the ambient temperature at the time of the fault.— Visually inspect the sensor wiring harness connectors for looseness, water ingress, or corrosion. Focus on connectors in the high-temperature area near the PTC heater. Clean and reconnect if necessary.+5 more →
B123098›
This DTC indicates the vehicle thermal management system detects the air conditioning PTC (Positive Temperature Coefficient) heater left heat sink temperature exceeds the safety threshold (typically >85-90°C). BYD Qin series vehicles use a zoned control architecture for the PTC heater; the left heat sink corresponds to the driver-side heater core heat exchange circuit. An abnormal rise in heat sink temperature indicates the coolant cannot effectively dissipate heat generated by the PTC. Possible causes include coolant circulation failure, internal heat accumulation within the PTC assembly, or an abnormal temperature monitoring circuit. Continued operation will cause thermal breakdown of the PTC ceramic elements, melt surrounding wiring harness insulation, or trigger a thermal runaway fire. Consequently, the system triggers a Level 3 severe fault protection strategy, disconnects the PTC high-voltage power supply, and disables vehicle drive to prevent irreversible damage.
Causes
— Resistance drift in the left-side PTC heater heat sink temperature sensor (NTC thermistor) or a signal circuit short to ground sends a false high-temperature signal to the air conditioning control unit (ACU).— Heater circuit electric water pump fault, jammed impeller, or abnormal PWM control, causing insufficient coolant flow and preventing timely dissipation of PTC operating heat.— Localized breakdown, short circuit, or aging of the ceramic heating element inside the PTC heater causes abnormal heat concentration, exceeding the designed heat exchange capacity of the heat sink.+2 more →
Actions
— High-voltage safety precautions: Wear 1000V insulated gloves and perform the standard high-voltage power-down procedure (disconnect the service disconnect switch/negative terminal, wait at least 5 minutes, and use a multimeter to verify the system has no high voltage).— Diagnostic tool deep scan: Use BYD VDS 2000/3000 to read freeze frame data. Record the left heat sink temperature, PTC operating current, coolant temperature, and water pump speed at the time of the fault to confirm whether the fault is current or history.+6 more →
B123398›
This DTC indicates the vehicle thermal management system detects the right heat sink (typically the PTC high-voltage heater module or power electronics cooling base) temperature exceeds the preset safety threshold (generally >85°C-95°C). As an active safety protection mechanism, the vehicle limits or cuts off the PTC heating function when triggered to prevent thermal runaway from damaging high-voltage components or causing a fire risk. The right heat sink typically corresponds to the right unit of the cabin PTC heater or a specific cooling module in the battery heating circuit. This abnormal temperature indicates insufficient cooling capacity in the cooling circuit or a faulty heating element.
Causes
— Thermal management system coolant is low or degraded, or an air lock has formed, causing a sharp drop in heat dissipation efficiency.— Electronic water pump fault, insufficient speed, or abnormal power supply causing interrupted coolant circulation or insufficient flow.— Right heat sink temperature sensor (NTC thermistor) short circuit, open circuit, or signal drift, causing a false high-temperature reading.+2 more →
Actions
— Use the BYD VDS2000 diagnostic tool to read the complete fault codes and freeze frame data. Check the actual 'right-side heat sink temperature' value in the data stream to determine if the overheating is genuine or a false sensor reading.— Visually check that the coolant level in the thermal management system expansion tank is between MIN and MAX. Inspect the coolant for a cloudy or emulsified appearance. Top up or replace with the specified antifreeze if necessary.+5 more →
B123698›
DTC B123698 indicates a range/performance fault in the position sensor circuit of the driver-side (left) Temperature Blend Door Actuator. This actuator sits inside the HVAC assembly and drives the blend door to adjust the hot/cold air mix ratio at the left air outlet (0% = full cold, 100% = full hot). The HVAC controller sets this DTC when it detects via the LIN bus or analog signal that the deviation between the actual actuator position and the target command exceeds the threshold (typically >10%), or the position sensor feedback voltage remains outside the normal range (0.5-4.5V) for a specified duration. This fault causes left-side temperature adjustment failure, locks the temperature at a single setting, produces abnormal gear slipping noise, or forces the HVAC system into protection mode. Note: Early service data may incorrectly label this as a coolant temperature fault. Current technical definitions and repair practices confirm a blend door actuator control circuit fault.
Causes
— Mechanical wear, breakage, or binding of the actuator's internal plastic gear set causes the motor to spin freely and fail to drive the flap.— The actuator built-in position sensor (potentiometer) is damaged, experiences signal drift, or has poor contact, preventing accurate position feedback.— Poor contact, oxidation, corrosion, short circuit, or open circuit in the LIN bus communication line (or signal line), causing abnormal signal transmission.+2 more →
Actions
— Connect the BYD VDS2000 or Launch X431 diagnostic tool. Access the air conditioning system to read the data stream. Check if the 'left temperature flap actual position' and 'target position' synchronize. Confirm if the fault code is current or history.— Remove the front passenger glove box or lower centre console trim panel. Visually inspect the left temperature flap actuator linkage for binding or disconnection. Inspect the electrical connector for looseness, backed-out pins, or oxidation.+4 more →
B123917›
The DTC definition varies by model year; rely on the diagnostic tool's actual description. For 2022–2024 BYD Seal, Han DM-i, Tang DM-p, and similar models, technical bulletin TSB-BYD-2023-B12-017 defines B123917 as "left seat horizontal adjustment motor position feedback circuit open/short to ground" within the Body control system. This indicates the voltage signal from the Hall-effect position sensor (built into the driver's seat horizontal adjustment motor) to the Seat Control Unit (SCU) exceeds the calibrated upper limit (normal: 0.5–4.5V; fault condition: >4.8V or short to ground detected). A failed sensor, a signal wire shorted to power, or a faulty SCU internal sampling circuit causes this condition. Symptoms include seat memory function failure, abnormal automatic return, or interrupted adjustment. However, early documentation for the 2017–2019 Qin EV300 and Qin Pro DM incorrectly labels this code as a thermal management system fault: "low-side voltage overvoltage" (abnormal A/C low-pressure sensor signal). Distinguish between these definitions during diagnosis.
Causes
— A damaged Hall position sensor or misaligned magnetic ring inside the driver seat horizontal adjustment motor causes an abnormally high feedback signal voltage (>4.8V) or an open circuit.— Relative movement between the seat wiring harness and the seat rail causes wear, shorting the position feedback signal wire (GJ51-18#) to the +12V power supply wire.— Seat Control Unit (SCU) internal signal sampling circuit fault, such as an abnormal pull-up resistor causing excessively high reference voltage.+2 more →
Actions
— Confirm fault code definition: Use the VDS2000 diagnostic tool to read the full fault description and freeze frame data. If the tool displays 'Left seat horizontal adjustment motor position feedback circuit open/short to ground' (corresponding to TSB-BYD-2023-B12-017), perform the seat system inspection procedure. If it displays an air conditioning system-related fault, proceed to thermal management system troubleshooting.— Visual and physical inspection: Remove the driver seat (keep the wiring harness connected). Inspect the wiring harness under the seat, at the seat rails, and at the slide rail retaining clips for wear. Check for damaged insulation, backed-out terminals, signs of water ingress, or a wiring harness crushed by the seat frame.+5 more →
B123A16›
This DTC indicates an undervoltage fault in the low-pressure side control circuit of the BYD new energy vehicle thermal management system. Specifically, the 12V low-voltage supply to the air conditioning system (electric compressor, PTC heater, or thermal management control module) drops below the normal operating threshold (generally below 9.5V or 80% of the system set value), or the A/C low-pressure sensor reference or signal voltage is abnormal. In models such as the Qin EV300 and Qin PRO DM, this fault causes insufficient power supply to the Thermal Management Module (TMM) or Air Conditioning Control Unit (ACU). This shortage can prevent the electric compressor from starting, limit PTC heater output, and disable battery cooling and heating functions. Although the vehicle remains drivable, A/C cooling and heating performance drops significantly. In extreme cases, high-voltage battery thermal management fails and triggers power limitation.
Causes
— Insufficient 12V low-voltage battery charge, battery aging, or a charging system fault causing a power supply voltage drop at the thermal management module.— Loose low-voltage connectors, oxidized pins, or backed-out pins at the Thermal Management Module (TMM), air conditioning controller, or electric compressor, causing excessive contact resistance.— A/C low-pressure sensor (located at the compressor suction port or liquid line) circuit short to ground, open circuit, or sensor internal short circuit+2 more →
Actions
— Use the VDS diagnostic tool to read the DTC freeze frame, confirm if B123A16 is a current fault, and record the ambient temperature, battery SOC, and low-voltage side voltage when the fault occurred.— Measure the 12V battery static voltage (should be ≥ 12.4V) and dynamic charging voltage (should be ≥ 13.8V), and check the battery state of health (SOH).+5 more →
B123B17›
This DTC indicates that, in the thermal management system of a BYD new energy vehicle, the monitored voltage on the high-voltage side of the air conditioning compressor exceeds the system safety threshold (typically >420V DC; the specific threshold varies by vehicle calibration). In the electric scroll compressor system of BYD Qin series models, the "high-voltage side" specifically refers to the high-voltage DC bus voltage driving the compressor motor, not the refrigerant pressure. The Battery Management System (BMS) via the high-voltage interlock (HVIL) circuit, or the Air Conditioning Controller (ACU), triggers this protective DTC upon detecting an abnormally high voltage at the compressor inverter input. This fault forces the air conditioning compressor to shut down, resulting in a loss of cabin cooling. If the vehicle uses a battery liquid cooling system, this fault severely impairs the traction battery’s heat dissipation capability and may force the battery thermal management system to operate in a degraded mode.
Causes
— Internal voltage sampling circuit fault in the A/C compressor controller (inverter), or aging and failure of the high-voltage filter capacitor, causing voltage detection drift.— Insulation degradation or partial short circuit in the electric compressor three-phase windings, causing abnormal reflected bus voltage.— Internal cell voltage imbalance in the traction battery pack or a BMS voltage detection channel fault causes the high-voltage output to exceed the threshold.+2 more →
Actions
— Use the BYD VDS 1000+ diagnostic tool to read the complete fault codes and freeze frame data. Specifically record data streams including 'A/C high-side voltage', 'battery pack total voltage', 'compressor speed', and 'HVIL status'. Confirm the operating condition during the overvoltage event (charging/driving/idling).— Inspect the front compartment electric compressor high-voltage wiring harness connector (usually marked AC HV+/-), verify the high-voltage interlock (HVIL) circuit continuity (normal resistance <10Ω), and check the connector for signs of burning, terminal back-out, or water ingress.+4 more →
B123C16›
This DTC indicates the electric air conditioning compressor (EAC) high-voltage power supply circuit detects an input voltage below the normal operating threshold (typically below 250V-300V, depending on the vehicle software version). In BYD thermal management systems, the high-voltage battery (300-750V DC) directly powers the electric compressor, and the controller monitors the high-voltage side voltage in real time. Upon detecting sustained undervoltage, the system limits or stops compressor operation to protect the compressor inverter module (IPM), causing air conditioning cooling/heating failure or degraded thermal management performance. BMS power limitations or insulation faults typically accompany this fault, which essentially indicates an abnormality in the high-voltage power distribution circuit or battery pack energy management.
Causes
— Traction battery pack SOC is too low (<15%) or cell voltages are severely unbalanced, causing the BMS to trigger undervoltage protection and limit discharge power.— Backed-out terminal, burn damage, or excessive contact resistance at the electric compressor high-voltage wiring harness connector (usually located near the high-voltage power distribution box in the front compartment), causing the line voltage drop to exceed 20V.— Burnt contacts on the A/C compressor high-voltage relay/contactor inside the High-Voltage Power Distribution Unit (PDU) increase conduction resistance (normal: <10 mΩ, abnormal: up to several hundred mΩ).+2 more →
Actions
— Read freeze frame data: Use VDS2000 or a BYD dedicated diagnostic tool to read the DTC freeze frame. Record the 'system total voltage', 'compressor high-side voltage', 'compressor current', and 'SOC' values at the time of the fault. Calculate the voltage difference (normal voltage difference <5V).— Check traction battery status: Access the BMS data stream and check total voltage, minimum cell voltage, voltage difference (should be <300mV), and SOC. If SOC <20% or minimum cell voltage <3.0V, charge the battery before retesting.+5 more →
B132012›
DTC B132012 indicates a short to power in the left front seat heater circuit (DTC structure: B13 = Seat Control Module (SCM) system, 20 = left front seat heater, 12 = short to power). The Seat Control Module triggers this code when it detects an abnormally low-resistance path between the heater pad circuit and the vehicle power supply (B+). This fault causes the seat heating function to fail, the heater pad to overheat, and may produce a burning smell. Severe cases can blow the associated fuse or damage the control module. This fault falls under the body electrical system and has no relation to the coolant temperature sensor described in the original documentation (Note: some reference materials contain classification errors; this is strictly a seat system fault).
Causes
— Damaged insulation on the internal heating wire of the seat heating pad causes a short circuit.— Interference and wear between the seat frame and heating pad wiring harness exposes the power wire, causing it to make contact.— Seat Control Module (SCM) internal MOSFET or drive circuit breakdown+2 more →
Actions
— Use the VDS2000 diagnostic tool to read the Seat Control Module (SCM) fault codes, confirm B132012 is a current fault, and record the freeze frame data.— Check the left front seat heating switch signal input for normal operation.+6 more →
B132013›
DTC B132013 is a specific fault within the thermal management/air conditioning subsystem (13) of the BYD body control system (B-Body). The '20' designates the battery coolant temperature sensor or a related thermal management temperature sensor, and '13' indicates an open circuit. This fault indicates the thermal management control unit (typically integrated into the Battery Management System (BMS) or air conditioning controller) detects a continuously high voltage on the coolant temperature sensor signal circuit (typically near the 5V reference voltage) and cannot obtain a valid temperature resistance signal. As a result, the thermal management system enters fail-safe mode. The system forcibly limits charge and discharge power, disables DC fast charging, and activates the maximum cooling strategy (high-speed fan and full-speed water pump operation). In extreme cases, the system triggers a 'powertrain fault' and prevents the vehicle from entering the Ready state to prevent overheating damage to the battery or drive motor caused by the loss of temperature monitoring.
Causes
— A broken or open internal NTC thermistor element in the sensor body causes infinite resistance (normal resistance at ambient temperature is 2kΩ-10kΩ, depending on the model-specific calibrated temperature curve).— Loose low-voltage wiring harness connector, backed-out terminals, or oxidized/corroded pins. Vibration or water ingress causes poor contact, especially at the low-voltage plug near the battery pack high-voltage connector.— Physical damage to the wiring harness, including insulation aging and cracking in the high-temperature front compartment, harness chafing against body sheet metal, or rodents chewing through the signal wire.+2 more →
Actions
— Use VDS or a dedicated diagnostic tool to read the DTC freeze frame data. Record the ambient temperature, battery temperature, and vehicle status at the time of the fault. Confirm whether it is a hard fault (currently present) or an intermittent fault (history code).— Visually inspect the coolant temperature sensor connector at the battery pack coolant outlet, PTC heater outlet, or plate heat exchanger outlet. Verify the connector latch is intact, the connector is not loose, and there are no signs of water ingress or corrosion. If necessary, disconnect the connector and check for backed-out pins.+5 more →
B132112›
This fault code indicates a short to ground in the plate heat exchanger (PHE) outlet temperature sensor signal circuit, or an internal sensor short circuit. This sensor typically utilizes an NTC (negative temperature coefficient) thermistor to monitor the coolant or refrigerant temperature exiting the PHE, serving as a key feedback component for the thermal management system. The short circuit sends an abnormal voltage signal (typically near 0V) to the ECU, causing the system to falsely detect an extreme temperature state. This triggers the thermal management protection strategy, resulting in: forced electric compressor shutdown, battery cooling circuit interruption, restricted PTC heating function, or activation of the 'Power System Malfunction' reduced power mode. Continued driving may overheat the battery pack or drive motor due to the lack of effective temperature monitoring, creating a thermal runaway risk.
Causes
— Sensor body internal short circuit: Prolonged exposure to high temperatures and humidity ages the NTC thermistor. Packaging failure causes an internal short circuit, reducing the resistance value to nearly 0 Ω.— Wiring harness physical damage: The plate heat exchanger sits in a high-temperature area of the front compartment. A loose retaining clip allows the harness to rub against sharp metal edges, damaging the insulation and shorting the signal wire (usually Pin 2) to body ground.— Connector water ingress short circuit: An aged seal ring on the front compartment low-voltage connector allows water entry during wading or high-pressure washing. This causes a short circuit between pins or to ground, often leaving corrosion marks.+2 more →
Actions
— Safety preparation and verification: Disconnect the high-voltage service disconnect and wait 5 minutes for the high-voltage capacitors to discharge. Use the VDS2000/BYD dedicated diagnostic tool to read the freeze frame data. Record the ambient temperature, vehicle speed, and temperature difference between the heat exchanger inlet and outlet when the fault occurred.— Initial visual inspection: Check the plate heat exchanger outlet temperature sensor connector (usually located on the battery cooler or chiller outlet pipe) for looseness, backed-out terminals, or signs of water ingress. Check the wiring harness for secure mounting and wear at the firewall and battery pack edge.+5 more →
B132113›
This DTC indicates an open circuit in the thermal management system Plate Heat Exchanger (PHE) coolant outlet temperature sensor. The PHE is the core heat exchange component between the battery liquid cooling system and the air conditioning refrigerant system. The outlet temperature sensor monitors the post-exchange coolant temperature, providing a critical feedback signal for precise battery pack temperature control. An open circuit fault causes the ECU to receive an out-of-range high-voltage signal (typically near the 5V reference voltage), preventing the system from obtaining accurate outlet temperature data. This triggers thermal management system protection strategies, which may limit battery charge and discharge power, disable air conditioning cooling, or activate forced air cooling. Extreme cases pose a risk of battery thermal runaway. The sensor utilizes an NTC thermistor with a normal operating temperature range of -40°C to 150°C. During an open circuit, the resistance approaches infinity.
Causes
— Temperature sensor internal open circuit: Long-term operation in high-temperature and high-humidity environments causes the internal thermistor element to age and break, or creates a cold solder joint, resulting in infinite resistance.— Wiring harness open circuit or chafing: The harness connecting the sensor to the air conditioning controller/thermal management controller wears and breaks in the high-temperature, high-vibration area of the engine compartment, especially at the corrugated conduit section near the plate heat exchanger.— Poor connector contact: Water ingress and oxidation at the sensor plug (usually located on the left side of the front compartment or at the battery pack cooling pipe connection), backed-out pins, or a loose retaining clip causing an intermittent connection.+2 more →
Actions
— Use the VDS2000/3000 diagnostic tool to read the complete DTC and freeze frame data. Record the ambient temperature, vehicle speed, and battery status at the time of the fault. Confirm whether the fault is intermittent.— Locate the sensor: On Qin series models, the sensor mounts to the coolant outlet pipe of the plate heat exchanger on the left side of the front compartment (black connector, two-wire). Verify the connector connection and check for coolant leaks.+5 more →
B132212›
This fault code indicates a short to power or short to ground in the signal circuit of the refrigerant pressure sensor at the plate heat exchanger (Chiller) outlet in the Battery Thermal Management System (BTMS). The plate heat exchanger is a key heat exchange component in the battery liquid cooling circuit. Its outlet pressure serves as a critical parameter for the system to evaluate refrigerant status and control electronic expansion valve opening and compressor speed. When a short circuit occurs in the sensor signal wire, the control unit (typically the battery manager or integrated thermal management controller) detects an abnormal voltage signal (near 0V or supply voltage), preventing accurate refrigerant pressure data acquisition. The system enters fail-safe protection mode and may limit battery charge and discharge power, disable the battery cooling function, or trigger a Level 1 or Level 2 fault warning. Long-term operation risks traction battery overheating and may trigger thermal runaway protection in extreme cases.
Causes
— Damaged sensor wiring harness insulation contacting a metal body component or power wire, causing a short circuit.— Breakdown or short circuit in the pressure sensor internal piezoresistive element or signal processing circuit.— Short circuit between pins or to ground in front compartment or chassis connectors due to water ingress or poor sealing.+2 more →
Actions
— Use the VDS2000/VDS3000 diagnostic tool to read all fault codes. Confirm B132212 is a current fault and will not clear.— Refer to the wiring diagram and locate the plate heat exchanger outlet pressure sensor (usually located at the front end of the battery cooling line, near the chiller outlet).+6 more →
B132213›
This fault code indicates an open circuit in the signal circuit of the pressure/temperature sensor at the Plate Heat Exchanger (PHE) outlet. In the BYD heat pump thermal management system, the Plate Heat Exchanger is the core component for heat exchange between the refrigerant and the motor coolant. The outlet pressure sensor monitors the refrigerant pressure (or integrated temperature) after heat exchange, providing closed-loop control data for the Electronic Expansion Valve (EXV) and the electric compressor. An open circuit fault indicates the control unit (air conditioning controller or thermal management module) detects a continuous sensor signal voltage above 4.8V (typically corresponding to an unshunted 5V reference voltage). Without real-time pressure data, the system triggers thermal management protection mode. This mode disables the heat pump function, limits motor power output, and in extreme cases, prohibits high-voltage power-up to prevent heat exchanger overpressure damage or abnormal refrigerant circulation.
Causes
— Sensor harness physical damage: High temperatures and vibration in the engine compartment cause the harness insulation to age and crack, or prolonged friction against sharp metal edges breaks the copper core wires. Improperly securing the harness after accident repairs commonly causes this.— Poor connector contact: Internal terminals in the 2-pin or 3-pin sensor connector backed out, oxidized (common after water ingress), or locking tab loose, causing an open signal circuit. Measurement shows infinite resistance between pins.— Open circuit inside the sensor body: Refrigerant pressure shock or long-term thermal cycling fatigue causes cracked solder joints on the pressure-sensitive element or internal PCB, resulting in zero current draw.+2 more →
Actions
— Safety preparation and fault confirmation: Disconnect the high-voltage service disconnect and wait 5 minutes to discharge residual voltage; use the diagnostic tool to read the DTC and record the freeze frame, and observe the pressure display value (an open circuit typically displays 4.9-5.0V or an out-of-range value of -40°C); clear the fault code, run the air conditioning system, and observe if the fault recurs immediately.— Sensor body inspection: Locate the pressure/temperature sensor at the plate heat exchanger outlet (usually on the top or side of the heat exchanger, with a 2- or 3-wire harness). Disconnect the connector and measure the resistance between the sensor terminals (normally about 2-3 kΩ at 25°C; refer to the workshop manual for specifics). If the resistance is infinite, replace the sensor. Measure the supply voltage (must be 5V ± 0.25V) and confirm normal reference voltage output.+3 more →
B132316›
This DTC indicates the 12V operating supply voltage of the thermal management system (specifically the air conditioning control unit or thermal management controller) falls below the 9V threshold. In the BYD new energy architecture, the low-voltage system has a nominal voltage of 12V (normal range 10.5V-14.5V). When the supply voltage drops below 9V, the controller’s internal microprocessor, sensor interface circuits, and power drive module fail to operate stably. This instability can cause abnormal air conditioning compressor control signals, inaccurate electronic expansion valve actuation, insufficient battery coolant pump speed, or a protective shutdown of the PTC heater. As a power supply fault, this condition does not directly trigger the high-voltage interlock, but it indirectly affects battery thermal management performance. In extreme cases, it can trigger battery over-temperature power derating protection.
Causes
— 12V low-voltage battery aging or deep discharge increases internal resistance, causing a sharp voltage drop under load.— DC-DC converter fault or high-voltage system malfunction preventing the conversion of high voltage into a stable 14V low-voltage power supply.— Poor contact in the A/C controller/TMS module power supply harness, including loose connectors, corroded pins, or oxidized fuse holders, resulting in a voltage drop exceeding 3V.+2 more →
Actions
— Connect the VDS diagnostic tool to read freeze frame data. Confirm the specific voltage value when the fault occurred and any accompanying fault codes (such as B132317 overvoltage or U-class communication faults).— Measure the low-voltage battery static voltage. If below 12.4V, charge the battery. Start the vehicle and measure the battery dynamic voltage. The normal range is 13.8V-14.5V. If below 13V, check the DC-DC converter.+4 more →
B132317›
This DTC indicates the air conditioning system control unit or a thermal management-related module detects its operating supply voltage exceeds the 16V threshold (BYD low-voltage system rated voltage: 12V; normal operating range: 9–16V). This is an overvoltage protection fault. When the module detects an abnormal rise in supply voltage, it stores this DTC and may enter protection mode, limiting air conditioning or thermal management functions to prevent electronic component damage. Overvoltage typically stems from abnormal output from the low-voltage charging system (DC-DC converter), alternator voltage regulator failure (hybrid models), or abnormal power supply circuit impedance. Prolonged overvoltage may burn out the control module internal circuits or damage the compressor driver.
Causes
— DC-DC converter fault: The internal voltage regulation circuit in the high-voltage to low-voltage DC-DC module fails, causing the output voltage to exceed 16V. This is the most common cause.— Severe low-voltage battery aging: Increased internal resistance or plate sulfation prevents the battery from accepting normal current during charging, causing the terminal voltage to rise abnormally.— Generator voltage regulator fault (hybrid models): ISG motor or generator controller fault causes unregulated charging voltage.+2 more →
Actions
— Use a high-precision multimeter to measure the low-voltage battery static and dynamic voltages (when applying the A/C load). Confirm whether the actual voltage exceeds 16V to rule out a false fault.— Connect the VDS diagnostic tool to read the data stream. Check the 'System Voltage' data stream in the air conditioning module or thermal management module to confirm whether the overvoltage is continuous or intermittent.+6 more →
B132816›
This DTC indicates the Battery Thermal Management Electric Water Pump supply voltage falls below the system normal operating threshold (typically below 9V or 10.5V, depending on vehicle calibration). In the BYD Qin EV thermal management system, this water pump circulates coolant between the battery pack and the heat exchanger to maintain cell temperature within the optimal 15–35°C operating range. During an undervoltage fault, the pump may experience an abnormal speed drop, stop intermittently, or fail completely, reducing battery cooling and heating efficiency. Prolonged operation with this fault can trigger the BMS power limit protection strategy (reduced-power driving) and, in extreme cases, pose a risk of battery thermal runaway. The air conditioning controller (or thermal management controller) triggers this fault upon detecting an abnormal PWM feedback signal from the water pump or an abnormal power supply voltage.
Causes
— Low-voltage battery (12V auxiliary battery) aging or under-voltage: Voltage drops below 9V during vehicle startup, causing unstable power supply to the water pump.— Loose connection in the water pump power supply circuit or damaged wiring harness: High temperatures in the front compartment oxidize the wiring harness connector or cause terminal back-out. These conditions, or body wiring harness wear, increase contact resistance and cause a voltage drop.— Water pump internal motor short circuit or seizure: Worn water pump bearings or a jammed impeller abnormally increase operating current, dropping the supply voltage.+2 more →
Actions
— Fault Confirmation and Freeze Frame Reading: Use the VDS2000/VDS6000 diagnostic tool to read the fault code and confirm if it is a current fault (Current). Record the ambient temperature, battery temperature, and water pump duty cycle data from the time the fault occurred.— Low-voltage battery check: Measure 12V battery static voltage (≥12.4V) and starting voltage (≥9.6V). Check battery state of health (SOH). Charge or replace as necessary.+5 more →
B132817›
This fault code indicates the supply voltage or feedback voltage of the heat pipe electric water pump in the Battery Thermal Management System (BTMS) exceeds the calibrated threshold (typically exceeding 16V in the low-voltage system, or abnormal high-voltage sampling). In models like the BYD Qin EV, the VCU or Thermal Management Controller (TMS) drives this water pump via a PWM signal (100-900Hz). Upon fault trigger, the system records freeze-frame voltage data. Overvoltage may cause water pump drive MOSFET breakdown and motor winding insulation aging, triggering battery thermal management derating protection (limiting charge and discharge power). Prolonged overvoltage may cause insufficient battery pack heat dissipation, but typically does not affect driving safety before triggering overheat protection. Differentiate between genuine overvoltage (power supply system fault) and false overvoltage (sampling circuit or sensor fault).
Causes
— DC-DC converter or low-voltage charging system fault causing the 12V system voltage to rise abnormally (exceeding 15.5V).— Partial short circuit or insulation failure in the internal windings of the battery thermal loop electric water pump, causing abnormal back electromotive force.— Poor contact in the water pump power supply circuit or connector (oxidized or loose), creating a high-resistance point that triggers voltage spikes.+2 more →
Actions
— Use the VDS2000/3000 diagnostic tool to read the complete fault codes and freeze frame data. Record the water pump voltage, duty cycle, coolant temperature, and ambient temperature at the time of the fault.— Check the low-voltage battery static voltage and dynamic charging voltage. Measure the DC-DC output voltage and verify it is within the normal 13.5-14.5V range to rule out charging system overvoltage.+6 more →
B132971›
This DTC indicates the electric water pump in the battery thermal management circuit (typically located in the battery pack liquid-cooling circuit or battery heat pipe circulation branch) detects a locked rotor condition. Specifically, the pump control module detects the drive current continuously exceeding the threshold (typically 3-5 times the rated current) while the speed feedback signal remains at zero or extremely low, determining a mechanical rotor seizure. This is a hard fault. Upon triggering, the thermal management controller immediately cuts pump power to protect the drive circuit. Consequences include interrupted battery pack coolant circulation, causing loss of battery temperature control during fast charging and reduced heat pump air conditioning heating efficiency (if equipped with a water-source heat pump system). Continued operation may trigger BMS power derating protection or high-voltage system shutdown. The DTC suffix '71' typically serves as a subtype identifier indicating a persistent locked rotor condition rather than a momentary overload.
Causes
— Water pump impeller mechanically jammed: After long-term use, scale, corrosion products in the coolant, or external contaminants enter the pump chamber, seizing the impeller against the pump housing; or in low-temperature conditions (below -20°C), localized freezing and expansion of the coolant jams the impeller.— Motor drive circuit fault: Damage to the MOSFET half-bridge driver chip inside the water pump controller causes abnormal three-phase drive waveforms. The motor cannot generate an effective rotating magnetic field and remains in a DC braking state (exhibiting locked-rotor current characteristics).— Electrical connection fault: The water pump wiring harness connector is loose, has backed-out terminals, or has oxidized due to water ingress. This causes phase loss in the three-phase power supply. The motor fails to start due to insufficient torque, resulting in a stalled rotor.+2 more →
Actions
— Initial diagnosis: Use the VDS2000/3000 diagnostic tool to read all DTCs. Check for related fault codes (e.g., B132A00 idling fault, U0121 communication fault). Record the battery temperature, ambient temperature, water pump duty cycle, and current values from the freeze frame data.— Safety preparation: Disconnect the low-voltage battery negative terminal, wait 5 minutes to discharge the high voltage, confirm the cooling system has no pressure (slowly open the expansion tank cap), and wear insulated gloves during operation.+5 more →
B132A00›
This fault code indicates the electric water pump in the battery thermal management system (typically integrated into the battery thermal pipe cooling circuit) is dry running. The system triggers this fault when the pump motor receives a PWM operating command from the TMS (Thermal Management Controller) or A/C controller and powers on to rotate, but the impeller fails to generate effective coolant flow. The system also triggers this fault if the actual speed detected by the speed feedback sensor (Hall effect sensor) deviates from the target speed by more than the threshold (typically >30%) for 5–10 seconds. This fault functions as flow abnormality protection. The condition can cause insufficient battery pack heat dissipation and excessive cell temperature differences, triggering reduced power operation (torque limiting). In extreme cases, it triggers a battery overheat warning. Causes include dry running due to a lack of coolant, impeller shaft breakage, magnetic coupling slip, cavitation, or seized bearings.
Causes
— Low battery coolant level or system leaks (e.g., at thermal pipe joints or battery pack cooling plate seals), causing the water pump to draw in air and run dry.— Electric water pump internal impeller magnetic coupling failure (permanent magnet rotor separated from impeller) or broken impeller shaft, causing the motor to spin freely while the impeller does not rotate.— Water pump power supply circuit fault, including blown fuse F2/26, open high-voltage interlock, or poor connection at connector CN112 causing a voltage drop.+2 more →
Actions
— VDS diagnostics: Connect the VDS diagnostic tool, read the DTC freeze frame, and check the 'battery thermal management water pump target speed' and 'actual speed' data streams to verify if the actual speed is 0 or significantly below the target value (<100rpm).— Cooling system inspection: Check that the expansion tank coolant level is between MIN and MAX. Inspect the battery pack cooling pipes, heat pipe heat exchanger, and water pump body for coolant crystallization (signs of leakage). If necessary, perform a pressure hold test (150kPa, 10 minutes) to locate the leak point.+3 more →
B1600-00›
This DTC indicates the SRS (Supplemental Restraint System) control unit (ACU) detects an open circuit or high resistance in the driver front airbag ignition circuit. The ACU continuously monitors the airbag module circuit resistance through its internal diagnostic circuit. Normal resistance is 2.0-2.4 Ω. Resistance exceeding the threshold (usually >6 Ω) or a completely open circuit triggers DTC B1600-00. The system then enters fail-safe mode and disables the driver-side airbag, preventing deployment during a collision. The instrument panel airbag warning lamp remains illuminated to alert the driver. Possible causes include the airbag module, clock spring (spiral cable), wiring harness connectors, or the ACU internal sampling circuit.
Causes
— Fatigue fracture or poor contact in the clock spring (airbag spiral cable) internal flat cable. Frequent steering wheel rotation commonly breaks the internal conductive coil, causing an intermittent or permanent open circuit.— Driver airbag module connector (yellow plug) loose, oxidized, terminals backed out, or locking mechanism failed, causing excessive contact resistance or a complete open circuit.— Open circuit or abnormal resistance in the airbag module internal gas generator igniter wire, usually due to internal defects or prolonged inactivity.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS backup power supply. Wear an anti-static wrist strap to prevent accidental airbag deployment.— Visual inspection: Verify the yellow dedicated SRS connectors under the steering wheel and instrument panel are fully seated and the locking tabs are engaged. Inspect the terminals for oxidation, corrosion, or deformation.+6 more →
B1600›
DTC B1600 indicates the SRS (Supplemental Restraint System) control unit detects an open circuit or connection failure in the driver front airbag (steering wheel airbag) circuit. Specifically, electrical circuit resistance between the airbag control unit and the driver airbag assembly exceeds the standard range (normal: approx. 2-3Ω; fault: typically >10Ω or infinite). This hard-wired connection fault indicates the control unit continuously fails to establish effective communication with the driver airbag during vehicle self-test or driving. Upon triggering, the SRS enters fail-safe mode, illuminates the airbag warning lamp, and disables driver airbag deployment. In a collision, this airbag may fail to inflate normally, severely compromising passive safety performance. Some early BYD petrol models or specific powertrain systems define B1600 as "mixture too rich." However, based on current DTC information and applicable models (Yuan, Tang, Song, Qin series), this analysis focuses on the airbag system circuit fault.
Causes
— Clock spring internal open circuit: Frequent steering wheel rotation causes fatigue breakage of the internal flat ribbon cable, resulting in an open circuit.— Wiring harness connector terminals backed out or loose: especially loose, backed-out, or oxidized pins at mating connectors such as GJK14, or poor contact at the airbag connector under the steering wheel.— Airbag assembly internal open circuit: Internal open circuit in the airbag squib or excessive contact resistance at the airbag connector.+2 more →
Actions
— Initial diagnosis: Use the dedicated diagnostic tool to read the fault code, confirm if B1600 is a current or stored fault, and observe if the airbag warning light remains illuminated.— Power supply system check: Measure battery voltage (should be >12V). Check the constant power (B+) and ignition switch power (IG) voltages at the SRS control unit to rule out false faults caused by unstable voltage.+5 more →
B16001B›
DTC B16001B indicates the SRS (airbag) system detects a range/performance fault in the driver seat occupancy sensor (OCS - Occupant Classification System) signal circuit. Specifically, the ACU (Airbag Control Unit) receives a sensor resistance value outside the calibrated range (typically an open circuit, short circuit, or abnormal resistance), or the signal characteristics fail to match the expected logic. This film pressure sensor, located inside the driver seat cushion or on the inner side of the seat rail, monitors seat occupancy in real time to determine whether to allow full-power airbag deployment during a collision. If the system cannot confirm driver presence, it illuminates the airbag warning light and may enter a degraded protection mode (such as disabling airbag deployment or reducing deployment force), posing a severe safety hazard.
Causes
— Fatigue fracture of the seat occupancy sensor membrane pressure-sensing element or an internal open circuit, causing infinite resistance or intermittent fluctuations. Commonly occurs after long-term, high-frequency seat use or after modification and removal.— Poor contact, an unlatched locking tab, or oxidized terminals at the under-seat wiring harness connector (usually a white 2-pin plug) causes high contact resistance (>5Ω), interrupting the signal during seat movement or vehicle jolting.— Excessive pulling of the wiring harness during installation of third-party aftermarket equipment (such as heated/ventilated seat cushions or racing seats) breaks the internal copper strands at the connector between the seat harness and body harness, or the aftermarket equipment generates electromagnetic interference affecting the sensor signal.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait 3 minutes for the SRS system to fully discharge to prevent accidental airbag deployment.— Fault Confirmation: Use the BYD VDS diagnostic tool to read the detailed fault code status (current/history) and freeze frame data to confirm whether B16001B is a persistent fault.+7 more →
B1601-00›
DTC B1601-00 indicates the airbag control unit (SRS ECU) detects an abnormally low-resistance path to body ground in the driver frontal airbag (DAB) ignition circuit. Under normal conditions, the airbag igniter circuit resistance measures 2.0-3.0 Ω, and the insulation resistance to ground exceeds 10 MΩ. Damaged wiring harness insulation, an internal clock spring short circuit, or a grounded connector terminal significantly reduces circuit resistance (typically below 1 Ω), causing the ECU to register a short-to-ground fault. This fault prevents the driver airbag from deploying during a collision (fail-safe mode) or, in extreme cases, causes unexpected deployment due to false triggering. As a critical passive safety hard fault, immediately remove the vehicle from service for repair.
Causes
— Aged and damaged insulation on the internal clock spring flat ribbon cable causes the airbag ignition circuit to short against the metal frame during steering wheel rotation. This is a common fault on BYD Qin series models.— Long-term chafing near the steering column damages the driver's airbag wiring harness insulation, causing the copper core to directly contact metal body components and create a ground path.— Water ingress or terminal corrosion in the yellow SRS connector (usually located under the steering wheel or on the left side of the dashboard) due to driving through water, interior cleaning, or a damp environment causes a short circuit between terminals or to ground.+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS backup power capacitor and prevent accidental airbag deployment during repair.— Visual inspection: Remove the trim panels on both sides of the steering wheel. Inspect the clock spring for burn marks or cracks. Check the mounting condition of the airbag wiring harness at the steering column and instrument panel frame. Inspect the harness for wear, crushing, or damaged insulation.+5 more →
B1601›
DTC B1601 indicates a short to ground in the driver frontal airbag (DAB) ignition circuit. In the BYD SRS (Supplemental Restraint System), this fault means damaged wire insulation in the circuit between the airbag control unit (ACU) and the driver airbag contacts the vehicle body ground, or an internal short to ground exists within the airbag inflator. This causes circuit resistance to drop well below the standard range (normally 2.0-3.0 Ω, approaching 0 Ω during a short circuit). When the ACU detects this abnormal drop in circuit impedance, it identifies a short-to-ground fault and triggers protection mode: the instrument cluster SRS warning light illuminates continuously, the system disables the driver airbag to prevent inadvertent deployment, and the airbag fails to deploy during a collision, severely compromising occupant safety.
Causes
— Worn or broken flat cable inside the clock spring causes the wiring to short to the steering wheel metal frame or ground wire.— Water ingress, corrosion, or deformed pins in the yellow airbag wiring harness connector below the steering wheel (usually near the combination switch), causing a terminal short to ground.— Abrasion or crushing damages the insulation on the wiring harness between the ACU and the steering wheel where it passes through the A-pillar, dashboard, or floor, causing a short to body ground.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS backup power supply and prevent accidental airbag deployment.— Fault confirmation: Connect BYD VDS or original diagnostic tool, read DTC B1601 and freeze frame data, confirm fault status is Current, and record vehicle condition when the fault occurred.+6 more →
B160111›
DTC B160111 indicates a short to ground in the driver frontal airbag (DAB) igniter circuit. The SRS (Supplemental Restraint System) airbag igniter utilizes a low-resistance circuit (typically 2.0–3.0Ω). The ACU (Airbag Control Unit) registers a short to ground when it detects circuit resistance below the threshold (<0.8Ω) or direct continuity to body ground. Wiring insulation failure or an internal component short circuit causes this fault, grounding the igniter circuit abnormally. Effects include: 1) the airbag may fail to deploy during a collision (current bypasses to ground); 2) electrostatic discharge or electromagnetic interference may cause unintended deployment in extreme cases; 3) the system enters fail-safe mode, disabling all airbag functions. This constitutes a Level 1 active safety system fault. Remove the vehicle from service immediately; the driver airbag serves as the final line of defense, and its failure drastically increases the risk of injury or fatality during an accident.
Causes
— A worn or broken flat ribbon cable inside the clock spring causes the conductor to contact the metal steering wheel frame and short to ground. Long-term full-lock steering fatigues the coiled cable, causing this common fault in high-mileage BYD Qin/E Series vehicles.— Water ingress and corrosion at the airbag wiring harness connector (usually located under the steering wheel or inside the steering column trim), especially due to a blocked A/C drain hose or defective front windshield seal. The resulting electrolyte shorts the pins to body ground.— Improper airbag removal or installation causes tools to scratch the wiring harness insulation, or improperly securing the harness after accident repairs allows metal bracket edges to chafe through the outer sheath, creating a short to ground.+2 more →
Actions
— Safety preparation: Turn off the ignition, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment. Discharge static electricity from your body before disconnecting the airbag connector.— Static visual inspection: Check the steering wheel area for signs of removal or installation, water stains, mildew odor, or exposed wiring harnesses. Specifically inspect the wiring harness sleeve below the steering column for damage. Check the airbag connector (yellow marking) for looseness or green copper corrosion.+5 more →
B1602-00›
This DTC indicates a short to power (positive) in the driver-side front airbag (steering wheel airbag) ignition circuit. Specifically, the airbag control unit (ACU/SRS ECU) detects abnormal continuity between the driver airbag ignition wiring harness (typically the W/L white-blue and G/R green-red wires) and the vehicle power supply. Resistance falls below the threshold (normal values exceed 1 MΩ; fault conditions may approach 0 Ω or display a voltage exceeding 1 V). This severe electrical fault in the airbag system poses two extreme risks: first, the short circuit can trigger unintended airbag deployment, injuring the driver; second, a continuous bypass of the airbag circuit prevents proper deployment during an actual collision. Potential fault locations include the clock spring (spiral cable), airbag module wiring harness, connectors, or inside the airbag ECU.
Causes
— Clock spring (spiral cable) internal short circuit: Long-term rotation wears the clock spring beneath the steering wheel, damaging the internal wire insulation and shorting the squib wire to the power wire.— Airbag wiring harness worn and shorted: Friction or pinching damages the insulation of the airbag wiring harness inside the steering wheel or steering column, causing it to contact the body power wire.— Connector water ingress or corrosion: Water exposure or moisture in the driver airbag connector (usually located under the steering wheel or on the airbag module) causes a short circuit between terminals.+2 more →
Actions
— Safety preparation: Turn the vehicle power mode to OFF, disconnect the battery negative terminal, and wait at least 90 seconds (to fully discharge the airbag capacitor).— Initial inspection: Check the driver airbag connector for proper connection and signs of looseness, water ingress, or corrosion. Clean and reconnect if necessary.+6 more →
B1602›
DTC B1602 indicates a short to power in the driver frontal airbag (DAB) igniter circuit. In the BYD SRS (Supplemental Restraint System) architecture, the Airbag Control Unit (ACU) continuously monitors the circuit resistance of each airbag igniter (normally about 2-3 Ω) and its insulation status. When the ACU detects abnormal continuity between the driver airbag igniter wiring and the vehicle power supply (12V+) (resistance below the threshold, typically <10 kΩ for a short to power), it triggers this fault. This fault means the airbag may deploy unexpectedly while driving (a serious safety risk) or fail to deploy properly in a collision because the power supply clamps the circuit. The fault may originate in the clock spring (spiral cable), airbag wiring harness, connector, or the ACU internal driver circuit.
Causes
— Clock spring internal damage: Frequent steering wheel rotation wears and breaks the internal ribbon cable, shorting the wire to the power line. Common in high-mileage BYD Tang and Song series vehicles.— Airbag wiring harness insulation damaged: The wiring harness below the steering wheel rubs inside the steering column, sustains cuts from sharp edges, or lacks proper securing after accident repairs, causing the harness to contact a 12V power wire (such as the horn circuit or multifunction switch power supply).— Water ingress or liquid corrosion: A/C condensate leakage or poor front windshield sealing causes water to flow under the steering wheel, corroding the airbag connector terminals (usually the yellow plug) and causing a short circuit between terminals or a short to power.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds (this ensures the SRS capacitor fully discharges, preventing accidental airbag deployment). Wear an anti-static wrist strap. Do not use non-explosion-proof test equipment near the airbag.— Visual inspection: Inspect the yellow airbag connector below the steering wheel (usually on the left side of the steering column) for oxidation or water ingress; inspect the clock spring connector for looseness or bent pins; inspect the steering wheel for signs of modification.+6 more →
B160212›
DTC B160212 indicates the SRS (Supplemental Restraint System) control unit detects an abnormal short circuit between the driver’s front airbag inflator circuit and the vehicle power supply (12V+B). The inflator circuit normally maintains a high-resistance state (typically 2-3Ω, determined by the inflator internal resistance). The control unit continuously monitors circuit voltage and resistance via an internal bridge detection circuit. A short circuit to power indicates the voltage at one or both ends of the circuit continuously exceeds the threshold (typically above 5V) and the resistance is abnormally low. This fault triggers the safety protection mechanism. The system immediately enters fail-safe mode and disables the airbag deployment function to prevent accidental deployment caused by short-circuit current. Hardware faults such as an internal clock spring short circuit, damaged wiring harness insulation contacting a power wire, or a driver transistor breakdown inside the SRS ECU may accompany this fault.
Causes
— A broken internal conductor or aged insulation in the clock spring (spiral cable/clockspring reel) shorts the airbag circuit to the horn power wire or steering wheel heating power wire.— Long-term steering friction damages the driver's airbag wiring harness insulation at the steering column sleeve, causing contact with the ignition switch power wire or constant power circuit.— Incorrect wiring during aftermarket steering wheel modifications (such as adding multifunction buttons or a steering wheel heating module) incorrectly connects the 12V power supply to the airbag circuit.+2 more →
Actions
— Use the BYD dedicated diagnostic tool VDS2000/VDS1000 to read the complete fault codes and freeze frame data. Confirm whether B160212 is a current fault (Active) or a historical fault (History). Record parameters such as vehicle speed and time when the fault occurred.— Perform the standard safe power-down procedure: disconnect the low-voltage battery negative terminal and wait at least 90 seconds (to fully discharge the SRS backup capacitor). Do not operate any electrical equipment during this period.+8 more →
B160A-00›
This DTC indicates the Airbag Control Unit (ACU) detects the Driver Airbag (DAB) firing circuit resistance is below the calibrated threshold (close to 0 Ω), indicating a short circuit. In the BYD SRS system, normal airbag circuit resistance ranges from 1.5 to 3.0 Ω. A resistance of 0 Ω typically indicates a short between the positive and negative terminals in the airbag wiring harness, clock spring, or connector. An internal driver circuit breakdown within the ACU can also cause this issue. This fault triggers the safety system fail-safe mode, illuminates the instrument panel SRS warning light, and may prevent airbag deployment during a collision. This severely compromises passive safety and requires immediate repair.
Causes
— Clock spring (airbag spiral cable) internal short circuit: Long-term steering wheel rotation wears and breaks the internal flexible ribbon cable insulation, causing direct wire contact and a short circuit.— Airbag wiring harness damaged and shorted to ground: Loose wiring harness retaining clip inside the instrument panel causes the harness to rub against the metal bracket, damaging the insulation and shorting the wire to the vehicle body ground.— Airbag connector water ingress and corrosion: Driving through water or cleaning the interior allows water to enter the driver-side airbag connector (located under the steering wheel or on the airbag module), causing an electrolytic short circuit between terminals.+2 more →
Actions
— Safe power-down: Disconnect the battery negative terminal and wait at least 3 minutes to dissipate residual system charge and fully discharge the SRS capacitor.— Fault confirmation: Connect the BYD dedicated diagnostic tool or a generic diagnostic tool, read and confirm B160A-00 is a current fault (Active), and record the freeze frame data.+6 more →
B160A›
DTC B160A indicates the driver front airbag (DAB) ignition circuit resistance is 0 ohms, representing a short circuit. Normally, the airbag squib has a standard resistance of 2-5 ohms. When the SRS ECU detects circuit resistance near 0 Ω, it identifies a short to ground, short to power, or internal short in the airbag module. This safety-critical fault prevents normal airbag deployment during a collision or causes accidental deployment. A 0-ohm resistance typically indicates an internal ribbon cable short in the clock spring (spiral cable), damaged harness insulation shorting to ground, or an internal igniter short within the airbag module.
Causes
— Short circuit caused by a worn or broken internal flat cable in the clock spring (spiral cable / Clock Spring): Long-term steering wheel rotation repeatedly bends the internal ribbon cable at its limit positions. This damages the insulation or breaks the wire, causing a short to ground. This is the most common root cause of this fault code.— Airbag module internal igniter short circuit: The resistance wire in the airbag internal igniter cartridge shorts to the housing, or the internal bridgewire breaks, causing direct contact between the two terminals.— Harness damage or short to ground: Chafing, crushing, or rodent bites damage the insulation on the harness between the SRS ECU and the clock spring (especially near the steering column), causing a short to vehicle body metal.+2 more →
Actions
— Safety Preparation: Turn the vehicle OFF, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS system backup power supply and prevent accidental airbag deployment during repair.— Fault confirmation: Connect the BYD dedicated diagnostic tool (VDS or ED400). Enter the SRS system, read fault codes, confirm B160A is a current fault (Current DTC), and record freeze frame data.+6 more →
B160A1A›
DTC B160A1A indicates abnormally high resistance (open circuit or high-resistance condition) in the driver-side front airbag (stage 1) ignition circuit. This is a critical Supplemental Restraint System (SRS) safety fault. Normal airbag igniter resistance is 1.5-3.5Ω. If the system detects resistance continuously exceeding the threshold (typically >5Ω or open circuit), it identifies an ignition circuit integrity fault. The SRS control unit then illuminates the instrument cluster airbag warning light and enters fail-safe mode. This condition may prevent the driver-side airbag from deploying during a collision. The fault indicates an electrical connection issue in the circuit, not an explosion risk from the airbag itself.
Causes
— Clock spring internal flat ribbon cable is broken, fatigue-damaged, or has poor contact. Internal open circuits easily occur after frequently turning the steering wheel to full lock or rotating it left and right over a long period.— Yellow airbag wiring harness connector beneath the steering wheel (usually with a double-locking mechanism) not fully seated; terminals backed out, oxidized, or corroded; or excessive contact resistance.— Abnormally high resistance or open circuit in the driver airbag module internal igniter, or damage to the module itself (rare but possible).+2 more →
Actions
— Safety Preparation: Disconnect the negative battery cable and wait at least 3 minutes to discharge residual capacitor charge and prevent accidental airbag deployment during repair.— Fault Confirmation: Use the BYD dedicated diagnostic tool to read SRS system fault codes. Confirm B160A1A is a current fault (Active) and cannot be cleared. Record freeze frame data.+6 more →
B160B-00›
DTC B160B-00 indicates the SRS (Supplemental Restraint System) ECU detects the driver's front airbag (steering wheel airbag) igniter circuit resistance is below the calibrated threshold (usually <1.0Ω). Normal airbag igniter resistance is 2.0-3.0Ω. Low resistance usually indicates a circuit short to ground, an internal short in the airbag module, or abnormal connector continuity. This fault causes the SRS ECU to register an abnormal airbag circuit. The airbag may fail to deploy during a collision or deploy unintentionally while driving. Consequently, the system illuminates the airbag warning lamp and disables the airbag function.
Causes
— Clock spring (spiral cable) internal short circuit: Frequent steering wheel rotation wears the internal flat cable insulation, causing a short circuit between the core wires or between a core wire and the housing. This is the most common cause.— Airbag connector short circuit: Water ingress, bent pins, terminal corrosion, or foreign objects entering the yellow dedicated connector (usually located under the steering wheel or on the side of the steering column) cause abnormal continuity.— Airbag module internal fault: Igniter bridge wire short circuit or moisture in the pyrotechnic charge causing abnormally low resistance.+2 more →
Actions
— Safety Preparation: Turn off the ignition, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor. Wear an anti-static wrist strap.— Visual inspection: Check the yellow airbag connector under the steering wheel for looseness, water ingress, or obvious corrosion; check the clock spring for visible damage or burn marks; check the steering column wiring harness for wear.+5 more →
B160B›
DTC B160B indicates the SRS (Supplemental Restraint System) control unit detects the driver frontal airbag (DAB) igniter (squib) circuit resistance is below the calibrated threshold (typically <1.5Ω; standard range is 2.0±0.3Ω). This active fault indicates an abnormally low-resistance path in the circuit. A partial short circuit, an internal turn-to-turn short in the igniter, or a wiring harness short to ground can cause this condition. The low resistance abnormally increases the airbag circuit current, creating a risk of unintended airbag deployment. Alternatively, during a collision, the excessive current may trigger the ACU protective cutoff and prevent normal deployment. When this DTC triggers, the SRS system typically enters fail-safe mode and disables the driver-side airbag.
Causes
— Turn-to-turn short circuit or wear in the clock spring (spiral cable) internal coil, reducing effective resistance. This is a common fault in BYD models, especially the Tang and Song series.— Internal short circuit in the driver airbag module (DAB) igniter, or moisture ingress into the pyrotechnic charge causing resistance drift, common after vehicle wading or in high-temperature, high-humidity environments.— Airbag wiring harness short to ground or power, typically caused by a damaged wiring harness sleeve below the steering wheel, a pinched harness during steering wheel modification, or backed-out terminal pins.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds (to fully discharge the ACU capacitor). Never measure the airbag terminals directly using a multimeter ohm setting (the test current may deploy the airbag).— Initial diagnosis: Connect the VDS or BYD dedicated diagnostic tool, read the fault code status (current/history), record the resistance value in the freeze frame data (e.g., 0.8Ω or 1.2Ω), and confirm fault persistence.+5 more →
B160B1A›
DTC B160B1A indicates the Driver Airbag (DAB) deployment circuit resistance falls below the normal threshold set by the SRS ECU (typically 2.0-3.0Ω; values below 1.0Ω trigger this fault). This constitutes a Supplemental Restraint System (SRS) hard-wire fault. The ECU detects an abnormally low-resistance path in the deployment circuit. Potential causes include a wiring short to ground, an internal short in the clock spring, an internal short in the airbag module, or a short between connectors. This fault forces the airbag system into fail-safe mode and continuously illuminates the instrument cluster airbag warning light. In extreme cases, the airbag may fail to deploy during a collision because the ECU misinterprets the condition as a short circuit and disables the deployment circuit. In very rare cases, wiring interference creates a risk of unintended deployment.
Causes
— Clock spring (spiral cable) internal short circuit: Frequent steering wheel rotation breaks the flat cable inside the clock spring or wears the insulation, causing the ignition wire to short to ground or power.— Airbag wiring harness short to ground: The wiring harness below the steering wheel chafes inside the steering column tube, or a metal edge cuts the wiring harness inside the dashboard, causing the ignition circuit wire to ground to the vehicle body.— Airbag connector water ingress and corrosion: Poor sealing of the driver-side airbag plug (usually located under the steering wheel or behind the airbag module) allows water ingress after vehicle washing or wading, causing a short circuit between pins.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Check the clock spring connector under the steering wheel and the yellow airbag module plug for looseness, water ingress, corrosion, or deformed pins.+5 more →
B160C›
DTC B160C indicates the SRS (Supplemental Restraint System) control unit detects the driver-side front airbag (steering wheel main airbag) ignition circuit resistance exceeds the normal upper limit (normal range: 2.0–3.0 Ω; fault threshold: ≥4.0 Ω or open circuit). This hard or intermittent fault indicates a high-resistance condition in the airbag ignition circuit. Poor contact, loose wiring connections, or component aging can cause this condition. Excessive resistance reduces circuit current. During a collision, the ACU (Airbag Control Unit) may fail to generate sufficient ignition current to trigger the gas generator, causing airbag deployment failure and severely compromising occupant protection. This DTC illuminates the SRS warning lamp, forces the system into a degraded protection mode, and disables airbag deployment for this circuit.
Causes
— Broken clock spring internal flat cable or worn carbon brush: Frequent steering wheel rotation causes fatigue fracture of the internal flexible circuit, creating intermittent or continuous high resistance.— Poor contact at the airbag connector (yellow double-lock waterproof plug): plug not fully locked, oxidized terminals, backed-out pins, or loose terminals, causing increased contact resistance.— Driver airbag module (DAB) internal igniter resistance drift: Bridgewire oxidation or poor welding inside the gas generator increases resistance.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Verify the yellow airbag connector below the steering wheel is fully inserted and locked. Inspect the wiring harness for damage, crushing, or signs of water ingress.+6 more →
B160C1B›
This fault code indicates the driver front airbag (DAB) igniter (gas generator) resistance exceeds the normal threshold range set by the SRS control module (typically 2.0–3.0 Ω, depending on the vehicle model). "High resistance" usually indicates a high-impedance point in the circuit. Causes include poor wiring connections, oxidized connectors, poor internal contact in the clock spring (spiral cable), or an aging airbag igniter. This active safety system fault causes the SRS control module to classify the driver airbag as unreliable. This condition may prevent airbag deployment during a collision, or in some cases, continuously illuminate the warning light and store a fault code, severely compromising passive safety protection.
Causes
— Internal open circuit or poor contact in the clock spring (spiral cable): Frequent steering wheel rotation causes fatigue fractures or increased contact resistance in the clock spring's internal flat cable, increasing airbag circuit resistance.— Poor contact at the airbag module connector: The connector linking the driver airbag to the wiring harness (usually located inside or below the steering wheel) exhibits oxidation, looseness, backed-out pins, or spread terminals, increasing contact resistance.— Airbag igniter internal fault: Aging, a cold solder joint, or a partial open circuit in the gas generator igniter bridge wire causes resistance to exceed the calibrated range.+2 more →
Actions
— Safety preparation: Turn the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS system capacitors and prevent accidental airbag deployment.— Fault Confirmation: Use the BYD dedicated diagnostic tool (VDS or ED400) to read the fault code. Verify B160C1B is a Current DTC, not a History DTC, and record the freeze frame data.+6 more →
B1610-00›
DTC B1610-00 indicates the SRS (Supplemental Restraint System) ECU detected abnormal resistance in the front passenger-side frontal airbag ignition circuit, specifically 0 Ω (short circuit) or infinite resistance (open circuit). In the BYD fault definition system, this code means "front passenger frontal airbag disconnected," indicating a loss of circuit integrity between the SRS ECU and the front passenger airbag module. This hard fault triggers the system fail-safe mode: the SRS ECU disables all airbag deployment (including the driver-side, side, and curtain airbags) and continuously illuminates the instrument cluster airbag warning lamp. Because this fault involves the occupant passive safety system, it carries the highest priority. The airbag system returns to normal standby status only after fault repair.
Causes
— Front passenger airbag connector loose, terminal backed out, or corroded: The yellow connector at the rear of the airbag module or on the right side of the dashboard is not fully locked, or oxidized terminals cause excessive contact resistance or an open circuit.— Internal clock spring (spiral cable) damage: The ribbon cable routed under the steering wheel breaks or shorts, interrupting the front passenger airbag circuit signal (on some models, this shares or links with front passenger airbag circuit detection).— Water ingress in the SRS ECU connector or damaged terminals: The ECU mounts beneath the centre console. After wading, corrosion or terminal back-out at connector G10/M40 prevents airbag resistance detection.+2 more →
Actions
— Use the BYD VDS or Launch X431 diagnostic tool to read fault codes. Confirm B1610-00 is a current DTC. Record the ambient temperature and vehicle status from the freeze frame data.— Perform the safe power-down procedure: turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.+7 more →
B1610›
DTC B1610 indicates the Airbag Control Unit (ACU) detects an open circuit in the front passenger airbag squib circuit. Resistance falls outside the normal range (normal: approximately 1.5-3.0Ω; fault: typically >10Ω or infinite). This indicates a physical break in the circuit between the ACU and the front passenger airbag module (located inside the right side of the dashboard). Possible causes include a loose wiring harness connector, an open circuit in the airbag module inflator, wiring harness wear or breakage, or a clock spring fault (if applicable). This fault prevents the front passenger airbag from deploying during a collision, severely compromising occupant protection. Other vehicle systems continue to operate normally.
Causes
— Front passenger airbag wiring harness connector loose or disconnected: Located inside the right side of the dashboard or at the floor harness joint. Incomplete seating of the connector during previous repairs or vehicle vibration during driving may loosen the connection.— Airbag module internal open circuit: Internal break in the gas generator igniter tube due to manufacturing defects or long-term environmental effects.— Wiring harness worn or broken: Long-term bending wear of the front passenger floor harness near the seat track, or a metal edge cutting the harness inside the dashboard.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes to fully discharge the SRS system capacitor and prevent accidental airbag deployment.— Initial inspection: Use the diagnostic tool to read and confirm DTC B1610 is a current fault (Active), check if the airbag warning light stays on, and record freeze frame data.+5 more →
B16101B›
B16101B is an ISO 15031-6 standard diagnostic trouble code (DTC). 'B' represents the Body system, '16' specifies the airbag system (SRS), '10' refers to the Passenger Frontal Airbag circuit, and '1B' is the sub-fault code indicating circuit resistance exceeds the threshold (open circuit or high resistance). This fault indicates the SRS ECU (airbag control unit) cannot establish effective communication with the Passenger Frontal Airbag module and cannot detect normal squib resistance (standard value: 2.0-3.0Ω). The ECU triggers this fault code when it detects infinite circuit resistance (open circuit) or resistance exceeding 6.0Ω. The airbag system enters fail-safe mode. The passenger frontal airbag will not deploy in a collision, and the instrument panel SRS warning light illuminates continuously, indicating a functional defect in the occupant restraint system.
Causes
— Poor contact, a backed-out pin, or terminal oxidation at the front passenger airbag module wiring harness connector interrupting signal transmission. This is the most common fault cause, especially likely to occur after the vehicle wades through water or operates in high-humidity environments.— Long-term vibration breaks internal copper wires or causes poor contact at bend points in the instrument panel wiring harness (such as near the air conditioning duct or instrument panel frame edge), resulting in an intermittent or permanent open circuit.— Airbag module internal squib open circuit or abnormally high resistance. This damage typically results from moisture inside the airbag module, component aging, or previous improper testing (direct measurement using a multimeter resistance setting).+2 more →
Actions
— Safety Preparation: Set the power mode to OFF. Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment. Wear an anti-static wrist strap. Do not use radio equipment near the airbag.— Initial diagnosis and code clearing: Connect the VDS or dedicated diagnostic tool, enter the SRS system, and read and record the fault code. Clear the fault code, set the power mode to ON, and wait 20 seconds for the system to complete the self-check. If the fault code reappears immediately, confirm it as a current fault. For historical faults, check for intermittent contact issues.+5 more →
B1611›
DTC B1611 indicates a short to ground in the front passenger airbag (PAB) ignition circuit. Specifically, the SRS control unit detects an abnormally low-resistance connection (typically less than 2-3Ω) between the passenger airbag inflator circuit (usually the high-level trigger wire) and vehicle ground (GND). This short circuit prevents normal airbag deployment (diverting ignition energy to ground) or, in extreme cases, causes inadvertent deployment due to static electricity or electromagnetic interference. This fault constitutes a severe active safety system failure. The SRS control unit immediately disables the front passenger airbag, illuminates the airbag warning light, and may simultaneously lock the seat belt pretensioner, severely compromising passive safety performance.
Causes
— Passenger-side dashboard wiring harness wear: Long-term vibration damages the airbag wiring harness insulation where it passes through the dashboard frame or near the steering column, causing contact with the metal body and creating a short to ground.— Connector water ingress and corrosion: The airbag connector (usually yellow) located under the center console or floor is poorly sealed. Driving through water or an A/C condensate leak causes electrolytic corrosion between the pins, resulting in a short to ground.— Repair damage: Tools scratching or crushing the wiring harness during A/C filter replacement, radio replacement, or dashboard removal and installation, damaging the wire insulation and causing the wire to contact metal body parts.+2 more →
Actions
— Safety preparation and diagnostic confirmation: Disconnect the battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor. Use a diagnostic tool to read freeze frame data and confirm vehicle conditions at the time of the fault (temperature, vehicle speed, etc.). Check for accompanying fault codes (such as B1610, B1612).— Visual inspection and connector check: Remove the lower trim panel under the front passenger glovebox. Inspect the yellow SRS connector (usually marked F-PAB) for signs of water ingress, corrosion, or bent pins. Measure the resistance from the connector terminals to ground. Normal resistance is greater than 10 MΩ.+3 more →
B161111›
DTC B161111 indicates a short to ground in the front passenger airbag (PAB) ignition circuit. In the BYD SRS (airbag) system architecture, this DTC sets when the airbag control unit (ACU) detects the resistance between the front passenger airbag ignition wiring and body ground falls below the calibrated threshold (usually < 2Ω). This constitutes a hard fault in the active safety system, indicating compromised airbag circuit integrity. Potential risks include: 1) the front passenger airbag fails to deploy during a collision, resulting in a loss of occupant protection; 2) abnormal wiring causes unintended airbag deployment in extreme cases. This latch-type fault (Latch DTC) requires a VDS or dedicated diagnostic tool to clear. It continuously illuminates the instrument cluster SRS warning lamp (solid, not flashing).
Causes
— Short circuit between internal conductor layers of the clock spring (spiral cable): The front passenger airbag wiring harness routes through the clock spring under the steering wheel. Prolonged use wears the internal flat cable insulation, shorting the ignition wire (typically an odd-numbered pin) to the metal frame or ground wire.— Airbag wiring harness physical damage: Bracket edges, screws, or metal clips crush the internal dashboard wiring harness during assembly or repair. The damaged insulation contacts body ground, especially at the Cross Car Beam routing hole.— Connector water ingress and corrosion: The front passenger airbag connector (usually located behind the glove box or on the right side of the dashboard) is poorly sealed. Following an A/C condensate leak or vehicle wading, electrolytic corrosion forms between the pins and creates a low-resistance path to ground.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal. Wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment. Wear an anti-static wrist strap. Do not measure airbag igniter pins directly with a multimeter resistance setting (use a dedicated high-impedance diagnostic device).— Initial diagnosis: Connect the VDS to read all DTCs and freeze frame data. Confirm if it is a current fault (Current DTC). Check the instrument cluster SRS warning lamp status. Record the vehicle condition when the fault occurred (e.g., driving over rough roads, driving through water, or recent repair history).+6 more →
B1612-00›
DTC B1612-00 indicates the airbag control module (SRS ECU) detected an unintended electrical connection between the front passenger frontal airbag inflator circuit and the vehicle positive power supply (B+), constituting a short to power. In the airbag system dual-stage ignition architecture, the ECU monitors the inflator circuit voltage state through internal diagnostic resistors. Normally, the circuit maintains high impedance to the power supply (open-circuit state). The ECU logs a short to power when it detects circuit voltage abnormally close to battery voltage (typically >5V or a sustained high level) instead of the expected low-voltage state. This is a hardwire circuit fault. Potential risks include: 1) the airbag fails to deploy in a collision because supply voltage clamps the ignition circuit, preventing sufficient firing current; 2) unintended airbag deployment in extreme cases if the safety capacitor design interacts with the short to power. Possible fault locations include the clock spring (spiral cable), instrument panel wiring harness, airbag module connector, or the internal SRS ECU driver circuit. On some BYD models, this DTC logic also monitors the front passenger seat Occupant Classification System (OCS) power supply circuit for abnormalities. Because the OCS sensor status directly determines whether the system permits front passenger airbag deployment, a short to power in the OCS signal circuit triggers the same DTC.
Causes
— Airbag wiring harness insulation wear causing a short circuit: Long-term vibration and friction against sharp metal edges damage the front passenger airbag wiring harness insulation where it passes through the dashboard crossmember, A-pillar trim panel, or floor channel. The exposed wire contacts a constant power circuit (such as the dashboard lighting circuit or cigarette lighter power supply), creating a short to power.— Connector water ingress and corrosion: An aged seal on the yellow airbag module connector (usually located behind the glove box or inside the center console) allows water entry. Following vehicle wading or an air conditioning condensate leak, electrolytic corrosion forms between the internal plug pins, creating a low-resistance path between the igniter pin and the adjacent power supply pin.— Clock spring internal interlayer short circuit: Long-term rotational fatigue damages the insulation of the flat ribbon cable inside the clock spring (spiral cable) below the steering wheel. Although this cable primarily connects the driver airbag, the front passenger airbag return circuit wiring also routes through this area on some models and may short circuit to internal power wires (such as the steering wheel heating or multifunction switch power supply).+2 more →
Actions
— Safe power isolation and capacitor discharge: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds (some BYD models require 3 minutes) to fully discharge the SRS ECU backup capacitor and prevent accidental airbag deployment.— Initial visual inspection: Inspect the front passenger airbag module connector (yellow marking, usually located inside the glove box or behind the instrument panel), floor wiring harness grommet, and A-pillar wiring harness sleeve for obvious damage, burn marks, fluid intrusion, or terminal corrosion.+4 more →
B1612›
DTC B1612 indicates the SRS (Supplemental Restraint System) detected an abnormally low-resistance connection between the front passenger frontal airbag igniter circuit and the vehicle power supply (B+), indicating a short to power. Under normal conditions, the airbag igniter circuit remains in a high-resistance state isolated from both power and ground (typically greater than 10kΩ). The SRS ECU momentarily connects power through an internal switch only during airbag deployment. A short to power means one or both sides of the igniter continuously connect to the 12V power supply. This condition causes: (1) failure of the airbag to deploy during a collision (the ECU detects the circuit fault and inhibits triggering); (2) unintended airbag deployment in extreme cases due to abnormal current; (3) damage to the diagnostic driver circuit inside the SRS ECU. This fault involves the connections between the front passenger airbag module, clock spring (spiral cable), floor wiring harness, and SRS ECU.
Causes
— Damaged internal wire insulation in the clock spring (spiral cable) shorts the airbag ignition wire to the power wire or ignition signal wire.— Front passenger airbag wiring harness chafes inside the dashboard and shorts to body power wires (e.g., instrument panel lighting circuit or cigarette lighter power supply).— Water ingress, oxidation, or metallic debris in the airbag connector (usually located under the center console or on the airbag module) causing a short circuit between terminals.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF. Disconnect the low-voltage battery negative terminal and wait at least 90 seconds for the SRS capacitor to fully discharge. Wear an anti-static wrist strap.— Visual inspection: Remove the front passenger-side dashboard trim panel and inspect the airbag module, clock spring, and wiring harness connectors for signs of burning, water ingress, or mechanical damage.+4 more →
B161212›
DTC B161212 indicates a short to battery in the passenger front airbag deployment circuit. In the SRS (Supplemental Restraint System) circuit, two wires (typically high-side and low-side deployment wires) connect the airbag module to the Airbag Control Unit (ACU). Under normal conditions, these two wires have no continuity to the vehicle power supply (+12V/B+). When the diagnostic system detects abnormally low resistance (typically <10Ω) between the airbag circuit wiring and the battery positive terminal, it identifies a short to battery. This fault forces the Airbag Control Unit into fail-safe mode, disabling the passenger airbag to prevent accidental deployment and personal injury. Damaged wiring harness insulation, an internal connector short, or an internal airbag module fault can cause this condition. Address this Level 1 safety fault immediately.
Causes
— Worn or aged front passenger airbag wiring harness insulation interferes and shorts to power wires inside the dashboard (such as cigarette lighter or audio power supply wires).— Internal contact damage or a shorted coil in the airbag clock spring causes power to feed into the airbag circuit.— Water ingress, oxidation, or conductive foreign matter (such as metal debris or spilled liquids) in the front passenger airbag module connector causes a short circuit between pins.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal, wait at least 90 seconds (to completely discharge the SRS capacitor), and wear an anti-static wrist strap.— Initial inspection: Read the DTC freeze frame data, record the vehicle speed, time, and other data when the fault occurred, and check the vehicle for a history of accidents, water ingress, or modifications.+6 more →
B161A›
DTC B161A indicates the Airbag Control Unit (ACU) detects abnormally low resistance, approaching 0 Ω (typically <1.0 Ω), in the front passenger frontal airbag ignition circuit. Normal airbag igniter resistance remains between 2.0-3.0 Ω. A resistance of 0 Ω usually indicates a short to ground, a wire-to-wire short, or an internal short in the airbag module igniter. This fault causes the SRS system to enter fail-safe mode: 1) The airbag may fail to deploy during a collision due to the short circuit, causing a loss of passive protection; 2) Short-circuit current may cause unintended airbag deployment in extreme cases; 3) The system illuminates the instrument cluster airbag warning light and may store related freeze frame data. This is a hard fault (continuous) requiring immediate repair for occupant safety.
Causes
— Front passenger side airbag module internal igniter short circuit: Moisture ingress, aging, or a manufacturing defect in the airbag igniter reduces internal resistance to almost 0.— Airbag wiring harness short to ground: Vibration wear or loose retaining clips damage the internal instrument panel or floor harness insulation, causing a short to body ground.— Wiring harness connector water ingress and oxidation: Vehicle wading or A/C condensate leakage causes a short circuit between the terminals of the yellow airbag connector (usually located on the right side of the center console, in the floor wiring harness, or behind the glove box).+2 more →
Actions
— Safety preparation: Turn off the ignition switch, disconnect the negative battery terminal and wait at least 3 minutes (to fully discharge the SRS capacitor). Do not use powered equipment or tools generating electromagnetic interference near the airbag wiring harness.— Visual inspection: Check the front passenger airbag connector (usually located behind the right side of the dashboard, in the floor wiring harness, or under the seat) for oxidation, water ingress, or deformed pins. Check the wiring harness for signs of abrasion, crushing, or damage.+5 more →
B161A1A›
DTC B161A1A indicates the Supplemental Restraint System (SRS) detects the front passenger airbag (PAB) ignition circuit resistance is 0 ohms or below the threshold (usually <0.8Ω). The SRS ECU monitors circuit integrity using a constant current source to measure the squib circuit resistance. Normal resistance is 1.5-3.5Ω (typical value 2.0-2.8Ω). A resistance of 0 indicates a short circuit. Possible causes include an internal short in the airbag module squib, an internal short in the clock spring, a wiring harness short to ground or power, or a faulty internal sampling circuit in the SRS ECU. This fault prevents the front passenger airbag from deploying during a collision (fail-safe mode) or causes unintentional deployment (extremely rare but dangerous). The system illuminates the airbag warning light and disables the front passenger airbag.
Causes
— Front passenger airbag module internal igniter short circuit: Short circuit in the internal bridgewire or moisture in the pyrotechnic charge causing conduction between terminals.— Clock spring (spiral cable) internal short circuit: Damaged spiral cable winding beneath the steering wheel, or broken internal ribbon cable shorted to ground or between terminals.— Physical damage to the wiring harness: Sharp edges cut or crush the dashboard wiring harness, causing a short circuit to body ground or the 12V power supply line.+2 more →
Actions
— Safety preparation: Turn off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation: Connect the diagnostic tool and read the freeze frame data. Confirm the fault is Current rather than History. Record the environmental data at the time of the fault.+6 more →
B161B-00›
DTC B161B-00 indicates the airbag control unit (SRS ECU) detects the front passenger airbag (PAB) igniter circuit resistance is below the calibrated threshold (typically below 1.5-2.0Ω, depending on the vehicle software version). The standard SRS airbag igniter resistance is generally 2.0±0.5Ω. Low resistance typically indicates a short circuit. Potential causes include an internal short in the airbag igniter, a wiring harness short to ground, a short between connector terminals, or an internal short in the clock spring. This fault forces the SRS system into a degraded mode. The system may disable the front passenger airbag (preventing deployment) or, in extreme cases, risk unintended deployment. When this DTC triggers, the instrument panel airbag warning light remains illuminated and the system halts collision detection for the front passenger airbag.
Causes
— Front passenger frontal airbag module (inflator) internal igniter short circuit: Long-term use, moisture ingress, or manufacturing defects damage the igniter resistance wire insulation, reducing resistance below the threshold.— Internal short circuit in the clock spring: A short circuit in the flat cable inside the clock spring beneath the steering wheel causes an abnormal drop in airbag circuit resistance. This commonly occurs in high-mileage vehicles or from frequent steering wheel rotation.— Harness short to ground: Insulation abrasion, crushing, or rodent damage to the wiring harness inside the passenger-side instrument panel causes the wire to contact the body ground, creating a low-resistance path.+2 more →
Actions
— Safety Preparation: Set the vehicle to OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault Confirmation: Use a diagnostic tool such as VDS2000 or Launch X431 to read fault codes. Confirm B161B-00 is a current (Active) fault, not a history fault, and record the freeze frame data.+6 more →
B161B›
DTC B161B indicates the Airbag Control Module (ACM) detects the Passenger Airbag (PAB) igniter (inflator) resistance is below the system-calibrated lower threshold (typically below 1.0–1.5 Ω; normal range is 1.5–3.5 Ω). This fault represents an abnormal electrical characteristic in the SRS circuit or components. Potential causes include an internal short circuit in the igniter, a wiring harness short to ground, a short between connector pins, or a faulty internal detection circuit within the control module. Upon detecting this fault, the system enters fail-safe mode and illuminates the airbag warning lamp. This condition compromises occupant safety; during a collision, the passenger airbag may fail to deploy (fail-safe) or, in rare cases, deploy unexpectedly due to false triggering.
Causes
— Water ingress, corrosion, or deformed pins in the front passenger airbag wiring harness connector cause a short circuit between the positive and negative pins, significantly reducing the measured resistance.— Damaged wiring harness insulation between the Airbag Control Module (ACM) and the front passenger airbag, causing a short to body ground or short to power.— Front passenger airbag assembly (inflator): Moisture in the internal igniter or a manufacturing defect causes an abnormal decrease in bridge wire resistance.+2 more →
Actions
— Use a BYD dedicated diagnostic tool (VDS or EDT) to read the fault code, confirm whether B161B is a current (Active) or history (History) fault, and record the freeze frame data.— Perform the safety procedure: disconnect the negative battery terminal and wait at least 90 seconds to discharge residual voltage in the SRS system to prevent accidental airbag deployment.+6 more →
B161B1A›
DTC B161B1A indicates the airbag control module (SRS ECU) detects the Passenger Front Airbag ignition circuit resistance is below the calibrated threshold (typically below 1.0-1.5Ω; normal range is generally 2.0-5.0Ω). Low resistance typically indicates a parallel short circuit path in the airbag circuit. Potential causes include a wiring harness short to ground, bridged connector pins, or an internal short circuit in the airbag inflator. The ECU classifies this as a "Low Resistance" fault. This condition can prevent proper airbag deployment during a collision because the short circuit diverts the current. In extreme cases, static electricity or electromagnetic interference can cause unintended deployment. Consequently, the SRS system enters fail-safe mode, illuminates the airbag warning light, and disables the passenger front airbag.
Causes
— Passenger airbag wiring harness wear causing short to ground: Vibration chafes the harness insulation against the edges of the instrument panel frame or air conditioning duct. The exposed copper core contacts the vehicle body metal, creating a parallel resistance.— Bent airbag connector pins or water ingress: Incorrect removal or installation causes the pins in the airbag connector (usually yellow, located inside the centre console or behind the glovebox) to touch the housing. Poor sealing causes electrolyte corrosion, forming a low-resistance path.— Clock spring internal short circuit: If the front passenger airbag uses a steering wheel-mounted trigger mechanism (some models), an interlayer short circuit in the clock spring flat cable decreases circuit resistance.+2 more →
Actions
— Safety preparation: Turn off the ignition, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation: Connect the VDS diagnostic tool, read the freeze frame data (Fault Frame), record the vehicle status when the fault occurred, and confirm B161B1A is a current fault (Present), not a history fault.+6 more →
B161C-00›
DTC B161C-00 indicates the Supplemental Restraint System (SRS) control unit detected the front passenger airbag (PAB) ignition circuit resistance exceeds the normal upper limit. In BYD SRS systems, the control unit continuously monitors each airbag squib resistance via a low-current detection circuit. The normal range is typically 2.0-3.0Ω. If the resistance exceeds approximately 6.0Ω (high-resistance threshold), the control unit logs a 'high resistance' fault. During a collision, this fault may prevent or delay front passenger airbag deployment, severely compromising occupant passive safety. High resistance in the ignition circuit causes this fault. Potential root causes include poor contact, oxidized wiring, loose connectors, or an aging squib inside the airbag module.
Causes
— Poor contact at the internal slip ring of the clock spring (spiral cable) or worn carbon brushes increases connection resistance between the steering wheel and the airbag wiring harness. This is the most common cause of this fault.— Front passenger airbag module connector (yellow dedicated connector) loose, pins backed out, or terminals oxidized/corroded, causing abnormal contact resistance.— Vibration and chafing inside the dashboard damage the airbag wiring harness insulation. The copper wire partially breaks but does not completely sever, creating a high-resistance point.+2 more →
Actions
— Safety preparation: Power down the vehicle, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS backup power supply and prevent accidental airbag deployment during repair.— Visual inspection: Inspect the front passenger airbag module for impact damage. Check that the yellow airbag connector on the instrument panel is fully connected and the locking tab is engaged. Inspect the wiring harness for crushing or abrasion.+6 more →
B161C›
DTC B161C indicates the SRS (Supplemental Restraint System) ECU detects the front passenger frontal airbag ignition circuit resistance exceeds the calibrated upper limit (typically >5Ω). Normal airbag igniter resistance is between 2.0Ω and 3.0Ω. Excessive resistance indicates high resistance or an open circuit risk in the ignition circuit. This prevents the ECU from supplying sufficient ignition current (typically 1.2A or higher) during a collision, causing the front passenger airbag to fail to deploy and severely compromising passive safety. This is a hard fault. The system illuminates the airbag warning lamp and disables the front passenger airbag. Inspect and repair immediately.
Causes
— Poor contact at pins 1 and 2 of front passenger airbag module connector X246 (located on the right side of the instrument panel cross beam), or black locating clip not fully seated (standard requirement: the top of the clip must sit below the terminal face).— A poor connection, oxidation, terminal back-out, or spread terminals in the wiring between the instrument panel harness and the airbag module causes increased contact resistance.— Aging, moisture ingress, or an internal open circuit in the front passenger airbag module squib causes increased resistance.+2 more →
Actions
— Safety preparation: Turn off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Remove the passenger-side lower dashboard trim panel and glove box. Locate airbag module connector X246. Check if the black locking clip sits lower than the terminal end (flush or protruding indicates incorrect installation). Confirm there is no looseness, backed-out pins, or signs of water ingress.+4 more →
B161C1B›
DTC B161C1B indicates the Passenger Front Airbag ignition circuit resistance exceeds the threshold set by the SRS control module (normal range is typically 2.0-3.0Ω; the module triggers the code upon detecting resistance >3.5Ω or an open circuit). This active SRS system fault means the passenger front airbag may fail to deploy during a collision, or abnormal signals may force the system into fail-safe mode. In the BYD diagnostic protocol, the '1B' suffix specifically denotes 'resistance too high/open circuit'. Poor wiring connections, oxidized connectors, poor clock spring contact, or increased internal airbag module resistance typically cause this condition. This fault illuminates the instrument panel SRS warning lamp and disables the passenger front airbag. As a safety-critical fault, it requires immediate repair.
Causes
— Front passenger airbag wiring harness connector loose, oxidized, or corroded (located on the right side of the dashboard or behind the glove box; front passenger foot impacts or liquid ingress often cause poor contact)— Worn internal carbon brushes or poor contact in the clock spring (spiral cable) increases signal transmission resistance.— Airbag module internal igniter resistance increased due to aging, or poor internal solder joint.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (to allow the SRS capacitor to discharge fully). Wear an anti-static wrist strap. Do not use a multimeter in resistance mode to measure directly near the airbag (to prevent accidental deployment).— Visual inspection: Inspect the front passenger airbag module connector (usually located inside the right dashboard trim panel or behind the glovebox) for looseness, water ingress, oxidized pins, or backed-out terminals. Clean and apply conductive grease if necessary.+4 more →
B1620-00›
DTC B1620-00 indicates the airbag control unit (SRS ECU) detects an open circuit or disconnected electrical connection at the left front seat side airbag (Driver Side Airbag). Specifically, this fault indicates a circuit interruption between the seat-integrated side airbag module (typically located on the side of the seat backrest) and the vehicle wiring harness. The SRS ECU continuously monitors the airbag igniter circuit resistance (standard value: 2.0-3.0Ω) via a low-level signal line. The ECU sets this DTC when the resistance exceeds the threshold (typically >6Ω or open circuit) for longer than the specified time (typically >2 seconds). This is a hard fault that prevents the left front seat side airbag from deploying during a collision. The system also illuminates the instrument cluster SRS warning lamp and may disable the entire airbag system deployment function, severely compromising passive safety.
Causes
— Loose or disconnected yellow airbag connector under the seat: Sliding the seat fore/aft or adjusting seat height can loosen or disconnect the dedicated yellow connector (typically equipped with a short-circuit protection tab) located under the seat. This is the most common root cause of this fault code.— Seat side airbag wiring harness wear and fracture: Frequent seat adjustment repeatedly bends the harness at the slide rail mounting point, causing fatigue fracture of the internal copper core. The insulation remains visually intact, creating a hidden open circuit.— Side airbag igniter internal open circuit: The igniter bridge wire inside the airbag module is blown or has poor contact. Airbag aging or incorrect replacement after a previous accident typically causes this fault.+2 more →
Actions
— Safety Preparation and Fault Confirmation: Disconnect the 12V battery negative terminal and wait at least 3 minutes. Use the dedicated diagnostic tool to read and confirm B1620-00 is a current fault (Active). Record freeze frame data and check for accompanying fault codes (such as B1621 right front seat side airbag).— Visually inspect the connector under the seat: Move the seat to the fully forward and fully rearward positions. Verify the yellow dedicated connector under the seat (usually marked 'AIRBAG' or 'SRS') is fully locked. Inspect the shorting bar inside the connector for normal condition. Disconnect and reconnect the connector; listen for a 'click' to confirm locking.+4 more →
B1620›
DTC B1620 indicates the left Body Domain Controller detects an abnormal condition in the driver's side (left front) door lock. Specifically, the controller detects an implausible door lock position sensor signal, an open or short circuit in the door lock drive circuit, or a missing door lock status feedback signal. Typical causes include faults in the door lock assembly microswitch, position sensor, actuator motor, or associated wiring harness connections. This fault causes abnormal door status displays, remote locking failures, false anti-theft alarms, and false 'door open' warnings while driving, compromising vehicle security and driving safety.
Causes
— Repeated flexing of the wiring harness at the door hinge causes wear, insulation damage, or internal wire breakage (common issue on BYD models).— A faulty internal microswitch or position sensor in the front left door lock assembly causes abnormal signal voltage (normal: 0V/5V switching).— Loose wiring harness connector, poor contact, or oxidized pins causing signal interruption or excessive resistance.+2 more →
Actions
— Use the BYD VDS diagnostic tool to scan the left body domain controller, read and confirm DTC B1620, and verify the door lock status signal in the data stream matches the actual status.— Visually inspect the left front door lock wiring harness connector. Check for a loose plug, oxidized pins, or water ingress. If necessary, clean the connector or secure the retaining clip.+4 more →
B16201B›
B16201B is a BYD SRS (Supplemental Restraint System) diagnostic code indicating a communication interruption or open electrical connection between the driver's seat side airbag and the SRS control unit. This DTC sets when the SRS ECU detects the driver's side airbag circuit resistance exceeds the standard range (typically 2.0-3.0Ω ±0.5Ω), indicating an open circuit or high resistance. This incomplete airbag deployment circuit prevents the system from igniting the gas generator during a side impact. This fault forces the SRS into a degraded mode. The driver's seat side airbag becomes inoperative, but other airbags (front, curtain) typically remain functional. Despite involving the high-voltage interlock and safety systems, the vehicle remains drivable with reduced occupant protection. This fault continuously illuminates the instrument cluster airbag warning light on some models.
Causes
— Loose or backed-out yellow SRS connector under seat: Frequent forward and backward adjustment of the driver seat pulls the wiring harness, loosening the connector latch or causing poor terminal contact.— Clock spring internal open circuit: Broken flat ribbon cable inside the rotary connector beneath the steering wheel disrupts side airbag signal transmission (applies to the side airbag wiring harness integrated into the seat backrest).— Airbag module internal open circuit: Broken inflator bridge wire or corroded connector causing infinite circuit resistance.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal, wait at least 3 minutes for the SRS capacitor to discharge, wear an anti-static wrist strap, and disable the high-voltage system (for electric vehicles, disconnect the service disconnect switch).— Initial diagnosis: Use a BYD VDS or X-431 diagnostic tool to read all DTCs. Confirm B16201B is a current fault, not a history fault. Record freeze frame data (seat position, vehicle speed, etc.).+6 more →
B1621-00›
DTC B1621-00 indicates a short to ground in the driver side airbag (typically the seat-mounted side airbag or side curtain airbag) igniter circuit. In the BYD SRS system, the ECU continuously monitors the circuit resistance of each airbag igniter (normal value: approximately 2.0-5.0 Ω). When the ECU detects resistance below 1.0 Ω or voltage close to 0 V, it identifies a short to ground. This fault causes the system to disable the affected airbag circuit, preventing normal deployment during a side impact. In extreme cases, unstable resistance at the short circuit causes intermittent contact, posing a risk of unintended airbag deployment. When this DTC triggers, the SRS control unit illuminates the instrument cluster airbag warning light and stores freeze frame data recording the vehicle status at the time of the fault.
Causes
— Under-seat wiring harness wear: Frequent fore/aft movement of the driver's seat wears through the side airbag wiring harness insulation (usually located on the inner side of the seat rail), causing it to contact the vehicle's metal frame and create a short to ground.— Connector water ingress and corrosion: Water enters the yellow SRS connector under the seat during vehicle wading, car washing, or due to a blocked sunroof drain tube, causing a short circuit between terminals or between a terminal and the housing.— Internal short circuit in the spiral cable (clock spring): The internal flat ribbon conductor in the spiral cable beneath the combination switch breaks and shorts to ground, or a chafed wiring harness near the steering column causes a short circuit (on some models, the side airbag circuit passes through this area).+2 more →
Actions
— Safety Preparation: Shift the vehicle into Park or Neutral, engage the parking brake, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation and freeze frame analysis: Use a dedicated BYD diagnostic tool (BYD-EDS or Launch X431) to read the fault code. Confirm B1621-00 is a current fault (Active). Record freeze frame data (mileage, temperature, voltage, etc.). Check for accompanying fault codes (such as B1622 passenger side short circuit).+6 more →
B1621›
DTC B1621 indicates the SRS (Supplemental Restraint System) electronic control unit detects an abnormally low-resistance path (typically <0.5Ω) between the driver side airbag squib circuit and body ground (GND). Under normal conditions, airbag squib resistance must measure 2.0-3.0Ω, and insulation resistance to ground must exceed 1MΩ. A short to ground indicates an unintended ground connection in the squib circuit. This causes: 1) During a collision, the ground connection bypasses current, preventing proper airbag deployment and resulting in a loss of side-impact protection; 2) In extreme cases, wiring vibration may cause the ECU to misinterpret the short as a valid deployment signal, creating a risk of unintended airbag deployment; 3) The SRS system enters fail-safe mode, illuminates the instrument cluster airbag warning light, and disables the associated airbag function. This fault affects a core active safety system component and requires immediate repair.
Causes
— Driver seat side airbag wiring harness wear: The seat backrest houses the side airbag, requiring the harness to route near the seat slide rail to connect to the body harness. Repeated fore-aft seat adjustment rubs the harness against the metal slide rail. This friction damages the insulation, shorting the exposed copper core to body ground.— Internal terminal displacement, corrosion, or water ingress in the yellow airbag connector under the seat (Clock Spring or Seat Connector) causes a short circuit between the terminal and the connector housing (ground). This commonly occurs after vehicle wading or deep interior cleaning.— Side airbag module internal squib short circuit: Moisture in the airbag igniter charge or a manufacturing defect causes the squib wire to short to the metal housing.+2 more →
Actions
— Safety preparation: Shift the vehicle into Park, apply the parking brake, turn off the ignition, and disconnect the 12V battery negative terminal. Wait at least 90 seconds to fully discharge the SRS backup power supply and prevent accidental airbag deployment.— Fault confirmation: Reconnect the battery. Use a dedicated BYD diagnostic tool (such as ED400 or VDS) to read the DTC. Confirm B1621 is a Current Code, not a history code. Record the Freeze Frame Data to check the vehicle speed and ambient temperature at the time of the fault.+6 more →
B162111›
DTC B162111 is a BYD SRS (Supplemental Restraint System) diagnostic code indicating a short to ground in the driver-side side airbag ignition circuit. In BYD electrical architecture, this fault indicates the airbag control unit (ACU) detects abnormally low igniter circuit resistance (close to 0Ω) in the driver seat side airbag (typically integrated into the seat backrest or B-pillar), falling below the calibrated threshold (typically < 1.0Ω). This signifies an unintended connection between the positive or negative wire in the ignition circuit and the vehicle chassis (GND). This fault causes the ACU to flag the airbag as unsafe, immediately illuminate the instrument cluster SRS warning lamp, and disable deployment of the affected side airbag. In a collision, this airbag fails to inflate, severely compromising occupant side-impact protection. Additionally, the short circuit can trigger overcurrent protection in the internal ACU driver chip and, in extreme cases, risk unintended deployment, forcing the system into fail-safe mode.
Causes
— Mechanical wear of the under-seat wiring harness: Frequent fore-and-aft or height adjustments of the driver's seat repeatedly bend the yellow SRS wiring harness (especially between the GJK mating connector and the seat frame). The insulation wears through, causing a short to ground against the metal seat frame or vehicle body.— Connector water ingress and corrosion: During interior cleaning or driving through water, liquid seeps into the dedicated SRS connector (GJK mating point) under the driver's seat, causing electrolyte conduction between terminals or a short to ground due to verdigris.— Airbag module internal igniter short circuit: Manufacturing defects or prolonged exposure to high temperatures and humidity cause the insulation layer to fail, shorting the gas generator bridgewire directly to the metal housing.+2 more →
Actions
— Safety Preparation and System Power-Down: Turn the vehicle OFF, disconnect the 12V low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment. Wear an anti-static wrist strap. Do not directly measure the airbag circuit with a standard multimeter (use a dedicated diagnostic resistance meter with a current-limiting function).— Fault Code Confirmation and Freeze Frame Analysis: Use a BYD VDS2000 or ED400 diagnostic tool to access the SRS system. Read and confirm B162111 is a current fault (Active). Record freeze frame data (such as vehicle mileage and ambient temperature) to determine if the fault is intermittent.+5 more →
B1622-00›
DTC B1622-00 indicates the driver side airbag squib circuit is shorted to the vehicle constant power supply (+B, battery voltage). The SRS (Supplemental Restraint System) ECU continuously monitors the airbag igniter circuit resistance and voltage. When detecting an abnormally high voltage on the igniter wiring (approaching the 12V supply voltage), the ECU registers a short to power. This fault is extremely dangerous and may cause: 1) accidental airbag deployment while driving, resulting in serious personal injury; 2) failure of the airbag to deploy during a collision due to the circuit fault; 3) the SRS entering fail-safe mode, disabling all airbag functions. This is a hard fault (Hard DTC). Once confirmed, the system triggers a severe warning and prohibits further vehicle operation.
Causes
— Under-seat wiring harness wear: Friction from long-term forward and backward seat movement damages the insulation of the driver's seat side airbag wiring harness (usually routed near the seat slide rail), causing a short circuit to power wires (such as seat heating or power adjustment supply wires).— Airbag connector fault: Poor sealing of the yellow dedicated airbag connector (CPA connector) under the seat allows water ingress or corrosion, causing a short circuit between pins; or incomplete locking after repair causes terminal misalignment and contact with the power terminal.— Internal short circuit in the spiral cable (clock spring): Damaged insulation on the internal ribbon cable of the spiral cable beneath the steering wheel shorts the airbag igniter wire to other power supply circuits.+2 more →
Actions
— Safety preparation: Disconnect the negative battery terminal and wait at least 90 seconds (ensuring the SRS capacitor discharges fully). Hang 'Do Not Operate' warning tags on the steering wheel and seat.— Initial visual inspection: Check the driver side airbag module connector (located on the side or under the seat, marked in yellow) and the clock spring connector for obvious burn marks, signs of water ingress, or physical damage.+5 more →
B1622›
DTC B1622 indicates the Supplemental Restraint System (SRS) control module detects an abnormally low-resistance connection (typically below 1.0Ω) between the driver side airbag inflator circuit and battery positive (B+, 12V). Normally, the airbag inflator circuit maintains a high-resistance state (open circuit or the 2-3Ω resistance of the inflator itself). A short to power means the SRS module detects supply voltage instead of the expected high-resistance signal when checking circuit integrity. This fault poses extreme safety risks. During a collision, the SRS module may fail to trigger the inflator circuit, preventing airbag deployment. Additionally, specific operating conditions (such as intermittent wiring contact or voltage fluctuations) can cause unintended airbag deployment, severely threatening driver safety.
Causes
— Aged or damaged insulation on the internal flat cable of the clock spring (spiral cable) causes the airbag ignition wire (usually the yellow harness) to short to power wires inside the steering wheel (such as the horn or multifunction button power supply).— The airbag wiring harness under the driver's seat or inside the A/B-pillar trim contacts the body power wiring harness due to insulation wear from frequent fore-and-aft seat adjustment or friction from opening and closing the door.— Airbag connector (usually located under the seat or steering wheel): Backed-out or bent terminal pins, or water ingress and corrosion inside the connector causing a short circuit between adjacent power supply terminals and airbag igniter terminals.+2 more →
Actions
— Safety preparation: Disconnect the negative battery terminal and wait at least 90 seconds (to ensure the SRS capacitor fully discharges). Hang an 'Airbag Under Repair' warning sign to prevent accidental deployment.— Fault freeze frame analysis: Use the BYD VDS diagnostic tool to read the DTC freeze frame. Record the vehicle speed, temperature, voltage, and other data from when the fault occurred to confirm whether the fault is continuous or intermittent.+6 more →
B162212›
DTC B162212 indicates abnormal continuity between the squib circuit of the driver side airbag (usually the seat-mounted side airbag) and the vehicle positive power supply (B+, battery voltage). In the SRS (Supplemental Restraint System) control logic, the airbag squib circuit must maintain a high-impedance open state at rest. The control unit determines circuit integrity by monitoring circuit voltage. Detecting a short to power in this circuit indicates damaged wiring insulation contacting a constant power wire, or an insulation failure of the igniter coil inside the airbag module. This fault immediately forces the SRS into fail-safe mode, which: 1) Disables the driver side airbag, preventing deployment during a side impact; 2) Illuminates the airbag warning lamp; 3) Creates a risk of unintended airbag deployment in extreme cases (despite multiple protections in modern systems). Because it involves a core component of the passive safety system, this fault classifies as severe and requires immediate repair.
Causes
— Mechanical damage to the under-seat wiring harness: The driver-side side airbag wiring harness moves back and forth with the seat. Repeated bending or crushing by foreign objects (such as coins or toys) wears through the insulation, causing a short circuit to the seat heater wire or constant power wire.— Water ingress and corrosion in the SRS connector: When driving the vehicle through water or cleaning the interior, liquid enters the dedicated yellow SRS connector under the seat, causing an electrolytic short circuit between the terminals, or verdigris creates continuity between the power terminal and the airbag circuit terminal.— Airbag module internal short circuit: Aging, static electricity, or manufacturing defects damage the igniter (squib) internal coil insulation, causing the primary coil to contact the secondary coil or housing and create a short to power.+2 more →
Actions
— Safe power-down: Turn off the ignition, disconnect the negative battery cable, and wait at least 3 minutes (some models require 90 seconds, but BYD SRS capacitor discharge usually takes 3 minutes) to fully discharge the system.— Fault status confirmation: Connect the BYD dedicated diagnostic tool (VDS2000 or EDT), enter the SRS system to read fault codes, confirm B162212 is a current fault (Current DTC), and check the voltage value in the freeze frame data (usually displaying 12V or battery voltage).+7 more →
B162A-00›
DTC B162A-00 indicates an abnormal left front seat side airbag ignition circuit resistance of 0 ohms, representing a short-to-ground fault. Normal airbag inflator resistance is 2.0-3.0 Ω. A 0 Ω reading means the ignition circuit shorts to the vehicle body ground. Potential causes include an internal airbag module short circuit, damaged wiring harness insulation shorting to ground, or shorted connector terminals. This fault causes the SRS system to detect a risk of accidental ignition or deployment failure. Consequently, the SRS system disables the airbag's collision protection function and illuminates the airbag warning light on the instrument cluster.
Causes
— Seat side airbag igniter internal short circuit (airbag module internal bridge wire short circuit or moisture in pyrotechnic charge)— Long-term friction from seat adjustment damages the wiring harness insulation under the seat or on the side of the backrest, causing a short circuit to the metal frame.— Water ingress, oxidation, corrosion, or bent pins at the seat side airbag connector (usually located under or on the side of the seat) causing a short circuit between the positive and negative terminals.+2 more →
Actions
— Safety preparation: Turn off the ignition, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS backup power capacitor and prevent accidental airbag deployment.— Freeze frame: Use the BYD VDS diagnostic tool to read the freeze frame data. Record environmental parameters such as vehicle speed, temperature, and voltage when the fault occurred to confirm if the fault is intermittent.+6 more →
B162A›
DTC B162A indicates the airbag control module (SRS ECU) detects a driver airbag ignition circuit resistance of 0 Ω or below the 1.5 Ω threshold, identifying a short to ground or a shorted circuit. In the BYD SRS system, this circuit includes the clock spring, spiral cable, connectors, and airbag inflator. A 0 Ω resistance means current may flow directly to ground. The ECU disables the airbag to prevent accidental deployment and illuminates the instrument cluster airbag warning lamp. This fault constitutes a hard short circuit, unlike an open circuit (infinite resistance). However, broken wires inside the clock spring contacting each other or grounding can also cause an intermittent short circuit. This fault prevents the driver front airbag from deploying during a collision, severely compromising passive safety.
Causes
— Damaged internal flat cable insulation in the steering wheel clock spring (spiral cable) causing a wire short to ground or inter-turn short circuit. Common in older vehicles or from frequent full-lock steering.— Driver's airbag connector (yellow plug) pins bent, backed out, or water-corroded, causing a short circuit between the positive and negative pins or a short to ground.— The airbag wiring harness chafes near the steering column. Damaged insulation allows the wire to contact the metal frame, causing a short to ground.+2 more →
Actions
— Safety Preparation: Disconnect the battery negative terminal and wait at least 3 minutes to discharge residual charge in the system capacitors. Wear an anti-static wrist strap. Do not measure directly in the airbag area using the resistance setting of a standard multimeter (use a high-impedance digital multimeter or a dedicated diagnostic tool).— Visual inspection: Verify the yellow airbag connector under the steering wheel is fully locked. Inspect the connector interior for water stains, oxidation, or deformed pins. Inspect the clock spring exterior for damage or burn marks.+4 more →
B162B1A›
This DTC indicates the driver side airbag squib resistance falls below the SRS control unit threshold (typically <1.6Ω). Normal airbag squib resistance ranges from 1.6Ω to 2.4Ω. Low resistance indicates an abnormal short-circuit path in the circuit. Potential causes include an internal airbag squib short circuit, a wiring harness short to ground, or a grounded connector terminal. The SRS system classifies this fault as an unintended deployment risk, automatically disconnects the airbag circuit, and illuminates the airbag warning lamp. During a side impact, the airbag may fail to deploy, disabling driver side protection. Additionally, the BYD SRS fail-safe mechanism may trigger the seat belt pretensioner linked protection logic, compromising overall passive safety system performance.
Causes
— Driver side airbag igniter internal short circuit (airbag assembly fault, possibly due to manufacturing defect or prolonged moisture exposure)— Worn wiring harness insulation under the seat or inside the B-pillar causing a short to ground (commonly due to frequent seat adjustment or foreign objects pinching and damaging the harness).— Airbag connector (yellow plug) short circuit due to water ingress, oxidation, or terminal deformation (common after vehicle wading or washing).+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000/VDS2100) to read all DTCs and freeze frame data. Record the environmental conditions at the time of the fault and confirm B162B1A is a current fault, not a history fault.— Disconnect the 12V battery negative terminal and wait at least 3 minutes (some models require 90 seconds; wait 3 minutes to fully discharge the SRS energy storage capacitor) to ensure the system enters a safe state.+6 more →
B162A1A›
DTC B162A1A indicates the airbag control module (SRS ECU) detects a resistance of 0 ohms, or close to 0, in the driver's side airbag circuit (usually integrated into the seat side). Normal airbag circuit resistance ranges from 2-3 ohms (including the airbag inflator resistance and wiring harness impedance). A resistance of 0 indicates a short circuit. Possible causes include damaged wiring harness insulation causing a short between positive and negative terminals, connector pins shorting to ground, an internal short in the airbag inflator, or an SRS control module sampling circuit fault. This fault prevents the side airbag from deploying during a collision, resulting in a loss of protection. In extreme cases, poor contact at the short circuit point can produce arcing and risk unintended deployment. Triggering this fault code illuminates the instrument cluster airbag warning light and may disable the entire airbag system.
Causes
— Seat slide rail or seat frame edge chafing the airbag wiring harness: Frequent forward and backward adjustment of the driver seat causes the yellow airbag wiring harness (located under the seat) to rub against the metal slide rail. Prolonged friction damages the insulation, causing a core wire short to ground or a short between the positive and negative terminals.— Connector water ingress and oxidation: Vehicle wading, car washing, or sunroof leaks cause water to enter the under-seat airbag connector (usually located at the lower left of the seat), causing a short circuit between pins or abnormally low resistance due to corrosion.— Improper seat removal or installation: After removing the seat during repair or modification, the airbag connector is not fully seated (no locking click heard), the connector locking tab is broken, or a foreign metal object enters the connector and shorts the pins.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Check the yellow dedicated wiring harness under the driver's seat (usually featuring yellow corrugated conduit or yellow tape) for wear, cuts, or crush marks. Focus on the seat slide rails, seat frame edges, and wiring harness bends.+6 more →
B162B-00›
DTC B162B-00 indicates the airbag control unit (SRS ECU) detects the driver side airbag (located on the side of the driver seat) igniter circuit resistance is below the system threshold (normal range: 2.0-5.0Ω; low resistance indicates a value below the lower limit or a near short circuit). Electrically, this indicates an abnormally low-resistance path in the circuit. Potential causes include a wiring short to ground, an internal short circuit in the airbag module, or abnormal connector conduction. This fault causes the SRS system to classify the driver side airbag as unsafe. During a collision, excessive current may prevent the igniter from deploying the airbag. Additionally, a risk of accidental deployment (non-collision deployment) exists. Consequently, the system illuminates the instrument cluster airbag warning light and may disable the entire airbag system, severely compromising occupant side-impact protection.
Causes
— Driver's seat side airbag wiring harness connector (usually located under the seat) is loose, oxidized, or has water ingress, causing abnormal continuity or abnormally low contact resistance between terminals.— Internal short circuit in the seat side airbag igniter (generator) due to internal resistance wire insulation failure from aging, moisture ingress, or a manufacturing defect.— Damaged seat wiring harness insulation causing a short to body ground, commonly resulting from prolonged friction between the harness and metal frame due to frequent seat adjustment.+2 more →
Actions
— Safety preparation: Turn the vehicle power mode to OFF, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS system backup power supply and prevent accidental airbag deployment during repair.— Visual inspection: Inspect the SRS wiring harness connector (KJ10) under the driver's seat for looseness, water ingress, corrosion, or deformed pins. Inspect the wiring harness near the seat rail for wear or damaged insulation.+5 more →
B162B›
DTC B162B indicates the SRS (Supplemental Restraint System) control module detects the driver-side side airbag (typically the seat side airbag or side curtain airbag) igniter (squib) resistance is below the system threshold (typically <1.0Ω or below the standard range of 2.0-3.0Ω). This fault indicates a short-circuit risk in the wiring or airbag assembly. The system enters safety mode to prevent accidental airbag deployment or failure. Triggering this fault disables the affected airbag circuit. The airbag may fail to deploy during a side-impact collision, severely compromising occupant protection. Additionally, a continuously illuminated SRS warning light indicates the entire airbag system may operate in a degraded protection mode.
Causes
— Airbag wiring harness under the driver's seat worn or pinched, causing a short to ground: Frequent forward and backward seat movement can wear through the insulation on the yellow airbag wiring harness near the seat slide rail, causing the wire to directly contact the vehicle body metal.— Short circuit in airbag connector (yellow plug) internal terminals: Water ingress, oxidation, corrosion, or terminal deformation causes abnormal contact between positive and negative terminals, resulting in abnormally low resistance.— Internal short circuit in the driver side side airbag assembly: A short circuit in the airbag igniter internal bridge wire or pyrotechnic charge causes the resistance value to drop far below the standard value (<1.0Ω).+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Initial inspection: Use the diagnostic tool to read all fault codes and freeze frame data. Confirm B162B is a current fault, not a history fault. Check the driver's seat side airbag yellow connector (located on the outer side of the seat backrest or the side of the seat cushion) for looseness, water ingress, or obvious damage.+4 more →
B162C-00›
DTC B162C-00 indicates the SRS (Supplemental Restraint System) control unit detects resistance exceeding the calibrated threshold in the driver side airbag ignition circuit. The driver side airbag typically mounts in the side of the driver seat backrest or inside the door trim panel. Normal circuit resistance ranges from 2-3 ohms; the fault threshold typically exceeds 3.5-4 ohms. The SRS ECU monitors circuit integrity by sending a low-current signal through its internal detection circuit to the airbag igniter. High-resistance connections (e.g., poor contact, loose harness connections, oxidation, or partial wire breaks) increase total circuit resistance, causing the ECU to register a high-resistance fault. This fault severely compromises side-impact protection. Excessive resistance limits current, potentially causing the driver side airbag to deploy late or fail to deploy during a collision. The system illuminates the SRS warning lamp and may disable the entire airbag system, resulting in a complete loss of collision protection.
Causes
— Fatigue fracture or poor contact in the under-seat wiring harness: Frequent forward and backward driver seat adjustment repeatedly bends the airbag wiring harness secured under the seat. This partially breaks the internal copper strands while leaving the insulation intact, creating a high-resistance connection.— Poor connector contact: Moisture, oxidation, or an incompletely engaged locking tab increases contact resistance at the seat side airbag connector (usually a yellow plug).— Improper modification or repair: Failure to fully seat the airbag connector during reinstallation after seat leather reupholstery, heating pad retrofitting, or accident repair, or the seat slide rail crushing and damaging the wiring harness.+2 more →
Actions
— Safety preparation: Switch off the ignition, disconnect the 12V battery negative terminal, and wait at least 3 minutes (to fully discharge the SRS capacitor and prevent accidental airbag deployment).— Fault confirmation: Connect the dedicated BYD diagnostic tool (VDS or ED400), read the SRS system fault codes, confirm B162C-00 is a current fault and not a history fault, and record the freeze frame data.+6 more →
B162C›
DTC B162C indicates the driver side airbag ignition circuit resistance exceeds the normal upper limit set by the SRS control unit (typically >3.5Ω; normal value 1.5-3.0Ω). The SRS ECU continuously monitors the airbag inflator (gas generator) circuit resistance via its internal detection circuit. Excessive resistance indicates poor contact, a partial open circuit, or inflator aging within the ignition circuit. This condition may prevent the circuit current from reaching the ignition threshold (typically 1.5-2.0A required) during a collision. This fault prevents the side airbag from deploying normally in a crash. Repair this safety-critical fault immediately.
Causes
— Fatigue fracture or poor contact of the internal flat cable in the clock spring (spiral cable). This is the most common point of failure for the driver's airbag, especially in vehicles with frequent steering wheel rotation.— Internal resistance of the driver seat side airbag module (gas generator) increased due to aging, or moisture in the internal igniter charge caused a resistance shift.— The dedicated yellow SRS connector under the seat or at the B-pillar (usually fitted with a shorting bar) is loose, oxidized, water-damaged, or has backed-out pins, causing increased contact resistance.+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation: Use the BYD ED400/ED600 diagnostic tool to read the live data stream. Record the current resistance value (normal: 1.5-3.0Ω; typically >3.5Ω or open circuit during a fault). Check the freeze frame to confirm vehicle status at the time of the fault.+5 more →
B1630-00›
DTC B1630-00 indicates the SRS (Supplemental Restraint System) control module detects an open circuit or high resistance in the right front seat side airbag module circuit. The resistance exceeds the calibrated range (typically >10Ω). This represents a hard fault in the airbag system; the right front seat side airbag fails to deploy during a side-impact collision. The system enters fail-safe mode and continuously illuminates the instrument cluster airbag warning light. Potential causes include an open wiring circuit, a disconnected connector, an open airbag squib, or excessive contact resistance.
Causes
— Loose or completely disconnected SRS-specific yellow connector under the seat: Vibration from moving the seat forward and backward, or passenger foot impacts, loosens the under-seat airbag wiring harness connector (usually equipped with a shorting bar protection mechanism).— Wiring harness wear and breakage at the seat slide rail: During fore-and-aft seat adjustment, the side airbag wiring harness (transition section from the body floor harness to the seat) bends repeatedly at the slide rail. This causes the internal copper wires to fatigue and break while the outer insulation remains intact.— Internal open circuit in the airbag module: Side airbag assembly squib open circuit or damaged clock spring, typically resulting from component aging or failure to replace the airbag after a previous accidental deployment.+2 more →
Actions
— Safe power-down: Switch off the ignition, disconnect the 12V battery negative terminal, and wait at least 90 seconds (to fully discharge the SRS capacitor). Do not operate any electrical equipment during this time.— Visual inspection and location: Move the right front seat to the fully forward position. Inspect the yellow SRS connector under the seat (usually located on the inner or rear side of the seat, featuring a double-locking mechanism). Confirm the connector seats fully with an audible locking 'click', and verify the shorting bar has sprung open.+5 more →
B162C1B›
DTC B162C1B is a BYD BMS (Battery Management System) fault code. It indicates abnormal communication between a specific Battery Information Collector (BIC) inside the battery pack and the main BMS, or excessive resistance in the sampling circuit. Specifically, "B16" designates the BMS subsystem, "2C" identifies a communication or sampling fault in a specific BIC module, and "1B" is the subtype code indicating excessive resistance, an open circuit, or poor contact in that BIC module's CAN communication circuit. This failure prevents the system from uploading voltage and temperature data for that battery cell group, affecting battery balancing management, SOC calculation, and the high-voltage interlock function. In severe cases, the fault may prevent the vehicle from enabling the high-voltage system or cause a loss of drive power while driving.
Causes
— BIC module connector loose, oxidized, or pins backed out, causing poor contact in the CAN communication line.— Wear, open circuit, or short circuit in the BIC sampling harness inside the battery pack, especially at the retaining clips.— BIC sampling board internal circuit fault (e.g., burnt balancing MOSFET or NTC resistor cold solder joint)+2 more →
Actions
— Use the BYD dedicated diagnostic tool (ED400 or X-431) to read complete fault codes and freeze frame data, and confirm which specific BIC module (e.g., BIC1, BIC5) is reporting the fault.— Read the BMS data stream and check the corresponding BIC cell voltage and temperature for abnormal readings (such as -40℃ or 0V).+6 more →
B174B1A›
This DTC indicates the left rear side airbag squib resistance falls below the normal threshold set by the SRS control module (ACU) (typically below 1.2Ω-1.5Ω; standard range is generally 1.5Ω-3.5Ω). Low resistance usually indicates a short circuit in the squib circuit. Possible causes include a wiring harness short to ground, a wire-to-wire short, an internal connector short, or an internal short within the airbag module itself. This fault causes the SRS system to classify the airbag as unsafe. The airbag may fail to deploy during a collision (as the system may disable the circuit to prevent accidental deployment), or it poses a risk of unintended deployment. This is an active safety system fault requiring immediate repair.
Causes
— Left rear side airbag igniter internal short circuit (gas generator fault)— Wiring harness wear under the seat or inside the C-pillar trim causes a wire short to ground or a short between positive and negative wires.— Water ingress, oxidation, or bent pins in the airbag wiring harness connector (usually located under the seat) causing abnormal continuity+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes to fully discharge the SRS system capacitors and prevent accidental airbag deployment.— Visual inspection: Remove the left rear seat and lower C-pillar trim panel. Check the side airbag wiring harness connector for looseness, water ingress, corrosion, or backed-out pins.+5 more →
B1630›
DTC B1630 indicates the SRS (Supplemental Restraint System) detected an open circuit or abnormally high resistance in the front passenger seat side airbag circuit. The ECU determines the airbag module is incorrectly connected. Potential fault locations include the front passenger seat side airbag assembly, connecting wiring, under-seat wiring harness connector, or the airbag control unit (ACU) internal driver circuit. During system self-check, the ACU confirms the connection status by monitoring the airbag squib circuit resistance. Normal resistance typically ranges from 2.0-3.0 ohms (depending on the vehicle model). If the ACU detects an open circuit (infinite resistance) or resistance exceeding the threshold, it triggers this fault code. This fault prevents the front passenger side airbag from deploying during a side-impact collision. The system also illuminates the instrument cluster airbag warning light and may disable the entire SRS, significantly reducing vehicle passive safety. Note: Some vehicle models or documentation define B1630 as a seat belt pretensioner circuit fault. Consult the specific vehicle service manual during repair.
Causes
— Front passenger seat side airbag connector loose or disconnected (common causes: yellow wiring harness plug under seat not fully seated, damaged retaining clip, or failure to reconnect after seat removal and installation)— Frequent seat adjustment causes fatigue fracture in the airbag wiring harness (especially the harness section between the seat rail and B-pillar, where long-term bending causes internal breakage or wear).— Front passenger side airbag module internal squib circuit open (internal open circuit due to airbag assembly internal fault or expired service life)+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 3 minutes (5 minutes on some models) to fully discharge the SRS capacitor and prevent accidental airbag deployment during repair.— Visual inspection: Remove the front passenger seat side trim panel and under-seat protective panel. Verify the airbag wiring harness connector (usually a yellow plug) is fully inserted and the locking tab is engaged. Inspect the plug for water ingress, corrosion, or recessed pins.+4 more →
B16301B›
This fault code indicates the Airbag Control Unit (ACU) detects an open circuit or high resistance in the communication circuit between the front passenger side airbag (usually installed on the outboard side of the front passenger seat or inside the B-pillar trim panel) and the ACU. Specifically, the ACU cannot detect the standard 2-3 ohm resistance value in this airbag circuit and determines a 'disconnected' state. This prevents the side airbag from deploying normally during a side impact, severely reducing side impact protection for the front passenger. The system simultaneously illuminates the SRS fault warning light on the instrument cluster and may trigger the system safety protection mechanism, disabling the entire airbag system to prevent accidental deployment.
Causes
— Front passenger side airbag yellow connector (usually located under or on the side of the seat) is loose, disconnected, or its locking mechanism is not fully engaged, causing poor contact or an open circuit.— Frequent fore/aft seat adjustment or seat frame pinching causes internal wire breakage or insulation damage to the airbag wiring harness at bend points (especially near the seat slide rails).— Open circuit or abnormal resistance (outside the standard 2-3Ω range) in the airbag module internal inflator coil, causing the ACU to detect an open circuit.+2 more →
Actions
— Use the dedicated BYD diagnostic tool (VDS2000/VDS3.0) to read fault codes. Confirm B16301B is a current fault (Current DTC), not a history fault, and record freeze frame data.— Perform safety procedure: turn off the ignition switch, disconnect the battery negative terminal, and wait at least 3 minutes for the SRS capacitor to discharge fully. Never work on the airbag system with the power supply connected.+6 more →
B1631-00›
DTC B1631-00 indicates the airbag control unit (SRS ECU) detected a short to ground in the front passenger (right front) seat side airbag inflator circuit. The SRS ECU verifies circuit integrity by monitoring the airbag inflator circuit resistance. Normally, this circuit exhibits high resistance (open circuit or a specific resistance range, typically >1MΩ insulation to ground). If the ECU detects an abnormal resistance drop between the inflator circuit and body ground (below the threshold, typically <1Ω), it registers a short to ground. This fault triggers the safety protection mechanism. The ECU disables the airbag to prevent accidental deployment, illuminates the instrument cluster SRS warning light, stores the DTC, and may sound a warning buzzer. Because the side airbag is critical for side impact protection, this fault disables front passenger side impact protection and constitutes a severe safety fault.
Causes
— Frequent seat movement and chafing damage the insulation of the SRS wiring harness under or beside the front passenger seat, causing it to contact metal body parts and create a short to ground.— Bent or backed-out pins in the airbag connector (KJ10), or water ingress or oxidation inside the connector causing a short circuit between terminals or to ground.— The internal igniter component in the right front seat side airbag module shorts out after aging, moisture exposure, or impact, causing the resistance to drop abnormally.+2 more →
Actions
— Safety preparation: Turn the power switch to OFF, disconnect the negative battery cable, and wait at least 90 seconds for the SRS capacitor to fully discharge to prevent accidental airbag deployment.— Visual inspection: Remove the front passenger seat (if necessary). Inspect the SRS wiring harness under the seat frame, around the seat tracks, and below the B-pillar for wear, crushing, cuts, or water stains. Focus on the condition of connector KJ10.+6 more →
B1631›
DTC B1631 indicates a short to ground in the front passenger side airbag ignition circuit. In the BYD SRS (Supplemental Restraint System), this fault code indicates the airbag control unit (ACU) detects an abnormally low resistance (typically <1Ω) between the front passenger side airbag (usually installed in the seat side or door trim panel) ignition wiring and body ground. Normal airbag circuit resistance should measure between 2.0 and 3.0Ω. This fault means: 1) the airbag may fail to deploy during a collision, resulting in a loss of side impact protection; 2) extreme cases pose a risk of unintended deployment; 3) the SRS system enters fail-safe mode, illuminating the instrument panel airbag warning light and potentially disabling other airbag functions. This hard short circuit requires immediate repair to ensure occupant safety.
Causes
— Front passenger side airbag module internal igniter short circuit: Moisture, aging, or manufacturing defects cause the internal squib terminals to short to the housing.— Harness wear or crushing causing a short to ground: Long-term chafing or crushing damages the insulation of the airbag harness under the seat rails, door hinges, or carpet, causing it to contact vehicle body metal.— Connector water ingress or corrosion: Poor sealing of the airbag connector under the seat or on the B-pillar allows water ingress after washing the vehicle or wading, causing a short circuit between terminals or to ground.+2 more →
Actions
— Safe power-off: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS system capacitors and prevent accidental airbag deployment.— Visual inspection: Check the front passenger seat side airbag (or door airbag) for visible damage. Inspect the yellow SRS wiring harness under the seat and inside the B-pillar trim for signs of abrasion, crushing, or puncture.+4 more →
B163111›
DTC B163111 indicates the SRS (Supplemental Restraint System) control module detects an abnormally low-resistance path to body ground (short to ground) in the front passenger side airbag squib circuit (typically the seat side airbag or curtain airbag). Under normal operating conditions, the airbag squib circuit resistance must remain around 2-3 Ω, and the insulation resistance to ground must exceed 1 MΩ. The control module logs a short to ground when it detects circuit resistance approaching 0 Ω or current leaking to ground. This fault prevents the side airbag from deploying during a side-impact collision, eliminating side-impact protection for the occupant. The circuit abnormality also creates a potential risk of unintended deployment, although a short to ground typically causes a non-deployment failure rather than accidental triggering. This fault constitutes a severe active safety system failure. Remove the vehicle from service immediately until repaired.
Causes
— Long-term chafing or compression damages the airbag wiring harness insulation near the front passenger seat slide rail or B-pillar, causing the wire to directly contact the vehicle body metal.— Internal water ingress and oxidation in the under-seat airbag wiring harness connector (usually located where the seat meets the floor) due to wading or improper cleaning, or misaligned or loose pins, causing a short to ground.— Internal short circuit in the front passenger side airbag module squib, shorting one of the two terminals to ground.+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 90 seconds (120 seconds for some models) to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Initial visual inspection: Inspect the airbag wiring harness connectors (typically yellow) under the front passenger seat, at the bottom of the B-pillar trim panel, and inside the sill trim panel for obvious damage, signs of water ingress, terminal corrosion, or loose connections.+6 more →
B1632›
DTC B1632 indicates the SRS (Supplemental Restraint System) ECU detected a short to power (B+) in the front passenger side airbag igniter circuit (typically the right seat airbag or side curtain airbag). Normally, the airbag igniter circuit maintains a low voltage (near 0V). The ECU supplies high current only when triggering airbag deployment. If the ECU continuously detects circuit voltage near battery voltage (12V), it identifies a short to power. This fault forces the SRS into fail-safe mode, disables front passenger side airbag deployment, and illuminates the airbag warning light. Potential causes include damaged wiring insulation, shorted connector terminals, an internal short in the airbag module, or a faulty internal ECU driver circuit.
Causes
— Wiring harness wear under the seat or inside the B-pillar: Frequent front passenger seat adjustment or door operation rubs the wiring harness against metal body edges, damaging the insulation and causing a short circuit to the power wire.— Connector water ingress or deformed terminals: Water enters the front passenger-side airbag connector (usually located under the seat or inside the B-pillar trim) during vehicle wading, car washing, or due to a blocked sunroof drain hose, causing a short circuit between terminals.— Airbag assembly internal fault: The internal igniter insulation layer of the front passenger side airbag (curtain or seat airbag) breaks down due to aging, causing the igniter pins to short to ground or power.+2 more →
Actions
— Safety Preparation: Set the vehicle to OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to allow the SRS capacitor to fully discharge and prevent accidental airbag deployment.— Fault Confirmation and Freeze Frame Analysis: Connect the diagnostic tool to read DTC B1632. Record the freeze frame data (vehicle speed, temperature, voltage, etc. at the time of occurrence) and confirm whether the fault is current or historical.+6 more →
B1632-00›
B1632-00 indicates a short circuit to vehicle power (B+) in the front passenger (right) side airbag ignition circuit. In the BYD SRS (Supplemental Restraint System) architecture, this fault specifically refers to abnormal continuity between the inflator circuit of the front passenger seat side airbag or the right curtain airbag and 12V constant power or ignition power. This fault is a hard short. The SRS control unit (ACU) detects the ignition circuit voltage continuously exceeding the threshold (typically >5V). To prevent unexpected deployment, the system immediately cuts off the affected airbag ignition circuit and illuminates the airbag fault warning lamp (SRS MIL). This fault presents an extremely high safety risk: the short circuit may cause unexpected airbag deployment resulting in personal injury. Additionally, the fault prevents normal airbag deployment, disabling collision protection.
Causes
— Worn wiring harness under the front passenger seat: Frequent fore-and-aft seat adjustment causes the side airbag wiring harness (usually integrated into the seat harness) to rub against the seat rail and slide rail bracket. Damaged insulation allows the harness to contact live parts on the metal frame.— Right front door hinge wiring harness crushed: The curtain airbag is located above the door or on the B-pillar. Frequent door opening and closing crushes and chafes the door-to-body wiring harness, causing power wires (e.g., door lock power, window regulator power) to short circuit to the airbag ignition wire.— Airbag igniter internal short circuit: The resistance wire of the front passenger airbag module internal igniter shorts to the housing or power terminal. Manufacturing defects, airbag aging, or previous physical impact typically cause this.+2 more →
Actions
— Safety isolation: Disconnect the 12V battery negative terminal. Wait at least 90 seconds for the SRS energy storage capacitor to discharge fully. Hang an 'Airbag Under Repair' warning sign. Do not reconnect power during the repair.— Fault Confirmation and Freeze Frame Analysis: Connect the VDS2000 or Launch X431 diagnostic tool. Read the freeze frame data for DTC B1632-00. Confirm the vehicle speed, temperature, and voltage conditions when the fault occurred to determine whether it is an intermittent fault.+6 more →
B163212›
DTC B163212 indicates a short to battery positive (B+) in the front passenger seat side airbag ignition circuit. Technically, this means an abnormal connection to the permanent 12V supply exists in the wiring harness or connectors between the airbag control module (SRS ECU) and the front passenger seat side airbag. Normally, the airbag igniter terminals maintain a high resistance (>10kΩ) in the non-deployed state or only receive a low-current monitoring signal from the ECU. A short to power causes the following: 1) The SRS system enters protection mode, cutting power to this circuit to prevent unintended deployment; 2) The front passenger seat side airbag completely fails, preventing deployment during a side impact; 3) A potential unintended deployment risk arises. Although the ECU typically features short-circuit protection, a continuous short to power can overheat and damage the control module's internal driver chip. ISO 26262 classifies this fault as a high Automotive Safety Integrity Level (ASIL D) fault, requiring immediate resolution.
Causes
— Wiring harness wear under the front passenger seat or inside the B-pillar trim panel: Seat fore-and-aft adjustment or passenger foot movement damages the harness insulation, causing a short circuit to body power wires (such as the seat heater wire or constant power supply wire).— Airbag connector (yellow dedicated plug) water ingress or corrosion: Vehicle wading, a blocked sunroof drain hose, or improper interior cleaning causes liquid to seep into the connector under the front passenger seat, resulting in electrolytic corrosion and a short circuit between the terminals.— SRS control module (ACU) internal power drive transistor breakdown: Hardware failure in the ECU internal ignition drive circuit causes the output terminal to continuously output a high-level voltage.+2 more →
Actions
— Safety preparation: Turn off the ignition switch, disconnect the low-voltage battery negative terminal, wait at least 90 seconds (120 seconds for some models) to fully discharge the SRS capacitor, and wear an anti-static wrist strap.— Fault Confirmation: Connect the BYD VDS or Launch X-431 diagnostic tool, read the fault code, and record the freeze frame data. Confirm B163212 is a current fault (Active) and not a history fault (History).+7 more →
B163A-00›
DTC B163A-00 indicates the SRS (Supplemental Restraint System) ECU detects 0Ω resistance in the right front seat side airbag circuit, technically defined as a short circuit. Normal airbag inflator resistance ranges from 1.5-3.5Ω (typically 2.0±0.5Ω). A 0Ω reading indicates a short to ground, a short to power, or an internal short within the airbag assembly. This fault prevents the side airbag from deploying during a collision or, in extreme cases, causes accidental deployment due to wiring interference. The seat houses the side airbag and undergoes frequent fore-aft and angle adjustments. This movement subjects the wiring harness between the seat and floor to long-term bending, making it a common failure point.
Causes
— Long-term bending and wear of the yellow SRS wiring harness under the seat damages the insulation, causing a short to ground or short to power. This is the most common cause.— Bent, backed out, or corroded internal pins, or water ingress in the right front seat side airbag connector (usually located under or beside the seat), causing a short circuit.— Internal short circuit in the side airbag assembly (gas generator) (low probability, but possible).+2 more →
Actions
— Safety preparation: Turn off the vehicle, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Remove the right front seat (if necessary). Carefully inspect the dedicated yellow SRS wiring harness under the seat and at the rails for wear, damaged insulation, or crush marks. Focus on friction points between the harness and the seat frame.+6 more →
B163A›
This fault code indicates the Supplemental Restraint System (SRS) detects a 0Ω resistance in the front passenger side airbag firing circuit (typically located in the seat side or B-pillar/curtain). Normal airbag igniter resistance is 1.6-2.4Ω. A 0Ω resistance indicates a low-impedance short circuit. Possible causes include a wiring harness short to ground, shorted connector pins, an internal short in the airbag inflator (igniter), or a faulty internal monitoring circuit in the SRS control unit (ACU). The ECU disables this airbag circuit to prevent accidental deployment. The airbag will fail to deploy during a side impact, severely compromising occupant protection. Some early repair data or specific vehicle models define B163A as an anti-theft system communication fault. Always reference the current vehicle repair manual for actual diagnosis.
Causes
— Front passenger side airbag wiring harness wear or damaged insulation causing a short to ground (commonly at the seat slide rail, B-pillar trim panel, or floor harness pass-through)— Water ingress, oxidation, or bent and touching pins in the under-seat airbag connector (usually located on the inboard side of the seat track or at the seat base), causing a short circuit.— Internal short circuit in the airbag gas generator (igniter) causing resistance to drop abnormally to 0 Ω (replace airbag assembly).+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment and personal injury.— Fault confirmation: Connect the VDS or X431 diagnostic tool to read the DTC. Verify B163A is a Current fault, not a History fault. Record the environmental conditions from the freeze frame data.+7 more →
B163A1A›
This fault code indicates the front passenger side airbag igniter circuit resistance measures 0 ohms, indicating a Short to Ground fault. Normal airbag igniter resistance in the SRS (Supplemental Restraint System) is typically 1.5-3.0 Ω. A 0 ohm reading indicates a direct ground path in the circuit. Damaged wiring harness insulation contacting ground, shorted connector terminals, or an internal short circuit in the airbag module igniter can cause this condition. This fault triggers the SRS control unit fail-safe mode, illuminates the airbag warning light, and can prevent the passenger side airbag from deploying during a collision, severely compromising occupant side impact protection. BYD E2/E3 and similar models use seat-integrated side airbags; frequent seat adjustment easily causes wiring harness fatigue damage.
Causes
— Front passenger seat side airbag wiring harness worn and short-circuited (seat rail pinching or long-term fatigue damages the insulation, causing a short to ground).— Short circuit at the yellow SRS connector under the seat due to water ingress, corrosion, or poor terminal contact (common after vehicle wading or improper interior cleaning)— Side airbag module (gas generator) internal igniter short circuit failure (manufacturing defect or aging)+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000/VDS2100) to read all DTCs and freeze frame data. Confirm B163A1A is currently present as a static fault and record the environmental data at the time of the fault.— Disconnect the 12V battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor. Never measure the airbag circuit directly while powered on.+6 more →
B163B-00›
DTC B163B-00 indicates the SRS (Supplemental Restraint System) ECU detects front passenger side airbag (typically seat side or curtain airbag) igniter circuit resistance below the calibrated threshold (normal range approximately 1.5-3.0 Ω; detected resistance <1.0 Ω or approaching 0 Ω). This fault indicates a short circuit risk in the airbag igniter circuit, which can cause: 1) Airbag deployment failure during a collision, resulting in loss of occupant protection; 2) Unintended airbag deployment due to the short circuit in extreme cases. The SRS enters fail-safe mode, illuminates the airbag warning light, and may disable the seat belt pretensioner function on some models.
Causes
— Airbag igniter internal short circuit: Damaged heating wire insulation inside the airbag module shorts the positive and negative terminals, dropping resistance to near 0 Ω.— Wiring harness wear and short circuit: Repeated bending of the front passenger seat side airbag wiring harness at the seat adjustment slide rail damages the insulation, causing a short circuit between wires.— Connector water ingress and corrosion: Poor sealing of the airbag connector under the seat or lower B-pillar allows water ingress after driving through water, causing a short circuit between pins.+2 more →
Actions
— Safety preparation: Disconnect the low-voltage battery negative terminal, remove the high-voltage service disconnect switch (if applicable), and wait at least 90 seconds to ensure the SRS capacitor discharges completely. Do not directly measure the airbag igniter using a multimeter ohm setting.— Visual inspection: Inspect the front passenger seat side airbag and B-pillar curtain airbag for damage. Check the yellow SRS connector under the seat for water ingress, corrosion, or looseness. Inspect the wiring harness at the seat slide rail for wear.+5 more →
B163B›
This DTC indicates a Parking Assist System (PAS/PSD) fault. Specifically, the Left Rear Ultrasonic Sensor detects an abnormally low resistance signal (typically <0.8kΩ or a short to ground). Normal ultrasonic sensor operating resistance ranges from 9-11kΩ. The sensor transmits and receives 40kHz ultrasonic signals to detect the distance to rear obstacles. The system sets this DTC when the sensor’s internal piezoelectric ceramic element shorts, wiring harness insulation chafes and grounds, connector water ingress shorts the signal wire to ground, or an incorrect sensor installation gap causes continuous false triggering. This fault prevents obstacle detection in the vehicle’s left rear blind spot, causes missing or false reversing sensor warning tones, and severely compromises parking safety. This DTC relates exclusively to the Parking Assist System, not the "front passenger side airbag" described in the original data. Airbag resistance faults typically trigger other codes (such as the B163C series).
Causes
— Left rear radar sensor damaged: Internal piezoelectric ceramic element cracking, aging, or seal failure causes a short circuit, dropping resistance to an extremely low level.— Wiring harness and connector fault: Pinched or chafed wiring harness inside the bumper causing a short to ground; or aged connector seal allowing water ingress and oxidized pins causing an abnormal signal.— Incorrect installation gap: Bumper modification, repair, or deformation causes the gap between the sensor and bumper surface to be too large (>2mm) or too small (<0.3mm). This affects ultrasonic transmission and triggers an impedance detection fault.+2 more →
Actions
— Diagnostic scan: Use VDS or Launch X-431 to read the fault code. Confirm whether B163B is a current (Active) or history (History) code. Check for accompanying sub-codes (e.g., B163B-11 short to ground, B163B-13 open circuit). Record freeze frame data.— Visual inspection: Check the left rear bumper radar sensor for cracks, dents, or contamination. Clean the sensor surface and confirm the sensor is flush with the bumper surface (tolerance <0.5mm).+5 more →
B163B1A›
DTC B163B1A indicates the squib circuit resistance of the front passenger side airbag (typically mounted on the outboard side of the front passenger seat or inside the right front door trim panel) falls below the minimum threshold set by the SRS control module (ACM) (typically below 1.0-1.5 Ω; normal range is 2.0-3.0 Ω). This condition indicates a partial or complete short in the squib circuit. Damaged wiring, water ingress at the connector, or an internal airbag fault can cause this issue. This fault triggers the safety protection mechanism. The SRS system disables the airbag circuit to prevent unintended deployment and illuminates the airbag warning light on the instrument cluster. During a side impact, this airbag may fail to deploy normally, severely compromising occupant safety.
Causes
— Airbag igniter internal short circuit: Aging, moisture ingress, overheating, or manufacturing defects cause an inter-turn short circuit in the front passenger side airbag igniter coil, resulting in abnormally low resistance.— Short circuit within the wiring harness: Wear, crushing, overly tight retaining clips, or animal damage caused a short circuit between the positive and negative wires of the 2-core harness connecting the airbag and ACM (routed through the right front door hinge or seat rail).— Connector water ingress or corrosion: Poor sealing of the right front door wiring harness connector (inside the rubber boot at the door hinge) or the airbag connector under the seat allows water entry after wading or washing the vehicle, causing a short circuit between pins or electrolytic conduction.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes to discharge the SRS capacitor to prevent accidental airbag deployment. Wear an anti-static wrist strap.— Fault code confirmation: Connect the diagnostic tool. Read and record the DTCs. Confirm B163B1A is a Current DTC, not a historical fault. Check the data stream to verify the airbag resistance value is <1.0Ω.+5 more →
B163C-00›
This DTC indicates the airbag control unit (SRS ECU) detects the resistance of the front passenger side airbag (typically the seat side airbag or door side airbag) ignition circuit exceeds the calibrated threshold (normal value typically 2.0-3.0Ω, fault threshold typically >4.0Ω). This indicates a high-resistance condition in the ignition circuit, classified as a soft fault (precursor to an intermittent open circuit). Poor connector contact, a partially broken wiring harness, increased contact resistance in the clock spring (spiral cable), or aging of the internal resistance wire in the airbag module can cause this condition. This fault causes the SRS system to mark the airbag as unreliable. During a collision, the airbag may fail to deploy normally or experience a deployment delay. The system illuminates the airbag warning lamp and disables the airbag function, severely compromising passive safety performance.
Causes
— Oxidation, loose connection, or water ingress at the airbag connector (yellow plug) under the front passenger seat, causing increased contact resistance (common after vehicle water wading or prolonged exposure to damp environments).— Wear, poor contact, or partial open circuit of the internal slip ring in the spiral cable (clock spring), causing unstable signal transmission resistance.— Aging, cold solder joint, or partial breakage of the internal igniter resistance wire in the side airbag module, resulting in increased internal resistance.+2 more →
Actions
— Safety Preparation: Disconnect the battery negative terminal and wait at least 3 minutes to fully discharge the SRS system and prevent accidental airbag deployment.— Data Reading: Use the BYD VDS2000/VDS2100 diagnostic tool to read the detailed data stream. Record the current resistance value, the ambient temperature during the historical fault, and the vehicle status.+6 more →
B163C›
Fault code B163C has different definitions across BYD vehicle platforms. On early e-Platform 2.0 models (e.g., Yuan 2019, Song MAX 2019, Qin 2020), this fault code indicates excessive resistance in the front passenger side airbag. The SRS system detects that the right-hand Seat Side Airbag ignition circuit resistance exceeds the calibrated threshold (normal range: 2.0–3.0 Ω; fault threshold: >4.5 Ω). This condition can prevent proper airbag deployment during a collision. On newer e-Platform 3.0 and DM-i models (e.g., Han EV, Tang DM-i, Seal, Qin Plus), the ADAS system defines B163C as a Front Millimeter Wave Radar sensor signal fault or communication interruption. This fault indicates abnormal communication between the radar and the ADAS controller (ACC/ESP module) exceeding the specified time (usually >100 ms), or a radar self-check detecting an internal hardware fault (e.g., RF front-end anomaly or signal processing unit fault). This disables functions including Adaptive Cruise Control (ACC), Automatic Emergency Braking (AEB), and Intelligent Cruise Control (ICC). Poor wiring harness connections, airbag unit aging, or connector oxidation typically cause excessive resistance in the airbag system. Physical damage, water ingress, or incorrect installation angles typically cause radar system faults.
Causes
— Front millimetre-wave radar sensor assembly damaged: Front bumper impact, stone strikes during high-speed driving, water ingress from high-pressure car washing, or long-term vibration causing internal circuit board corrosion or RF module failure.— Radar mounting misalignment: Failure to tighten the radar to the standard torque (typically 8-10 Nm) during reinstallation after front bumper repairs (painting, sheet metal repair), causing the horizontal or pitch angle to deviate beyond the allowable ±3° range.— Wiring harness and connector faults: backed-out radar plug terminals, oxidized pins, seal failure causing rainwater ingress (common after car washes or heavy rain), poor CAN-H/CAN-L connections, or abnormal resistance.+2 more →
Actions
— Initial inspection: Visually inspect the front bumper area for signs of impact, radar mounting bracket deformation, and scratches or contaminants on the radar surface. Check the vehicle for recent front-end repairs or high-pressure washing history.— Diagnostic tool check: Use the BYD dedicated diagnostic tool (VDS2000/3000) to read the fault code status and confirm if B163C is a current fault (Current). View the Freeze Frame data to check the vehicle speed and ambient conditions when the fault occurred. Access the ADAS system to read the data stream. Check the radar communication status, supply voltage, and horizontal/vertical angle data.+5 more →
B163C1B›
DTC B163C1B indicates the front passenger side airbag igniter circuit resistance exceeds the normal threshold (typically 2.0–3.0 Ω). The system triggers this fault upon detecting resistance > 6 Ω or an open circuit. This fault falls under the SRS (Supplemental Restraint System) passive safety category, specifically indicating a high-resistance fault in the front passenger seat-mounted side airbag or curtain airbag electrical circuit. High resistance indicates poor circuit contact, a broken wiring harness, an oxidized connector, or an open airbag igniter. This condition may prevent proper airbag deployment during a collision, constituting a safety-related functional fault.
Causes
— Loose or oxidized airbag wiring harness connector under the front passenger seat: Qin PRO series seats feature electric adjustment. Frequent fore-and-aft movement causes the yellow airbag connector under the seat (usually located on the inner side of the seat rail) to loosen, terminals to back out, or pins to oxidize, increasing contact resistance.— Clock spring (spiral cable) internal open circuit: Although the clock spring under the steering wheel primarily connects the driver-side airbag, some models route the passenger-side airbag signal through it. Fatigue fracture of the internal flat cable causes abnormal circuit resistance.— Airbag igniter internal open circuit: The internal igniter resistance wire in the front passenger side airbag module (integrated into the side of the seat backrest) broke due to aging, or poor welding in the production batch caused resistance drift.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes to discharge residual charge from the system capacitors. Use a multimeter to confirm the SRS system voltage is 0V. Wear an anti-static wrist strap.— Read data stream: Access the SRS system using the BYD VDS2000/VDS3000 diagnostic tool. Read the B163C1B freeze frame data, check the current resistance value (typically >10Ω or displaying 'open circuit'), and verify the fault status (current/history).+4 more →
B1640-00›
This DTC indicates the Airbag Control Unit (ACU) detects an open circuit or abnormal resistance in the driver-side seat belt pretensioner circuit. The pretensioner contains a squib and a resistance wire; normal resistance typically measures 2.0-3.0Ω. The ACU triggers B1640-00 when it detects infinite resistance (open circuit) in the pretensioner circuit or when the resistance remains outside the threshold range for a specified time. During a collision, this fault may prevent the driver-side seat belt pretensioner from deploying and tightening, severely compromising occupant restraint protection. The fault also forces the SRS system into a degraded protection mode and continuously illuminates the airbag warning light.
Causes
— Dedicated yellow airbag connector under the seat (usually located on the inboard side of the seat track) is loose, oxidized, or has recessed pins, causing poor contact or an open circuit.— Open circuit inside the seat belt pretensioner unit, mostly due to an open igniter circuit or burnt internal coil. Common causes include vehicle water ingress, failure to replace a deployed pretensioner, or end of service life.— Broken pretensioner wiring harness wire in the transition area between the seat frame and the body (inside the seat outer trim panel or floor harness corrugated conduit) due to long-term bending and wear.+2 more →
Actions
— Safe power-down: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS system capacitors and prevent accidental airbag deployment during repair.— Visual inspection: Verify the yellow dedicated connector under the driver's seat (marked AIRBAG or SRS) is fully locked. Inspect the inside of the connector for water stains, green copper corrosion, backed-out pins, or deformed pins.+4 more →
B1640›
DTC B1640 indicates the SRS (Supplemental Restraint System) ECU detects an open circuit or out-of-range resistance in the driver-side seat belt pretensioner circuit (normal resistance is typically 2.0–3.0 Ω). The pretensioner is a key component of the passive safety system. During a collision, it ignites a pyrotechnic charge to generate gas, pulling the seat belt retractor and instantly tightening the seat belt to secure the occupant. This fault indicates the driver-side pretensioner may fail to deploy during a collision, increasing occupant forward displacement and injury risk. The SRS ECU also illuminates the instrument cluster airbag warning light. The system may enter a fail-safe mode, restricting certain airbag functions.
Causes
— The pretensioner wiring harness connector (yellow connector) under the driver's seat is loose, has a backed-out pin, or has poor contact. This usually results from wear during fore/aft seat movement or failing to fully seat the connector after removing the seat.— Seat belt pretensioner internal resistance wire open circuit or resistance drift beyond tolerance (>5Ω or <1Ω). Common causes include pretensioner aging, moisture ingress, or internal pyrotechnic charge deterioration.— Oxidized or corroded pins, or broken wires at the seat wiring harness to body floor wiring harness connector (usually located on the inner side of the seat slide rail), commonly resulting from vehicle wading or prolonged use in damp environments.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000/VDS3000) to read the fault code. Confirm B1640 is a current fault (Active), not a historical fault. Record the ambient temperature and vehicle status from the freeze frame data.— Disconnect the negative battery terminal. Wait at least 3 minutes for the SRS system capacitor to fully discharge. Remove the driver's seat (retain the 4 bolts for easier handling). Visually inspect the yellow pretensioner connector under the seat to confirm it is fully inserted and locked. Verify the connector waterproof seal is intact.+4 more →
B16401B›
DTC B16401B indicates the Airbag Control Unit (ACU) detects the driver-side seat belt pretensioner circuit resistance falls outside the normal range (typically 2.0-3.0 Ω), indicating an open circuit or disconnected state. This active SRS fault means the driver-side seat belt pretensioner may fail to ignite and retract during a collision, increasing seat belt slack and reducing occupant restraint protection. The '1B' fault code suffix typically represents a specific subtype high-byte/low-byte coding, specifically denoting an open circuit or high-resistance fault. This fault illuminates the airbag warning light continuously. Some models may sound a warning buzzer and force the airbag system into a degraded protection mode, allowing only partial airbag deployment.
Causes
— Loose or poor contact at the under-seat pretensioner wiring harness connector: Frequent seat adjustments and vibration may loosen the yellow pretensioner connector near the seat rail (usually located on the inner side or underside of the seat), or pin oxidation may increase contact resistance.— Seat belt pretensioner internal open circuit: Moisture in the pretensioner gas generant, an aging and broken igniter tube, or an open internal bridge wire breaks the circuit.— Seat wiring harness worn and broken: As the seat slides forward and backward, the pretensioner wiring harness (especially sections routed through the seat rails or under the carpet) bends repeatedly over time, causing fatigue fractures in the internal copper wires while the outer insulation remains intact.+2 more →
Actions
— Safety preparation: Switch the vehicle OFF, disconnect the low-voltage battery negative terminal, and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Remove the driver's seat (or lift only the front of the seat) and verify the yellow pretensioner connector under the seat (usually marked 'SBT' or 'D-PRET') is fully connected. Inspect the connector latch for breakage and the pins for oxidation or backing out.+6 more →
B2AB0-49›
DTC B2AB0-49 indicates an abnormality in the electric A/C compressor current sampling circuit. In electric compressors driven by a three-phase permanent magnet synchronous motor (PMSM), the controller (MCU) monitors the motor phase currents (U/V/W phases) in real time via a Hall effect sensor or precision shunt resistor for field-oriented control (FOC) and overcurrent protection. This fault indicates the sampling signal exceeds the valid threshold (open circuit, short circuit, or short to power/ground). Consequently, the compressor controller cannot accurately read the motor current value and triggers a protection mechanism to stop the compressor, impairing A/C cooling and battery thermal management functions. This is a hardware-level circuit fault, not a software logic error.
Causes
— Damaged or aged internal Hall current sensor in the electric compressor causes output signal drift or interruption.— The current sensing resistor (typically a milliohm precision resistor) on the compressor controller board (PCB) is burnt or has a cold solder joint.— Poor contact, backed-out terminals, or corrosion from water ingress in the low-voltage signal wiring harness causes abnormal transmission of the 5V reference voltage or sampled signal.+2 more →
Actions
— Use the VDS2000/VDS3000 diagnostic tool to read all fault codes, check for accompanying faults such as B2AB049 and B2AC000, and record the freeze frame data.— Inspect the electric compressor low-voltage connector (usually located on the top or side of the compressor, 4-5 pins) for looseness, water ingress, or pin oxidation. Measure the connector terminal voltages to verify normal power (+12V/+5V), ground (GND), and CAN line (approximately 2.5V) values.+4 more →
B1641-00›
DTC B1641-00 indicates an abnormal short to body ground in the driver-side seat belt pretensioner igniter circuit. In the BYD SRS (Supplemental Restraint System) architecture, a low-impedance igniter (normal resistance 2.1–3.0 Ω) triggers the pretensioner. When the ECU detects circuit resistance below the threshold (typically <0.8 Ω), it determines a short to ground. This fault causes the following: 1) The SRS system enters fail-safe mode, disabling the driver-side airbag and pretensioner functions; 2) The pretensioner may fail to deploy during a collision, causing occupant restraint failure; 3) Continuous short-circuit current risks unintended pretensioner deployment or SRS ECU driver circuit burnout. This DTC is a hard fault requiring physical repair before clearing.
Causes
— Worn wiring harness insulation under the seat rail: Frequent forward and backward movement of the driver seat causes the pretensioner wiring harness (usually located near the left seat rail) to rub against the metal bracket. Damaged insulation allows the copper core to contact the chassis ground.— Pretensioner connector water ingress and oxidation: When driving through water or cleaning the interior, poor sealing of the pretensioner connector (usually a yellow plug) located below the B-pillar or under the seat causes an electrolytic conductive path to form between the terminals.— Internal short circuit in the pretensioner unit: Moisture in the gas generator igniter propellant or a manufacturing defect causes igniter coil insulation failure, resulting in a short circuit to the metal housing.+2 more →
Actions
— Safety preparation: Switch the vehicle to OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation: Use the VDS2000 or Launch PAD5 diagnostic tool to read all DTCs, check for accompanying fault codes (such as B1642 passenger side short circuit), and record the ambient temperature and vehicle status from the freeze frame data.+6 more →
B1641›
DTC B1641 indicates an abnormally low-resistance path to body ground (short circuit) in the driver-side seat belt pretensioner ignition circuit. In the BYD SRS (Supplemental Restraint System) architecture, the pretensioner is a pyrotechnic safety device with a normal squib resistance of approximately 2.0-3.0 Ω. The SRS control unit triggers this DTC when it detects the circuit resistance to ground falls below the threshold (typically <1.0 Ω). This fault forces the SRS into fail-safe mode: the airbag warning lamp remains illuminated, and the fault may completely disable the system. During a collision, the pretensioner fails to deploy and retract the seat belt, severely threatening occupant safety. Furthermore, a continuous short to ground can overheat and damage the internal driver circuit of the SRS control unit, expanding the repair scope.
Causes
— Worn insulation on the pretensioner wiring harness under the driver's seat contacts the metal seat frame or seat rail, causing a short to ground. This commonly occurs in vehicles with frequent seat adjustments or detached wiring harness retaining clips.— Water ingress, pin corrosion, or bent pins in the yellow SRS connector under the seat (usually located on the inner side of the seat rail) cause a short circuit between the signal wire and ground wire. This typically occurs after wading or deep interior cleaning.— Manufacturing defects or aging in the seat belt pretensioner internal igniter cause an internal short to ground. This commonly occurs in aftermarket parts installed after accident repairs or components aged by prolonged high-temperature environments.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental deployment. Before disconnecting, record radio presets and one-touch window up/down positions.— Fault Confirmation: Connect the VDS or dedicated diagnostic tool, verify DTC B1641 is Active, and record the ambient temperature and operating voltage from the Freeze Frame data.+7 more →
B164111›
This DTC indicates the driver-side seat belt pretensioner ignition circuit shorts to body ground (GND). The BYD SRS (Supplemental Restraint System) pretensioner typically uses a pyrotechnic or motor-driven design with an operating resistance of approximately 2.0–3.0 Ω. When the ACU (Airbag Control Unit) detects the insulation resistance between the driver pretensioner circuit and ground drops below the threshold (typically <100 Ω), it logs a short to ground. This fault triggers the SRS fail-safe mode: the airbag warning light remains illuminated, the affected pretensioner may fail to deploy during a collision, and the system may stop monitoring other restraint devices, posing a severe safety hazard. The short circuit may occur at the pretensioner itself, the under-seat wiring harness, the floor wiring harness, or the ACU connector.
Causes
— Harness under seat worn: During driver seat fore/aft adjustment, the pretensioner harness rubs against the seat track or floor metal edge over time, damaging the insulation and shorting the copper core to body ground.— Connector water ingress and corrosion: Vehicle wading, a blocked sunroof drain tube, or water entering the B-pillar/under-seat area during washing causes oxidation of the pretensioner connector terminals (typically located under the seat or inside the B-pillar trim). A conductive water film or verdigris forms between the pins, causing a short to ground.— Pretensioner internal fault: Aged and cracked internal squib insulation, or poor internal coil insulation during manufacturing, causes a short circuit between the two terminals.+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 90 seconds for the SRS capacitor to discharge. Ensure the high-voltage system is in a safe state (applicable to hybrid/pure electric vehicles).— Initial inspection: Visually inspect the pretensioner connectors (usually yellow plugs) under the driver's seat and inside the lower B-pillar trim panel for signs of water ingress, corrosion, looseness, or physical damage.+6 more →
B1642-00›
DTC B1642-00 indicates the driver-side seat belt pretensioner ignition circuit shorts to the vehicle power supply (B+). In the BYD SRS (Supplemental Restraint System) architecture, the pretensioner operates as a pyrotechnic actuator. Normally, both terminals exhibit a high-resistance state (open circuit) to power and ground. This fault indicates a wire in the pretensioner harness or connector shorts to constant power. This condition can cause: 1) the SRS ECU to detect abnormal voltage, illuminate the airbag warning lamp, and disable the airbag system; 2) the pretensioner to deploy accidentally in extreme cases; 3) the pretensioner to fail during a collision, endangering occupant safety. This fault involves the dedicated yellow SRS harness under the driver's seat, an area prone to mechanical wear from fore-aft seat movement.
Causes
— Worn SRS wiring harness under the driver's seat rail: Frequent fore-and-aft seat adjustment causes the seat rail edge to cut the harness insulation, shorting the harness to body power wires (such as the seat heating power supply wire or constant power memory wire).— Floor harness connector water ingress: Liquid enters the driver's footwell during wading or cleaning, causing an electrolytic short circuit between the pretensioner connector pins (usually located under the seat or B-pillar), especially when foreign material bridges the pins.— SRS ECU internal drive circuit fault: Airbag control module internal ignition drive transistor breakdown causes the pretensioner port to continuously output supply voltage.+2 more →
Actions
— Safety preparation: Turn off the ignition, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Remove the driver's seat (leave the wiring harness connected), inspect the yellow SRS wiring harness sleeve under the seat rail for wear, and check the connector under the seat (usually marked DAB or Pretensioner) for water ingress, corrosion, or bent pins.+4 more →
B1642›
DTC B1642 indicates a short to power (+B) in the driver seat belt pretensioner ignition circuit. The pretensioner is a key actuator in the SRS safety system containing a pyrotechnic igniter and a gas generator. Normal static resistance is approximately 1.5-3.0Ω. The SRS ECU sets this fault code upon detecting abnormal continuity between the pretensioner circuit and the vehicle power supply (12V constant power or IGN power). This fault presents two risks: first, it can cause the pretensioner to deploy and tighten unexpectedly while driving, startling or injuring the driver; second, during an actual collision, the power supply clamps the circuit, preventing the pretensioner from receiving sufficient ignition current and neutralizing its protective function. Additionally, this fault forces the SRS system into fail-safe mode, potentially disabling the entire airbag system.
Causes
— Worn wiring harness under the driver's seat: Forward and backward seat movement causes the pretensioner wiring harness to rub against the seat track or frame. This prolonged friction damages the insulation, causing the internal copper wire to contact and short-circuit to a power wire (such as the seat heater or seat power wire).— Floor wiring harness interference: A detached vehicle floor wiring harness retaining clip causes the pretensioner wiring harness and the main wiring harness power wire to chafe and short-circuit due to vehicle vibration.— Internal connector short circuit: Water ingress, corrosion, or bent pins in the pretensioner connector (usually yellow) under the driver's seat or lower B-pillar bridge the power and signal pins.+2 more →
Actions
— Safety preparation: Switch off the vehicle, disconnect the negative battery cable, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Move the driver seat to the fully forward and fully rearward positions. Inspect the pretensioner wiring harness (yellow corrugated conduit) under the seat, inside the B-pillar trim panel, and under the floor carpet for wear, cuts, or burn marks. Check the connector for looseness or water ingress.+4 more →
B164212›
This DTC indicates an abnormal electrical connection between the driver-side seat belt pretensioner squib circuit and vehicle power positive (B+), causing the SRS control unit to detect a continuous high voltage (near 12V) across the pretensioner terminals. As a key actuator in the passive safety system, the pretensioner has a normal operating resistance of 2.0-3.0 ohms. The SRS ECU supplies a momentary deployment current only upon receiving a collision signal. A short to power causes the SRS ECU to immediately enter fault protection mode and disable all airbag deployment functions. During a collision, the pretensioner fails to deploy and tighten the seat belt. In extreme cases, the short circuit may trigger unintended pretensioner activation, severely threatening occupant safety. This is a hard fault; once confirmed, it typically does not self-recover.
Causes
— Mechanical wear of under-seat wiring harness: Long-term movement of the driver's seat fore-and-aft adjustment mechanism rubs the pretensioner wiring harness against the seat rail and metal bracket. Damaged insulation allows the core wire to contact the power wire, causing a short circuit.— Connector water ingress or corrosion: Vehicle wading, interior cleaning, or a sunroof leak allows liquid to enter the under-seat pretensioner connector (such as the KJG series plug). Terminal oxidation produces conductive material, causing a short circuit between adjacent pins.— Pretensioner internal squib fault: Damaged insulation on the internal initiator or bridge wire shorts the internal coil to the housing or power terminal, usually accompanied by abnormal resistance.+2 more →
Actions
— Safety Preparation: Turn the ignition switch to OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds (3 minutes for some models) to fully discharge the SRS energy storage capacitor and prevent accidental airbag deployment.— DTC confirmation and freeze frame analysis: Connect the diagnostic tool to read the complete fault codes and freeze frame data. Record the vehicle status when the fault occurred (such as seat position and ambient temperature). Confirm whether it is a current fault (Current Code).+6 more →
B1645›
DTC B1645 indicates the driver-side seat belt pretensioner squib circuit resistance measures 0 Ω or close to 0 Ω, confirming a short circuit. The pretensioner is a critical SRS (Supplemental Restraint System) component. During a collision, it fires the squib to rapidly tighten the seat belt and secure the occupant in the seat. A 0 Ω resistance typically indicates an internal short circuit in the pretensioner squib, a wiring harness short to ground, bridged connector terminals, or a faulty internal driver circuit in the SRS control module. This fault forces the SRS into fail-safe mode and continuously illuminates the instrument panel airbag warning light. In a collision, the affected pretensioner will fail to deploy. This condition may also disrupt normal airbag deployment logic, creating a severe safety hazard.
Causes
— Pretensioner squib internal short circuit: Moisture ingress, aging, or manufacturing defects caused an internal bridge wire short circuit in the seat belt retractor pretensioner.— Harness short to ground: Floor harness chafes and wears through the insulation near the seat slide rail, causing the pretensioner power wire or signal wire to short to body ground.— Connector fault: Water ingress, terminal corrosion, or short circuit between terminals at the yellow SRS connector under the seat (usually located at the B-pillar or seat base), or incorrect connection during repairs causing terminal bridging.+2 more →
Actions
— Safety Preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (or the time specified in the workshop manual) to fully discharge the SRS backup capacitor and prevent accidental airbag deployment. Wear an anti-static wrist strap and disable the vehicle high-voltage system (for new energy vehicles).— Preliminary inspection: Visually check the instrument panel airbag warning light status. Use a diagnostic tool to read and record the complete fault codes, and confirm B1645 is a current fault (not a history fault). Check the yellow SRS connectors under the driver's seat and at the B-pillar for looseness, water ingress, corrosion, or foreign matter.+5 more →
B1645-00›
This DTC indicates the SRS control module detects the driver-side seat belt pretensioner squib circuit resistance at or near 0 ohms, indicating a short circuit. As a key actuator in the passive safety system, the pretensioner ignites the squib during a collision to generate gas and tighten the seat belt, eliminating slack between the occupant and the belt. A 0-ohm resistance indicates an internal short circuit in the squib, a short to ground in the wiring harness, or a fault in the internal driver circuit of the SRS module. This fault causes the SRS system to enter degraded mode. The driver-side airbag may fail to deploy properly, and the airbag warning lamp illuminates. On some BYD new energy models, similar DTCs may relate to the high-voltage system (such as the traction battery charging circuit). However, the official repair manual explicitly assigns B1645-00 to the SRS restraint system.
Causes
— Driver seat belt pretensioner squib internal short circuit (blown internal bridge wire or damp propellant causing continuity)— Pretensioner wiring harness worn or crushed, causing a short to body ground (commonly near the seat rail or inside the B-pillar trim).— SRS control module internal igniter driver circuit fault (MOSFET breakdown or filter capacitor short circuit)+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation: Use VDS or a dedicated diagnostic tool to read complete DTCs, check for accompanying fault codes (such as B1644-00 Driver Pretensioner Resistance Too High), and record freeze frame data.+5 more →
B1646-00›
DTC B1646-00 indicates the driver-side seat belt pretensioner circuit resistance is below the standard threshold set by the SRS control unit (typically 2.0Ω±0.1Ω). The pretensioner is a pyrotechnic actuator containing an igniter pellet and a heating wire; normal resistance is 1.5-3.0Ω. Low resistance typically indicates a short circuit (such as a short to ground, a wire-to-wire short, or an internal pretensioner short), reducing current path resistance. This fault forces the SRS system into a degraded mode. During a collision, the system may fail to deploy the driver-side pretensioner or, in extreme cases, cause unintended deployment, severely compromising passive safety system functionality.
Causes
— Water ingress or moisture in the pretensioner connector: Water accumulation on the driver's side floor from wading, car wash fluid intrusion, or an air conditioning condensate leak causes a short circuit between connector terminals, reducing circuit resistance.— Harness insulation damaged and shorted to ground: Frequent fore-and-aft seat adjustment causes the pretensioner harness (usually routed along the seat rail) to rub against the metal bracket. This damages the insulation and shorts the wire to the vehicle body ground.— Connector terminal deformation or oxidation: Loose plugs, bent pins, or electrolytic corrosion cause abnormal continuity between terminals, creating a parallel resistance path.+2 more →
Actions
— Safe power-off procedure: Turn off the ignition switch, disconnect the battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Locate the pretensioner assembly: Remove the driver's seat (the Qin series usually requires removing 4 retaining bolts), then find the yellow pretensioner connector under the seat (usually a 2-pin connector marked SRS).+5 more →
B1646›
DTC B1646 indicates the SRS (Supplemental Restraint System) detects driver-side seat belt pretensioner circuit resistance below the calibrated threshold (typically <1.0Ω or near a short circuit). The pretensioner contains an internal squib with a normal resistance between 1.5 and 3.0Ω (depending on specific vehicle calibration). Low resistance indicates a short circuit risk. Potential causes include an inter-turn short within the pretensioner igniter, a wiring harness short to ground, or abnormal connector continuity. The SRS control unit classifies this fault as a high-risk condition, illuminates the airbag warning lamp, and may trigger the system self-protection mechanism (disabling the driver-side airbag and pretensioner). This prevents the seat belt from retracting properly during a collision, severely compromising passive safety functions.
Causes
— Pretensioner internal igniter short circuit: Moisture, aging, or manufacturing defects damage the insulation layer of the igniter resistance wire inside the seat belt retractor, causing an internal short circuit.— Worn under-seat wiring harness: Frequent fore-and-aft adjustment of the driver's seat wears through the pretensioner wiring harness insulation (usually located under the seat or at the base of the B-pillar), causing contact with vehicle body metal and creating a short to ground.— Connector water ingress or corrosion: Vehicle wading, car wash fluid seepage, or electrolytic corrosion creates continuity between the internal terminals of the yellow SRS connector (with shorting bar), causing abnormally low resistance.+2 more →
Actions
— Safety preparation: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault code analysis: Connect the BYD VDS or dedicated diagnostic tool. Read the B1646 freeze frame data and record the resistance value when the fault occurred (e.g., 0.3Ω, 0.8Ω) to distinguish between a hard fault and an intermittent fault.+8 more →
B16461A›
This DTC indicates the measured resistance of the driver-side seat belt pretensioner ignition circuit falls below the SRS control module threshold (typically <1.0Ω). The seat belt pretensioner is a pyrotechnic actuator containing a resistance wire and ignition charge; normal resistance ranges from 2.0-5.0Ω. Low resistance typically indicates a circuit short to ground, a wire-to-wire short, a partial short in the pretensioner internal resistance wire, or grounded connector pins. This fault causes the SRS system to enter fail-safe mode. During a collision, the pretensioner may fail to deploy and tighten the seat belt, or in extreme cases, poses a safety risk of unintended deployment.
Causes
— The seat slide rail crushes and wears the pretensioner wiring harness (yellow harness) under the driver's seat, exposing the wire core and causing a short to ground.— Water ingress, oxidation, corrosion, or bent pins at the pretensioner connector (located at the B-pillar or under the seat) causing abnormally low resistance.— Internal resistance wire short circuit in the seat belt pretensioner assembly (due to aging, moisture ingress, collision impact, or manufacturing defects)+2 more →
Actions
— Safety preparation: Disconnect the low-voltage battery negative terminal and wait at least 90 seconds to allow the SRS capacitor to discharge fully. Wear an anti-static wrist strap. Do not use a multimeter in resistance mode to measure energized airbag components.— Initial inspection: Remove the driver-side B-pillar lower trim panel and the seat. Visually inspect the yellow dedicated wiring harness for damage, crushing, or signs of water ingress. Check specifically for interference points between the seat slide rail travel path and the wiring harness.+3 more →
B167600›
This DTC indicates the airbag control unit (SRS ECU) detects a communication loss or open circuit between the Left Rear Side Impact Sensor (typically installed on the left rear quarter panel or C-pillar area) and the main control unit. Specifically, during the ignition ON self-check or continuous monitoring while driving, the ECU detects the sensor circuit resistance exceeds the normal range (exhibiting high resistance or an open circuit) and fails to receive a valid acceleration signal. This fault causes the SRS system to disable deployment of the left side airbag and side curtain airbag. In a left-side collision, these airbags may fail to deploy, severely compromising passive safety performance. The vehicle drive system remains unaffected.
Causes
— Sensor wiring harness connector loose or poor contact (common after vehicle wading, severe vibration, or failing to fully seat the connector after repairs)— Left rear side impact sensor internal open circuit (component aging, fractured internal circuit board, or water ingress corrosion)— Wiring harness open circuit or damaged insulation (caused by long-term rubbing against the left rear door frame weatherstrip, or a detached retaining clip pulling and breaking the harness)+2 more →
Actions
— Use the BYD VDS2000 or Launch X431 diagnostic tool to read all DTCs and freeze frame data. Confirm B167600 is the current fault code and record the vehicle status at the time of the fault.— Turn off the ignition, disconnect the negative battery terminal, and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment.+7 more →
B1647-00›
This fault code indicates the airbag control unit (SRS ECU) detects the driver-side seat belt pretensioner circuit resistance exceeds the standard range (normal: 2.0-3.0Ω; high resistance generally indicates >5Ω or a near open circuit). The pretensioner contains an electrothermal igniter (squib). The ECU continuously monitors circuit resistance using a low-current signal to verify continuity. High resistance typically indicates high impedance or an open circuit. This condition may prevent the pretensioner from deploying and retracting the seat belt during a collision, severely compromising occupant protection. The SRS system enters fail-safe mode, illuminates the instrument cluster airbag warning light, and may disable the front airbags on certain models.
Causes
— Poor contact or oxidation at the pretensioner connector: Frequent vibration or damp environments cause terminal oxidation, terminal back-out, or looseness in the dedicated yellow connector located at the bottom of the B-pillar or under the seat, creating contact resistance.— Pretensioner internal open circuit: Aging, moisture ingress, or a previous abnormal voltage impact caused an internal open circuit in the pretensioner igniter (squib), resulting in infinite resistance.— Wiring harness worn or broken: Long-term seat adjustment wears the wiring harness insulation near the seat rail, or B-pillar trim panel removal and installation pinches the harness, breaking the copper core.+2 more →
Actions
— Safety Preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS backup capacitor. Wear an anti-static wrist strap. Never use a multimeter resistance setting to directly measure the pretensioner (use a dedicated diagnostic tool or high-impedance test equipment).— Visual inspection: Verify the dedicated yellow SRS connector under the B-pillar (or under the seat) is fully locked. Inspect the terminals for green oxidation or burn marks, and check the wiring harness sheath for damage.+3 more →
B1647›
DTC B1647 indicates the driver-side seat belt pretensioner circuit resistance exceeds the upper limit set by the SRS control unit (standard value typically 2.0-3.0 Ω; refer to the vehicle workshop manual). The seat belt pretensioner uses a pyrotechnic squib; its resistance reflects the electrical integrity of the firing element. High resistance indicates an additional high-impedance point in the circuit. Potential causes include an aging or broken internal pretensioner resistance wire, oxidized or corroded harness connectors, internal wire breaks, or poor contact. This fault causes the SRS system to deem the pretensioner circuit unreliable. During a collision, the pretensioner may fail to deploy, preventing the seat belt from retracting in time and severely compromising occupant protection.
Causes
— Seat belt pretensioner unit internal aging: Internal resistance wire oxidizes and breaks due to time, temperature, or manufacturing defects, gradually increasing resistance.— Poor wiring harness connector contact: Oxidation, looseness, or corrosion from water ingress increases contact resistance at the pretensioner connector below the driver-side B-pillar or under the seat.— Wiring harness mechanical damage: Frequent fore-and-aft seat adjustment or improper removal and installation of the B-pillar trim causes fatigue breakage of the internal copper strands (exterior intact but partially broken internally), resulting in high resistance.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds to ensure the SRS backup power supply fully discharges, preventing accidental airbag deployment.— Visual inspection: Remove the driver-side B-pillar lower trim panel and check the seat belt pretensioner wiring harness connector (usually located at the base of the B-pillar or under the seat) for looseness, oxidation, or signs of water ingress.+6 more →
B16471B›
DTC B16471B indicates the driver-side seatbelt pretensioner circuit resistance exceeds the normal threshold set by the SRS control module (typical normal range: 1.5-4.0 Ω; detected value is high). The pretensioner is a pyrotechnic component of the passive safety system, containing a resistance wire and an igniter charge. Excessive resistance indicates high circuit impedance resulting from poor contact, wiring harness oxidation, connector corrosion, or pretensioner aging. This fault forces the SRS system into a degraded mode and continuously illuminates the airbag warning light. During a collision, the driver-side seatbelt pretensioner may fail to deploy and retract, severely compromising occupant restraint protection.
Causes
— A loose yellow pretensioner connector under the driver's seat (usually marked D+, D-), backed-out terminals, or oxidized pins causes increased contact resistance. This is the most common cause, especially after frequent fore-and-aft seat adjustment or wading.— Internal slip ring wear in the clock spring (spiral cable) or poor contact in the ribbon cable causes unstable or excessively high resistance in the pretensioner signal circuit.— Aging, breakage, or moisture corrosion of the internal resistance wire in the seat belt pretensioner unit causes the resistance to exceed the tolerance range (typically measuring 5-10 Ω or higher).+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal. Wait at least 3 minutes for the SRS capacitor to discharge. Disable the airbag system. Wear an anti-static wrist strap.— Visual inspection: Verify the yellow SRS connector under the driver's seat is fully locked, inspect the pins for green corrosion, burn marks, or backed-out pins, and check the wiring harness at the seat slide rail for wear.+5 more →
B164A-00›
This DTC indicates the airbag control unit (SRS ECU) detects an open circuit or abnormal resistance in the front passenger seat belt pretensioner circuit. Specifically, the ECU continuously monitors the pretensioner deployment circuit resistance via an internal bridge circuit (standard range: 1.6–3.0 Ω). The ECU triggers DTC B164A-00 if it detects a resistance >6 Ω (open circuit) or <1 Ω (short circuit), or a communication interruption with the pretensioner. As an active safety device, the pretensioner uses a pyrotechnic gas generator to generate tension within approximately 15 milliseconds of a collision, instantly retracting the seat belt webbing to eliminate slack against the occupant. This fault indicates complete failure of this protective function. Per the BYD SRS safety strategy, the system may enter a degraded mode (e.g., disabling side or curtain airbags), significantly increasing the risk of injury to the front passenger during a collision.
Causes
— Loose or poor contact at the dedicated yellow SRS connector under the front passenger seat (most common; frequent forward and backward seat adjustment causes the plug to loosen or partially disconnect).— Long-term fatigue of the pretensioner wiring harness at the seat slide rail bend breaks the internal copper strands (outer insulation remains intact but the core wire breaks, creating an intermittent open circuit).— Open circuit in the seat belt pretensioner internal resistance wire (aging, moisture ingress, or previous collision impact causing an internal break in the pyrotechnic unit)+2 more →
Actions
— Safety preparation and initial diagnosis: Disconnect the negative battery terminal for 3 minutes to discharge residual system voltage. Use a dedicated BYD diagnostic tool (VDS or X-431) to read freeze frame data. Record the vehicle speed and seat position at the time of the fault. Clear the fault code and test drive the vehicle to determine if the fault is intermittent.— Visually inspect the connector: Move the front passenger seat to the rearmost position and inspect the yellow dedicated SRS connector under the seat (usually with a red locking tab). Confirm the plug is fully inserted and the locking clip is engaged. Check inside the plug for water ingress, oxidation, or foreign matter.+4 more →
B164A›
DTC B164A indicates the SRS (Supplemental Restraint System) electronic control unit detects abnormal resistance in the deployment circuit of the front passenger seat belt pretensioner (or driver-side airbag, depending on vehicle configuration), identifying an open circuit (disconnected). The SRS system continuously monitors the circuit resistance of the airbag/pretensioner gas generator (normal value approximately 2-3 Ω, including the series diagnostic resistor) to ensure reliable ignition during a collision. The ECU triggers DTC B164A when it detects infinite resistance (>6 Ω) or a communication interruption. This fault prevents the deployment circuit from firing correctly during a collision, illuminates the airbag warning light continuously, and forces the system into fail-safe mode. On some BYD models, DTC B164A specifically indicates a driver airbag (DAB) circuit fault. The underlying issue remains the same type of abnormal connection in the deployment circuit.
Causes
— Broken internal spiral cable or burnt contacts in the clock spring (airbag spiral cable/Clock Spring), causing an intermittent open circuit during steering wheel rotation.— Loose connector, backed-out pins, or oxidized/corroded terminals under the front passenger seat or at the B-pillar seat belt pretensioner, or the connector position assurance (CPA) lock not fully engaged, causing poor contact.— After vehicle accident repairs, the airbag module or pretensioner wiring harness connector is not fully seated, or pulling during repair deformed the pins.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds (2 minutes for some models) to fully discharge the SRS capacitor and prevent accidental deployment.— Diagnostic confirmation: Use the BYD VDS2000/VDS diagnostic tool to read the fault code and check the freeze frame data. Determine if the fault is historical or current, and confirm the specific fault location (front passenger pretensioner or driver airbag).+5 more →
B164A1B›
This fault code indicates the Supplemental Restraint System (SRS) detected an open circuit or high resistance condition in the front passenger seat belt pretensioner circuit (resistance value outside the calibrated range of 2-5Ω). As a key actuator in the passive safety system, the seat belt pretensioner contains a pyrotechnic device. During a frontal collision, electronic detonation generates a reaction force to rapidly tighten the seat belt and remove slack between the occupant and the belt. Fault code B164A1B indicates the SRS control unit (ACU) cannot establish an effective electrical connection with the front passenger pretensioner. This condition prevents the pretensioner from deploying during a collision, continuously illuminates the instrument cluster airbag warning light, and forces the system into a degraded protection mode. Some models may also limit power output or disable other associated safety functions.
Causes
— Loose or disconnected pretensioner connector: Frequent seat adjustment or foreign object impact loosens the yellow dedicated connector (usually equipped with a shorting bar) under the front passenger seat. This is the most common cause on E2, E3, and Qin EV models.— Wiring harness mechanical damage: Long-term repeated movement of the seat slide rail wears through the harness insulation, or sharp edges on the seat frame cut the pretensioner circuit wiring, causing an intermittent open circuit.— Internal open circuit in the pretensioner assembly: Moisture, static electricity, or manufacturing defects cause an open circuit in the pretensioner igniter or bridge wire, resulting in infinite resistance.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes to fully discharge the SRS system and prevent accidental airbag deployment during repair.— Fault Code Confirmation: Use a VDS2000 or Launch X431 diagnostic tool to access the SRS system. Read current fault code B164A1B and freeze frame data. Record the vehicle speed, timestamp, and ambient temperature at the time of occurrence. Confirm if this is a current hard fault.+4 more →
B164B-00›
DTC B164B-00 indicates the airbag control unit (SRS ECU) detects an abnormally low-resistance path (typically <1Ω) from the front passenger seat belt pretensioner ignition circuit to body ground. The pretensioner is a pyrotechnic safety device containing an igniter and a gas generator, with a normal resistance of approximately 2.0-3.0Ω. A short to ground indicates damaged insulation on at least one of the two ignition circuit wires contacting vehicle body metal, or an internal short circuit within the pretensioner igniter. The system classifies this fault as severe because: 1) the short circuit can cause unintentional pretensioner deployment, injuring the occupant; 2) it can prevent pretensioner deployment during a collision, causing a loss of restraint protection; 3) the SRS system enters fail-safe mode, which can disable the front airbags.
Causes
— Damaged pretensioner wiring harness sleeve under the front passenger seat: Frequent fore-and-aft seat adjustment causes long-term bending of the wiring harness below the B-pillar or near the seat rail, wearing through the insulation and shorting it to the vehicle body metal.— Pretensioner connector water ingress and oxidation: Driving through water, a blocked sunroof drain tube, or deep interior cleaning allows liquid to seep into the front passenger pretensioner connector (usually located under the seat or behind the B-pillar trim), causing a short circuit between terminals or a short to ground.— Pretensioner internal igniter damaged: Physical impact, dropping, or aging caused a short circuit between the internal bridge wire and the housing, or moisture in the pyrotechnic charge abnormally reduced the resistance.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the low-voltage battery negative terminal, wait at least 90 seconds (to fully discharge the SRS capacitor), and wear an anti-static wrist strap.— Visual inspection: Remove the front passenger seat (or lift the rear section only). Inspect the yellow pretensioner wiring harness connector under the seat and below the B-pillar (inside the door sill trim) for obvious damage, burn marks, or liquid ingress.+6 more →
B165D›
DTC B165D indicates the airbag control unit (ACU/SRS ECU) detects an open circuit in the right front impact sensor (RFIS) communication circuit. The ECU fails to receive a valid signal from the sensor within the specified monitoring period or detects infinite circuit resistance. Typically mounted on the right front side member (behind the headlamp or inside the fender), the sensor detects collision acceleration at the right front of the vehicle. This fault forces the airbag system into degraded mode. In a frontal collision, the ACU may fail to accurately determine impact severity. This failure delays or prevents the deployment of passive safety devices, such as airbags and seat belt pretensioners, severely increasing occupant injury risk. The vehicle remains drivable, but safety protection functions are compromised.
Causes
— Sensor wiring harness connector loose, disconnected, or making poor contact: Long-term vehicle vibration, water ingress, or incomplete seating during previous repairs causes a gap or oxidation between the plug and socket.— Wiring harness open circuit: Crushed or cut wiring harnesses during accident repairs, or broken wires from long-term wear and aging, open the signal circuit.— Sensor mounting failure: A broken sensor mounting bracket or retaining clip causes the sensor to loosen, straining the wiring harness connector and resulting in poor contact.+2 more →
Actions
— Safety preparation: Set the power mode to OFF, disconnect the battery negative terminal and wait 3-5 minutes (to allow the SRS capacitor to discharge fully), and hang a high-voltage/airbag repair warning sign.— Visual inspection: Remove the right front fender liner or bumper. Inspect the right front crash sensor for visible damage. Check the wiring harness for obvious damage, crushing, or wear. Verify the connector is fully inserted.+6 more →
B164B›
DTC B164B indicates the airbag control unit (SRS ECU) detects an abnormally low-resistance path (typically <1.5Ω) between the front passenger seat belt pretensioner ignition circuit and body ground (GND). As a pyrotechnic safety device, the pretensioner igniter has a normal resistance of approximately 2.0-3.0Ω. A short to ground causes the SRS system to detect a front passenger pretensioner circuit fault, illuminate the 'Airbag Fault Warning Light' continuously, and enter fail-safe mode. During a collision, the system may fail to deploy the front passenger pretensioner and may subsequently disable the front passenger airbag. This fault is a hard short to ground. Repair immediately to ensure passive safety system integrity.
Causes
— Damaged yellow SRS wiring harness sleeve under the front passenger seat; prolonged friction between the wire and the seat slide rail or body metal wore through the insulation, causing a short to ground.— Poor sealing of the pretensioner connector (usually located below the B-pillar or under the seat) allows water ingress after car washing or wading, causing a short circuit between terminals or a short to ground.— Frequent fore-and-aft seat adjustment causes the seat rails to pinch the wiring harness, or loose harness retaining clips allow the wires to contact sharp edges on the body.+2 more →
Actions
— Safety preparation: Turn off the ignition, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation: Connect the BYD dedicated diagnostic tool (ED400 or VDS). Read the DTC B164B status. Confirm it is a current fault (Active) rather than a history fault. Record the freeze frame data.+6 more →
B164B11›
This DTC indicates the SRS (Supplemental Restraint System) control unit detected a short to ground in the front passenger seat belt pretensioner ignition circuit. The seat belt pretensioner is a pyrotechnic safety device containing a gas generator and a resistance wire igniter, with a normal operating resistance of approximately 1.5-2.5Ω. The BYD diagnostic protocol defines the DTC suffix '11' as a short to ground fault. The SRS module sets this code when it detects pretensioner circuit resistance below the threshold (typically <1.0Ω) or abnormal voltage to ground. This fault forces the SRS into a degraded mode, disables the front passenger pretensioner, and illuminates the instrument cluster airbag warning lamp. Because the pretensioner contains pyrotechnics, a short circuit risks accidental deployment or failure during a collision. Address this highest safety level (Level 3) fault immediately.
Causes
— The pretensioner wiring harness insulation under the front passenger seat rail or at the base of the B-pillar is worn, aged, or pinched by the seat adjustment mechanism, causing the wire to directly contact the vehicle body metal frame (ground).— Pretensioner connector (usually a yellow waterproof plug located beside the seat or in the floor wiring harness): water ingress, bent or corroded pins, or loose terminals contacting nearby grounded components.— Insulation breakdown of the gas generator resistance wire inside the pretensioner body causes an internal short circuit (resistance typically drops abnormally to <1Ω).+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds for the SRS capacitor to discharge completely. Never use a multimeter on the resistance setting to measure the pretensioner terminals directly, as the test current can trigger the igniter.— Visual inspection: Remove the front passenger seat (keep the wiring harness connected) and the lower B-pillar trim panel. Check the pretensioner wiring harness (wrapped in yellow corrugated conduit) for damage, water stains, or pinch marks. Focus on wiring harness wear points within the seat slide rail adjustment range.+4 more →
B164C-00›
This DTC indicates an abnormal short circuit between the front passenger seat belt pretensioner ignition circuit and the vehicle power supply (+B, typically the positive terminal of the 12V battery). The pretensioner is a pyrotechnic device. During a collision, the SRS control unit sends an ignition signal to trigger the internal gas generator and rapidly tighten the seat belt. A short to power in the pretensioner circuit indicates damaged wiring insulation or internal connector bridging, applying a continuous high potential across the pretensioner terminals. This condition forces the SRS system into fail-safe mode, disabling the front passenger airbag and pretensioner functions. Extreme cases risk unintended pretensioner deployment or complete failure, posing a severe safety hazard.
Causes
— Worn or crushed wiring harness under the front passenger seat: Seat fore-and-aft adjustment or passenger foot activity damages the pretensioner wiring harness insulation (usually located near the seat rail), causing a short circuit to a power wire (such as the seat heater or seat adjustment motor power wire).— Water ingress into the B-pillar or sill wiring harness connector: Vehicle wading or poor sealing corrodes the internal terminals of the pretensioner connector (usually located behind the B-pillar trim panel or under the seat). This creates a conductive path, resulting in a short to power.— Pretensioner internal fault: Insulation failure of the squib inside the pretensioner assembly shorts the ignition terminal to the housing or power terminal. Abnormal resistance (below 1.5Ω or above the normal range) typically accompanies this condition.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault Confirmation: Use a dedicated BYD diagnostic tool (VDS or ED400) to read fault codes. Confirm B164C-00 is an active fault. Record freeze frame data and check for accompanying B164B (open circuit) or B164D (short to ground) fault codes.+5 more →
B164C›
DTC B164C indicates an unintended electrical connection between the front passenger-side seat belt pretensioner control circuit and the vehicle power supply (B+). The seat belt pretensioner is a key actuator in the SRS system and contains a pyrotechnic device. Under normal conditions, the airbag ECU triggers the pretensioner only during a collision via a low-level signal. A short to power continuously exposes the pretensioner supply or control circuit to 12V. This fails the system self-check, illuminates the SRS warning lamp, and creates a severe safety risk: the short-circuit current may accidentally trigger the pretensioner (instantly and permanently locking the seat belt), or circuit protection mechanisms may prevent proper pretensioner deployment during a collision. Repair this hard short-circuit fault immediately to ensure full passive safety system functionality.
Causes
— Mechanical wear of the under-seat wiring harness: Frequent fore/aft movement of the front passenger seat or crushing by objects damages the pretensioner wiring harness insulation, causing it to contact the seat frame or power harness and create a short circuit.— Connector water ingress or corrosion: Spilled drinks, improper car washing, or wading causes a short circuit in the pretensioner connector internal terminals (usually located below the B-pillar or under the seat), or metal terminal oxidation causes electrochemical migration.— Pretensioner internal coil insulation failure: Aging, overheating, or manufacturing defects damage the pretensioner internal squib coil insulation layer, causing the coil to short to the housing (ground) or power wire.+2 more →
Actions
— Safe power-down and wait: Turn the power switch to OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds (to fully discharge the SRS capacitor and prevent accidental deployment).— Fault status confirmation: Reconnect the diagnostic tool, read the Freeze Frame data, confirm B164C is an Active fault rather than a historical fault, and record the vehicle status at the time of the fault.+5 more →
B164C12›
DTC B164C12 indicates the airbag control unit (SRS ECU) detects an abnormally low-impedance connection between the front passenger seat belt pretensioner drive circuit and the vehicle power supply (B+). The pretensioner is essentially an electric squib with a normal operating resistance of approximately 2.0-3.0Ω. When damaged wiring harness insulation causes contact with a constant power wire, the ECU detects an abnormal voltage (approaching 12V/B+ voltage) instead of the expected open circuit or low-resistance state. This fault triggers the SRS fail-safe mode. The system disables the front passenger airbag and pretensioner functions to prevent injury from accidental deployment, and illuminates the airbag warning light to alert the driver. Excessive short-circuit current also risks unintended pretensioner deployment or burning out the SRS driver chip.
Causes
— Wiring harness abrasion under the front passenger seat: Frequent fore-and-aft seat adjustment wears through the insulation on the pretensioner wiring harness (usually routed near the seat rail), causing it to contact the seat heating power wire or constant power harness and create a short circuit.— Connector terminal displacement or water ingress: Water exposure, improper cleaning, or vibration causes terminal bridging in the pretensioner connector (yellow plug) under the seat or at the lower B-pillar; or locking tab failure allows the terminal to contact the metal frame.— Internal short circuit in the pretensioner unit: Although rare, insulation breakdown in the pretensioner igniter may cause a short circuit between the terminals, to the housing (ground), or to the power supply line.+2 more →
Actions
— Safety preparation: Switch the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds (to fully discharge the SRS capacitor). Wear an anti-static wrist strap. Never measure the pretensioner directly using a multimeter in resistance mode.— Visual inspection: Remove the front passenger seat (keep the wiring harness connected). Check the pretensioner wiring harness (yellow corrugated conduit) under the seat rail for wear or crush marks. Focus on the crossing points with the seat heating module and seat belt reminder sensor harnesses.+5 more →
B164F-00›
B164F-00 indicates the measured resistance of the front passenger seat belt pretensioner is 0 ohms, signifying a short circuit fault in the pretensioner circuit (short to ground or internal short). In the SRS (airbag) system, normal pretensioner resistance is typically 2.0-3.0 ohms. The ECU monitors circuit current to determine component status. A 0-ohm resistance indicates an abnormal current path. The ECU registers a short circuit fault, illuminates the airbag warning light, and may disable the passenger airbag and pretensioner functions, severely compromising occupant protection during a collision. Differentiate this fault from "resistance too high" (open circuit). A 0-ohm reading typically indicates a hard short circuit or a direct harness short to ground.
Causes
— Pretensioner internal short circuit: The front passenger seat belt pretensioner squib shorts internally, causing resistance to approach 0. Component aging or manufacturing defects usually cause this.— Harness chafed to ground: Frequent forward and backward seat adjustment wears the insulation of the pretensioner harness (yellow dedicated harness) under the front passenger seat, resulting in direct contact with the body metal and a short to ground.— Connector water ingress short circuit: Water enters the pretensioner connector under the seat (usually near the seat rail) due to vehicle wading or improper cleaning, causing a short circuit between pins or a short to ground.+2 more →
Actions
— Safe power down: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds (to fully discharge the SRS capacitor). Never work on an energized airbag system.— Visual inspection: Remove the front passenger seat (or lift the seat carpet). Inspect the yellow SRS wiring harness under the seat for obvious wear, cuts, or crush marks. Focus on the seat slide rail mounting points and harness bend points.+5 more →
B164F›
DTC B164F indicates the measured circuit resistance of the front passenger side (front right) seat belt pretensioner is 0 ohms. In BYD SRS (Supplemental Restraint System) circuit logic, a 0-ohm resistance typically indicates a short to ground or a low-impedance short, rather than an open circuit. The pretensioner contains a squib and heating wire; normal resistance is 1.5-3.0 Ω. This fault causes the SRS control module to register an abnormal pretensioner circuit, meaning the pretensioner may fail to tension the seat belt during a collision. The instrument cluster AIRBAG/SRS warning light remains illuminated, the system enters fail-safe mode, and the SRS module may simultaneously disable the front airbags, severely compromising occupant protection.
Causes
— Water ingress, oxidation, or bent metal terminals in the pretensioner wiring harness connector under the front passenger seat causing a short circuit between positive and negative terminals.— Insulation breakdown of the seat belt pretensioner internal heating wire causes an internal short circuit (squib fault).— Long-term friction from the seat rail adjustment mechanism damages the wiring harness insulation, causing the core wire to directly contact the vehicle body ground.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Remove the front passenger seat (or lift the front of the seat). Inspect the yellow pretensioner connector (usually located on the outer side or bottom of the seat) for looseness, water ingress, corrosion, or foreign objects causing terminal short circuits. Inspect the wiring harness at the seat slide rails for wear.+4 more →
B164F1A›
DTC B164F1A indicates the Airbag Control Unit (ACU) detects a front passenger seat belt pretensioner circuit resistance of 0 ohms or close to 0 ohms, determining a short circuit fault. The pretensioner contains a pyrotechnic squib with a normal resistance between 1.5 and 3.0 Ω. A resistance of 0 indicates an internal short circuit in the pretensioner, a wiring harness short to ground, or a pin-to-pin short at the connector. This fault prevents the SRS system from triggering the front passenger seat belt pretensioner during a collision (failing to tighten the seat belt). In extreme cases, the short circuit illuminates the airbag warning light continuously and locks the entire airbag system, severely compromising passive safety performance.
Causes
— Pretensioner squib internal short circuit: Damaged insulation on the internal heating wire of the pretensioner body shorts the positive and negative terminals, typically resulting from manufacturing defects or hidden damage from failing to replace the pretensioner after an accident.— Wiring harness damaged and shorted to ground: Frequent seat sliding, foreign object pinching, or metal edge chafing damages the pretensioner wiring harness insulation under the front passenger seat or inside the B-pillar trim panel, causing a short to the vehicle body ground.— Connector water ingress causing corrosion and short circuit: Vehicle wading, car washing, or sunroof leaks cause water to enter the pretensioner connector (usually located below the B-pillar or under the seat), causing electrolyte conduction between the pins and creating a short circuit.+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 3 minutes to fully discharge the SRS system high-voltage capacitor and prevent accidental airbag deployment.— Fault confirmation: Connect the VDS2000 or Launch X-431 diagnostic tool, read the SRS system fault codes, and confirm B164F1A is a current fault that returns after clearing.+8 more →
B1650-00›
DTC B1650-00 indicates the passenger seat belt pretensioner circuit resistance falls below the normal threshold set by the SRS control module (typically <2.0Ω; normal range is 2.0-3.0Ω). The pretensioner contains a pyrotechnic squib. The ECU continuously monitors the squib resistance using a low-current signal. Low resistance typically indicates a short to ground in the squib circuit, a ground fault from damaged wiring insulation, an internal connector short, or an internal short within the pretensioner component. This fault forces the SRS system into a degraded mode, meaning the pretensioner may fail to deploy during a collision (seat belt fails to tighten) or may deploy inadvertently (unexpected firing). ISO 15031 and BYD safety system design classify this as a Level 2 safety fault requiring immediate repair.
Causes
— Wiring harness wear under the seat or inside the B-pillar causing a short to ground: Frequent fore-and-aft adjustment of the front passenger seat or passenger foot movement wears through the harness insulation, allowing the copper core to contact the vehicle body ground.— Pretensioner internal component short circuit: Moisture ingress, aging, or a manufacturing defect in the squib causes a short circuit in the internal resistance wire, reducing the resistance to <1.0Ω.— Connector short circuit: Bent pins, backed-out pins, or corrosion from water ingress in the yellow SRS connector (usually located under the seat or inside the B-pillar trim) causing a short circuit between pins or to ground.+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation and freeze frame recording: Use the VDS2000/VDS1000 diagnostic tool to read the fault code, confirm B1650-00 is a current fault (Active), and record freeze frame data (mileage, temperature, voltage, etc.).+7 more →
B1650›
DTC B1650 indicates the SRS (Supplemental Restraint System) control module detects the front passenger-side seat belt pretensioner igniter circuit resistance is below the calibrated threshold (typically <1.0 Ω; normal range: 2.0-3.0 Ω). This indicates a potential short circuit in the internal pretensioner bridge wire, or a short to ground or wire-to-wire short in the harness. This fault prevents the SRS from triggering the front passenger seat belt pretensioner during a collision (loss of pretensioning protection), or creates a risk of unintended deployment in extreme cases. The system illuminates the airbag warning lamp and may disable the front passenger airbag deployment function. In some BYD model years, this code may also indicate an Occupant Classification System (OCS) communication fault. However, based on the provided fault context, prioritize checking the pretensioner assembly and its wiring harness resistance.
Causes
— Seat belt pretensioner internal squib short circuit (internal bridge wire broken and shorted to ground, or manufacturing defect causing excessively low resistance)— Chafed wiring harness insulation under the seat or inside the B-pillar trim panel causes the power wire to short to body ground.— Pretensioner connector (yellow waterproof plug, usually located under the seat or at the base of the B-pillar): water ingress, oxidation, or bent or deformed pins causing a short circuit between pins.+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Locate component: Remove the front passenger lower B-pillar trim and seat side trim, then locate the seat belt pretensioner yellow connector (usually integrated into the bottom of the seat belt retractor or below the B-pillar).+5 more →
B16501A›
DTC B16501A indicates the airbag system (SRS) detects the front passenger seat belt pretensioner resistance is below the calibrated threshold (typically below 1.0Ω-1.5Ω; normal range is approximately 2.0Ω-3.5Ω; refer to the repair manual for exact specifications). The seat belt pretensioner is a pyrotechnic actuator containing a resistance wire (squib) and an ignition charge. Low resistance typically indicates an internal short circuit in the pretensioner, a wiring harness short to ground, a short between connector terminals, or a sampling circuit fault in the SRS control module (ACU). This fault causes the SRS to register a pretensioner circuit fault, illuminate the airbag warning lamp, and potentially fail to deploy the front passenger seat belt pretensioner during a collision, severely compromising occupant protection.
Causes
— Front passenger seat belt pretensioner internal short circuit: Moisture, aging, or manufacturing defects cause the squib internal resistance wire to short circuit, dropping resistance to nearly 0Ω.— Harness short to ground: Wear, crushing, or rodent chewing damages the wire insulation on the pretensioner harness under the seat or near the B-pillar, causing contact with the vehicle body ground.— Connector fault: Water ingress, oxidation, terminal back-out, or short circuit between terminals in the yellow pretensioner connector (usually located under the seat or inside the B-pillar trim), causing abnormal resistance.+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the battery negative terminal, and wait at least 90 seconds to fully discharge the SRS system capacitors and prevent accidental airbag deployment.— Visual inspection: Remove the front passenger seat (or move it to the fully forward/rearmost position). Check the seat belt pretensioner connector (usually a yellow plug) for looseness, water ingress, or oxidation; check the wiring harness under the seat and at the B-pillar for signs of abrasion, crushing, or damage.+4 more →
B1651-00›
This DTC indicates the airbag control unit (SRS ECU) detects the front passenger seat belt pretensioner circuit resistance exceeds the calibrated upper limit (typically >3.5Ω, standard value approximately 2.0Ω±0.4Ω). Electrically, the pretensioner is essentially a squib consisting of a resistance wire and an igniter charge. High resistance usually indicates high impedance or an open circuit. Potential causes include a partially blown internal resistance wire in the pretensioner, increased connector contact resistance, or a hidden open circuit in the wiring harness. This fault causes the SRS system to enter degraded mode: during a frontal collision, the front passenger seat belt fails to pretension automatically, and the system may suppress the front passenger airbag deployment strategy, severely compromising passive safety performance.
Causes
— Seat belt pretensioner assembly internal aging: Long-term vibration or thermal cycling oxidizes and thins the pretensioner igniter resistance wire, causing the resistance value to drift beyond the threshold.— Poor wiring harness connector contact: The yellow SRS connector under the seat or at the B-pillar (usually beside the front passenger seat rail or inside the lower B-pillar trim panel) has oxidized or loose terminals, or the interlock shorting bar fails to fully disengage, causing increased contact resistance.— Damaged floor wiring harness: water ingress from driving through water, carpet cleaning, or liquid spills in the front passenger area causes harness corrosion; frequent fore-and-aft seat adjustment causes harness fatigue and breakage (especially repeated bending when the under-seat harness retaining clip detaches).+2 more →
Actions
— Safety preparation: Turn the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds for the SRS capacitor to fully discharge. Wear an anti-static wrist strap and disable wireless communication devices.— Fault confirmation: Connect the VDS2000 or BYD dedicated diagnostic tool and read the fault code status. Confirm whether B1651-00 is 'Active' or 'History'. If multiple SRS fault codes exist, troubleshoot common power supply and ground issues first.+6 more →
B1651›
DTC B1651 indicates the Airbag Control Unit (ACU) detects the front passenger-side seat belt pretensioner circuit resistance exceeds the calibrated threshold (typically above 4.8Ω or open circuit). The pretensioner utilizes a squib structure with a normal resistance of 2.0±0.3Ω. Excessive resistance indicates a high-resistance or open-circuit risk in the firing circuit. During a collision, this prevents the ACU from reliably triggering the pretensioner, leaving the seat belt unable to tighten promptly and severely compromising occupant protection. This constitutes a Level 2 SRS fault. The system illuminates the airbag warning lamp and may force the front passenger airbag into a degraded protection mode.
Causes
— Loose or oxidized wiring harness connector under the seat: Frequent forward and backward movement of the front passenger seat loosens the pretensioner wiring harness connector (usually located beside the seat rail or below the B-pillar), oxidizes the pins, or causes pin back-out, increasing contact resistance.— Pretensioner internal squib open circuit: The igniter cartridge bridge wire inside the seat belt pretensioner assembly breaks due to long-term vibration, moisture ingress, or manufacturing defects, resulting in high resistance or an open circuit.— Seat wiring harness broken: Repeated bending breaks the copper core of the pretensioner wiring harness in the transition area between the seat and the body (inside the wiring grommet), leaving only a few fine strands connected or severing the wire completely.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds to fully discharge the airbag capacitor and prevent accidental pretensioner deployment.— Fault confirmation: Use the BYD VDS diagnostic tool to read the fault code. Confirm B1651 is a current fault (Active) rather than a history fault, and record the freeze frame data (ambient temperature, voltage, etc.).+5 more →
B16511B›
This DTC indicates the SRS (Supplemental Restraint System) detects the front passenger-side seat belt pretensioner squib resistance exceeds the system calibration threshold (typically >4Ω or near open circuit). The pretensioner is a critical component of the airbag system. During a collision, it fires a pyrotechnic charge to rapidly tighten the seat belt and eliminate slack between the occupant and the belt. High resistance indicates the ECU may fail to supply sufficient current to deploy the pretensioner during a collision. This deprives the front passenger of pretensioner protection and increases injury risk. This is a hard fault. The SRS warning lamp remains illuminated and the system enters degraded mode.
Causes
— Loose pretensioner connector plug, oxidized terminals, or water ingress corrosion causing increased contact resistance (common after water wading or vehicle washing).— Aging, moisture ingress, or a partial open circuit in the seat belt pretensioner internal igniter increases internal resistance (the pretensioner is a single-use component; resistance drifts after aging).— A hidden open circuit, a partial break in the copper core, or a poor crimp connection in the wiring causes abnormally high circuit resistance (common in accident-repaired vehicles or crushed wiring harnesses).+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the negative battery terminal, and wrap it with insulating tape. Wait at least 90 seconds to ensure the SRS capacitor discharges completely and prevent accidental airbag deployment.— Visual inspection: Inspect the dedicated yellow pretensioner connector below the front passenger B-pillar (or on the outer side of the seat) for looseness, backed-out terminals, oxidation, or water ingress. Inspect the wiring harness sleeve for damage.+5 more →
B2A5113›
DTC B2A5113 indicates an open circuit in the signal circuit of the A/C system low-pressure line pressure-temperature (PT) sensor. This sensor typically mounts on the low-pressure line between the evaporator outlet and the compressor inlet. It monitors low-side refrigerant pressure and temperature in real time, providing a key input signal to the heat pump/A/C control unit (integrated into the right domain controller or A/C controller) for compressor speed regulation, system protection, and thermal management. When the controller detects the sensor signal voltage continuously exceeding the normal range (typically 0.5-4.5V) or a communication interruption, it sets this open circuit fault. The system then triggers a protection mechanism and forces the electric compressor to stop, resulting in a complete loss of A/C cooling and heating functions. In extreme cases, this affects the battery pack cooling circuit and creates an overheating risk.
Causes
— Internal open circuit in the low-pressure line pressure sensor body (damaged pressure-sensitive element, detached internal solder joint, or open coil circuit)— Poor contact at the sensor connector (terminal back-out, oxidation/corrosion, or loose locking tab causing intermittent connection)— Physical damage to the wiring harness (wear at the firewall pass-through, detached harness retaining clip causing interference with the body and wearing through the insulation, corrosion and breakage after water ingress)+2 more →
Actions
— Safety preparation: Disconnect the low-voltage battery negative terminal, wait at least 5 minutes to ensure the high-voltage system discharges completely, and wear insulated gloves and safety goggles.— Fault confirmation: Connect the VDS diagnostic tool, read the fault code, and record the freeze frame data. Confirm whether the B2A5113 status is Active or a history fault.+7 more →
B1654-00›
DTC B1654-00 indicates a communication interruption or abnormal signal between the airbag control unit (SRS ECU) and the left front impact sensor. This sensor typically mounts inside the left front fender or on the longitudinal beam. It uses a two-wire communication circuit (signal wire and ground wire) and contains a piezoelectric or MEMS accelerometer with a normal resistance of approximately 2-3 kΩ. The ECU sets this DTC if it cannot detect the sensor feedback signal during a self-test or drive cycle, if the resistance falls outside the calibrated range (open or short circuit), or if communication verification fails. This fault disables the left front collision detection zone. During a collision, it may prevent accurate airbag deployment or cause unintended deployment, making it a safety-critical fault.
Causes
— Loose connector, backed-out pins, or oxidation: Sensor plug locking tab failure, terminal corrosion, or water ingress causes excessive contact resistance. This is the most common cause of intermittent faults.— Wiring harness open circuit or damage: Sharp sheet metal edges cut the wiring harness after a left front fender repair or collision, or long-term vibration breaks the wire.— Internal sensor fault: Piezoelectric element aging, or moisture causing an internal circuit short or open, preventing generation of the correct acceleration signal.+2 more →
Actions
— Safety preparation: Power off the vehicle, disconnect the battery negative terminal, and wait at least 90 seconds to prevent accidental airbag deployment.— Fault confirmation: Connect a BYD dedicated diagnostic tool (such as X-431 or ED400), read and record the DTC, and confirm B1654-00 is a current fault, not a history fault.+8 more →
B1654›
DTC B1654 indicates the SRS (Supplemental Restraint System) ECU detected a communication interruption or abnormal circuit impedance between the Left Front Impact Sensor and the main controller during self-check or operation. This sensor typically mounts to the left front longitudinal beam, headlamp bracket, or fender reinforcement beam to monitor collision acceleration on the left front side of the vehicle. The ECU sets this DTC if it fails to receive a valid signal from the sensor within a predetermined time, or if it detects an open or short circuit in the wiring. Under this condition, the airbag system enters fail-safe mode, potentially disabling the left front collision detection function. This compromises the deployment logic of the airbags and seatbelt pretensioners during a frontal collision, posing a major safety risk.
Causes
— Sensor wiring harness open or short circuit: Improperly secured wiring harness after front-end collision repairs, harness damage from vibration and friction over long-term use, or severed wiring from rodent damage.— Poor connector contact: Loose left front crash sensor plug, backed-out pins, or oxidized/corroded pins (common in vehicles driven through water or after high-pressure washing), interrupting signal transmission.— Sensor hardware fault: Damaged internal piezoelectric or capacitive accelerometer element, or open circuit in the sensor internal diagnostic resistor, preventing the sensor from returning the correct bias voltage or PWM signal to the SRS ECU.+2 more →
Actions
— Diagnostic confirmation: Use VDS2000 or a dedicated BYD diagnostic tool to read the fault code and confirm whether B1654 is an active or history fault. For history faults, check the trigger conditions (vehicle speed, timestamp) in the freeze frame data.— Visual inspection: Open the engine compartment and locate the left front crash sensor (usually at the front end of the left front longitudinal beam, with a yellow connector). Check the sensor for physical damage or cracks, inspect the mounting bracket for deformation, and check the installation torque mark for misalignment.+5 more →
B165400›
DTC B165400 indicates the airbag control unit (SRS ECU) detects a communication interruption with the Left Front Impact Sensor during a self-test or drive cycle. This sensor typically mounts on the left front longitudinal member (inside the fender or near the headlamp bracket) and detects front collision acceleration signals. "Not connected" indicates a disconnected physical plug, an open circuit in the sensor power/ground wiring, an open CAN/LIN communication line, an internal sensor open circuit, or a poor connection at the ECU connector. An active fault forces the SRS system into a degraded mode. This condition may prevent the left front airbag, driver airbag, or seatbelt pretensioner from deploying correctly during a collision, and illuminates the instrument cluster airbag warning light (flashing or solid).
Causes
— After front-end accident repairs, the left front crash sensor connector is not fully seated, or a broken locking tab causes it to detach. This commonly occurs after removing and installing the front bumper, headlight, or fender.— Sensor wiring harness wear causing an open circuit. This typically occurs in the front longitudinal beam area. Bottoming out, wading, or prolonged vibration damages the harness insulation and breaks the internal copper wires, especially due to protective sleeve aging where the harness passes through the front longitudinal beam hole.— Internal sensor fault, such as a damaged piezoelectric element, internal open circuit, or ID chip failure, preventing effective communication with the SRS ECU.+2 more →
Actions
— Connect the VDS2000/Launch X431 diagnostic tool, enter the SRS system, and read all fault codes to confirm if B165400 is a current fault (Active) or a history fault (History). Clear the fault code, perform a road test or simulated vibration test, and observe if the fault returns. Simultaneously record Freeze Frame data to check the vehicle speed and ambient temperature when the fault occurred.— Disconnect the battery negative terminal (follow the high-voltage power-down procedure; for hybrid models, ensure the READY light is off). Wait 90 seconds for the capacitors to discharge. Remove the left front fender liner or front bumper. Visually inspect the 2-pin or 3-pin connector on the left front crash sensor (located at the front of the left front longitudinal beam or below the headlamp) for a secure connection. Inspect the locking tab for breakage and the terminals for backing out, corrosion, or white oxidation from water ingress.+3 more →
B1655-00›
DTC B1655-00 indicates the airbag control unit (SRS ECU) detects an abnormally low-resistance path (typically <10Ω) between the left front impact sensor (FIS) signal circuit and body ground. In the BYD SRS architecture, this sensor is typically a piezoelectric acceleration sensor. It communicates with the SRS ECU via a shielded twisted-pair wire and operates on a 2.5V reference bias voltage. A short to ground causes the ECU to continuously receive a 0V low-level signal, potentially causing the following: 1) the system misinterprets the condition as a sensor fault, enters fail-safe mode, and disables airbag deployment; 2) in extreme cases, intermittent changes in short-circuit resistance may cause unintended airbag deployment. This is a hard-wire fault, not a communication fault. It directly affects the trigger logic for the driver front airbag and seat belt pretensioner.
Causes
— Damaged wiring harness insulation in the left front longitudinal beam area: The sensor wiring harness routes along the left front longitudinal beam. Road debris impacts or chassis bottoming out can wear through the outer sheath, causing the copper core to contact the body metal and create a short to ground.— Connector seal failure causing water ingress: The sensor connector is located near the front wheel arch or side member. An aging sealing ring allows water ingress during wading or high-pressure washing. Electrolytes in the water cause a short circuit between pins or to ground.— Internal sensor circuit breakdown: A voltage surge (e.g., improper battery connection or welding without disconnecting the wiring harness) breaks down the internal capacitor or Zener diode of the crash sensor, causing an internal short circuit between the power supply and ground pins.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal. Wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation: Connect the VDS or Launch diagnostic tool to read freeze frame data. Record the vehicle speed and ambient temperature at the time of the fault. Clear the fault code, then perform an SRS self-check to confirm if B1655-00 is a current code.+5 more →
B1655›
DTC B1655 indicates a short to ground in the Left Front Impact Sensor signal circuit. In the BYD SRS (Supplemental Restraint System) architecture, this sensor typically mounts on the left front longitudinal beam or bumper reinforcement to detect frontal collision acceleration. A short to ground means the resistance between the sensor signal wire (usually the positive or communication wire) and the vehicle body ground drops abnormally (<1Ω). This prevents the SRS control module (ACU) from receiving a valid acceleration signal or causes it to continuously receive a 0V level. This fault forces the airbag system into fail-safe mode: during a collision, the system may fail to deploy the left front airbag and side curtain airbag, or extreme signal interference could cause unintended deployment. ISO 26021 classifies this as a Class A passive safety system fault. Immediately remove the vehicle from service to avoid safety risks.
Causes
— Front bumper wiring harness wear: Vibration and chafing damage the left front crash sensor wiring harness insulation where it passes through the longitudinal beam or bumper bracket, causing direct contact with the metal body and creating a short to ground.— Sensor connector water ingress: Poor sealing allows water to enter the left front sensor connector (usually located inside the left front wheel housing or on the inner side of the side member) during vehicle wading or washing, causing a short circuit between terminals or a short to ground.— Internal sensor fault: Damage to the piezoelectric element or integrated circuit inside the crash sensor causes an internal short between the signal output terminal and the ground terminal.+2 more →
Actions
— Safety Preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds for the SRS capacitor to fully discharge to prevent accidental airbag deployment.— Fault confirmation: Use VDS2000 or the BYD dedicated diagnostic tool to read fault codes. Confirm B1655 is an active code, not a history code. Record the short-circuit resistance value from the freeze frame data.+6 more →
B165511›
B165511 is a BYD SRS (Supplemental Restraint System / airbag system) circuit diagnostic trouble code. B1655 specifically designates the Left Front Frontal Impact Sensor circuit, and 11 is the subtype code indicating a Short to Ground. This fault indicates the SRS control module detects an abnormally low-resistance path (typically less than 1 ohm) between the left front impact sensor signal circuit and vehicle body ground, preventing the control module from correctly receiving the sensor acceleration signal. This fault forces the airbag system into fail-safe mode and continuously illuminates the instrument panel SRS warning light. During a collision, this condition may prevent the left front airbag from deploying normally or delay its deployment. This constitutes a severe fault affecting occupant safety.
Causes
— Incorrect wiring harness connection after accident repairs (e.g., reversed pin positions or mismatched color markings causing the signal wire to short to ground)— A metal edge pinched or chafed the wiring harness inside the front bumper or left front fender, damaging the insulation and causing a short to ground.— Water ingress, corrosion, or deformed pins in the crash sensor connector, causing a short circuit between the signal terminal and ground terminal.+2 more →
Actions
— Use a dedicated diagnostic tool (such as VDS or Launch X-431) to read fault codes and confirm B165511 is a current fault (Current DTC), not a history fault.— Turn off the ignition switch. Wait at least 90 seconds for the SRS capacitor to discharge, then disconnect the left front crash sensor connector (typically located at the front of the left front longitudinal beam or the left side of the bumper).+6 more →
B165600›
This fault code indicates the SRS (airbag) control module detects an abnormal signal from the Left Front Impact Sensor or an internal sensor fault. The Left Front Impact Sensor mounts to the front section of the left front longitudinal rail or near the headlamp bracket to detect deceleration changes during a frontal collision. The SRS module sets DTC B165600 when it detects a sensor signal voltage outside the normal range (typically 0.5-4.5V), a signal interruption, or an internal sensor self-check failure. This fault degrades frontal collision protection. In extreme cases, it may prevent the front airbags from deploying correctly during a collision or cause unintended deployment. The sensor uses a piezoelectric or capacitive accelerometer and communicates with the SRS module via a hardwired connection. The fault may involve the 12V sensor power supply, ground, or signal circuit (PWM or analog signal).
Causes
— Internal circuit damage in the sensor body: Piezoelectric element aging, internal IC chip failure, or seal failure causing water ingress and corrosion, resulting in signal drift or no signal output.— Wiring harness and connector fault: Vibration, water ingress, or accidents during vehicle operation cause loose connectors, oxidized pins, broken wiring, or shorts to ground or power in the left front side member harness.— Installation issue: Incorrect sensor installation after front-end accident repairs, deformed mounting bracket causing abnormal stress on the sensor, or incorrect fastening torque (standard is usually 8-10 N·m).+2 more →
Actions
— Safety preparation: Use a diagnostic tool (VDS or dedicated equipment) to read all DTCs, confirm B165600 is a current fault (Active), and record the freeze frame data. Turn the ignition OFF, disconnect the battery negative terminal, and wait at least 90 seconds to fully discharge the SRS system capacitors.— Visual inspection: Inspect the left front crash sensor (located at the front of the left front longitudinal rail or below the headlamp bracket) for physical damage, cracks, or signs of water ingress. Inspect the mounting bracket for deformation and verify correct sensor installation direction (arrow pointing toward the front of the vehicle).+4 more →
B165700›
DTC B165700 indicates abnormal configuration parameters for the Left Front Impact Sensor. This sensor is a critical component of the SRS (Supplemental Restraint System/Airbag System) and detects frontal collision acceleration. "Parameter error" indicates the calibration data, configuration code, or communication protocol stored within the sensor does not match the SRS control module (ACU), or the sensor's physical installation angle/position deviates from the design specification. This fault may cause: 1) Delayed or failed airbag deployment during a collision; 2) Unintended airbag deployment in non-collision scenarios; 3) Vehicle high-voltage interlock shutdown (some models cut off high voltage upon detecting abnormal collision signals). Unlike DTC B165600 (hardware fault) and B165800 (communication fault), this fault relates specifically to data configuration and installation geometry parameters.
Causes
— Incorrect physical sensor installation: Deformed or loose mounting bracket, or incorrect installation direction (sensor directional arrow typically must point toward the front of the vehicle), causing installation angle deviation to exceed the allowable ±5° range.— Poor connector contact: Terminal oxidation, corrosion from water ingress, backed-out pins, or insufficient contact pressure at plug KJG05-18 and other connectors causes configuration data read errors or supply voltage fluctuations.— Low-voltage power supply system fault: Faulty DC-DC converter causing unstable output voltage (outside the 9-16V range) or a loose ground point affects sensor internal memory data integrity.+2 more →
Actions
— Connect the VDS or Launch X-431 diagnostic tool, enter the SRS system, and read the complete fault codes and freeze frame data. Check for accompanying fault codes such as B167200 (right sensor fault), B17A400 (abnormal SRS hardwire signal), or U029800 (DC communication fault).— Visually inspect the left front crash sensor installation: confirm the sensor retaining bolt torque (usually 8-10 N·m), check the mounting bracket for deformation, and verify the sensor arrow points directly to the front of the vehicle without tilt or rotation.+8 more →
B165800›
This DTC indicates a communication link fault between the SRS (Supplemental Restraint System) control unit and the Left Front Impact Sensor (LFIS). This typically indicates an interrupted LIN bus or private CAN communication between the sensor and the Airbag Control Module (ACM), a data validation failure, or a signal timeout. The LFIS monitors deceleration changes in the vehicle's left front area and provides the SRS control unit with critical collision severity data to determine whether to deploy the driver airbag, left curtain airbag, and seatbelt pretensioner. This communication fault prevents the control unit from receiving collision information for this zone. Consequently, it may cause unintended airbag deployment (fail-safe mode) or delay or prevent the activation of left-side protection devices during an actual collision. This constitutes a critical fault in the active safety system.
Causes
— Water ingress, oxidation, or terminal pin back-out at the left front crash sensor wiring harness connector: The sensor is located near the left front longitudinal beam or bumper bracket. Poor connector sealing allows water entry after driving through water, car washes, or driving in rain, causing terminal corrosion and increased contact resistance.— Sensor power supply or ground circuit fault: Includes blown fuses and wiring open/short circuits (especially improperly secured wiring harnesses after front-end collision repairs rubbing against metal body edges and damaging the insulation).— Left front crash sensor internal fault: Damaged internal accelerometer or communication chip prevents response to the SRS control unit handshake signal.+2 more →
Actions
— Use the BYD VDS2000 or Launch X431 diagnostic tool to access the SRS system. Read the complete fault codes and record the freeze frame data. Confirm whether B165800 is a current fault (Present) or a history fault (History), and check for associated fault codes (such as B165700 parameter error).— Disconnect the 12V battery negative terminal and wait 3 minutes for the SRS capacitor to fully discharge. Locate the left front crash sensor (typically located on the front section of the left front longitudinal beam or behind the headlamp bracket). Inspect the sensor housing for physical damage, cracks, or signs of water ingress.+5 more →
B165D-00›
DTC B165D-00 indicates a communication link interruption between the Supplemental Restraint System (SRS) Electronic Control Unit (ECU) and the Right Front Frontal Impact Sensor (RFFIS). In BYD vehicle architectures, this sensor typically features a 2-wire (signal loop) or 3-wire (power/signal/ground) design. It communicates via a hard-wired connection through the SRS ECU G10 connector, specifically the G10-3 signal terminal and G10-14 return terminal. The ECU sets this DTC if it detects the sensor circuit resistance exceeds the threshold (open circuit >10kΩ or short circuit <200Ω) during a monitoring cycle, or if it receives no valid sensor data for 3 consecutive monitoring cycles. This fault forces the SRS into a degraded mode, disabling the right-side frontal collision detection function. During a frontal impact, the system may delay or fail to deploy the right front airbag and right-side seat belt pretensioner. The instrument cluster SRS warning light remains illuminated to indicate a system fault.
Causes
— Sensor electrical connector loose, terminal backed out, or poor contact: Commonly caused by failing to fully engage the connector locking tab after front bumper repairs, headlamp replacement, or accident repairs, or by prolonged driving on rough roads vibrating the connector loose.— Wiring harness open circuit or damaged insulation: Panel adhesive covering the front longitudinal beam harness during accident repairs, sharp edges cutting the harness, or long-term bending breaking the internal copper strands; rodents chewing the harness insulation, causing a hidden short circuit.— Connector corrosion and oxidation: Driving through water, washing the motor compartment directly with a high-pressure washer, or an aging sealing ring allows water to seep into the sensor connector, causing copper corrosion on the terminals and increasing contact resistance (>5Ω).+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the 12V battery negative cable, and wait at least 90 seconds to allow the SRS capacitor to fully discharge, preventing accidental airbag deployment during repair.— Locate the component: Open the hood, remove the right front wheel arch liner or front bumper upper cover, and find the right front crash sensor on the right side of the radiator support or behind the right front headlamp.+8 more →
B165D00›
DTC B165D00 indicates the airbag control unit (SRS ECU) detects a communication interruption or physical connection loss with the Right Front Frontal Impact Sensor. This sensor typically mounts inside the right front bumper reinforcement beam or at the front of the right fender to monitor collision acceleration at the right front of the vehicle. The SRS ECU sets this fault code if it fails to receive a valid signal from the sensor within a predefined cycle, or if it detects an open circuit or abnormal resistance in the sensor circuit. The airbag system then enters fail-safe mode, which may prevent the right front airbag, side airbag, or seat belt pretensioner from deploying normally during a collision. The instrument cluster airbag warning light remains illuminated, and some models may sound a warning buzzer.
Causes
— Sensor wiring harness connector loose, disconnected, or making poor contact: Commonly occurs after front bumper removal and installation, accident repairs, or wading, leaving the connector improperly seated or the retaining clip broken.— Wiring harness open or short circuit: A front-end collision pulls and severs the wiring harness, long-term friction against the fender or bumper reinforcement damages the harness, or rodent chewing shorts the signal wire to ground.— Crash sensor internal fault: Internal accelerometer damage, electronic component aging, or seal failure causes an internal short circuit, preventing the sensor from returning the correct resistance value (normally 2-3kΩ) to the SRS ECU.+2 more →
Actions
— Safety preparation: Switch the vehicle OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the airbag system capacitor and prevent accidental airbag deployment during repair.— Inspection procedure: Remove the right front bumper cover or right fender liner. Locate the right front impact sensor (usually marked 'Front Impact Sensor' or with a part number). Visually verify the connector is fully seated, the locking tab is intact, and the wiring harness shows no damage.+5 more →
B165E-00›
DTC B165E-00 indicates an abnormally low-impedance connection (short to ground) between the airbag system (SRS) right front impact sensor signal or power circuit and body ground (GND). This sensor typically mounts on the right front side member, radiator support, or fender reinforcement to detect collision acceleration on the right front side of the vehicle. A short to ground prevents the SRS control unit (ACU) from correctly reading the sensor's acceleration signal output (typically an analog or digital signal from a piezoelectric or MEMS sensor). This causes the following conditions: 1) airbags failing to deploy during an actual collision; 2) the system entering fail-safe mode and illuminating the SRS warning lamp; 3) in extreme cases, abnormal signals causing unintended airbag deployment. This safety-critical fault requires immediate repair.
Causes
— Front bumper wiring harness wear: Vehicle vibration causes the right front crash sensor wiring harness to rub against the body metal frame (such as the side member or fender liner). This friction damages the insulation, exposes the wire, and creates a short to body ground. This issue commonly occurs on vehicles with improperly secured wiring harnesses or missing retaining clips following accident repairs.— Wading or water ingress corrosion: When driving through water (water level above the wheel center) or during high-pressure washing, water seeps through the sensor connector seal or wiring harness corrugated conduit. This oxidizes and electrolytically corrodes the connector terminals, forming a short-to-ground path. This issue is common in older vehicles with poor sealing.— Improper modification or repair damage: When routing aftermarket wiring for LED headlights, front radar, or dash cams, technicians tie the aftermarket harness too tightly to the SRS harness with cable ties, or cut the original harness insulation when drilling holes. This exposes the core wire, causing a short circuit to the vehicle body.+2 more →
Actions
— Safety preparation: Shift the vehicle into P or Neutral, apply the parking brake, turn off the ignition, and disconnect the negative battery cable. Wait at least 90 seconds to fully discharge the airbag system capacitor and prevent accidental airbag deployment during repair.— Fault Confirmation: Connect the BYD dedicated diagnostic tool (VDS2000/3000). Access the SRS system to read fault codes. Verify B165E-00 is a current fault (not a history fault). Record freeze frame data (e.g., vehicle speed and time of occurrence). Attempt to clear the fault code and check if it returns immediately.+5 more →
B165E›
DTC B165E indicates the Right Front Impact Sensor detects a low-impedance or zero-impedance circuit, meaning the sensor signal wire or power wire is shorted to body ground. This piezoelectric acceleration sensor monitors collision deceleration at the front right side of the vehicle. A short to ground prevents the SRS ECU from receiving the correct collision signal and triggers a Level 3 severe fault: 1) the right-side airbag and seat belt pretensioner may fail to deploy in time during a collision; 2) the system may falsely report a collision signal, causing unintended deployment; 3) the entire SRS system enters fail-safe mode, restricting all airbag functions. Typical causes for this fault include damaged wiring harness insulation, water ingress in the connector, an internal sensor short circuit, or an ECU drive circuit fault.
Causes
— Wiring harness chafing in the right front side member area: During vehicle operation, continuous rubbing between the wiring harness and body metal edges, retaining clips, or the front bumper bracket causes insulation damage and a short to ground. This commonly occurs due to improper harness securing after accident repairs or from underbody scraping.— Sensor connector water ingress and corrosion: Car washing, wading, or poor front sealing causes water ingress into the connector (usually located inside the right front fender liner or below the headlamp). Pin oxidation causes a short to ground, accompanied by white or green corrosion marks.— Internal sensor circuit fault: Internal breakdown of the piezoelectric element or signal processing chip causes a power-to-ground short circuit. This typically occurs with physical damage to the sensor housing or internal seal failure.+2 more →
Actions
— Safety preparation: Turn off the ignition switch. Disconnect the 12V battery negative terminal and wait at least 90 seconds for the SRS capacitor to discharge. Wear an anti-static wrist strap. Do not use a multimeter resistance setting to directly measure the airbag circuit.— Fault confirmation and freeze frame analysis: Use the diagnostic tool to read the DTC B165E status (current/history). Record the vehicle speed and sensor voltage values from the freeze frame data, and confirm the environmental conditions when the fault occurred.+6 more →
B165E11›
DTC B165E11 indicates the SRS (Supplemental Restraint System) control unit detects an abnormally low-resistance path (typically <1Ω) between the right front impact sensor signal or power circuit and body ground, constituting a short to ground. In BYD E2/E3/Qin EV architectures, this sensor utilizes a bipolar MEMS accelerometer and communicates with the SRS ECU via a hardwire or LIN bus connection. A short to ground causes the ECU to continuously receive a 0V reference signal, preventing it from distinguishing between "no collision" and "circuit fault" states. Per ISO 26262 functional safety requirements, the system enters Fail-Safe mode: it immediately illuminates the airbag fault warning lamp and disables right front airbag and side curtain airbag deployment to prevent unintended triggering or failure to deploy. This represents a severe ASIL-D fault.
Causes
— Internal short circuit in the sensor: Overvoltage, static electricity, or aging causes a breakdown between the power supply pin and ground within the right front crash sensor integrated circuit (ASIC). This commonly occurs after vehicle wading or a battery system insulation fault.— Harness mechanical damage: Front bumper removal and installation, accident repairs, or overly tight fender liner retaining clips abrade the sensor harness insulation (usually located on the outside of the right front side member), causing the copper core to directly contact the vehicle body metal frame.— Connector water ingress and corrosion: An aged sealing ring on the right front bumper wiring harness connector (usually located behind the headlamp or on the right side of the radiator support) allows water to accumulate inside after car washing or wading, causing an electrolytic short to ground between the pins.+2 more →
Actions
— Safe power-down and discharge: Switch off the ignition, disconnect the low-voltage battery negative terminal, wait at least 90 seconds (to fully discharge the SRS energy storage capacitor), and wear an anti-static wrist strap.— Initial visual inspection: Remove the right front bumper cover. Inspect the right front crash sensor (located at the front of the right front longitudinal beam or below the headlamp bracket) for physical damage or cracks. Inspect the wiring harness corrugated conduit for wear or crush marks. Inspect the connector for looseness or signs of water ingress (white powder or verdigris).+6 more →
B165F00›
DTC B165F00 indicates the SRS (Supplemental Restraint System) ECU detected a functional fault or communication error in the right front impact sensor. This sensor mounts near the right front side member or bumper reinforcement beam. It detects deceleration changes during a frontal collision and sends a crash signal to the airbag control unit. The '00' in the fault code typically indicates an internal sensor self-test failure, an out-of-range signal, or a communication interruption between the sensor and the ECU (non-specific short or open circuit). This fault disables the right front crash detection circuit. During a frontal collision, this failure may delay or prevent the deployment of the right front airbag and side curtain airbags, severely compromising passive safety performance. Consequently, the SRS illuminates the airbag warning light and may disable related airbag functions.
Causes
— Internal sensor fault: A damaged accelerometer element inside the right front crash sensor or a signal processing circuit failure causes an abnormal output signal or no response. This commonly occurs after minor frontal impact vibrations or natural component aging.— Wiring harness connector issue: The sensor connector located in the right front fender or bumper has a loose connection, backed-out terminals, oxidation/corrosion, or water ingress. Poor contact typically results from driving through water, washing the vehicle, or failing to fully seat the connector during accident repairs.— Wiring harness physical damage: Accident repairs or front bumper removal/installation crushed, chafed, or severed the right front wiring harness, causing an intermittent open circuit in the signal wire, power wire (12V), or ground wire.+2 more →
Actions
— Preliminary diagnosis and freeze frame recording: Use the dedicated diagnostic tool (VDS or ED400) to read complete DTC information. Record freeze frame data (vehicle speed, timestamp, etc. at the time of the fault). Verify B165F00 is a current fault (Active) and check for other related crash sensor fault codes (such as B165E11 short to ground).— Visual and physical inspection: Turn off the ignition switch, remove the right front bumper or fender liner, and inspect the exterior of the right front crash sensor for damage or cracks. Check the mounting torque (typically 8-10 N·m), verify the sensor direction arrow points directly to the front of the vehicle, and check that the connector is fully locked and the sealing ring is intact.+3 more →
B166000›
DTC B166000 indicates the airbag control unit (SRSECU) detects the internal parameters of the Front Right Impact Sensor exceed the calibrated tolerance range. This sensor typically uses a MEMS capacitive or piezoelectric accelerometer to detect collision deceleration at the front right of the vehicle. "Parameter error" specifically indicates the sensor self-check detected sensitivity drift, zero offset exceeding the ±5% standard value, an abnormal temperature compensation curve, or corrupted calibration data stored in the EEPROM. This fault prevents the ECU from accurately interpreting the analog/digital signals transmitted by the sensor, potentially causing delayed deployment, non-deployment, or unintended deployment of the airbag during a collision (although unintended deployment probability remains low because the ECU utilizes a multi-sensor fusion algorithm). This represents a critical safety fault in the SRS system.
Causes
— Aging, debonding, or microcracks from severe impact within the internal accelerometer chip of the sensor body permanently alter its piezoelectric or capacitive characteristics, causing the output signal slope to deviate from the factory calibration curve.— A deformed sensor mounting bracket, loose retaining bolts (standard torque: 8-10 N·m), or paint/rust on the mounting surface reduces connection rigidity between the sensor and the vehicle body. This affects collision mechanical wave transmission characteristics, causing the ECU to detect a 'parameter abnormality'.— Oxidation, looseness, or water ingress at the wiring harness connector terminals increases contact resistance (>1Ω) or causes signal interference, triggering the ECU to detect an abnormal sensor response time constant or amplitude-frequency characteristics.+2 more →
Actions
— Safety preparation: Turn the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 3 minutes (90 seconds for some models) to fully discharge the SRS backup power capacitor and prevent accidental airbag deployment.— Visual inspection: Locate the right front crash sensor (usually installed on the front section of the right front longitudinal beam, the right side of the radiator support, or the inner side of the right front fender reinforcement). Check the housing for cracks, deformation, or signs of water ingress. Check the mounting bracket for deformation.+5 more →
B166100›
DTC B166100 indicates a communication interruption or data abnormality between the Airbag Control Unit (ACU) and the Front Right Impact Sensor. The sensor mounts on the right front longitudinal beam or the right side of the bumper reinforcement beam to detect front-right collision acceleration. This communication error prevents the ACU from receiving real-time collision signals from this area, forcing the airbag system into a degraded mode. During a frontal collision, the system cannot accurately determine impact severity and direction, delaying or preventing deployment of the front right airbag and right-side pretensioner, which severely compromises occupant protection. This fault constitutes an active safety system failure and requires immediate repair.
Causes
— Right front crash sensor wiring harness connector loose, oxidized, or corroded by water ingress (sensor located in the front bumper area, susceptible to impact from wading or high-pressure car wash jets).— Internal fault in the accelerometer or communication IC chip within the sensor body (due to prolonged vibration or electromagnetic interference)— Open or short circuit in the front wiring harness (improperly secured harness after front-end accident repairs, or long-term vibration causing wire breakage)+2 more →
Actions
— Use the BYD VDS diagnostic tool to read all fault codes. Check for accompanying DTC B166000 (parameter error) or other communication faults, and record freeze frame data.— Switch off the ignition, disconnect the battery negative terminal, and wait 90 seconds. Check the right front crash sensor connector (located at the front of the right front longitudinal beam or the right side of the bumper reinforcement) for looseness, water ingress, or corroded pins.+4 more →
B1666-00›
DTC B1666-00 indicates the Airbag Control Unit (ACU) detected a communication loss or abnormal signal from the Left Side Impact Sensor (LSIS). This sensor, typically located in the left B-pillar or left front door area, monitors vehicle side-impact acceleration. Root causes include: 1) Open circuit in the sensor power or ground lines; 2) Open circuit, short circuit, or short to ground in the communication harness (LIN bus or hardwire); 3) Failure of the sensor internal piezoelectric accelerometer or signal processing circuit; 4) Incorrect sensor installation causing the signal to fall outside the calibrated range. This safety-critical fault may prevent the left side airbag and curtain airbag from deploying during a side impact, or cause unintended deployment during normal driving.
Causes
— Loose connector, backed-out pins, or oxidized/corroded terminals in the left front door or B-pillar wiring harness, especially common after frequent door cycling or driving through water.— Internal fault in the left side impact sensor, such as a damaged accelerometer element or open internal circuit.— Physical damage to the wiring harness, including crushing or breakage after accident repairs, or broken copper wires from long-term bending.+2 more →
Actions
— Use the dedicated diagnostic tool to read the complete fault codes and freeze frame data. Confirm if B1667 (right side impact sensor) or other SRS fault codes are present, and check the vehicle status when the fault occurred.— Disconnect the battery negative terminal and wait 3 minutes. Visually inspect the appearance of the left side impact sensor (located inside the left B-pillar trim panel or behind the left front door trim panel) and the condition of the wiring harness connector. Check for water stains, corrosion, or physical damage.+6 more →
B1666›
This DTC indicates interrupted communication or a physical disconnection between the airbag control unit (SRS ECU) and the Left Side Impact Sensor. The Left Side Impact Sensor typically mounts in the lower left B-pillar or the left front seat side trim area. It monitors left-side collision acceleration signals and provides key input for side airbag deployment decisions (including side airbags and side curtain airbags). The ECU records B1666 if it fails to receive the sensor ID response code within the specified monitoring period, if LIN bus communication times out, or if it detects an open power or ground circuit. This fault forces the left-side airbag system into fail-safe mode. During a side impact, the airbags may fail to deploy or deploy late, severely compromising occupant side-impact protection. Additionally, the instrument panel SRS warning lamp (airbag warning light) illuminates continuously, and the system may report the safety system fault status to the vehicle control unit via the CAN bus.
Causes
— Sensor harness connector loose, terminal backed out, or completely disconnected: Commonly occurs after accident repairs or interior trim removal/installation (such as replacing the left front door or B-pillar trim) due to failure to tighten the connector to the specified torque (usually 8-10 N·m), or a broken connector latch causing the connector to vibrate loose during driving.— Wiring harness physical damage or corrosion: Wading, underbody scraping, or rodent damage to the left-side sill wiring harness causes an open circuit or short to ground in the power supply wire (+B), ground wire (GND), or LIN communication wire. Connector pin oxidation causes high resistance (>5Ω).— Internal sensor body fault: damaged internal accelerometer element, cold solder joints on the PCB, aged sealing ring causing water ingress and internal short circuit, or sensor software version mismatch with the ECU (common when installing non-genuine parts after an accident).+2 more →
Actions
— Diagnostic confirmation: Use a BYD VDS2000/3000 or Launch X-431 diagnostic tool to access the SRS system. Read all fault codes. Confirm whether B1666 is an Active or History code. Check the vehicle status (vehicle speed, timestamp) in the freeze frame data. Check for accompanying B1667 (left-side communication error) or U-series communication fault codes.— Safety preparation and visual inspection: Turn off the ignition, disconnect the negative battery terminal, and wait 90 seconds (allow the SRS capacitor to discharge). Remove the left B-pillar lower trim panel (clip locations are usually beside the seatbelt retractor cover). Verify the white crash sensor connector (part number usually starts with 5A-) is fully inserted and locks with an audible 'click'. Check the connector for a missing waterproof sealing ring.+3 more →
B166600›
DTC B166600 indicates a communication interruption between the SRS (Supplemental Restraint System) ECU and the left side impact sensor, or circuit resistance exceeding the calibrated range (typically >10kΩ or open circuit). On BYD E2/E3/Qin series models, the left side impact sensor mounts below the left B-pillar or on the left front door inner sheet metal to monitor left-side impact acceleration. The ECU triggers this DTC and illuminates the airbag warning lamp upon detecting a continuous open sensor signal circuit, an open internal sensor circuit, or an abnormal sensor power/ground circuit. Under this condition, side and curtain airbags may fail to deploy, but front airbag function usually remains unaffected.
Causes
— Loose or oxidized left front door wiring harness connector: Frequent door operation can loosen the wiring harness connector installed near the door hinge. Water ingress after car washing can also corrode the terminals, causing poor contact or an open circuit in the signal line.— Side impact sensor internal open circuit: Damage to the internal piezoelectric element or integrated circuit prevents the sensor from sending a crash signal to the SRS ECU. This commonly occurs due to vehicle water ingress or sensor aging (vehicles over 5 years old).— Physical wiring harness damage: The seat rail crushing the wiring harness inside the left front door sill trim panel or B-pillar, an aftermarket audio wiring harness chafing the harness, or incorrect routing during accident repairs causes the signal wire to short to ground or open circuit.+2 more →
Actions
— Safety precautions: Disconnect the 12V battery negative terminal. Wait at least 90 seconds for the SRS capacitor to fully discharge to prevent accidental airbag deployment. Wear an anti-static wrist strap.— Fault confirmation: Connect the VDS or Launch diagnostic tool. Read all DTCs and record the freeze frame data. Confirm the fault is current (Active) and not historical. Check for accompanying communication fault codes (such as the B165X series).+5 more →
B1667-00›
DTC B1667-00 indicates the airbag control unit (SRS ECU) detects a short to body ground in the signal circuit of the left side impact sensor (typically installed inside the left B-pillar reinforcement panel). This sensor is typically a MEMS capacitive or piezoelectric accelerometer. During normal operation, it returns a bias resistance of approximately 2.1-2.9 kΩ and a signal voltage of approximately 2.5 V to the ECU. When wiring harness insulation breaks, water enters the connector, or the sensor shorts internally, the ECU detects a continuous voltage signal below 0.5 V (short-to-ground threshold) and triggers this DTC. This fault disables the trigger threshold determination for the left side airbag and curtain airbag. During a side collision, the airbags may fail to deploy promptly, or signal interference during normal driving may cause unintended deployment. This is a highest-level safety fault.
Causes
— Damage to the sensor wiring harness insulation causing a short to ground: Common causes include underbody scraping, loose wiring harness retaining clips causing the harness to rub against metal body edges, or crushing the wiring harness during sill trim panel removal and installation.— Connector water ingress and corrosion: Poor sealing in the left B-pillar area, a blocked sunroof drain tube causing leaks, or direct high-pressure washing of the B-pillar causes connector terminal oxidation, resulting in a short to ground.— Internal sensor body damage: Severe vibration (from improper removal and installation, or accidents) causes electrical breakdown of the internal piezoelectric element or circuit board, or electronic components age and fail after the sensor exceeds its 5-year service life.+2 more →
Actions
— Safety preparation: Wear insulated gloves, disconnect the 12V low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the SRS system capacitor (for new energy vehicle high-voltage systems, confirm the READY light is off).— Fault confirmation: Use a BYD dedicated diagnostic tool (VDS or ED400) to read SRS system fault codes, verify B1667-00 is the current fault code, and record freeze frame data (ambient temperature, voltage value).+8 more →
B1667›
System definitions for DTC B1667 vary across BYD models. Original documentation classifies it under the SRS as "left side impact sensor short to ground." However, in practice for BYD F3, G6, S6, S7, Song, Tang, and Qin series models, B1667 generally indicates a Body Control System fault: "driver side (left) door mirror vertical adjustment motor fault/stuck." Based on circuit operation, the BCM (Body Control Module) identifies the fault by monitoring the drive current and position feedback signal of the door mirror vertical adjustment motor. The BCM stores this DTC when it detects a short to ground, abnormal current (too high or too low), motor stall, or an open circuit in the motor circuit. This fault disables the electric vertical adjustment of the door mirror. It typically does not affect horizontal adjustment, mirror heating, or folding functions (if equipped).
Causes
— Worn carbon brushes, oxidized commutator, or internal short circuit in the rearview mirror vertical adjustment motor, resulting in abnormal drive current.— Rearview mirror drive mechanism (plastic worm gear, gear set) lacks lubrication, shows wear or breakage, or binds due to foreign matter (such as dust or rust particles).— Long-term bending of the door wiring harness at the A-pillar or hinge damages the insulation, causing a power wire short to ground or a signal wire open circuit.+2 more →
Actions
— Use a BYD dedicated diagnostic tool or generic OBD device to read the Body Control Module (BCM) fault codes. Confirm B1667 is present and check for an accompanying B1668 (right side) or other related fault codes.— Check the rearview mirror/window system fuse in the engine compartment or dashboard fuse box (commonly F16/15A or F17/20A). If blown, do not install a higher-capacity fuse. Locate the short circuit first.+5 more →
B166711›
DTC B166711 indicates a short to ground in the signal circuit of the airbag system (SRS) left side impact sensor. This sensor typically mounts inside the driver-side B-pillar trim panel and detects left-side impact acceleration. The SRS control unit sets this fault when it detects abnormal voltage to ground on the sensor signal wire (continuous low level) or a resistance value below the threshold. This fault causes the airbag system to enter fail-safe mode. During a side collision, the left side airbag and left curtain airbag may fail to deploy. The instrument panel continuously illuminates the airbag warning light. The BYD diagnostic protocol defines the DTC suffix '11' as 'Shorted to Ground', distinguishing it from '00' (open circuit/not connected) or other fault types.
Causes
— Left B-pillar wiring harness worn or crushed: During long-term vehicle use, frequent door operation causes the wiring harness inside the B-pillar to rub against the metal body frame. Damaged insulation shorts the wire to body ground.— Sensor connector water ingress or corrosion: Driving in rain, improper car washing, or poor window seals allow water to seep into the left B-pillar, causing oxidation or a short circuit at the sensor connector terminals.— Side impact sensor internal fault: Damage to the internal piezoelectric element or circuit board shorts the signal terminal to ground, causing an abnormal drop in resistance (normal: 2-3kΩ).+2 more →
Actions
— Connect the VDS diagnostic tool to the vehicle OBD port, read the SRS system fault codes, confirm DTC B166711 (left side impact sensor short to ground) is present, and record the freeze frame data.— Switch off the ignition and remove the driver-side B-pillar lower trim panel (requires removing the seat belt pretensioner trim panel) to expose the left side impact sensor assembly.+6 more →
B166800›
DTC B166800 indicates a functional fault in the Left Side Impact Sensor within the Supplemental Restraint System (SRS). This sensor typically mounts inside the left B-pillar trim panel or near the left side sill beam. It contains a built-in accelerometer to detect side-impact acceleration on the left side of the vehicle. When the sensor detects acceleration exceeding a specific threshold, it sends a crash signal to the SRS ECU, which then determines whether to deploy the left side airbag and side curtain airbag. This DTC triggers when the SRS ECU continuously fails to receive a valid signal from the sensor (due to communication loss, abnormal signal voltage, or sensor unresponsiveness), disabling the left-side impact protection function. In this fault state, the side airbag and side curtain airbag may fail to deploy during a side collision, severely endangering occupant safety.
Causes
— Loose connection, water ingress, or terminal corrosion at the left side impact sensor harness connector (commonly at the B-pillar, due to long-term harness bending from frequent door operation).— Damaged accelerometer element inside the sensor body or signal processing circuit failure (caused by aging, vibration, or electromagnetic interference).— Sensor power supply circuit (usually 5V reference voltage) shorted to ground, shorted to power, or open circuit; or signal circuit (LIN or CAN communication line) shorted or open circuit.+2 more →
Actions
— Use the BYD VDS diagnostic tool to read complete fault codes and freeze frame data. Confirm environmental parameters at the time of the fault, such as vehicle speed and temperature. Check for related stored fault codes (such as B166711 short to ground or B166900 configuration error).— Turn off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds (allow the SRS capacitor to discharge). Remove the left B-pillar lower trim panel. Visually inspect the left side impact sensor for physical damage, cracks, or loose mounting.+6 more →
B166900›
This fault code indicates the SRS (Supplemental Restraint System) control module detects the configuration parameters for the left side impact sensor (typically mounted on the left B-pillar, left front door intrusion beam, or under the driver's seat, depending on vehicle configuration) do not match expected system values. This is not a simple electrical open/short circuit (DTC B166800) or communication interruption (DTC B166A00). Instead, it indicates the SRS control module EEPROM contains abnormal or missing data for the sensor's hardware ID code, calibration coefficients, software version identifier, or installation position parameters. Specifically, the control module cannot correctly identify the sensor. This may cause the side airbag and curtain airbag deployment thresholds to deviate from design values, or cause the system to fail to deploy during a side impact. Common trigger scenarios include: failing to perform online configuration (coding) after sensor replacement, failing to migrate data after an SRS control module software update, using non-genuine parts (lacking vehicle configuration data), or SRS module data area damage following a collision. This fault is a functional safety configuration error. Repair immediately to restore normal side impact protection function.
Causes
— After replacing the left-side impact sensor (or following accident repairs), failure to perform the 'Sensor ID Learning' or 'SRS System Configuration' procedure using the BYD VDS diagnostic tool prevents the system from writing the new sensor hardware ID to the control module.— The SRS control module software version does not match the sensor hardware version. Common causes include a failed vehicle OTA software update, mixing parts from different model years (e.g., installing a 2020 sensor in a 2018 vehicle), or failing to synchronize the configuration after replacing the control module.— Water ingress, oxidation, or terminal back-out at the left side impact sensor wiring harness connector (typically the GJK plug inside the left B-pillar trim or the G10 plug under the seat), causing a CRC check failure when reading configuration data.+2 more →
Actions
— Connect the BYD VDS2000/VDS3100 diagnostic tool to the vehicle. Read all DTCs and freeze frame data. Confirm whether B166900 is a current fault (Active) or a history fault (History). Check for accompanying DTCs B166A00 (communication error) or B166800 (hardware fault) to rule out multiple faults.— Visually inspect the left side impact sensor installation (located inside the lower-middle left B-pillar trim panel or under the seat). Verify the part number (e.g., BYD-3636900-XX) matches the vehicle model year. Inspect the wiring harness connector for looseness, water ingress, or oxidation (focus on the GJK connector sealing ring inside the B-pillar trim panel). Measure the sensor supply voltage (should be 9-16V with ignition ON).+3 more →
B166A00›
DTC B166A00 indicates interrupted communication or abnormal data between the airbag control unit (SRS ECU) and the Left Side Impact Sensor. This sensor typically mounts at the lower B-pillar or under the left front seat and monitors left-side impact acceleration. A communication error prevents the ECU from receiving real-time impact data from the sensor, causing the side and curtain airbags to fail to deploy accurately during a collision, or risking unintended deployment. This fault constitutes an active safety system failure. The vehicle remains drivable, but side-impact protection functions degrade.
Causes
— Left side impact sensor wiring harness connector loose, pins backed out, or oxidized/corroded; commonly occurs after water wading, car washes, or failing to fully seat the connector following collision body repairs.— Internal sensor fault, including MEMS accelerometer chip damage, internal water ingress, or dry solder joints from prolonged vibration.— Wiring harness short or open circuit, especially the sill wiring harness pinched by seat rails, chewed by rodents, or damaged during modification work (such as installing illuminated scuff plates or ambient lighting).+2 more →
Actions
— Use a VDS or X431 diagnostic tool to read all SRS fault codes, confirm whether B166A00 is a current fault (Active) or history fault (History), and record the freeze frame data.— Visually check the instrument panel airbag warning light status to confirm the lamp circuit operates normally during the system self-check (the light should turn off 6 seconds after turning the ignition switch ON; if it remains illuminated, confirm the fault is present).+6 more →
B166F-00›
DTC B166F-00 indicates the airbag control unit (SRS ECU) detects a communication loss or electrical disconnection with the right side impact sensor. This sensor typically mounts in the right B-pillar or inside the door to monitor side-impact acceleration and serves as the key input device to trigger the right side airbag and curtain airbag. The ECU sets this fault code if it fails to receive a valid signal from the sensor within the set cycle, or detects an open or short circuit in the wiring. This fault forces the right side airbag system into fail-safe mode. The airbags may fail to deploy during a side impact, severely compromising occupant passive safety. The instrument cluster continuously illuminates the SRS warning light.
Causes
— Loose connector or poor contact: Right side impact sensor connector not fully locked, or terminals backed out or oxidized, interrupting signal transmission. Commonly occurs after vehicle wading, car washing, or vibration from repeated door opening and closing.— Wiring harness open or short circuit: The wiring harness connecting the sensor to the SRS ECU shows wear, chafed insulation, or breaks at the door hinge, B-pillar pass-through, or body bend points, or shorts to ground or power.— Internal fault in the sensor body: An open circuit in the sensor internal circuit or a damaged communication chip prevents the ECU from recognizing the sensor ID and signal.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS or ED400) to read fault codes, confirm B166F-00 is an active fault, record freeze frame data, and check for other accompanying SRS fault codes.— Set the power to OFF, disconnect the battery negative terminal, and wait at least 90 seconds for the system to discharge. Inspect the right side impact sensor (usually located inside the right B-pillar trim panel or inside the door) for physical damage or impact marks.+6 more →
B166F›
DTC B166F indicates a loss of communication between the SRS (Supplemental Restraint System) ECU and the Right Side Impact Sensor (RSIS). This sensor typically mounts below the B-pillar on the right front door frame or the lower section of the right centre pillar to detect side-impact acceleration on the right side of the vehicle. The SRS ECU sets this fault code if it fails to receive a signal from the sensor within a predetermined time, or detects circuit resistance outside the normal range (open/short circuit). This fault may prevent the right side airbag and right curtain airbag from deploying correctly during a side impact, severely compromising occupant side-impact protection. It does not affect frontal impact protection.
Causes
— Poor connector contact: Right crash sensor connector K05(B) and body wiring harness connector KG10 are not fully locked, retaining clip is damaged, or terminals are oxidized, interrupting signal transmission.— Wiring harness open circuit or wear: Long-term vibration at the wiring harness retaining clip inside the B-pillar trim panel damages the insulation and causes partial wire breakage, or pinching the harness during repairs causes an intermittent open circuit.— Sensor body damaged: Collision impact, water ingress, or electrical overload damaged the sensor's internal piezoelectric accelerometer element or signal processing circuit, causing an open circuit.+2 more →
Actions
— Safety preparation: Turn the power switch to OFF, disconnect the negative battery cable, and wait at least 90 seconds for the SRS capacitor to fully discharge and prevent accidental airbag deployment.— Locate component: Remove the right B-pillar lower trim panel. Find the right side impact sensor (usually marked RSIS or SIS-R). Verify the connection status of connector K05(B).+6 more →
B166F00›
This fault code indicates the airbag control unit (SRS ECU) detects a communication loss or open circuit at the right side impact sensor. The sensor typically mounts inside the right front door trim panel or below the B-pillar and monitors the right-side collision acceleration signal. The SRS ECU triggers DTC B166F00 if it fails to receive a valid signal from the sensor within the preset monitoring period or detects an open circuit in the sensor power or communication lines. This fault may prevent the side airbag and side curtain airbag from deploying correctly during a side impact, but does not cause accidental deployment. The system illuminates the instrument cluster SRS warning light to indicate a safety system fault.
Causes
— Repeated bending of the right front door wiring harness at the door hinge causes internal wire breakage or poor connection (common fault point).— Right-side impact sensor connector (usually marked K05(B)) loose, backed-out terminals, oxidized due to water ingress, or poor contact.— Internal circuit fault in the sensor body, damaged chip, or signal processing module failure+2 more →
Actions
— Use the VDS2000 or BYD dedicated diagnostic tool to read the fault code. Confirm whether B166F00 is a current (Active) or historical (History) fault, and record the freeze frame data.— Disconnect the battery negative terminal and wait at least 3 minutes to discharge the SRS system. Check the right side impact sensor connector (located inside the right front door trim panel or below the B-pillar) for a secure connection. Inspect for signs of water ingress, pin corrosion, or backed-out pins.+4 more →
B1670-00›
DTC B1670-00 indicates an abnormally low-resistance connection between the right side impact sensor (SIS) signal circuit and body ground, resulting in a short to ground. The BYD SRS (Supplemental Restraint System) architecture utilizes a piezoelectric or MEMS accelerometer for the right side impact sensor. This sensor mounts inside the right B-pillar or the right front or rear door cavity and monitors side impact acceleration. A short to ground prevents the SRS control unit (ACU) from receiving a valid analog acceleration signal (typically a 0.5-4.5V voltage signal). Instead, the ACU receives a ground potential near 0V. This condition triggers the ACU to enter fault protection mode, disable the right side airbag and curtain airbag deployment, and illuminate the airbag fault warning lamp. If the short circuit occurs during an impact, it can cause unintended airbag deployment or failure to deploy, creating a serious safety hazard.
Causes
— Repeated flexing of the right front or right rear door wiring harness at the door hinge wears the insulation, causing the signal wire (usually yellow) to contact the metal door frame and create a short to ground.— Internal sealing failure of the right side impact sensor body allows rainwater or car wash fluid to enter the sensor, causing a short circuit on the circuit board. This commonly results from incorrect installation of the waterproof sealing ring after accident repairs.— Water ingress or a damp environment oxidised or corroded the sensor connector terminals (2-pin or 3-pin plug) below the right B-pillar, causing a partial short circuit or a complete short to ground.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal. Wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment. Wear an anti-static wrist strap. Prepare a multimeter and insulated probes.— Locate the sensor: Refer to the vehicle repair manual (E1/Qin series) to confirm the location of the right side impact sensor (usually inside the right B-pillar lower trim panel or the front of the right front door cavity). Remove the corresponding interior trim panel to expose the sensor.+4 more →
B1670›
DTC B1670 indicates an abnormally low-resistance connection (short to ground) between the right Side Impact Sensor (SIS) signal circuit and body ground (GND). Electrically, this typically indicates damaged signal wire insulation contacting body metal, an internal connector short, or a sensor internal integrated circuit fault shorting the signal output terminal to the housing. This fault causes the Airbag Control Unit (ACU) to continuously receive a false 'crash trigger' signal (voltage near 0V) or completely lose sensor communication. Consequently, the ACU enters fail-safe mode, disabling the right airbag and side curtain airbag to prevent accidental deployment. Additionally, if the system identifies the short circuit as a continuous crash signal on certain models, it may trigger unintended airbag deployment. This fault constitutes a severe safety hazard and requires immediate repair.
Causes
— Right side impact sensor wiring harness wear: During long-term vehicle use, the sensor wiring harness inside the right B-pillar or sill trim rubs against body metal edges or retaining clips, damaging the insulation and shorting the copper core to body ground.— Connector water ingress or corrosion: Vehicle wading, a blocked sunroof drain, or improper car washing introduces moisture into the right crash sensor connector (usually located below the B-pillar or under the seat), causing a short circuit between pins or to ground.— Internal sensor body fault: Damage to the crash sensor piezoelectric element or signal processing circuit causes the signal output terminal to short to the sensor housing (ground).+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes to discharge the airbag system energy storage capacitor and prevent accidental airbag deployment during repair.— Fault confirmation and freeze frame recording: Use the BYD VDS diagnostic tool to read the DTC B1670 status (current/history), record the freeze frame data (vehicle speed, timestamp, and sensor voltage values at the time of the fault), and confirm the specific right-side sensor location (front/center/rear).+5 more →
B167011›
DTC B167011 indicates a short to ground in the Right Side Impact Sensor (RSIS) signal circuit. This sensor typically mounts on the right B-pillar, right front door, or right front side member to monitor acceleration changes during a side impact. The SRS control module logs this fault when it detects the sensor signal wire resistance to ground falls below the threshold (typically 0-5Ω). An insulation failure in the sensor circuit causes this fault. The control module receives a continuous 0V signal (ground potential), preventing it from correctly determining impact severity. This fault triggers fail-safe mode, disabling the right side airbag and side curtain airbag, and illuminates the instrument panel airbag warning light. It severely compromises occupant protection during a side impact and constitutes a high-risk safety fault.
Causes
— Harness mechanical damage: Long-term bending, wear, or accident-related crushing damages the harness insulation at the right B-pillar or door hinge, causing the wire to directly contact the body metal and create a short to ground.— Sensor connector fault: Aged connector seal or internal water ingress after driving through water causing pin corrosion and a short circuit; improperly seated connector during maintenance; or a bent pin contacting the connector housing (ground terminal).— Internal short circuit in sensor body: Damage to the crash sensor internal piezoelectric element or processing circuit shorts the power supply or signal terminal to ground. Measured resistance typically reads near 0Ω (normal: 1.9-2.3kΩ).+2 more →
Actions
— Safe power-down: Turn off the ignition, disconnect the negative battery terminal, and wait at least 3 minutes to fully discharge the SRS system capacitor and prevent accidental airbag deployment during repair.— Fault confirmation: Read fault codes using VDS or a Launch diagnostic tool. Confirm B167011 is a current fault (Present). Record freeze frame data. Check for accompanying related fault codes (such as U0151 communication fault).+6 more →
B167100›
The Right Side Impact Sensor is a key safety component of the Supplemental Restraint System (SRS). The sensor typically mounts in the right B-pillar, right front door, or right C-pillar. It monitors acceleration changes on the right side of the vehicle. Upon detecting severe deceleration from a side impact, the sensor sends a crash signal to the SRS control unit to trigger the right side airbag and/or side curtain airbag deployment. DTC B167100 indicates the SRS control module fails to receive a valid signal from the Right Side Impact Sensor, or the received signal falls out of range (including open circuit, short circuit, signal distortion, or no sensor response). This fault disables the right side impact protection function. The airbags may fail to deploy during a side collision. The system illuminates the airbag warning light to alert the driver of a safety system fault.
Causes
— Right side impact sensor internal damage or sensitivity drift (e.g., piezoelectric element aging or internal circuit fault)— Sensor harness open circuit, short to ground, or short to power (commonly harness chafing at the door hinge or inside the B-pillar trim).— Poor contact at the sensor connector, oxidized pins, loose connections, or corrosion from water ingress (especially after wading or washing the vehicle)+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS/VDS2000) to read the DTC freeze frame data and confirm the environmental conditions (vehicle speed, temperature, voltage) when the fault occurred. Attempt to clear the DTC and observe if the fault is intermittent.— Switch off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor. Inspect the right side impact sensor for physical damage, cracks, or signs of water ingress.+4 more →
B167200›
DTC B167200 indicates the airbag system (SRS) detects a mismatch between the configuration parameters of the Right Side Impact Sensor (typically mounted inside the right B-pillar) and the calibration data stored in the SRS control module. This is not a basic circuit continuity fault; it involves sensor ID recognition failure, hardware parameter verification errors, or lost/corrupted software configuration data. In the BYD architecture, this sensor monitors lateral acceleration changes and provides critical data for side airbag and side curtain airbag deployment decisions. This fault forces the SRS into a degraded mode. The right side airbag and side curtain airbag may fail to deploy during a collision. Additionally, the system may send an abnormal crash signal via a hardwired connection to the BMS and Vehicle Control Unit (VCU), triggering high-voltage system power cut-off protection or a reduced power mode.
Causes
— Poor contact or terminal back-out at the sensor wiring harness connector: The right side impact sensor is located on the B-pillar. Long-term vibration or a loose connection causes internal connector terminals to oxidize or back out, resulting in intermittent signal interruption or abnormal resistance values and triggering a configuration verification failure.— SRS control module software defect or calibration data loss: Early-batch SRS module software versions contain bugs, or the module loses stored sensor ID matching data and calibration parameters during vehicle power loss or low battery voltage.— Sensor hardware fault: Damage to the internal MEMS accelerometer or ASIC chip causes output signal parameters to exceed the SRS module tolerance range.+2 more →
Actions
— Initial diagnosis: Connect the VDS2000 or BYD dedicated diagnostic tool. Access the SRS system to read the complete fault codes. Confirm if B167200 is a current or history code. Read the data stream to check the right side impact sensor status (should display 'Normal' or a specific voltage value). Check for other related fault codes (e.g., B165700, B17A400).— Physical inspection and cleaning: Disconnect the negative battery terminal, wait 3 minutes, then remove the right B-pillar lower trim panel. Locate the right side impact sensor (usually a black square component with a 2-3 pin connector). Check the connector for looseness, water ingress, or oxidation. Unplug the connector and check the terminals for recession or deformation. Clean with electrical contact cleaner and apply conductive grease.+4 more →
B167300›
This fault code indicates a communication failure between the airbag control module (SRS ECU) and the right side impact sensor (SIS). On models such as the BYD Qin PRO, the right side impact sensor typically mounts inside the right front door trim panel, below the right B-pillar, or beside the right front seat. The sensor connects to the SRS ECU via a LIN bus or hardwire to monitor real-time lateral acceleration changes on the right side of the vehicle. The ECU triggers DTC B167300 if it fails to receive valid data frames from the sensor over several consecutive ignition cycles, detects a bus short or open circuit, or encounters a data checksum failure. This fault may prevent the right side airbags (curtain and seat side airbags) from deploying during a side impact. Consequently, the airbag warning lamp (SRS lamp) illuminates continuously, and the vehicle passive safety system enters degraded protection mode.
Causes
— Internal circuit damage in the right side impact sensor (e.g., MEMS accelerometer chip failure or internal capacitor breakdown). Commonly occurs after vehicle water ingress or a previous side impact.— Loose connectors, backed-out terminals, oxidation, or water intrusion in the wiring harness between the sensor and the SRS ECU, especially harness wear at the door hinge and inside the sill trim caused by frequent door operation or wading.— Poor contact in the sensor power supply circuit (+B power) or ground circuit (GND), resulting in abnormal voltage (normal: 9-16V; dropping below 8V may trigger a communication fault).+2 more →
Actions
— Use BYD dedicated diagnostic tool VDS2000 or Launch X-431 to access the SRS system. Read the complete DTC freeze frame data (record vehicle speed, temperature, and voltage at the time of the fault). Clear the fault code to distinguish between an intermittent and persistent fault.— Visually inspect the right front door trim panel, lower B-pillar trim panel, and sill wiring harness sleeve. Inspect the wiring harness at the door hinge specifically for breaks, wear, or signs of water ingress. Check the right front carpet and under the seat for water stains to determine if the vehicle has flood damage.+5 more →
B167500›
DTC B167500 indicates a communication interruption or data anomaly between the Airbag Control Unit (ACU) and the Left Rear Side Impact Sensor (typically mounted in the left C-pillar, left rear door frame, or rear seat side panel area). This sensor communicates with the ACU via a LIN bus or dedicated CAN line to monitor collision acceleration at the left rear of the vehicle. The ACU sets this code when it fails to receive a valid data frame from the sensor within a set cycle (typically 100-500ms) or receives data with a checksum error. This safety-critical fault prevents the side curtain airbag (CAB) and left rear side airbag from triggering accurately during a side impact, or in extreme cases, causes unintended airbag deployment.
Causes
— Loose, oxidized, or poor contact at the left rear side impact sensor wiring harness connector (commonly results from water ingress through an aged left rear door frame seal, or failing to fully seat the connector after C-pillar trim panel removal and installation).— Internal sensor unit fault (MEMS accelerometer chip damage, LIN transceiver fault, or internal power regulation circuit failure)— Wiring harness open or short circuit (long-term bending, water ingress, or rodent damage to the main wiring harness inside the sill trim causes a LIN wire short to ground or power, or a short between the signal wire and shielding layer)+2 more →
Actions
— Use VDS2000 or the BYD dedicated diagnostic tool to access the SRS system. Read all DTCs and record the freeze frame data. Check for accompanying fault codes such as B1676 (sensor not connected). Verify the ACU software is the latest version.— Remove the left C-pillar trim panel or left rear door seal. Locate the left rear side impact sensor (part number usually starts with 5A-). Visually inspect the connector for looseness and the pins for oxidation or discoloration. Measure the voltage between pin 1 (power) and pin 2 (ground) at the sensor connector. The voltage must be 9-16V.+4 more →
B1676-00›
DTC B1676-00 indicates the airbag control module (SRS ECU) detects a communication interruption or circuit fault in the Left Rear Side Impact Sensor (LR-SIS). The sensor typically mounts on the vehicle's left rear side panel, inside the C-pillar trim panel, or on the side of the rear seat to monitor collision acceleration at the left rear of the vehicle. The ECU sets this fault code when it detects an open circuit, a short circuit, or internal sensor resistance outside the calibrated range (typically 2.0–3.0 kΩ, depending on the vehicle model). This SRS communication link fault may prevent the side airbags and side curtain airbags from deploying correctly during a side impact. It can also force the entire airbag system into a degraded protection mode, severely compromising passive safety performance.
Causes
— Sensor connector loose, oxidized, or experiencing water ingress: Because the left rear side impact sensor mounts in the vehicle side body panel, wading, car washing, or damp conditions can oxidize or corrode the connector. Vehicle vibration may also loosen the connector.— Wiring harness wear or breakage: Rear seat adjustment, heavy objects, or aftermarket audio/soundproofing installations can pinch or cut the wiring harness in the C-pillar or under the seat, causing an open circuit or intermittent poor contact.— Sensor fault: Damaged internal piezoelectric element or processing circuit causes abnormal resistance or no signal output.+2 more →
Actions
— Safety preparation: Turn the vehicle OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the SRS system capacitor and prevent accidental airbag deployment.— Locate the sensor: Refer to the repair manual, remove the left rear side trim panel or lower C-pillar trim panel, and locate the left rear side impact sensor (usually marked 'SIS LR' or similar).+5 more →
B1676›
DTC B1676 indicates the airbag control unit (SRS ECU) detected a communication loss or physical disconnection at the Left Rear Side Impact Sensor. Located in the left rear C-pillar or rear door frame area, this sensor monitors collision acceleration at the left rear of the vehicle. The SRS ECU stores this DTC if it fails to receive a sensor signal within a predetermined time or detects abnormal circuit resistance (open/short circuit). This fault forces the side airbag system (including the side curtain and/or rear seat side airbags) into a degraded mode. The airbags may fail to deploy during a left-side collision, severely compromising passive safety. Repair immediately.
Causes
— Loose sensor connector, backed-out pins, or oxidized/corroded terminals behind the left rear C-pillar trim panel (common after vehicle wading, high-pressure washing, or prolonged exposure to damp environments)— Long-term bending and wear at the door hinge or C-pillar sheet metal opening causes internal wire breakage in the sensor wiring harness.— Side impact sensor internal accelerometer failure (e.g., vehicle experienced a previous side impact without airbag deployment, or sensor aging and failure)+2 more →
Actions
— Safety preparation: Turn off the ignition, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS system energy storage capacitor and prevent accidental airbag deployment.— Visual inspection: Remove the left rear C-pillar trim panel and sill trim panel. Locate the side impact sensor (usually marked 'SIDE IMPACT' or with a part number). Verify the connector is fully seated and check for a broken locking tab. Inspect the pins for green oxidation, corrosion, or backed-out terminals.+3 more →
B1677-00›
DTC B1677-00 on BYD new energy vehicles (including DM hybrid and EV models) is a manufacturer-defined fault code. It denotes a communication fault between the Battery Management System (BMS) and the Motor Control Unit (MCU/VTOG), or a High Voltage Interlock Loop (HVIL) fault, rather than an SRS airbag crash sensor fault. This fault indicates an open circuit, short circuit, or communication interruption in the high-voltage safety interlock loop. When the BMS detects a high-voltage safety risk, it triggers a protection mechanism and cuts off the high-voltage power supply, preventing the vehicle from powering on, driving, or charging. This fault involves high-voltage safety and requires immediate repair.
Causes
— Loose high-voltage interlock (HVIL) connector, backed-out terminals, poor connection, or corroded/oxidized pins causing abnormal circuit resistance.— High-voltage interlock circuit open or short to ground, or wiring harness wear, interference, or water ingress.— CAN communication wiring harness fault between BMS and MCU (open circuit, short circuit, electromagnetic interference)+2 more →
Actions
— Use the BYD dedicated diagnostic tool (ED400/Launch X-431) to read BMS system fault codes. Verify B1677-00 and related freeze frame data, and check for accompanying communication fault codes.— Perform the high-voltage interlock loop continuity test: Disconnect the low-voltage battery negative terminal, wait 5 minutes, and measure the total HVIL circuit resistance using a multimeter. Normal resistance is less than 10Ω. If the resistance is excessive or infinite, check the interlock pins of each high-voltage component section by section (BMS → service disconnect switch → power battery → PDU → MCU → compressor → PTC).+4 more →
B1677›
DTC B1677 indicates a short to ground in the left rear side impact sensor (SIS) signal circuit. In the BYD SRS (Supplemental Restraint System) architecture, the left rear side impact sensor typically mounts below the B-pillar or near the left rear door frame to monitor collision acceleration at the left rear of the vehicle. When the sensor signal wire shorts to the vehicle body ground, the SRS control module (ACM) detects a signal voltage continuously below the threshold (usually <0.5V) and logs a short-to-ground fault. This fault disables the left rear side collision detection function, forces the system into fail-safe mode, and illuminates the instrument cluster SRS warning lamp. During a side collision, the left-side curtain airbag and seat side airbag may fail to deploy, posing a serious safety risk.
Causes
— Internal short circuit in the sensor body: Damage to the piezoelectric element or signal processing circuit inside the left rear side impact sensor causes the resistance between the signal terminal and ground terminal to drop abnormally (<10Ω).— Harness insulation worn and shorted to ground: Vibration and friction damage the insulation where the harness passes through body sheet metal holes, retaining clips, or floor routing channels, causing the copper core to contact the vehicle body metal.— Connector water ingress and corrosion: Vehicle wading, car washing, or poor sealing causes water to enter the sensor connector (usually located inside the B-pillar trim panel or under the seat), forming an electrolytic conductive path between the pins.+2 more →
Actions
— Safety Preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds for the SRS system capacitor to discharge to prevent accidental airbag deployment.— Fault Confirmation: Use a BYD VDS or Launch X-431 diagnostic tool to read fault codes, confirm B1677 is a current fault (Active), and record freeze frame data (vehicle speed, timestamp, etc.).+8 more →
B167711›
B167711 is a BYD Supplemental Restraint System (SRS) diagnostic code indicating a short to ground in the left rear side impact sensor signal circuit. This sensor typically mounts in the left B-pillar or C-pillar area. It detects acceleration changes during a side impact and provides a collision severity signal to the Airbag Control Unit (ACU). A short to ground indicates insulation failure between the sensor signal wire (SIG) or power wire (VB) and the vehicle body ground (GND), dropping the resistance below the normal threshold (typically <5Ω). This fault prevents the ACU from receiving the collision signal, triggers the system fail-safe mechanism, disables deployment of the left rear side airbag and side curtain airbag, and illuminates the airbag warning light. During a severe collision, the affected airbags may fail to inflate, posing a severe safety hazard.
Causes
— Wiring harness physical damage: Long-term vibration, compression, or wear damages the sensor wiring harness insulation inside the left rear side trim panel, below the B-pillar, or near the seat rails, causing it to contact the vehicle body metal and create a short to ground.— Internal sensor fault: Breakdown of the crash sensor's internal IC circuit, filter capacitor, or Zener diode causes internal conduction between the signal and ground terminals. Common causes include sensor aging or severe vibration.— Connector water ingress and corrosion: Vehicle wading, direct high-pressure washing, or aging seals cause water to seep into the left rear side panel. The water oxidizes and electrolytically corrodes the sensor connector pins (usually located below the B-pillar or inside the sill beam), creating a short circuit path.+2 more →
Actions
— Safety preparation: Park the vehicle on a level surface, turn the ignition switch to OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault Confirmation: Use the BYD VDS2000/VDS3000 diagnostic tool to access the SRS system. Read DTC B167711 to confirm the fault is active, and record the freeze frame data (ambient temperature and vehicle status).+6 more →
B167800›
This DTC indicates the SRS electronic control unit detects a functional fault in the Left Rear Side Impact Sensor (mounted in the lower left B-pillar or inside the left rear quarter panel). Specifically, the ECU receives no valid acceleration signal, the signal exceeds the normal threshold (typically 0.5-4.5V), or the system detects an open or short circuit. This sensor monitors side-impact acceleration on the left rear of the vehicle. The ECU uses this signal to determine whether to deploy the left curtain airbag and rear side airbag. When this fault occurs, the system enters fail-safe mode, illuminates the airbag warning light, and disables the related side airbags, significantly increasing the risk of occupant protection failure during a side collision.
Causes
— A damaged piezoelectric accelerometer or signal processing IC inside the sensor body causes output signal drift or no signal.— Water ingress and oxidation at the wiring harness connector at the bottom of the left B-pillar (common after car washing or wading), causing increased contact resistance or a short circuit in the signal wire.— A broken body wiring harness at the B-pillar hinge bend, or improper wiring harness routing after accident repairs, causes an open circuit.+2 more →
Actions
— Use the BYD VDS3000 diagnostic tool to read the complete fault codes and freeze frame data. Check for accompanying sub-fault codes such as B167711 (short to ground) or B167712 (short to power). Record the vehicle speed and ambient temperature at the time of the fault.— Disconnect the negative battery terminal and wait at least 90 seconds to allow the SRS capacitor to fully discharge. Remove the left lower B-pillar trim panel and the left rear door sill trim panel. Visually inspect the crash sensor exterior for cracks and misaligned installation torque marks (standard torque is typically 8-10 N·m).+6 more →
B167900›
DTC B167900 indicates a logic error or communication protocol mismatch in the parameter data transmitted from the left rear side impact sensor (typically installed in the left C-pillar or rear door frame area) to the SRS airbag control unit. This is not a simple circuit fault (such as an open or short circuit). Instead, specific identification parameters uploaded by the sensor (such as part number ID, calibration zero offset value, sensitivity coefficient, or communication checksum) exceed the SRS ECU storage range or fail verification. Possible causes include: - Incorrect sensor configuration (e.g., failing to write parameters after accident repairs) - Corrupted parameter data stored in the sensor's internal ASIC chip - LIN/CAN bus communication interference causing data frame errors - Unstable sensor supply voltage causing abnormal analog-to-digital conversion This fault prevents the SRS system from confirming sensor data reliability. The system may enter a degraded mode, disabling window airbag or side curtain airbag deployment and significantly reducing side impact protection.
Causes
— Long-term bending of the left rear side impact sensor wiring harness at the C-pillar or rear door hinge causes internal wire wear and intermittent contact, resulting in power supply or signal voltage drift.— Oxidized or backed-out pins in the sensor connector (yellow waterproof connector), or seal failure, causing increased contact resistance or intermittent open circuit.— Water enters the left rear sensor mounting hole during vehicle wading or washing, causing moisture damage to the parameter storage unit on the sensor's internal circuit board.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes to discharge residual charge from the SRS capacitor. Use the VDS2000 or a dedicated diagnostic tool to read the complete fault codes. Confirm B167900 is a current fault (Active) and check for an accompanying B167800 (hardware fault) or communication fault codes.— Physical inspection: Remove the left rear C-pillar interior trim panel and sill trim panel. Locate the side impact sensor (yellow marking). Visually inspect the sensor housing for impact marks, cracks, or water ingress. Disconnect the connector. Check the terminals for oxidation, backout, or deformation. Inspect the connector sealing ring integrity.+3 more →
B167A-00›
DTC B167A-00 indicates the airbag control unit (SRS ECU/ACU) detects an open circuit, abnormal resistance, or complete loss of communication in the Right Rear Side Impact Sensor (RR-SIS) circuit. This sensor typically mounts in the right rear C-pillar, D-pillar, or inside the right rear quarter panel to monitor collision acceleration signals from the right rear of the vehicle. The ACU sets this DTC if it fails to receive a valid signal from the sensor within a predetermined time, or if it detects circuit resistance exceeding the threshold (typically >10kΩ or an open circuit). This fault forces the right side airbag system (side airbag/side curtain airbag) into fail-safe mode. The system may fail to deploy correctly during a side impact, severely compromising occupant protection. The front airbag system typically remains operational.
Causes
— Sensor connector loose or disconnected: The right rear side impact sensor is located behind the C-pillar or D-pillar trim panel. Incorrectly connecting the sensor after accident repairs, interior trim removal and installation, or rear quarter panel sheet metal repairs, or a broken connector locking tab, causes a poor connection.— Wiring harness open circuit or chafing: The harness from the ACU to the right rear sensor routes through the right B-pillar, C-pillar sill, or under the rear seat. Pinching by the seat adjustment mechanism, water ingress corrosion, rodent damage, or accident deformation can break the internal copper wires.— Internal sensor fault: Damaged internal piezoelectric accelerometer element or open internal circuit prevents valid crash signal generation or interrupts communication.+2 more →
Actions
— Safety preparation: Switch the vehicle to OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds (120 seconds for some models) to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Location and removal: Refer to the vehicle repair manual (E1/Qin series). Remove the right rear C-pillar trim panel or right rear fender liner. Locate the right rear side impact sensor (usually a black or yellow 2-pin or 3-pin connector).+6 more →
B167A›
DTC B167A indicates the SRS (Supplemental Restraint System) ECU detects a communication interruption or physical disconnection of the Right Rear Side Impact Sensor (SIS). This sensor mounts in the right C-pillar area or near the rear door frame to monitor collision acceleration signals from the right rear of the vehicle. The SRS ECU sets this DTC if it fails to receive a valid signal from the sensor within the specified detection period, or if it detects circuit resistance outside the calibrated range (open circuit ∞Ω or short circuit 0Ω). This safety-critical fault severely compromises rear occupant side-impact protection. During a right-side collision, it may cause the side and curtain airbags to fail to deploy or deploy with incorrect timing.
Causes
— Sensor wiring harness connector is loose, disconnected, or has poor contact (common after accident repairs, failure to properly seat the connector after interior trim installation, or the plug vibrating loose from prolonged driving on rough roads).— Open or short circuit in the wiring harness (harness damage caused by frequent friction from rear passengers entering and exiting, compression by luggage, crushing in a vehicle accident, or rodent chewing)— Internal sensor fault (accelerometer element aging, cracked internal solder joints, moisture ingress, or physical impact damage resulting in no signal output)+2 more →
Actions
— Safety preparation: Switch the vehicle to OFF, disconnect the battery negative terminal, and wait at least 3 minutes to completely discharge the SRS system capacitors and prevent accidental airbag deployment.— Fault Confirmation: Use the BYD dedicated diagnostic tool (VDS2000/VDS6000) to read fault codes. Confirm B167A is a Current DTC rather than a history DTC. Check for other SRS-related DTCs (such as B1675, B1676, etc.).+5 more →
B167A00›
This DTC indicates the airbag control unit (SRS ECU) detects a communication loss or open circuit at the Right Rear Side Impact Sensor. The sensor typically mounts in the right C-pillar, rear sill, or right rear door frame area to monitor acceleration changes during a right rear side impact. The ECU sets DTC B167A00 when it fails to receive the sensor signal or detects abnormal circuit resistance (open circuit). This fault disables the right rear side collision detection function. During a side impact, the system may fail to accurately determine collision severity, causing the side airbag and curtain airbag to fail to deploy or deploy at the incorrect time, severely compromising occupant safety.
Causes
— Loose sensor wiring harness connector or poor contact: The right rear side impact sensor mounts in the body sill or C-pillar area. Driving through water, rough roads, or previous repairs can cause the connector to loosen, terminals to back out, or oxidation and corrosion.— Wiring harness open circuit or wear: The sensor wiring harness routes through the door hinge, sill trim panel, or under the carpet. Long-term bending, pinching, or underbody scraping may cause internal wire breakage or insulation damage.— Internal sensor fault: Damage to the internal accelerometer or communication chip prevents the sensor from sending a valid signal to the SRS ECU or causes a high-impedance state.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS) to read the fault code. Confirm whether B167A00 is a current or history fault. View the freeze frame data and record the vehicle status when the fault occurred.— Disconnect the negative battery terminal and wait at least 3 minutes for the SRS system to fully discharge. Remove the right rear door sill trim, C-pillar interior trim, or right rear seat (depending on the vehicle model), then locate the right rear side impact sensor (usually marked SR or SRS, with a yellow connector).+4 more →
B167B-00›
This DTC indicates the airbag control unit (SRS ECU) detects an abnormally low-resistance connection (short to ground) between the right rear side impact sensor (SIS) signal circuit and body ground (GND). BYD SRS architecture typically uses piezoelectric or acceleration-type side impact sensors. These sensors mount inside the right rear door, behind the C-pillar trim panel, or beside the rear seat to monitor lateral impacts to the right rear of the vehicle. When the sensor signal wire shorts to ground, the ECU continuously receives a low-level signal near 0V and cannot correctly identify actual collision deceleration signals. This causes the following: 1) the right rear airbag (side airbag/curtain airbag) may fail to deploy during a side impact; 2) the system enters fail-safe mode, illuminates the airbag warning lamp, and may disable the entire airbag system. Cycling the ignition typically cannot clear this hard fault.
Causes
— Internal integrated circuit fault in the right rear side impact sensor, causing a short circuit between the signal output terminal and the sensor housing (ground).— Sensor wiring harness chafes at the door hinge, inside the harness corrugated conduit, or at the floor harness grommet, damaging the wire insulation and causing the wire to contact the vehicle body metal frame.— Vehicle wading, a leaking blocked sunroof drain, or direct high-pressure spray during washing causes water to enter the sensor connector (usually located below the C-pillar or inside the sill beam). This creates an electrolytic short circuit between the pins or a short to ground.+2 more →
Actions
— Safety preparation: Shift the vehicle into P, apply the parking brake, turn off the ignition, and disconnect the 12V battery negative terminal. Wait at least 90 seconds for the SRS system backup power supply to fully discharge and prevent accidental airbag deployment.— Fault confirmation: Use the BYD dedicated diagnostic tool (VDS or ED400) to read fault codes, confirm B167B-00 is a current fault (Active), record freeze frame data, and check for accompanying crash sensor fault codes.+7 more →
B167B›
DTC B167B indicates the Supplemental Restraint System (SRS) detects an unintended low-resistance connection (short to ground) between the Right Rear Side Impact Sensor signal circuit and vehicle ground (GND). This sensor typically mounts in the right C-pillar, rear rocker panel, or rear seat side panel area to monitor side-impact acceleration at the right rear of the vehicle. During a short to ground, the SRS control module detects an abnormal drop in sensor voltage (approaching 0V) and registers a sensor circuit fault. This fault forces the SRS into a degraded mode: the right side airbag and curtain airbag may fail to deploy during a collision, or the system may falsely trigger its fail-safe mechanism, keeping the airbag warning lamp illuminated and severely compromising passive safety.
Causes
— Physical damage to the wiring harness: Long-term vibration and chafing of the right rear wiring harness near the door sill, C-pillar, or seat rail damages the insulation, allowing the wire to directly contact the body metal and create a short to ground.— Connector fault: improperly locked sensor connector, aged sealing ring causing water ingress and corrosion, or bent pins causing a short circuit between the signal and ground terminals.— Internal sensor short circuit: A fault in the collision sensor's internal piezoelectric element or processing circuit shorts the power supply/signal line to the housing (ground).+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal. Wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation: Connect the diagnostic tool and read the freeze frame data. Verify the sensor voltage when the fault occurred (normally about 2.5V; close to 0V when shorted to ground). Clear the fault code and observe if it returns.+5 more →
B167B11›
DTC B167B11 has different definitions depending on the vehicle model. Early models, such as the BYD E2, E3, and Qin EV, define this fault as a short to ground in the right rear side impact sensor (SIS) signal circuit within the SRS airbag system. Newer models, such as the Han EV, define it as a short to ground in the left front seat heater circuit. Regardless of the application, sub-code '11' indicates a short to ground. For the SRS system, this fault indicates the airbag control unit (ACU) continuously detects 0V on the right rear side impact sensor signal wire (below the 0.3V threshold), preventing the ACU from receiving the correct collision acceleration signal. This triggers the SRS fail-safe mode, constituting a serious safety hazard. The fault may prevent the side airbag or side curtain from deploying correctly during a side impact, or falsely trigger the airbag warning lamp while driving. For the seat heater definition, this fault indicates the heating element circuit current increased abnormally, causing the control module to activate overcurrent protection.
Causes
— Right rear side impact sensor harness insulation wears through and contacts the body sheet metal or seat frame, causing a short to ground (common due to improper harness securing after rear fender liner removal and installation).— Water ingress and corrosion in the sensor connector causing the signal pin to short to ground (common after vehicle wading, car wash fluid residue, or an aging seal ring)— Crash sensor internal electronic component failure causes the signal wire to short to ground (internal capacitor breakdown or IC damage).+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds (to ensure the SRS system capacitors fully discharge) to prevent accidental airbag deployment. Wear an anti-static wrist strap.— Locate the sensor: Remove the right rear C-pillar trim panel and rear fender liner, then locate the right rear side impact sensor (usually above the rear sill beam, at the lower C-pillar, or behind the rear seat backrest).+6 more →
B167C00›
DTC B167C00 indicates the Right Rear Side Impact Sensor in the Supplemental Restraint System (SRS) detects an internal functional fault. The sensor typically mounts in the vehicle C-pillar or right rear quarter panel area to monitor collision acceleration on the right rear side. The SRS control module sets this fault code when the sensor experiences an internal circuit fault, communication interruption, or abnormal signal. This fault may prevent the right rear side airbag or curtain airbag from deploying normally during a side impact, severely compromising passive safety performance. It does not directly affect normal vehicle driving functions.
Causes
— Damage or degradation of the sensor body internal circuit causes abnormal signal output.— Poor contact, oxidation, or terminal back-out at the sensor wiring harness connector. Repeated bending easily damages the wiring harness inside the C-pillar trim.— Improper sensor installation position or insufficient retaining bolt torque after rear-end accident repairs reduces sensor detection sensitivity.+2 more →
Actions
— Use the BYD VDS diagnostic tool to read and confirm the DTC status. Check for related DTCs (such as B167B11, B167D00). Record the freeze frame data, attempt to clear the DTC, and observe if the fault is intermittent.— Remove the right rear C-pillar trim panel and inspect the side impact sensor for physical damage, cracks, or water stains. Verify the correct sensor installation direction and confirm the fastening torque meets the standard (usually 8-10 N·m).+5 more →
B167D00›
This DTC indicates the internal parameters of the right rear side impact sensor (typically located in the right C-pillar or rear door frame area for side impact detection) exceed the normal tolerance range or fail validation. Unlike a simple communication error, this fault confirms a normal communication link between the sensor and the SRS control module. However, the sensor detected abnormal internal calibration data, sensitivity parameters, or zero-point offset during self-check. Potential causes include corrupted internal sensor EEPROM data, physical characteristic drift from long-term use, A/D conversion errors resulting from unstable supply voltage, or internal accelerometer reference shift due to sensor installation stress deformation. This fault prevents the SRS system from accurately determining right-side impact severity. It may delay or incorrectly trigger the side airbag or side curtain airbag, severely compromising passive safety performance. The system typically defaults to a degraded protection mode.
Causes
— Corrupted or missing sensor internal calibration data (EEPROM fault) causes parameter verification failure during self-check.— Sensor mounting bracket looseness, deformation, or stress concentration causing a physical offset in the internal accelerometer reference.— Excessive voltage drop in the power supply circuit (contact resistance >1Ω) or poor ground connection, causing the operating voltage to fall outside the standard 5V±0.25V range.+2 more →
Actions
— Use the BYD VDS diagnostic tool to read the DTC freeze frame data. Record key parameters from when the fault occurred, including ambient temperature, battery voltage, and vehicle status, to confirm whether the fault is intermittent.— Disconnect the battery negative terminal, wait 3 minutes, then remove the right rear C-pillar trim panel. Visually inspect the crash sensor for physical damage or cracks, verify the mounting bolt torque (standard is usually 8-10 N·m), and check the bracket for deformation.+5 more →
B167E00›
This DTC indicates interrupted data communication between the Airbag Control Unit (ACU) and the right rear Side Impact Sensor (SIS). The sensor typically mounts inside the right rear door trim panel or below the C-pillar and connects to the ACU via a LIN bus or hardwire connection. The fault occurs when the ACU fails to receive a valid data frame from the sensor within the specified time window (typically 100-500ms) or receives incorrect checksum data. Consequently, the ACU cannot obtain real-time collision acceleration data from the vehicle's right rear, directly affecting the deployment logic for the side and curtain airbags. The system enters fail-safe mode, illuminates the airbag warning lamp, and may disable the right-side airbag circuit. This condition can prevent proper airbag deployment during a side collision, posing a severe safety risk.
Causes
— Long-term repeated bending of the right rear door wiring harness at the door hinge causes internal wire breakage or insulation damage, resulting in a LIN line open circuit or intermittent poor contact.— Water ingress and oxidation in the sensor connector (typically from vehicle wading, high-pressure wash fluid penetration, or aging door seals), causing a short circuit between terminals or increased resistance.— Right rear side impact sensor internal fault (e.g., damaged MEMS accelerometer chip, communication IC fault, or internal power supply circuit failure)+2 more →
Actions
— Use the BYD VDS 2000 or Launch X431 diagnostic tool to read all DTCs. Confirm if B167E00 is a current or history fault. Check for accompanying B167D00 (parameter error) or U-series communication fault codes.— Disconnect the battery negative terminal and wait 3 minutes for the SRS system capacitor to discharge. Remove the right rear door trim panel. Visually inspect the side impact sensor (part number usually starts with 95920-) for secure mounting and physical damage.+6 more →
B1680-00›
DTC B1680-00 indicates the SRS (Supplemental Restraint System) control module detected an open circuit in the Passenger Airbag Cutoff Switch or its related wiring. This switch, typically located in the center console or glovebox area, manually disables the airbag when a child seat occupies the front passenger seat. The fault occurs because the SRS ECU fails to detect a valid resistance signal from the switch during the self-check cycle (normally a specific resistance range, such as 2-5kΩ, or a ground signal), triggering a level-two safety warning. This condition may forcibly disable the front passenger airbag or place it in an uncertain state, severely compromising the occupant protection strategy during a collision. The fault also illuminates the SRS warning light on the instrument cluster and prevents the vehicle from passing a safety inspection.
Causes
— Physical damage to the front passenger airbag deactivation switch or oxidized internal contacts, causing signal interruption.— Pin back-out, looseness, or corrosion between the switch and wiring harness connector, especially under damp conditions in the front passenger footwell.— Open circuit, crushed or damaged wires, or short circuit to ground or power in the wiring harness from the switch to the SRS ECU. Improper harness routing after dashboard removal and installation commonly causes this.+2 more →
Actions
— Connect the BYD dedicated diagnostic tool (VDS or ED-400). Read all fault codes and confirm B1680-00 is current (Active). Record the freeze frame data and check for accompanying SRS-related fault codes.— Locate the front passenger airbag deactivation switch (typically on the right side of the center console or inside the glove box on Qin series models). Visually inspect the switch exterior for damage, verify the connector is fully inserted, and confirm the locking tab is intact.+4 more →
B1680›
This DTC indicates the airbag control unit (SRS ECU) detects a communication loss or abnormal signal from the passenger airbag cutoff switch (PAD switch). Typically located on the right side of the center console or inside the glovebox, this switch manually controls the front passenger airbag activation/deactivation status (e.g., when installing a child safety seat). The ECU triggers DTC B1680 if it fails to detect a valid resistance signal within a set cycle (normal operation uses different resistance values to distinguish ON/OFF positions, such as 2.2kΩ/4.7kΩ) or detects an open circuit (infinite resistance). This fault causes: 1) the front passenger airbag status to enter an unknown mode, where the system may default to disabling the airbag to prevent unintended deployment, reducing crash protection; 2) the instrument panel airbag warning light to illuminate continuously; 3) some models to record abnormal crash event readiness data, affecting accident liability determination.
Causes
— Loose or disconnected switch connector: Commonly occurs after removing or installing the dashboard, replacing the cabin air filter, repairing the center console, or retrofitting a large display. This results from failing to fully seat the PAD switch connector or from a broken locking clip causing a poor connection.— PAD switch assembly internal fault: Internal carbon film resistor wear, contact oxidation or sulfidation, or spring plate fatigue causes the output resistance value to fall outside the ECU recognition range (typically ±5% tolerance), especially on vehicles operated in high-humidity areas.— Wiring harness open or short circuit: Sharp frame edges, rodents, or crushing during accident repairs damage the internal dashboard wiring harness, causing the signal wire (usually the yellow wire) to open or short to ground.+2 more →
Actions
— Diagnostic tool deep scan: Use the VDS2000 or a dedicated BYD diagnostic tool to read the B1680 freeze frame data. Confirm the fault frequency (intermittent/continuous), ambient temperature, and voltage at the time of occurrence. Check for other accompanying SRS communication fault codes.— Physical connection check: Locate the PAD switch (Song MAX/Yuan EV: usually on the right side of the glovebox; Tang/Qin: on the right side of the center console). Visually verify the connector is fully seated, confirm the locking mechanism (CPA lock) is intact, and gently pull the wiring harness to confirm it is secure.+5 more →
B168000›
DTC B168000 indicates the SRS (Supplemental Restraint System) control module detected a communication interruption or physical disconnection between the Passenger Airbag Disable (PAD) switch and the main control unit. The PAD switch typically mounts in the center console or near the glovebox to manually disable the front passenger airbag (e.g., when installing a child safety seat). The SRS module triggers this fault code if it fails to receive the switch resistance signal (typically a specific resistance range, such as 2kΩ-5kΩ indicating different states) within a predetermined time, or if it detects an open circuit (infinite resistance). This fault forces the front passenger airbag system into fail-safe mode and continuously illuminates the instrument cluster airbag warning lamp. During a collision, the front passenger airbag may fail to deploy or exhibit unpredictable behavior, severely compromising passive safety.
Causes
— Loose, disconnected, or poor contact at the front passenger airbag deactivation switch wiring harness connector, especially due to incorrect reconnection after glove box or center console removal and installation.— Long-term chafing of the floor or instrument panel wiring harness against moving parts (such as the front passenger seat slide rail or hinges) causes an open circuit, or the internal copper wire breaks while the insulation remains intact (hidden open circuit).— Internal contact oxidation, spring failure, or mechanical binding within the airbag deactivation switch assembly causes the resistance value to fall outside the standard range (normally 2.5kΩ-4.8kΩ, depending on switch position).+2 more →
Actions
— Connect the BYD VDS2000 or Launch X-431 diagnostic tool. Access the SRS system to read DTC B168000 and freeze frame data. Confirm the vehicle status at the time of the fault (voltage, temperature, mileage). Attempt to clear the DTC to determine if the fault is intermittent.— Visually inspect the front passenger airbag deactivation switch near the center console or glove box. Confirm the switch body has no physical damage. Verify the wiring harness connector is fully seated and the locking mechanism is securely engaged. If necessary, disconnect the connector and inspect the terminals for push-out, oxidation, or deformation.+5 more →
B1681-00›
On BYD vehicles, B1681-00 typically indicates an immobilizer authentication failure or communication fault between the Body Control Module (BCM), the smart key, and the immobilizer reader coil (antenna). This fault prevents the BCM from verifying key validity, triggering the anti-theft lockout. Symptoms include failure to start, failure to engage high-voltage power (OK mode), or the instrument cluster displaying "Please check the starting system". Although some documents describe this code as an airbag switch short to ground, repair experience and fault code definitions confirm it primarily points to an interrupted immobilizer authentication process involving the low-frequency antenna, immobilizer coil, or a BCM software or hardware fault.
Causes
— Internal open circuit in the immobilizer coil, or a loose or oxidized connector, preventing the system from reading the key chip signal.— BCM software defect (e.g., authentication logic flaws in early versions such as Ver 1.02) or cold solder joint on the internal EEPROM chip.— Low smart key battery (<2.8V) or damaged key chip causing insufficient signal strength.+2 more →
Actions
— Connect the VDS2000 or Launch X431 diagnostic tool, read all BCM (Body Control Module) fault codes, and confirm B1681-00 and any accompanying U-class communication or antenna fault codes.— Check the smart key battery voltage (standard: ≥3.0V) and signal strength. Test with the spare key to rule out a fault with the key itself.+5 more →
B1681›
DTC B1681 indicates the Passive Anti-Theft System (PATS) transceiver module fails to receive a valid signal or cannot establish normal communication with the engine control module (PCM/ECM). This fault belongs to the Body Security system, not the SRS airbag system (Note: original documentation may misclassify the airbag switch). The fault triggers the vehicle anti-theft immobilizer, preventing the engine from starting (No Crank/No Start). The instrument cluster Security Light typically flashes rapidly. The fault stems from abnormalities in key transponder recognition, 125kHz radio frequency signal transmission at the transceiver coil, or data exchange on the dedicated communication line between the PATS module and the PCM. Consequently, the PCM cannot verify key validity and inhibits engine starting.
Causes
— Internal circuit fault or poor thermal stability in the PATS transceiver module (located around the ignition lock cylinder or under the steering wheel) prevents it from generating the 125kHz excitation signal or demodulating the 64-bit rolling code returned by the key chip.— Transceiver coil (induction coil around ignition lock cylinder) open circuit, short circuit, or abnormal resistance (normal resistance approx. 0.5-1.5 Ω), preventing key chip energization or signal reception.— Open circuit, short circuit, or short to ground in the communication wiring between the PATS module and the PCM/ECM (typically a twisted pair, such as grey/orange and white/light green wires), especially if wiring harness expansion causes poor contact after the vehicle warms up.+2 more →
Actions
— Initial diagnosis: Use the diagnostic tool to read the fault code and confirm if B1681 clears or reappears immediately; observe the immobiliser indicator on the instrument cluster to confirm if the vehicle entered immobiliser lock mode; attempt to start the vehicle with the spare key to rule out a single key fault.— Basic circuit inspection: Check the PATS transceiver module power fuse and measure the voltage drop on the constant power (+12V) and ground (GND) circuits. Verify the connectors are secure and free of oxidation. Check the continuity and insulation of the communication twisted pair between the module and the PCM. Inspect the harness for wear, focusing on areas passing through the firewall and near the steering column.+3 more →
B168111›
DTC B168111 indicates the front passenger Occupant Classification System (OCS) detects a short to ground or abnormal signal. The system uses pressure or capacitive sensors integrated into the seat to monitor passenger occupancy status and weight data to control the passenger airbag deployment strategy. When the system detects a sensor circuit short to ground, internal sensor damage, or an abnormal signal, it logs this DTC and illuminates the airbag warning light. Under these conditions, the passenger airbag may enter fail-safe mode (forced off or deployed based on the worst-case scenario) and fail to provide effective protection during a collision. This is a severe safety fault.
Causes
— Front passenger seat Occupant Detection Sensor (ODS) wiring harness connector loose, terminal backed out, or locking tab damaged, causing poor contact or intermittent short to ground.— Long-term chafing of the under-seat wiring harness against the seat rail or bracket damages the insulation. The exposed copper wire contacts the vehicle body metal, causing a short to ground.— Sensor damage from liquid corrosion (spilled drinks, water ingress) or an internal circuit fault causes abnormal signal output.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000 or Launch X431) to read the SRS system fault codes, confirm whether B168111 is a current or historical fault, and check the front passenger occupancy status in the data stream.— Visually inspect the ODS wiring harness connector under the front passenger seat (usually a white 4-pin connector) for looseness, water ingress, or corrosion. Verify the connector locking mechanism is intact and inspect the connector pins for verdigris or oxidation.+5 more →
B1684-00›
DTC B1684-00 indicates a functional fault in the Occupant Classification System (OCS). The OCS is a key subsystem of the Supplemental Restraint System (SRS). Located inside the front passenger seat, the system uses a pressure sensing mat and an electronic control module to monitor the seat load status in real time (empty seat/child/adult). It sends classification signals to the SRS ECU to determine the front passenger airbag deployment strategy during a collision (deployment decision, force, and timing). This DTC triggers when the OCS and SRS ECU lose communication, a sensor signal exceeds its threshold, the system loses calibration data, or a hardware failure occurs. This fault forces the airbag system into fail-safe mode. During a collision, this condition may cause unintended airbag deployment (injuring a child) or failure to deploy (loss of protection). This poses a serious safety risk and requires immediate repair.
Causes
— Physical damage or aging of the front passenger seat OCS pressure sensor mat (common causes include water ingress, liquid seepage, prolonged pressure from heavy objects, or pet scratches breaking the sensor mat)— Loose, oxidized, poor contact, or backed-out pins at the OCS control module wiring harness connector (plug wear caused by frequent seat fore/aft movement or height adjustment)— Failure to perform OCS system zero-point and weight calibrations after vehicle accident repairs, seat removal/installation, or replacement, or an interrupted calibration process causing abnormal data.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000/3000) to read SRS system fault codes, confirm B1684-00 is an active fault, record freeze frame data, and check for related fault codes such as B1685 (OCS sensor fault).— Check the OCS module connector under the front passenger seat (usually a yellow waterproof plug). Confirm the locking tab fully engages. Inspect the pins for oxidation, retraction, or water ingress. Measure the power supply voltage (should be 12V ± 0.5V), ground resistance (<1Ω), and CAN-H/CAN-L line voltage (approximately 2.5V).+4 more →
B1684›
In BYD vehicles, DTC B1684 indicates an Occupant Classification System (OCS) fault. The OCS mounts inside the front passenger seat and consists of the OCS control module and pressure sensors. The system detects pressure distribution and weight on the seat surface to identify the front passenger seat status (empty/child/adult). It sends occupant presence and type signals to the airbag control unit (SRS ECU). The SRS ECU uses these signals to determine the front passenger airbag deployment strategy (whether to deploy and deployment force) during a collision. When the SRS ECU detects a communication loss with the OCS module, an abnormal sensor signal, or missing system calibration data, it logs DTC B1684-00, illuminates the airbag warning light, and enters fail-safe mode (typically disabling front passenger airbag deployment). Consequently, the system may fail to protect the front passenger effectively during a collision, or it may deploy accidentally when no one occupies the seat, causing secondary injury.
Causes
— Internal circuit fault or software crash in the OCS control module (located under the front passenger seat), preventing sensor signal processing or causing loss of communication with the SRS ECU.— The seat pressure sensor (bladder sensor, integrated into the seat foam) is damaged, leaking air due to aging, or has an open circuit, preventing accurate pressure change detection.— Under-seat wiring harness connector (yellow waterproof connector) is loose, oxidized, corroded by water ingress, or has poor contact, especially common after driving the vehicle through water or cleaning the interior.+2 more →
Actions
— Connect the BYD VDS or Launch X-431 diagnostic tool and enter the SRS (airbag) system. Read and record the fault codes. Confirm B1684-00 is present and will not clear. Check for accompanying OCS-related fault codes such as B1680 and B1681.— Visually inspect the yellow OCS module connector under the front passenger seat. Verify the connector lock is fully engaged. Inspect the terminals for signs of oxidation, backed-out pins, or water ingress. If necessary, clean with electrical contact cleaner and apply conductive grease.+4 more →
B168400›
DTC B168400 indicates the Occupant Classification System (OCS) detects an internal fault or abnormal signal. Installed inside the front passenger seat, this key subsystem of the SRS airbag system uses a pressure sensor matrix to monitor seat occupancy status in real time (empty seat/child/adult). The OCS controls the front passenger airbag deployment strategy (suppression, low-power deployment, or full-power deployment) based on the occupant weight class (usually Class 0, Class 1, Class 2, or Class 3). When this DTC triggers, the SRS ECU cannot accurately determine the front passenger occupant status. The system enters fail-safe mode, disables the front passenger airbag by default (to prevent injury to children), and illuminates the airbag fault warning lamp. This fault may prevent correct front passenger airbag deployment during a collision or cause unintended deployment when the seat is empty, severely compromising passive safety performance.
Causes
— Internal fault in the front passenger seat OCS pressure sensor assembly (damaged sensor diaphragm, open strain gauge circuit, or damaged signal processing chip), typically due to long-term fatigue or excessive seat load.— Poor contact, pin oxidation, or water corrosion between the OCS control module and wiring harness connector. Commonly occurs after vehicle wading, seat cleaning fluid leakage, or parking in a damp basement.— Short to ground, short to power, or open circuit in the OCS system power supply or CAN communication circuit, involving wiring harness wear at the dedicated yellow SRS connector under the seat.+2 more →
Actions
— Use the BYD VDS or DTS diagnostic tool to read the complete fault code stream. Check for accompanying sub-codes B168401-B1684FF, and verify if the Occupancy Status and Weight Class values in the OCS live data stream display 'Invalid' or 'Error'.— Switch off the ignition, disconnect the negative battery terminal, and wait 3 minutes (for SRS system capacitor discharge). Visually inspect the yellow OCS connector under the front passenger seat for looseness, water ingress, or green pin corrosion. If necessary, clean with electrical contact cleaner and apply conductive grease.+5 more →
B168500›
DTC B168500 indicates an invalid configuration fault in A/C System Circuit 1 (specifically the electric compressor drive circuit). On BYD Qin PRO models, 'Circuit 1' typically refers to the electric A/C compressor high-voltage drive and LIN communication circuits. 'Invalid configuration' indicates mismatched communication parameters between the HVAC ECU and the compressor control unit, an unconfigured LIN address, or abnormal circuit topology recognition. This fault completely disables the A/C cooling function and may limit vehicle power output. Although some sources classify this as an SRS fault, the BYD fault code structure (B16xxxx) categorizes it under the body HVAC system, with no direct relation to the airbags.
Causes
— Electric compressor LIN line communication fault (open circuit, short circuit, or high contact resistance)— Failure to perform control unit coding/parameter configuration after replacing the electric compressor.— Air conditioning controller (HVAC ECU) software version outdated or internal fault.+2 more →
Actions
— Connect the diagnostic tool, enter the HVAC system, read the complete fault codes and freeze frame data, and check 'Compressor Status' and 'LIN Communication Status' in the data stream.— Check the front compartment electric compressor wiring harness connectors (especially the high-voltage plug and low-voltage signal plug) for looseness, water ingress, oxidation, or burning.+5 more →
B168600›
DTC B168600 indicates the SRS (Supplemental Restraint System/airbag) control module detects an abnormal configuration status in "Circuit 2" (typically the front passenger-side airbag deployment circuit). In the BYD Qin PRO airbag architecture, the control module determines system status by monitoring circuit resistance (standard value 2.0–3.0 Ω) and configuration data. "Invalid configuration" means the control module reads a circuit resistance outside the threshold (open circuit >10 Ω or short circuit <1 Ω), or detects circuit configuration data that does not match the vehicle VIN or lacks correct coding. This fault may prevent the passenger-side airbag from deploying properly during a collision. The system also illuminates the instrument cluster airbag warning light and may disable the entire airbag system to enter fail-safe mode.
Causes
— Resistance drift or damage in the front passenger airbag module internal igniter, causing abnormal circuit resistance.— Yellow connector between the floor wiring harness and the airbag module (usually behind the glove box or on the right side of the center console) is loose, or has backed-out pins, oxidation, or corrosion from water ingress.— Internal open or short circuit in the spiral cable (clock spring) affecting the circuit 2 signal transmission path.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000/VDS3000) to read all DTCs. Verify B168600 is a current fault, not a history fault, and record the circuit resistance value from the freeze frame data.— Disconnect the battery negative cable and wait at least 3 minutes to allow the SRS capacitor to fully discharge, preventing accidental airbag deployment.+6 more →
B168700›
DTC B168700 indicates the Airbag Control Module (SRS ECU) detects that the configuration parameters for Ignition Circuit 3 (typically the left front seat belt pretensioner or left side airbag deployment circuit) do not match the actual vehicle configuration. Specifically, the airbag type, resistance range, or circuit topology data stored in the control module does not match the installed hardware, preventing the system from validating the circuit. This fault prevents the safety device corresponding to Circuit 3 from deploying during a collision, creating a severe safety hazard that requires immediate repair. Common causes include failing to complete online programming after replacing the SRS control module, installing non-genuine parts with different resistance characteristics, or modifying or damaging the wiring harness, which alters the circuit's electrical properties.
Causes
— Failure to perform vehicle configuration (coding) after replacing the SRS control module, or incorrect programming data, prevents the control module from identifying Circuit 3 hardware parameters.— The seat belt pretensioner or side airbag assembly for circuit 3 does not match the vehicle configuration (e.g., installing a part from a different model year or trim level results in a resistance outside the 1.5-3.5Ω standard range).— Poor contact at the SRS wiring harness connector under the seat (usually beside the left front seat slide rail), oxidized or corroded pins, or worn wiring harness insulation causing an intermittent short or open circuit, resulting in the control module falsely detecting a configuration fault.+2 more →
Actions
— Connect the VDS2000/VDS diagnostic tool. Read the complete fault codes and freeze frame data. Confirm whether 'Circuit 3' specifically indicates the left front seat belt pretensioner or the left side airbag, and record the environmental data when the fault occurred.— Run the SRS control module 'Vehicle Configuration' function and verify the VIN, vehicle model code, and airbag configuration code programmed correctly. If you just replaced the control module, perform Online Coding to match the actual vehicle hardware configuration.+4 more →
B168800›
DTC B168800 indicates the SRS (Supplemental Restraint System) control unit detects invalid configuration parameters in circuit 4 (typically the driver-side seat belt pretensioner circuit). Specifically, the control unit detects the circuit resistance falls outside the standard range (normally 2-3 ohms), or the identified hardware configuration does not match the software calibration. This constitutes a hard fault in the passive safety system. During a collision, the corresponding restraint device (seat belt pretensioner or airbag) may fail to deploy, severely compromising occupant protection. Upon fault detection, the SRS control unit illuminates the instrument cluster airbag warning light and may disable the entire airbag system.
Causes
— Driver-side seat belt pretensioner internal open circuit or resistance drift (pretensioner deployed or internal coil damaged)— Loose or oxidized under-seat pretensioner wiring harness connector, or backed-out terminals, causing excessive contact resistance.— Long-term chafing of the wiring harness near the seat slide rail causes insulation damage, wire breakage, or intermittent short circuits.+2 more →
Actions
— Use BYD dedicated diagnostic tool VDS2000/VDS3000 to read all fault codes, record freeze frame data, and check for accompanying communication fault codes such as U0151.— Inspect the driver-side seat belt pretensioner for obvious signs of deployment (webbing retraction or housing cracks). Measure the pretensioner resistance (standard value: 2.0-3.0 Ω; if out of range, replace the assembly).+7 more →
B168900›
DTC B168900 indicates the SRS (Supplemental Restraint System) control module detects invalid configuration data for deployment loop 5 (typically the right front seat side airbag or right curtain airbag, depending on vehicle trim level). This constitutes a Configuration Error rather than a simple open or short circuit. The electrical characteristics of this loop (e.g., igniter resistance, loop integrity detection parameters) do not match the calibration data stored in the ECU. Possible causes include: loop resistance outside the threshold (>5Ω or <1Ω), incorrect ECU coding, failure to write configuration data after replacing the airbag module, crash data corruption, or a software version mismatch. This fault may prevent the specific airbag from deploying during a collision and illuminates the airbag warning light.
Causes
— Loose or oxidized Circuit 5 wiring harness connector, or backed-out pins (On Qin PRO models, Circuit 5 typically routes under the right front seat or at the B-pillar; frequent seat adjustment causes wiring harness fatigue)— Internal igniter resistance drift or failure in the airbag module (side airbag or curtain airbag corresponding to circuit 5) causes the ECU to identify the component as 'invalid'.— Corrupted configuration data stored in the SRS control unit (ACU) internal EEPROM. Common causes include vehicle battery disconnection for more than 30 minutes, an interrupted software update, or circuit board corrosion after water ingress.+2 more →
Actions
— Safety preparation: Switch the vehicle to OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation: Use the BYD VDS2000/2100 diagnostic tool to read DTCs. Confirm B168900 is a current (Active) fault, not a history fault. Record the environmental conditions from the freeze frame data.+7 more →
B168A00›
DTC B168A00 indicates the Airbag Control Unit (ACU) detects the configuration parameters for Circuit 6 (typically the right side airbag/side curtain or right rear side airbag ignition circuit) do not match the system calibration data. This is an SRS configuration fault, not a simple open or short circuit. "Invalid configuration" means the control unit's internal algorithm detects the circuit's electrical characteristics (such as squib resistance, capacitance, or internal ECU configuration code) differ from the vehicle factory settings or current hardware configuration. This condition can prevent the airbag from deploying correctly or cause unintended deployment during a collision, constituting a Level 2 safety fault.
Causes
— Incorrect coding configuration after Airbag Control Unit (ACU) replacement, or software version mismatch.— Installed a non-genuine or incorrectly programmed side airbag module (aftermarket or used part with a mismatched part number).— Circuit 6 wiring harness modifications or accident repairs altered the circuit resistance (e.g., non-OEM seat cover installation, compressed wiring, or oxidized connectors caused the resistance to deviate from the 2.0Ω±0.3Ω standard range).+2 more →
Actions
— Use the BYD VDS2000/VDS3100 diagnostic tool to read complete fault codes and freeze frame data, verify the fault frequency (current/history), and record the vehicle VIN and specific configuration.— Refer to the vehicle repair manual to identify the specific component for Circuit 6 (on the Qin PRO, this is typically the right side airbag or right curtain airbag). Inspect the component appearance, connector condition, and wiring harness integrity.+3 more →
B168B00›
DTC B168B00 indicates the SRS (airbag system) control module detects invalid configuration parameters for Airbag Loop 7. In the BYD Qin PRO SRS architecture, Loop 7 typically corresponds to the right front seat side airbag or the right rear side curtain module. During self-diagnosis, the SRS control module detects that the loop's electrical impedance, squib resistance, or configuration coding does not match the calibrated value (typically 2.0-3.0Ω), or the configuration data stored in the module's internal EEPROM is corrupted or missing. This is a configuration validity fault rather than a simple open or short circuit. This fault can prevent the corresponding airbag from deploying during a collision, illuminates the airbag warning lamp continuously, and forces the system into fail-safe mode.
Causes
— Abnormal resistance in the circuit 7 airbag assembly (seat airbag or curtain airbag) internal igniter due to aging, moisture, or mismatched model, causing impedance to fall outside the standard 1.6-3.5Ω range.— Poor contact at the wiring harness connector, especially the yellow SRS connector under the seat (G07 or GJK20 series), where frequent seat sliding causes terminal back-out, oxidation, or intermittent connections.— SRS control module software version defect (early versions contain a configuration verification algorithm flaw), or power fluctuations (discharged battery, improper jump-starting) corrupted the internal module configuration data.+2 more →
Actions
— Use the VDS2000/VDS2100 diagnostic tool to read the complete fault codes and Freeze Frame data. Record environmental data at the time of the fault, including vehicle speed, voltage, and temperature. Confirm whether the fault is Current rather than History.— Check the SRS system power supply: Measure the battery voltage (should be ≥12.4V). Check if dashboard fuses F2/3 (SRS power) and F2/4 (SRS ignition power) are blown. Verify ground points G201 and G301 are secure and free of oxidation.+5 more →
B168C00›
DTC B168C00 indicates the airbag control unit (SRS ECU) detects an invalid or missing configuration parameter for Trigger Circuit 8 (Loop 8). In the BYD Qin PRO SRS architecture, Loop 8 typically corresponds to the driver-side airbag ignition circuit or the front passenger-side pretensioner circuit. This is a Configuration Fault, not a hardware short or open circuit. The ECU recognizes the loop hardware, but the internally stored configuration data (such as resistance thresholds, ignition characteristic curves, and installation position coding) mismatches the actual vehicle, or the ECU programming table does not activate the loop. This fault disables the safety function of the affected loop, but typically does not affect the protective functions of other correctly configured loops.
Causes
— Failure to perform online programming or configuration writing after replacing the airbag control module (SRS ECU) results in the new module lacking vehicle-specific circuit configuration data.— After accident repairs, the technician replaced airbag assemblies (such as the driver airbag or pretensioner) but did not use a diagnostic tool to update the SRS ECU configuration or perform coding.— SRS ECU internal memory data corruption or checksum error. Attempting system startup with low battery voltage (<9V) or an ECU hardware fault can cause configuration area data loss.+2 more →
Actions
— Connect the BYD dedicated diagnostic tool (ED400/ED300). Enter the SRS system to read the complete fault codes and freeze frame data. Confirm the specific physical location (driver airbag/passenger airbag/pretensioner) and configuration status of Circuit 8.— Visually inspect the Circuit 8 wiring harness connector (usually located on the steering column below the steering wheel or under the center console). Check the terminals for oxidation or backed-out pins. Measure the circuit resistance (normal resistance is 2.0-3.0 Ω, including igniter and wiring harness resistance).+3 more →
B168D00›
DTC B168D00 indicates the Airbag Control Unit (ACU) detects invalid configuration data for Ignition Loop 9. In the BYD Qin PRO SRS system, Loop 9 typically corresponds to the front passenger knee airbag or rear seat side airbag circuit, depending on the vehicle configuration level. "Invalid configuration" means the "configuration present flag", "rated resistance parameter", or "capacity type" in the ACU EEPROM data does not match the installed hardware. This condition also occurs if the ACU detects a load on a circuit marked "not installed", or detects an open circuit on a loop marked "installed". This fault causes the ACU to enter degraded mode. During a collision, the ACU may fail to deploy the airbag on this circuit, or it may trigger a fail-safe strategy that restricts overall SRS functionality.
Causes
— Failure to write configuration data, or writing incorrect data, after replacing the Airbag Control Unit (ACU) (e.g., installing a used ACU with a stored configuration that does not match the original vehicle configuration).— ACU internal data corrupted after a vehicle collision, or failure to update configuration parameters after replacing the airbag assembly (e.g., installing a high-spec airbag in a low-spec vehicle without reconfiguring).— Poor contact, short circuit, or abnormal resistance in the Circuit 9 wiring harness connector causes the ACU to incorrectly detect a configuration error (actual hardware does not match the configuration).+2 more →
Actions
— Connect the VDS2000 or the BYD dedicated diagnostic tool to the vehicle. Read the complete fault codes, confirm B168D00 is a current fault (Active), and record the freeze frame data.— Confirm the specific vehicle configuration: Check the vehicle VIN and configuration sheet to verify the vehicle actually has the specific component corresponding to Circuit 9 (knee airbag/rear side airbag) installed.+6 more →
B168E00›
DTC B168E00 indicates an invalid configuration in Ignition Loop 10 of the Supplemental Restraint System (SRS). On the BYD Qin PRO, Loop 10 typically corresponds to the ignition circuit for the right seat belt pretensioner or the right side curtain airbag. "Invalid configuration" means the SRS control unit detects a circuit resistance outside the standard range (2.0-3.0Ω), or the stored configuration data does not match the installed hardware. This fault prevents the corresponding airbag or pretensioner from deploying normally during a collision. The system also illuminates the airbag warning lamp and may disable the entire SRS, severely impacting passive safety performance.
Causes
— Abnormal internal resistance in the seat belt pretensioner or airbag module (short or open circuit), causing circuit resistance to deviate from the standard value (normal: 2-3Ω; below 1Ω is a short circuit; above 6Ω is an open circuit).— Poor contact at the wiring harness connector, corrosion from water ingress, or backed-out pins causing unstable circuit resistance or communication faults.— SRS control unit (ACU) internal configuration data is missing, corrupted, or does not match the vehicle hardware configuration (e.g., failing to perform online coding or write configuration parameters after replacing the control unit).+2 more →
Actions
— Use the BYD VDS diagnostic tool to read the complete fault code and freeze frame data. Verify the environmental conditions at the time of the fault (temperature, voltage, etc.) and attempt to clear the fault code. If the fault code is intermittent, check the trigger conditions in the history log.— Refer to the BYD Qin PRO workshop manual wiring diagram to identify the specific component for circuit 10 (typically the right front seat belt pretensioner R19 or the right curtain airbag). Disconnect the battery negative terminal and wait 3 minutes. Unplug the SRS control unit connector and measure the resistance between the circuit 10 pins.+4 more →
B168F00›
DTC B168F00 indicates the Airbag Control Unit (ACU) detects the configuration data for ignition circuit 11 (typically the driver-side seat side airbag or left seat belt pretensioner circuit) does not match the actual vehicle configuration. On the BYD Qin PRO, circuit 11 typically corresponds to the side airbag module built into the driver seat. This fault occurs when configuration parameters stored in the ACU (such as airbag resistance threshold, serial number, and installation status) do not match the actual detected circuit characteristics. This mismatch can prevent the airbag from deploying properly during a collision or trigger the system to enter a safety downgrade mode (cutting power to the circuit). Common causes include replacing the seat assembly, ACU, or wiring harness without performing online configuration (Coding), or a loose wiring harness connector under the seat preventing the ACU from correctly identifying the airbag module.
Causes
— Failure to perform online configuration or coding in the ACU after replacing the driver seat assembly (including side airbag) causes the new airbag resistance/ID to mismatch the system record.— The under-seat SRS wiring harness connector (yellow connector) is loose, oxidized, or has backed-out pins, causing abnormal circuit resistance and leading the ACU to incorrectly detect a configuration error.— Airbag Control Unit (ACU) software is outdated, or internally stored configuration data is corrupted/lost (e.g., due to prolonged vehicle power loss or discharged battery).+2 more →
Actions
— Use a BYD VDS2000 or Launch X-431 diagnostic tool to access the SRS system. Read the freeze frame data and verify the Circuit 11 resistance value at the time of the fault (normal range: 2.0-3.0 Ω; an invalid configuration typically displays 0 Ω or >10 Ω).— Check the yellow SRS wiring harness connector under the driver's seat (usually located on the inner side of the seat rail). Verify the connector is fully locked and free of oxidation or corrosion. Inspect for backed-out connector pins. Clean and apply special conductive grease if necessary.+4 more →
B169000›
DTC B169000 indicates the airbag control unit (SRS ECU) detects an abnormal configuration parameter in Loop 12. In the BYD Qin PRO SRS system, "Loop 12" typically corresponds to the communication/ignition circuit for the left front seat side airbag (or seat occupancy recognition sensor). "Invalid configuration" means the configuration data stored in the ECU does not match the connected hardware. Causes include circuit resistance outside the standard range (normal: 2.0-3.0 Ω), wiring open or short circuits, or failing to write the configuration after replacing the airbag assembly or control unit. This fault may prevent the corresponding airbag from deploying properly during a collision or create an unintended deployment risk, classifying it as a functional safety fault.
Causes
— Worn or broken wiring harness under the seat: Frequent seat adjustment on Qin PRO models repeatedly bends the yellow airbag wiring harness (circuit 12) under the seat frame. This long-term bending breaks the internal copper strands or damages the insulation, causing abnormal resistance.— SRS control unit configuration data lost: Vehicle power loss (e.g., discharged battery or battery replacement) or control unit software malfunction causes verification of stored circuit configuration parameters to fail.— Seat airbag assembly not programmed after replacement: After replacing the left front seat assembly or side airbag module, failing to perform the 'Airbag Configuration' function using VDS2000 prevents the ECU from recognizing the correct resistance configuration.+2 more →
Actions
— Diagnostic scan: Use BYD VDS2000/VDS3000 to access the SRS system, read the freeze frame data, and verify the resistance value of Circuit 12 at the time of the fault (normal: 2.0-3.0 Ω, >6 Ω indicates an open circuit, <1 Ω indicates a short circuit).— Locate the circuit 12 component: Refer to the Qin PRO workshop manual wiring diagram to confirm circuit 12 corresponds to the left front seat side airbag (on some models, this may indicate the seat occupancy sensor). Inspect the component for visible damage.+5 more →
B1691-00›
B1691-00 (Factory Encrypted) is a safety configuration fault code for the BYD SRS (Supplemental Restraint System). It indicates an error in the unique encrypted configuration data stored within the airbag ECU (Electronic Control Unit) and bound to the vehicle VIN. This fault indicates the ECU detected missing, corrupted, or mismatched internal safety configuration data, triggering the system safety lock mechanism. In this state, the airbag system disables deployment to prevent accidental deployment or failure caused by an unauthorized ECU, incorrect configuration, or data corruption. This condition severely compromises the vehicle's passive safety performance. Reconfigure the system using the manufacturer's dedicated diagnostic equipment.
Causes
— Failed to perform the 'ECU Configuration' or 'Factory Mode' encrypted write operation using the BYD dedicated diagnostic tool (VDS/ED-400) after replacing the airbag ECU.— Severe vehicle battery discharge, prolonged power disconnection, or power interruption during servicing causes the ECU's internal volatile memory to lose encrypted configuration data.— After a vehicle collision, the SRS system triggers lockout protection and the ECU enters the 'deployed' or 'requires reconfiguration' state.+2 more →
Actions
— Basic circuit check: Measure the battery voltage (must be ≥12V). Verify normal voltage at power supply pins (B+, IG1) of SRS ECU connector G36. Measure the resistance between ground pin G36-35 and body ground (should be <1Ω) to rule out wiring faults.— Fault Confirmation and Recording: Connect the BYD dedicated diagnostic tool, access the SRS system, and read and record all fault codes. Verify B1691-00 is present. Check history faults and freeze frame data to confirm no other accompanying hardware fault codes exist.+3 more →
B1691›
DTC B1691 indicates the Airbag Control Module (ACM) detects a verification failure of its internally stored factory-encrypted data or security authentication key. This fault involves the SRS security authentication mechanism. The module triggers this fault when its stored factory configuration data, encryption key, or anti-theft authentication information does not match the reference data stored in the VCU/BCM. Common causes include: installing a non-genuine airbag module without online matching, corrupted internal EEPROM data, vehicle power system anomalies causing encrypted data loss, or failing to complete the module matching procedure correctly during production or repair. This safety-related fault causes the airbag system to enter a degraded mode and may limit normal airbag deployment.
Causes
— Installation of a non-genuine Airbag Control Module (ACM) or failure to perform online matching, resulting in an encryption key mismatch with the vehicle.— Electromagnetic interference, static electricity, or a hardware fault corrupted the factory configuration data or encryption key stored in the airbag module.— Severe vehicle battery discharge, improper jump-starting, or power supply system voltage fluctuations resulting in module data loss.+2 more →
Actions
— Use the BYD VDS diagnostic tool to read the complete fault codes and freeze frame data. Confirm if B1691 is a current fault and record the vehicle status at the time of the fault.— Check the airbag control module (ACM) power supply (constant B+, ignition IG1), ground, and CAN-H/CAN-L circuit connections. Measure the power supply voltage to verify it is within 12V±0.5V, and verify the ground resistance is less than 1Ω.+3 more →
B169100›
DTC B169100 indicates the Supplemental Restraint System (SRS) is in "Factory Lock" mode. BYD uses this protective locking mechanism during production, transport, or after SRS control module replacement. This state forces the Airbag Control Unit (ACU) into factory test mode and electrically disables all airbags, side curtain airbags, and seat belt pretensioners. These components will not deploy even in a severe collision. This status is a software configuration issue, not a hardware fault. It continuously illuminates the airbag warning light and completely disables the vehicle's passive safety functions. Resolve this condition immediately.
Causes
— Failure to complete the pre-delivery inspection (PDI) procedure before new vehicle delivery, and failure to use the dedicated diagnostic tool to execute the "Exit Factory Mode" operation.— Failure to perform online programming, coding configuration, or immobilizer matching after replacing the airbag control module (SRS ECU) causes the new module to default to a locked state.— Severe vehicle battery discharge, disconnection, or excessive voltage fluctuation causes the SRS control module to lose data or fail checksum verification, triggering a protective lockout.+2 more →
Actions
— Connect the BYD VDS2000/3000 or ED400 diagnostic tool and enter the SRS airbag system to read fault codes. Confirm B169100 is the primary fault code and check for accompanying related fault codes such as B169200 (Factory Mode Active).— Check the vehicle repair history to confirm if the vehicle is new or if the SRS module was recently replaced. Measure the SRS control module power supply (constant B+, ignition IG1) and ground circuits to verify the voltage is 12V±0.5V.+4 more →
B1693-00›
DTC B1693-00 indicates high resistance or an intermittent open circuit in the Supplemental Restraint System (SRS) Electronic Control Unit (ECU) ground circuit. Specifically, the resistance of the ground path from the SRS ECU through connector G36 (specifically terminal G36-35) to the main body ground point exceeds the calibrated threshold (normally less than 1Ω). This fault causes an unstable ECU power supply reference potential, triggers a system self-check failure, and continuously illuminates the airbag warning lamp (SRS lamp). In extreme cases, this condition prevents airbag deployment during a collision or causes unintended deployment, severely compromising passive safety system functionality.
Causes
— Ground point bolt loose or under-torqued: Long-term driving vibration loosens the SRS ECU ground bolt on the instrument panel frame or center tunnel, increasing contact resistance.— Ground point oxidation or corrosion: Wading, high humidity, or battery leakage causes the ground terminal to rust or oxidize, forming an oxide layer that obstructs current flow.— Internal damage to the ground wiring harness: Crushing or excessive bending during accident repairs breaks or partially breaks the internal copper strands, creating hidden high resistance.+2 more →
Actions
— Connect the BYD dedicated diagnostic tool (VDS or ED400) to read fault codes, confirm B1693-00 is present, and record freeze frame data.— Turn the power mode to OFF, disconnect the battery negative terminal, and wait at least 90 seconds for the SRS capacitor to fully discharge.+9 more →
B1693›
The BYD SRS (Supplemental Restraint System) strictly defines DTC B1693 as "Driver Airbag Circuit Resistance Low/Short to Ground", not a simple ground connection issue. This fault indicates the airbag control unit (ACU) detects the driver-side airbag (steering wheel airbag) firing circuit resistance is below the standard threshold (normal range 2.0–3.0 Ω; values below 1.5 Ω trigger this code). Potential causes include an internal short circuit in the steering wheel clock spring flexible printed circuit, abnormal contact resistance at the airbag connector, damaged wiring harness insulation causing a short to ground, or a faulty ACU internal firing driver circuit. This fault prevents airbag deployment during a collision (open-circuit condition) or causes unintentional deployment without a collision (short-circuit condition), representing a critical safety function failure.
Causes
— Short circuit or break in the steering wheel clock spring internal FPC ribbon cable: Prolonged steering wheel rotation causes fatigue damage to the flexible printed circuit inside the clock spring, resulting in abnormal circuit resistance or an intermittent short to ground.— Poor contact at the driver-side airbag connector: A loose airbag plug latch at the rear of the steering wheel, oxidized terminals, or water ingress causes resistance fluctuations or a false short circuit.— Steering column wiring harness mechanical wear: Steering wheel rotation causes the airbag wiring harness to rub against the steering column and instrument panel frame, damaging the insulation and shorting the harness to body ground.+2 more →
Actions
— Safe power-off: Disconnect the battery negative terminal and wait at least 3 minutes for the SRS system capacitors to discharge completely to prevent accidental airbag deployment.— Initial visual inspection: Inspect the airbag wiring harness under the steering wheel for obvious wear or damaged insulation. Verify the airbag connector (usually yellow) is fully inserted and locked, and check the retaining clip for breakage.+6 more →
B1694-00›
The SRS (airbag system) control unit records DTC B1694-00 when it detects its operating supply voltage falls below the calibrated threshold (typically 9.0V-10.5V, depending on specific vehicle calibration). This fault indicates a voltage drop in the airbag ECU constant power or IGN supply circuit, which may prevent the airbag system from deploying properly during a collision or cause unintentional deployment while driving. This fault triggers a safety system degraded mode. The ECU illuminates the airbag fault warning lamp and stores the fault code. On some models, this condition also limits functions such as the seat belt pretensioners and airbag backup power supply.
Causes
— Battery aging, low charge, or charging system fault: Battery voltage is below 11V, or generator output voltage is unstable, causing a voltage drop during startup or high-current load operation.— Ground point loose or oxidized: Loose or corroded SRS ECU housing ground and G10/G36 connector ground points (G10-28, G10-35, G36-35) increase circuit resistance (>1Ω).— Instrument panel junction box power supply fault: Abnormal output voltage at terminal G2C-3, or burnt IG1 main relay contacts or coil fault, causing insufficient power supply in the ON position.+2 more →
Actions
— Basic check: Measure battery static voltage (should be ≥12.4V) and startup/charging voltage (should be 13.5-14.5V). Check battery terminals for tightness and oxidation. Charge or replace battery if necessary.— Fuse check: Check if the SRS-related fuses in the instrument panel power distribution box (such as F2/17) are blown or have poor contact. Measure the voltage drop across the fuse holder.+4 more →
B1697-00›
DTC B1697-00 indicates the airbag control unit (SRS ECU) internal self-test detected a critical function fault. The ECU integrates the acceleration sensor, safing sensor, firing decision logic, and diagnostic communication module. Potential root causes include: 1) Data verification failure in the ECU internal microprocessor or memory (EEPROM/Flash); 2) Abnormal output from the power management module (12V-5V/3.3V voltage regulator circuit); 3) The crash detection algorithm continuously detecting an internal logic conflict; 4) Communication interface circuit fault with the crash sensors (front door, side airbag, center sensor). This fault causes the ECU to enter a degraded mode, disabling deployment of the airbags, seat belt pretensioners, and pedestrian protection devices. In extreme cases, it may cause unintended airbag deployment or failure to deploy during a collision. This is a safety-critical fault.
Causes
— SRS ECU内部电源IC（如TLE7263或同类车规级稳压芯片）热疲劳虚焊或击穿，导致内核供电电压跌落至3.0V以下（正常需3.3V±0.1V）— 车辆蓄电池亏电或搭电操作时产生电压浪涌（>16V），导致ECU内部EEPROM数据块损坏或校验和错误— 前碰/侧碰传感器回路对地或对电源短路（阻抗<1Ω或>5Ω），ECU启动保护性锁止并记录内部故障+2 more →
Actions
— 安全断电：断开低压蓄电池负极，等待至少90秒（确保SRS备用电容电压<1V），禁止在通电状态下插拔气囊相关线束— 外观与连接检查：拆卸中控台下方饰板，检查SRS ECU连接器（通常为24针或32针黑色插头）是否存在松脱、退针、铜绿氧化或进水痕迹，测量端子保持力+6 more →
B1694›
DTC B1694 indicates the airbag control unit (SRS ECU) detects its operating supply voltage is below the system threshold (usually 9.0V-9.5V, depending on vehicle calibration). The SRS system uses a dual power supply design: constant power (+B, memory power) and ignition switch power (IG). This ensures airbag deployment during a collision even if the ignition switch is off. Low voltage prevents normal operation of the airbags, seat belt pretensioners, crash sensors, and CAN communication. The system enters fail-safe mode (the instrument cluster airbag warning light remains illuminated). In extreme cases, this causes deployment failure during a collision or risks unintended deployment. New energy vehicles use a DC-DC converter instead of a traditional alternator for low-voltage charging. Abnormal DC-DC output or high-voltage system power loss also triggers this code.
Causes
— Low-voltage battery aging or deep discharge: Battery state of health (SOH) below 70% and insufficient cold cranking amps (CCA), causing static voltage to drop below 12.0V or excessive voltage drop under dynamic load.— Poor contact in SRS power supply circuit: Increased contact resistance caused by an oxidized SRS fuse (usually F1/14 or F2/03) in the instrument panel junction box (EJB), a loose fuse socket, or water ingress and oxidation at the SRS ECU connector (32-pin/48-pin).— DC-DC converter fault (new energy vehicles): DC-DC output voltage drops below 13.5V or becomes unstable, failing to maintain the 12V low-voltage system supply. High-voltage interlock faults or DC-DC module damage commonly cause this on models such as the Tang DM-i and Song PLUS EV.+2 more →
Actions
— Read freeze frame: Use the VDS 2000/3000 diagnostic tool to access the SRS system and record the freeze frame data for DTC B1694. Check the 'Battery Voltage' value and mileage at the time of the fault to determine if the fault is intermittent.— Battery inspection: Measure CCA and SOH using a battery tester. Static voltage must be ≥12.4V and cranking voltage must be ≥9.6V. If voltage is below 12.0V or SOH <70%, charge or replace the battery (requires ≥60Ah AGM specification). Clear the fault code and road test the vehicle.+5 more →
B169416›
DTC B169416 indicates the airbag control unit (SRS ECU) detects an internal operating voltage below the calibrated threshold (typically below 9V), or a functional fault in the ECU internal power management module or voltage regulation circuit. This hardware-level fault indicates the SRS ECU cannot maintain the stable operating voltage required for its internal microprocessor, acceleration sensor, and ignition circuit. When triggered, the ECU enters fail-safe mode. This condition can cause complete airbag system failure (airbags fail to deploy during a collision), prevent seat belt pretensioner activation, or generate a false alarm resulting in unintended airbag deployment. This fault poses a severe safety risk and requires immediate repair.
Causes
— Damaged SRS ECU internal power management chip or voltage regulator circuit, preventing the ECU from converting battery voltage into a stable 5V/3.3V internal operating voltage.— Severely discharged vehicle battery, generator failure, or excessive voltage drop in the dedicated SRS power supply circuit causes the ECU input voltage to remain below 9V.— Terminal oxidation, back-out, or poor contact at the SRS ECU connector (usually located under the center console), causing abnormally high resistance in the power supply circuit.+2 more →
Actions
— Read the complete fault code stream using the BYD VDS2000 or Launch X431 diagnostic tool. Confirm B169416 is currently active. Check for accompanying fault codes such as B1694-00 (power supply voltage too low) or U0151 (lost communication with SRS). Record the voltage value in the freeze frame data.— Measure the battery static voltage (should be ≥12.4V) and the charging voltage after starting (should be 13.5-14.5V). Check if the SRS ECU fuse (F1/15, usually 10A or 15A) in the instrument panel fuse box is blown. Measure the voltage between pin 1 of the ECU connector (constant power) and body ground.+3 more →
B1695-00›
DTC B1695-00 indicates the airbag control unit (SRS ECU) detected its operating supply voltage exceeds the system safety threshold (typically >16V). On BYD new energy vehicles, this fault means the 12V low-voltage system supply voltage rose abnormally, exceeding the tolerance range of the SRS ECU internal circuits. The SRS system is highly sensitive to voltage. Excessive voltage can cause reference voltage drift in the internal A/D converter, capacitor breakdown, or unintended airbag deployment. As a safety mechanism, the ECU illuminates the airbag warning lamp, stores the fault code, and enters a fail-safe mode. This mode disables the airbags and seat belt pretensioners, preventing abnormal voltage from causing unintended deployment or failure during a collision.
Causes
— DC-DC converter (high voltage to low voltage) fault or regulator failure causing output voltage to exceed 16V and fail to stabilize within the normal 13.5-14.5V range.— 12V battery aging, sulfation, or internal short circuit reduces charge acceptance, causing the terminal voltage to spike to an abnormally high level during initial charging.— Intermittent short circuit between the SRS ECU power supply circuit and the high-voltage circuit, or poor ground circuit (GND) contact causing reference voltage drift, resulting in the ECU detecting a falsely high voltage.+2 more →
Actions
— Use the VDS2000 or a dedicated BYD diagnostic tool to read the DTC freeze frame data. Record the exact voltage, vehicle speed, timestamp, and system load status when the fault occurred. Determine whether the fault is persistent or intermittent.— Measure the current 12V battery static voltage (12.4-12.8V with ignition off). Enter Ready mode or start the engine and measure the dynamic charging voltage. Verify if the voltage continuously exceeds 15.5V or shows fluctuation spikes.+5 more →
B1695›
In the BYD SRS (airbag) system, DTC B1695 indicates a front passenger Occupant Classification System (OCS) fault, rather than the literal "power supply voltage too high". This DTC indicates the SRS ECU detected an abnormal front passenger seat occupancy sensor signal, a communication interruption, or calibration data outside the valid range. The OCS uses a piezoelectric sensor mat to detect front passenger seat occupancy and occupant weight category to control airbag deployment and staged inflation force. If sensor resistance drifts, signal voltage is abnormal (standard no-load value is 1.2-1.5V), the communication circuit opens, or system calibration is incorrect, the SRS ECU triggers DTC B1695 and illuminates the airbag warning lamp. This creates a serious safety risk, as the front passenger airbag may deploy incorrectly or fail to deploy during a collision.
Causes
— OCS sensor body aging, internal piezoelectric film breakage, or moisture ingress causing resistance drift (normal: 2.3-2.7kΩ) or abnormal output voltage.— Oxidation or water ingress in the under-seat wiring harness connector (especially in high-humidity southern environments), terminal back-out, or a broken locking clip causing intermittent poor contact.— Vehicle modifications (such as installing leather seat covers or replacing seat foam) or accident repairs deformed the sensor mounting bracket, causing abnormal fitment between the sensor and the seat foam (gap must be <2 mm).+2 more →
Actions
— Use the BYD VDS or Launch X-431 diagnostic tool to access the SRS system, read the DTC B1695 freeze frame and live data stream, and check the sensor no-load voltage (normal 1.2-1.5V) and load change rate for abnormalities.— Remove and inspect the OCS module connector under the front passenger seat. Inspect the pins for oxidation or copper corrosion (typically green), and measure the sensor resistance. Check the wiring harness for interference with the seat slide rail and verify the connector locking mechanism is intact.+4 more →
B169517›
DTC B169517 indicates the airbag control unit (SRS ECU/ACU) detected an anomaly during internal self-check, usually pointing to a fault in the ECU internal processor, memory, or power management module. In the BYD diagnostic protocol, sub-code '17' specifically indicates an internal ECU circuit fault or a logic error resulting from supply voltage exceeding the threshold. When the SRS ECU detects an internal oscillator fault, EEPROM data checksum failure, ADC conversion error, or watchdog reset, it sets this code and enters degraded mode. This mode may disable some or all airbag deployment functions. Because the ECU is the core of the passive safety system, this fault presents a severe safety risk and can prevent normal airbag deployment during a collision.
Causes
— Abnormal battery voltage or power supply fluctuation: Prolonged battery depletion, battery aging, or a charging system fault causes the SRS ECU supply voltage to drop below 9V or exceed 16V, triggering ECU undervoltage/overvoltage protection and logging an internal fault.— Internal SRS ECU hardware damage: Aging internal control unit capacitors, PCB corrosion (common in water-damaged vehicles), or physical damage to the processor chip causes the self-test program to fail.— Poor wiring harness connector contact: Oxidized or loose power, ground, or CAN bus pins on the ECU connector (usually located under the center console or behind the armrest box) cause intermittent communication loss or unstable power supply.+2 more →
Actions
— Preliminary inspection: Use VDS or a dedicated diagnostic tool to read the complete fault codes and freeze frame data. Confirm whether B169517 is a Current or History fault. Check the battery voltage (standard: above 12.6V; engine running: 13.8-14.5V) to rule out power supply system issues.— Visual and connection inspection: Disconnect the battery negative terminal, wait 3 minutes, then inspect the SRS ECU exterior (usually located below the gear selector or inside the center tunnel) for physical damage, signs of water ingress, or a burnt smell. Inspect connector CA1 (or the corresponding vehicle connector) for looseness, and check the pins for oxidation or backing out. Measure the resistance at ground point G101 (or the corresponding ground point). The resistance must be less than 1Ω.+4 more →
B1696-00›
DTC B1696-00 indicates an internal hardware or software fault in the airbag electronic control unit (SRS ECU). This fault points to an abnormality in the ECU internal microprocessor, memory (EEPROM), power management module, or internal communication bus, preventing the ECU from completing self-checks or running safety algorithms normally. This fault is a current hard fault (Present DTC), meaning the ECU has detected substantial internal damage and cannot perform normal crash detection and airbag deployment decision functions. While the fault is present, the airbag system may enter fail-safe mode (fully disabled or partially restricted). In a collision, the airbags may fail to deploy properly, creating a severe safety hazard. This fault differs from external wiring or sensor faults; repairing the wiring harness will not resolve it.
Causes
— Dry or broken solder joints on the internal ECU circuit board, or aging and failure of key components (capacitors, resistors, chips). Commonly occurs after exposure to high temperatures or prolonged vibration.— During a vehicle collision, even if the airbags do not deploy, high surge currents or mechanical stress may physically damage internal ECU chips or the data memory.— Power system fault (such as incorrect jump-starting, voltage surge, or reversed battery polarity) causing breakdown of the internal ECU power management module.+2 more →
Actions
— Use a dedicated diagnostic tool (such as BYD ED400 or Launch X431) to read SRS system fault codes, confirm B1696-00 is a current fault (Active), and record history fault codes.— Check the SRS ECU power supply circuit: Disconnect connector G36. Measure the voltage at G36-34 (constant power) and G36-33 (IGN power); the standard value is 11-14V. Measure the resistance between G36-35 (ground) and body ground; the resistance must be less than 1Ω.+6 more →
B1696›
For the BYD SRS (Supplemental Restraint System/airbag system), DTC B1696 indicates a fault in the Seat Occupancy Sensor or its related circuit, not hardware damage to the SRS ECU itself. This sensor mounts inside or underneath the driver or front passenger seat. It detects seat occupancy and classifies occupant weight, serving as a key input signal for the airbag deployment logic. When the ECU detects an open circuit, short circuit, abnormal signal, or communication failure in the sensor circuit, it illuminates the airbag warning lamp. The system may default to disabling the corresponding airbag and illuminate the 'airbag off' indicator. This severely compromises occupant protection during a collision. On some models, failing to perform the online configuration learning procedure after replacing the seat or sensor also triggers this code.
Causes
— Seat occupancy sensor wiring harness connector loose, oxidized, or making poor contact: Frequent fore-and-aft seat adjustment or cleaning loosens the yellow connector (usually 4-pin), and terminal oxidation interrupts the signal.— Seat wiring harness mechanical damage: Seat frame edges or slide rails wear through the wiring harness insulation over time, causing a signal wire short to ground or open circuit, especially during water fording or driving on rough roads.— Sensor body damaged: Water ingress (wading repair), aging, or heavy loading causes abnormal internal resistance in the internal seat pressure sensor, preventing it from outputting the normal 0.5-4.5V pressure signal.+2 more →
Actions
— Use the BYD VDS or Launch X-431 diagnostic tool to read the complete fault codes and freeze frame data. Confirm whether the fault is on the driver or passenger side. Check if the 'seat occupancy status' in the data stream changes when applying pressure.— Visually inspect the yellow wiring harness connector under the affected seat (usually marked 'SRS' or 'Airbag'). Check for looseness, water ingress, pin oxidation, or corrosion. Clean with electrical contact cleaner and re-secure.+5 more →
B1697›
DTC B1697 indicates the airbag control unit (SRS ECU) detected an internal hardware fault or critical support circuit error, forcing the system into fail-safe mode. This fault involves an internal microprocessor calculation error, EEPROM data corruption, an abnormal internal accelerometer signal, an ignition driver circuit fault, or a severe fault in the external power supply, ground, or communication lines. When triggered, the SRS ECU disables deployment of all airbags and seat belt pretensioners. The vehicle provides no passive safety protection during a collision. This severe fault compromises driving safety.
Causes
— SRS ECU internal hardware fault: Functional failure due to main control chip (MCU) damage, internal memory data checksum failure, swollen capacitors, or cold solder joints.— Abnormal power supply: Loose connection or unstable voltage in the constant power (B+) circuit, poor contact in the ignition switch power (IG1) circuit, or oxidized dedicated fuse socket (usually 10A-15A) causing power interruption.— Grounding system fault: Corrosion at SRS ECU ground terminals (G101/G102), broken ground wiring harness, or excessive contact resistance (>1Ω), causing control unit reference voltage drift.+2 more →
Actions
— Fault Confirmation and Data Recording: Use a dedicated BYD diagnostic tool (VDS2000 or Launch X431) to read the complete DTC list. Record the freeze frame data for B1697. Determine if it is a current or history fault. Check if the instrument cluster SRS warning light is solid or flashing.— Power and ground circuit inspection: Disconnect the battery negative terminal and wait 90 seconds (for capacitor discharge). Unplug the SRS ECU connector. Measure the voltage at the power supply terminals (constant power and IG power) (standard value: 11-14V, 13.5-14.5V with the engine running). Measure the resistance between the ground terminal and body ground (should be <1Ω). Check the connector pins for oxidation or backing out.+4 more →
B169700›
This DTC has two definitions across different BYD vehicle platforms: 1) In early models such as the E2, E3, and Qin EV, it indicates an internal fault in the SRS_ECU (airbag control unit) involving communication, power supply, or internal circuit failures in the main safety system control module, potentially affecting crash protection functions. 2) In models equipped with seat memory such as the Song MAX, Song Pro, Tang, and Song PLUS, repair databases indicate this DTC usually flags a Driver Seat Position Memory - Store 1 Malfunction. This involves Seat Control Module (SCM) storage or recall failures for memory position 1, or distorted signals from related position sensors (fore-aft/height/tilt). In either case, the control module detects abnormal internal storage, a communication timeout, or actuator feedback signals exceeding the threshold. Confirm the fault subtype using the VDS diagnostic tool based on the specific vehicle model.
Causes
— Abnormal power supply or ground to the Seat Control Module (SCM) or SRS ECU, especially a voltage drop or momentary power loss in the IG1 power supply under specific operating conditions.— Abnormal seat position sensor (fore-aft position, height adjustment, backrest recline) signal, damaged sensor, or seat rail movement pinched or chafed the sensor wiring harness, causing a short or open circuit.— Oxidized or loose wiring harness connector under the seat (such as the M1 connector), or backed-out terminal causing excessive contact resistance.+2 more →
Actions
— Scan the entire vehicle system using the VDS2000 diagnostic tool. Confirm the specific definition, freeze frame data, and environmental conditions of DTC B169700. Read the seat position sensor data stream (fore/aft, height, and backrest angle values) or the SRS system status.— Check the power supply circuits (constant B+ and ignition switch IG1) and ground points of the relevant control module (seat control module or SRS ECU). Measure the voltage to verify it is within 12V±0.5V. Check if fuse F2/14 (seat control) is blown.+4 more →
B1698-00›
B1698-00 indicates the airbag system electronic control unit (SRS ECU) detects an internal fault or critical function abnormality. This fault code typically indicates an SRS ECU internal memory error, processor fault, power supply voltage out of operating range (overvoltage or undervoltage), or a persistent communication bus fault between the ECU and the crash sensors or airbag modules. In BYD Qin series vehicles, this fault forces the airbag system into fail-safe mode and continuously illuminates the instrument panel airbag warning lamp. During a collision, the vehicle may fail to deploy the airbags and seat belt pretensioners, posing a severe safety hazard. This fault code is a hard fault that does not clear automatically and requires professional diagnosis and repair.
Causes
— SRS ECU power supply circuit fault: unstable battery voltage, blown fuse (e.g., SRS-dedicated fuses F1/14, F1/15), poor power supply circuit connection, or excessive voltage drop.— Poor ground connection: Loose, oxidized, or corroded SRS ECU ground terminal (usually located on the instrument panel frame or under the A-pillar) causing excessive ground resistance (standard: < 1Ω).— SRS ECU internal hardware fault: internal capacitor aging, memory data corruption, microprocessor malfunction. Common in early-batch 2017-2018 Qin series models.+2 more →
Actions
— Safety check and preliminary inspection: Disconnect the high-voltage service disconnect (MSD) and wait 5 minutes for the high-voltage system to discharge. Disconnect the battery negative terminal and wait at least 3 minutes for the SRS capacitor to fully discharge to prevent accidental airbag deployment.— Visual inspection: Inspect the SRS ECU for physical damage, water stains, or burn marks. Inspect the SRS ECU wiring harness connector located under the dashboard or in the center tunnel (usually 24-48 pins) for looseness, backed-out pins, or corrosion.+5 more →
B1698›
DTC B1698 indicates the airbag system electronic control unit (ACU/SRS ECU) detects an internal system fault or critical function failure. This fault involves an ECU internal processor self-check anomaly, memory data checksum error, power supply monitoring circuit fault, firing circuit diagnostic system anomaly, or interrupted communication with the vehicle CAN network. As the core control module of the passive safety system, the SRS ECU monitors crash sensor signals in real time and controls the firing circuits for multiple airbags and seat belt pretensioners. When B1698 triggers, the system typically enters fail-safe mode and automatically disables all airbag and pretensioner deployment. This causes a complete loss of vehicle crash protection capability and poses a severe safety hazard.
Causes
— SRS ECU internal hardware fault: damaged internal processor, corrupted EEPROM data, failed power management chip, or aged internal capacitors causing unstable operating voltage.— Power supply system fault: battery voltage too low (<9V) or too high (>16V), loose connection in the ECU constant power/ignition power circuit, poor contact at fuse F1/FB07, corrosion on ground wires G103/G303 causing increased contact resistance (>1Ω)— CAN communication bus fault: Network failure caused by interrupted communication with the Gateway Controller (GWC), CAN-H and CAN-L lines shorted to ground or power, an open circuit in the wiring harness, or an abnormal terminating resistor (120Ω).+2 more →
Actions
— Use the VDS2000 or BYD dedicated diagnostic tool to read the complete DTC list and record the freeze frame data. Check specifically for accompanying U-class communication fault codes (such as U0151, U0164) and save screenshots of the data stream.— Check SRS ECU power and ground: Disconnect the battery negative terminal for 3 minutes, then unplug the ACU connector (usually located under the center console or behind the center armrest box). Measure the voltage at Pin 30 (constant power B+) and Pin 28 (ignition power IG1); the voltage should be 9-16V. Measure the resistance between Pin 24 (ground GND) and body ground; the resistance should be <1Ω. Check the connector for water ingress, pin corrosion, or backed-out pins.+4 more →
B169800›
DTC B169800 indicates an internal fault or communication failure in the airbag control unit (SRS ECU). As the core control module of the airbag system, the SRS ECU monitors crash sensor signals, processes crash algorithms, and controls airbag and seat belt pretensioner deployment. This DTC indicates the ECU self-check detected an internal processor fault, memory error, power supply fault, or CAN communication interruption with other modules (such as the Vehicle Control Unit or Body Control Module). This fault poses a severe safety risk and may cause the airbags to fail to deploy or to deploy inadvertently during a collision. Repair immediately.
Causes
— Poor contact in the SRS ECU power supply circuit or ground circuit, or abnormal voltage (below 9V or above 16V)— SRS ECU internal hardware fault (damaged processor, memory, or internal sensor)— CAN bus communication fault (communication interruption or signal interference between the SRS ECU and vehicle network)+2 more →
Actions
— Use BYD VDS or a dedicated diagnostic tool to read the complete fault codes and freeze frame data. Confirm whether B169800 is a current or historical fault. Check for accompanying communication fault codes (such as codes starting with U).— Check the instrument cluster SRS warning light status (solid or flashing). Disconnect the negative battery terminal for 5 minutes, then restore power. Perform a system self-check and observe if the fault code returns.+4 more →
B1699-00›
B1699-00 indicates an internal hardware or basic software fault in the airbag electronic control unit (SRS ECU). This ECU integrates a central acceleration sensor, a crash detection algorithm processor, ignition driver circuits, and an energy storage capacitor. The following conditions trigger the DTC: abnormal ECU supply voltage (below 9V or above 16V for longer than the set time), internal memory (EEPROM/Flash) checksum failure, main control chip (MCU) watchdog reset, acceleration sensor self-test failure, or CAN communication controller fault. This is a hard fault. The ECU enters fail-safe mode and disables all airbag ignition circuits, preventing the airbags and seat belt pretensioners from deploying during a collision and posing a severe safety hazard.
Causes
— SRS ECU internal hardware damage (voltage regulator chip breakdown, main control MCU cold solder joint, acceleration sensor module failure)— Power supply system fault (discharged battery, blown fuse SB09, unstable voltage caused by burnt ignition switch contacts)— Ground circuit fault (loose or oxidized G36 connector, or broken ground wiring harness causing contact resistance greater than 1 Ω)+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal. Wait at least 3 minutes for the SRS ECU energy storage capacitor to fully discharge to prevent accidental airbag deployment.— Visual inspection: Check the SRS ECU housing located under the dashboard or center console for physical damage, burn marks, or liquid ingress.+8 more →
B1699›
DTC B1699 indicates an internal self-check fault in the airbag system Electronic Control Unit (SRS ECU). As the core control module of the passive safety system, the SRS ECU integrates acceleration sensors, safing sensors, ignition driver circuits, and a microprocessor. This DTC triggers when the ECU detects an internal processor fault, memory data checksum error, internal communication bus anomaly, or power management module fault during the self-check. The airbag system enters fail-safe mode, meaning the airbags and seat belt pretensioners may fail to deploy during a collision. The instrument panel SRS warning light illuminates continuously. External power supply or ground faults typically trigger specific DTCs such as B1693 (poor ground) and B1694/B1695 (abnormal supply voltage). DTC B1699 specifically indicates an internal circuit fault within the ECU itself.
Causes
— Hardware damage to the main control chip, memory, or ignition drive circuit inside the SRS ECU, typically occurring in older vehicles or vehicles exposed to strong electromagnetic interference.— Abnormal ECU power supply voltage (battery voltage continuously exceeding 16V or dropping below 9V) causes internal power management module breakdown or protection circuit lock-up.— During a previous collision, the ECU internal acceleration sensor detected an impact but the airbag did not deploy, causing internal diagnostic circuit lock-up or physical sensor damage.+2 more →
Actions
— Connect the BYD dedicated diagnostic tool (VDS or ED400). Enter the SRS system to read all fault codes and freeze frame data. Verify B1699 is a current fault and the only code present. Rule out any accompanying communication or sensor faults.— Check the SRS ECU power supply circuit: Measure the voltage between connector G36 pin 35 (constant power +B) and ground; it should be battery voltage. The voltage at pin 34 (IG1 power) should be 12V with the ignition ON. Check fuse F4/9 and related relays.+8 more →
B169A-00›
B169A-00 indicates an internal fault in the airbag control unit (SRS ECU) or a system-level communication fault. The SRS ECU is the core control module of the vehicle’s passive safety system, responsible for monitoring crash sensors, controlling airbag deployment, triggering seat belt pretensioners, and recording crash data. This fault code indicates the ECU self-check detected an internal processor fault, memory checksum failure, internal bus communication interruption, or critical circuit abnormality. This fault constitutes a serious safety hazard; it may prevent the airbag system from deploying correctly during a collision or cause unintended deployment. In BYD Qin series vehicles, the SRS ECU typically mounts beneath the center console or in the central armrest area, communicating with the vehicle network via the CAN bus.
Causes
— SRS ECU internal hardware fault: Damaged microprocessor, EEPROM memory chip, or internal power supply circuit causing self-test failure.— Power supply system fault: battery voltage too low (below 9V) or too high (above 16V), dedicated SRS fuse (ECU-B, AIR BAG) blown, or ground terminal loose or oxidized.— CAN bus communication fault: Short circuit, open circuit, or abnormal terminal resistance in the CAN-H and CAN-L lines, interrupting communication between the ECU and the vehicle network.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS or ED400) to read the complete fault codes. Check for accompanying U-series communication fault codes (such as U0151, U0164) and historical freeze frame data.— Check the vehicle battery voltage (static voltage ≥12.4V; 13.5-14.5V after starting). Check if the SRS system fuse in the dashboard fuse box (usually labeled SRS, AIR BAG, or ECU-B) is blown.+4 more →
B169A›
DTC B169A indicates the airbag control unit (SRS ECU) detects an internal system fault or critical function failure. This fault code typically indicates an abnormality in the ECU internal processor, memory, or power management module, forcing the airbag system into a degraded mode or complete failure state. Specific symptoms include crash detection algorithm failure, ignition loop driver circuit faults, or interrupted communication with other safety modules (such as seatbelt pretensioners and crash sensors). This fault directly prevents airbag deployment during a collision, disables seatbelt pretensioners, and continuously illuminates the instrument cluster airbag warning light. On some models, this fault restricts Child Presence Detection (CPD) and smart key system functions, as these systems share sensor data or communication buses.
Causes
— SRS ECU internal hardware fault: Main control chip (MCU) damage, EEPROM data corruption, internal capacitor aging, or short/open circuit in the ignition drive circuit.— Power supply system fault: Unstable battery positive (+B) line voltage (below 9V or above 16V), loose or corroded ground terminal, or abnormal ignition switch signal causing ECU restart.— Communication bus fault: CAN-H and CAN-L line short/open circuit, terminating resistor deviation (not 60Ω), LIN bus crash sensor communication timeout.+2 more →
Actions
— Initial diagnosis: Use the BYD dedicated diagnostic tool (VDS2000/VDS6000) to read all DTCs, confirm whether B169A is a current (Active) or historical (History) fault, and read the freeze frame data to record the vehicle status at the time of the fault.— Power supply and ground check: Measure the voltage at SRS ECU connector terminal +B (constant power) (standard: 11-14V), check the resistance at ground terminals G101/G102 (must be less than 1Ω), and confirm the IGN signal is battery voltage with the ignition in the ON position.+5 more →
B169B-00›
DTC B169B-00 indicates an internal self-diagnostic fault or severe communication error within the airbag control unit (SRS ECU). This fault indicates the microprocessor, memory (EEPROM/Flash), power supply monitoring circuit, or watchdog circuit within the SRS ECU detected an abnormality, preventing guaranteed airbag deployment. When this fault occurs, the SRS ECU enters fail-safe mode, illuminates the airbag warning light, and disables all airbags, seat belt pretensioners, and crash unlock functions, severely compromising passive safety. This is a Hard Fault; disconnecting the power typically will not clear it. Repair the power supply or communication wiring, or replace the ECU.
Causes
— SRS ECU internal circuit board damage: Voltage surges (such as reversed polarity during jump-starting or charger surges), cracked solder joints from long-term thermal cycling, or internal capacitor aging causing power supply filtering failure.— Abnormal power supply: Battery voltage remains too low (<9V) or too high (>16V) for an extended period, poor connection in the IGN power circuit, poor fuse contact, or oxidation at earth point G201 (left side of instrument panel) causing reference voltage drift.— CAN bus communication fault: Short or open circuit in the CAN-H (orange/black) or CAN-L (orange/brown) lines between the SRS ECU and the gateway or vehicle control unit, abnormal terminating resistance (120Ω), or bus voltage outside standard values (CAN-H 2.5-3.5V, CAN-L 1.5-2.5V).+2 more →
Actions
— Diagnostic scan: Use the VDS2000 or a dedicated BYD diagnostic tool to enter the SRS system and read the Freeze Frame data. Confirm if B169B-00 is an Active or History fault. Record parameters such as vehicle speed, battery voltage, and temperature at the time of the fault. Check for accompanying fault codes (such as U-prefix communication faults or B16XX series sensor faults).— Power and ground check: Turn off the ignition. Measure the voltage to ground at SRS ECU connector pin 16 (constant B+) and pin 15 (IGN). The voltage must be 11-14V. Measure the resistance between the ground pin (usually pin 14) and the vehicle body. The resistance must be <1Ω. Check fuses SB11 (10A, instrument panel power distribution box) and SB15 (15A) for blown elements or poor contact. Check the power supply waveform using an oscilloscope to rule out excessive ripple voltage (>100mV).+4 more →
B169B›
DTC B169B (usually with sub-code -00) indicates a range/performance fault or invalid signal in the driver seat horizontal position sensor (DSeat Horizontal Position Sensor) circuit. This three-wire sensor (5V reference supply, signal ground, analog signal output) mounts on the driver seat slide rail to monitor the fore-and-aft seat position in real time (0-240 mm travel range). The BCM or seat control module sets this DTC when it detects the sensor output voltage falls outside the calibrated range (normally 0.5-4.5V, changing linearly with position), an open or short circuit, or a value that remains unchanged for an extended period. This fault directly affects the seat memory and welcome seat rearward movement functions. It may also prevent the airbag system from optimizing pretensioner force based on seat position (linked with the SRS on some models). This fault compromises user experience and vehicle safety.
Causes
— Loose sensor plug or oxidized terminals: Frequent fore-and-aft seat movement causes wiring harness fatigue. A loose 5-pin plug or copper corrosion interrupts the signal (accounts for 80% of cases).— Water ingress and corrosion under the seat: Car wash fluid penetration, water leakage from aging door seals, or a blocked sunroof drain tube causes the sensor connector or wiring harness to short to ground.— Wiring harness mechanical interference with the seat slide rail: The wiring harness retaining clip between the seat slide rail and the vehicle body detaches. As the seat moves, the harness rubs against the metal slide rail, breaking the internal copper wires.+2 more →
Actions
— Use VDS2000 or an equivalent diagnostic tool to read the fault code and data stream. Move the seat forward and backward. Observe if the 'Driver Seat Horizontal Position' value changes accordingly (normal range: 0-240 mm) to confirm the fault symptom.— Visually inspect the sensor connector under the seat (usually located in front of the left seat rail). Check for looseness and pin oxidation (green copper corrosion). If necessary, clean the connector with electrical contact cleaner and apply conductive grease. Fully seat the connector and secure it with a cable tie.+7 more →
B169C›
DTC B169C indicates the airbag control unit (SRS ECU) detects a critical internal function failure or self-diagnostic abnormality. This typically involves an ECU internal processor (MCU) calculation error, a non-volatile memory (EEPROM/Flash) data verification failure, abnormal power management module (PMIC) output, or the safety monitoring circuit (Watchdog) triggering a reset. As the core of the passive safety system, the SRS ECU receives crash sensor signals, determines collision severity, and triggers airbag deployment and seat belt pretensioners. This fault means the ECU cannot guarantee a normal response during a collision, potentially causing the airbags to fail to deploy or deploy unintentionally. This constitutes an Automotive Safety Integrity Level (ASIL) D functional safety fault.
Causes
— SRS ECU internal hardware fault: damaged main control chip (e.g., Infineon TriCore series), damaged memory data block, or failed internal voltage regulator (supplying 5V/3.3V sensor reference voltage)— Power supply system fault: Poor connection in the constant power (B+) circuit, voltage drop in the ignition switch power supply (IG1/IG2), corrosion at ground points (G101/G102, etc.) causing increased contact resistance (>1Ω)— Communication bus fault: Short circuit between CAN-H and CAN-L, short to power or ground, or terminating resistor drift (standard 60Ω, deviation exceeding 5Ω), preventing the ECU from establishing secure authentication communication with the BCM and instrument cluster.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS ECU internal energy storage capacitor. Inspect the ECU exterior for physical damage, water ingress, or burn marks.— Power and ground check: Use a multimeter to measure the voltage at ECU connector terminal 30 (constant power) and terminal 15 (ignition power). Standard value: 11-14V. Measure the ground resistance; it must be less than 1 Ω. Check the fuse (usually a dedicated 10A-15A fuse in the instrument panel fuse box).+5 more →
B169C00›
DTC B169C00 indicates the airbag control unit (SRS ECU) detected a severe fault during its internal self-check. This typically involves an ECU internal memory (EEPROM/Flash) data checksum failure, a main processor (MCU) calculation error, or an internal power supply/clock circuit fault. This is a hard fault; the ECU cannot guarantee correct deployment of the airbags, seat belt pretensioners, and high-voltage interlock cut-off function during a collision. Upon triggering, the SRS ECU enters fail-safe mode, illuminates the instrument cluster airbag warning light, and disables the entire airbag system. Although the vehicle remains drivable, crash protection functions fail completely, posing a major safety risk.
Causes
— SRS ECU internal memory data corruption or checksum failure (due to electromagnetic interference, voltage transients, or memory aging)— ECU power supply system fault (constant power (BAT+) or ignition power (IG+) voltage instability, or ground point oxidation causing reference voltage drift)— CAN communication bus physical layer fault (CAN-H and CAN-L shorted together or to ground, preventing the ECU from synchronizing with the vehicle network)+2 more →
Actions
— Use the VDS2100/VDS3.0 diagnostic tool to read all DTCs, confirm B169C00 is a current fault (Active), record freeze frame data, and check for accompanying U-class communication fault codes.— Perform a key cycle test and observe if the fault code resets. If the fault persists, disconnect the 12V battery negative terminal for 5 minutes, clear the fault code, power on the vehicle for a self-check, and verify fault reproducibility.+6 more →
B169D-00›
DTC B169D-00 indicates the airbag control unit (SRS ECU) detects an internal fault or abnormal system communication. This ECU is the core control module of the airbag system. It monitors crash sensor signals, determines crash severity, controls the deployment timing of the airbags and pretensioners, and records crash data (EDR). Faults in the ECU internal processor, memory, or power management circuit, interrupted communication with the vehicle CAN network, or data checksum errors trigger this fault code. This fault may cause the airbag system to enter fail-safe mode, preventing normal airbag deployment during a collision and severely compromising occupant passive safety protection. This is a critical safety-related fault.
Causes
— SRS ECU internal hardware fault: Damage to the control module internal CPU, memory chip, or voltage regulator circuit causes the self-test program to fail.— Power supply and ground fault: Unstable voltage or excessive voltage drop in the constant power (+BAT) or ignition switch power (+IG), or ground harness contact resistance exceeding specifications (>10Ω), causing abnormal ECU power supply.— CAN bus communication fault: Short circuit, open circuit, or abnormal terminal resistance (normally 60Ω in parallel) in the CAN-H/CAN-L lines between the SRS ECU, vehicle gateway, and instrument cluster, interrupting data exchange.+2 more →
Actions
— Use the BYD VDS2000 or Launch X431 diagnostic tool to access the SRS system. Read and record all DTCs and freeze frame data. Confirm B169D-00 is a current fault (Active), not a history fault.— Check the SRS ECU appearance and installation condition. Confirm there is no physical damage or signs of water ingress. Inspect the wiring harness connector (usually located under the center console or central tunnel) for looseness, water ingress, or oxidized pins.+5 more →
B169D›
DTC B169D indicates the SRS (Supplemental Restraint System) ECU (Electronic Control Unit) detected a critical fault during its internal self-check. Specifically, this code indicates the airbag control module's internal monitoring circuit detected a processor fault, memory checksum error, power management circuit abnormality, or safety watchdog timeout. As the core of the passive safety system, the SRS ECU monitors crash sensor data in real time, diagnoses system integrity, and precisely controls the deployment timing of the airbags, seat belt pretensioners, and active head restraints during a collision. When B169D sets, the ECU cannot guarantee its decision-making logic reliability. It enters fail-safe mode and disables all airbag deployment functions. As a result, the airbags may fail to deploy during a frontal, side, or rear-end collision, and the instrument cluster airbag warning light remains illuminated. Although the vehicle remains drivable, the significantly reduced passive safety protection creates a serious safety risk.
Causes
— SRS ECU internal integrated circuit fault: Physical damage, cold solder joints, or aging in the control unit's microprocessor, memory chip, or power regulation circuit causes the self-test procedure to fail.— Abnormal power supply: battery voltage too low (<10V) or too high (>16V), poor contact in the SRS ECU constant power (B+) circuit, momentary interruption of the ignition power (IGN), or excessive resistance in the ground circuit (>1Ω), causing unstable ECU power supply or ECU reset.— Communication bus fault: Diagnostic CAN bus (CAN-H or CAN-L) short to power or ground, open circuit, or abnormal terminating resistance (deviating from 60Ω), interrupting communication between the ECU and the vehicle network or causing data verification failure.+2 more →
Actions
— Initial diagnosis: Use VDS2000 or the dedicated BYD diagnostic tool to read the complete DTC list. Check for accompanying U-class (communication) or B16XX (sensor) fault codes, and record the voltage values and mileage from the freeze frame data.— Power supply system check: Measure the battery static voltage (standard 12.6V±0.2V) and the voltage with the engine running (13.8-14.4V). Check the voltage drop at the SRS ECU connector terminals (constant B+, IGN power, GND). Verify the voltage drop is <0.1V and the ground resistance is <1Ω.+5 more →
B169D00›
DTC B169D00 indicates the airbag control unit (SRS ECU/ACU) detects an internal systemic fault. The ECU sets this code when it detects an abnormality in the processor core, non-volatile memory (NVM), safety sensor interface, or internal communication bus during the Power-on Self Test or cyclic monitoring. As the core controller of the passive safety system, the SRS ECU monitors crash acceleration sensor signals in real time, processes crash algorithm decisions, and controls the firing circuits for the airbag modules and seat belt pretensioners. This fault causes the ECU to enter Limp Home mode or fail completely. Consequently, the ECU cannot correctly determine crash severity or trigger the corresponding protective devices during a collision, leading to airbags failing to deploy or deploying unintentionally. This is an ASIL-D safety-critical fault. Potential causes include ECU hardware damage, software runaway, abnormal supply voltage (below 9V or above 16V lasting beyond the set threshold), CAN/LIN communication physical layer faults, or system lockout resulting from a short or open circuit in the external crash sensor wiring.
Causes
— SRS ECU internal hardware fault: damaged main control chip (e.g., Infineon TC2xx/TC3xx series MCU), memory (Flash/EEPROM) data checksum failure, or internal safety watchdog timeout— Power supply and ground system fault: unstable battery voltage (depleted battery or charging system fault); loose or oxidized dedicated SRS ECU ground points (G101/G102, etc.) causing excessive voltage drop; excessive contact resistance at the constant power (+B) circuit fuse.— Communication bus fault: Diagnostic CAN or private security CAN bus (CAN-H/CAN-L) short to power or ground, open circuit (common at the dashboard wiring harness connector), or terminating resistor drift (not the 60Ω standard value) compromising signal integrity.+2 more →
Actions
— Perform a full system scan using the BYD VDS2000 or DMS diagnostic tool and record the B169D00 freeze frame data. Note the vehicle status when the fault occurred (ignition cycle, vehicle speed, supply voltage). Check for accompanying U-class communication fault codes (such as U0151 Lost Communication With SRS) or B13xx-class sensor fault codes.— Perform an SRS ECU software flash: Attempt to flash the latest ECU firmware via OTA or offline (usually located in the safety system flashing menu). If the flash interrupts or fails, directly diagnose an ECU hardware fault. After a successful flash, perform a key cycle test and observe if the fault code returns.+4 more →
B169E-00›
DTC B169E-00 indicates the airbag electronic control unit (SRS ECU/ACU) detected a fault during its internal self-check. Specifically, this constitutes a hardware or logic fault in the ACU internal processor, memory (EEPROM/Flash), power management module, or internal communication bus, rather than a problem with external sensors, wiring harnesses, or crash detection circuits. This fault indicates the ACU cannot guarantee reliable execution of the airbag deployment logic during a collision, making it a safety-critical fault. In BYD Qin series vehicles, the ACU typically mounts in the center tunnel or beneath the dashboard and manages multiple deployment circuits, including the front airbags, side curtain airbags, and seat belt pretensioners.
Causes
— ACU internal power management IC fault: Internal voltage regulator chip damage causes abnormal power supply to the 3.3V or 5V logic circuit, triggering an internal watchdog reset failure.— EEPROM data corruption: Electromagnetic interference, voltage transients, or aging causing CRC check errors in memory configuration data, crash records, or calibration parameters.— Main control MCU crash or program runaway: ARM core processor enters an unrecoverable state due to abnormal clock signal, PCB dry solder joints, or software bug.+2 more →
Actions
— Use a dedicated diagnostic tool (such as BYD VDS or Launch X431) to read all fault codes, check for B169E-00 and any accompanying U-series communication fault codes, and record the freeze frame data.— Perform the ACU power supply integrity check: measure constant power (B+, should be 12V±0.5V), ignition power (IGN, should be 12V at key ON), and ground (GND, resistance <1Ω) to rule out external power supply faults.+6 more →
B169E›
B169E (SRS_ECU Fault) indicates the Airbag Control Unit (ACU) detected an internal circuit abnormality, a power supply/ground fault, or a critical communication bus interruption. This fault code signifies the SRS ECU cannot execute the self-test procedure, or it detected a functional failure in the internal processor, memory, or ignition loop monitoring circuit. This is a Hard Fault, meaning the airbag system may be in a complete failure or degraded mode. In a collision, the airbags or pretensioners may fail to deploy, posing a severe safety hazard.
Causes
— Abnormal SRS ECU power supply circuit: Causes include a blown constant power (BAT+) fuse, poor IGN power relay contact, or loose or corroded ground points (G701/G702, etc.), causing ECU operating voltage to drop below 9V or momentary power loss.— ECU internal hardware fault: internal capacitor aging and leakage, main control chip (MCU) damage, ignition circuit driver transistor breakdown, or memory (EEPROM) data checksum failure.— CAN communication bus fault: Open or short circuit in the power CAN or dedicated safety CAN lines between the SRS ECU and the vehicle gateway (GWM), or an abnormal terminating resistor (120Ω), causing communication timeout.+2 more →
Actions
— Safety preparation and initial diagnosis: Disconnect the high-voltage system (perform the high-voltage power-down procedure for new energy vehicles). Use a dedicated diagnostic tool (VDS3000/BYD dedicated diagnostic tool) to read the complete fault code stream. Record whether B169E is a Current or History code. Check for accompanying B1650-B1680 series sensor faults.— Power supply and ground circuit inspection: Open the dashboard panel and locate the SRS ECU (typically under the center console or in front of the gear selector). Measure the voltage between ECU connector terminal 30 (constant power), terminal 15 (IG power), and ground. Verify static voltage is ≥12V and ≥10.5V during startup. Verify ground resistance is <1Ω. Inspect fuses SB13 and SB14 (refer to the specific vehicle wiring diagram).+3 more →
B16FB11›
DTC B16FB11 indicates abnormal continuity between the Supplemental Restraint System (SRS) crash sensor (or pressure sensor) signal circuit (the third wire, typically the SIG signal wire) and body ground. In the BYD SRS circuit architecture, the front crash sensor typically uses a three-wire system: power supply (+B), ground (GND), and signal (SIG). When the signal wire shorts to ground, the SRS ECU detects a continuous 0V (or near 0V) signal. This contradicts the pulse signal or specific voltage value present during normal operation, causing the ECU to determine a sensor circuit fault. This fault forces the airbag system into fail-safe mode and continuously illuminates the airbag warning lamp. In a collision, the airbags may fail to deploy or deploy unintentionally, posing a severe safety hazard.
Causes
— Vehicle vibration, aging, or prolonged friction against metal edges damages the insulation of the collision sensor wiring harness in the front longitudinal beam or front bumper, shorting the signal wire core to body ground.— Water enters the sensor connector (usually located inside the front fender liner or front bumper) when driving through water or washing the vehicle, causing a short circuit between terminals or between a terminal and the connector housing (ground).— Improperly secured wiring harness after accident repairs. Clips, cable ties, or metal brackets pinch the harness, damaging the internal wire insulation and causing a short to ground.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS or ED400) to read the freeze frame data, confirm the specific sensor location triggering the fault (left front crash sensor, right front crash sensor, or center sensor), and record the vehicle status at the time of the fault.— Perform the SRS system safety procedure: turn the ignition switch to OFF, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the backup power supply and prevent accidental airbag deployment.+5 more →
B169F-00›
DTC B169F-00 indicates the Airbag Control Unit (SRS ECU) detected a severe internal self-check fault, preventing normal system operation. As the core of the passive safety system, the SRS ECU monitors subsystems in real time, including crash acceleration sensors, side pressure sensors, and seat occupancy detection. Upon detecting a collision, the ECU triggers the airbags, seat belt pretensioners, and high-voltage interlock cut-off. This fault indicates a hardware-level error in the internal ECU processor, memory unit, power management module, or communication interface, or a communication interruption or error between the ECU and the vehicle network (CAN/LIN). When this fault triggers, the SRS system enters fail-safe mode and the airbag warning lamp illuminates continuously. All airbags and pretensioners disarm and may fail to deploy during an actual collision. Additionally, the vehicle high-voltage system may fail to execute the collision power cut-off, creating a severe safety hazard.
Causes
— SRS ECU internal circuit board fault: Long-term thermal cycling causes swollen capacitors, cold solder joints, or internal processor chip damage.— Power supply system fault: Discharged battery or alternator regulator fault causing voltage to drop below 9V or exceed 16V, outside the ECU operating range.— Poor connector contact: Oxidized or backed-out ECU pins, loose retaining clips, or wiring harness wear causing an intermittent open or short circuit.+2 more →
Actions
— Safety preparation: Turn the power switch to OFF, disconnect the negative battery terminal, and wait at least 90 seconds for the SRS system capacitor to completely discharge.— Visual inspection: Remove the instrument panel trim. Inspect the SRS ECU exterior for physical damage or signs of water ingress. Verify the connector is secure and the locking tab is engaged.+6 more →
B169F›
In BYD new energy vehicles, DTC B169F indicates an ESP (Electronic Stability Program) control unit communication fault, not an SRS airbag fault (early documentation may contain classification errors). This fault code indicates the powertrain CAN or chassis CAN bus fails to receive a valid data frame from the ESP control module (integrated into the vehicle stability system, typically located on the left side of the engine compartment or inside the left front wheel arch), or the received signal fails verification. This disables the Electronic Stability Program, traction control, anti-lock braking system (ABS), and advanced driver assistance functions relying on ESP signals (such as adaptive cruise control and lane keeping). Root causes include a physical-layer CAN bus communication interruption, abnormal terminating resistance, a control unit power supply/ground fault, or a software version mismatch.
Causes
— Poor contact, oxidation, or water ingress at the ESP control module wiring harness connector (the module mounting location exposes it to mud splash and car wash water intrusion, causing terminal corrosion).— CAN bus circuit fault (CAN-H or CAN-L short or open circuit, damaged twisted-pair spacing, or terminating resistance deviating from the standard value of 60Ω)— Abnormal power supply or ground to the ESP control unit (blown fuse, poor relay contact, or loose ground point causing voltage drop)+2 more →
Actions
— Use the BYD dedicated diagnostic tool VDS2000/VDS3000 to read all fault codes and freeze frame data. Check for accompanying related fault codes such as U010104 (lost communication with ESP) or U030198 (software version mismatch).— Check the power supply voltage (standard 12V±0.5V) and ground resistance (less than 1Ω) of the ESP control module (part number usually in the BYD-3636100 series) to confirm the power and ground circuits are normal.+5 more →
B169F00›
DTC B169F00 indicates the Airbag Control Unit (SRS ECU) detected a severe fault during its internal self-test. As the core controller of the passive safety system, the SRS ECU integrates lateral/longitudinal acceleration sensors, the crash algorithm processor, and the ignition drive circuit. This DTC triggers when the ECU internal processor, memory (EEPROM/Flash), power monitoring module, or internal communication bus experiences an irreversible hardware or software anomaly. Upon detecting this fault, the ECU enters a degraded mode and may disable the ignition output for the airbags and seat belt pretensioners, resulting in partial or complete loss of crash protection functions. This safety-critical fault requires immediate action.
Causes
— SRS ECU internal hardware fault: main control chip (MCU) damage, internal accelerometer signal processing circuit fault, ignition drive transistor breakdown, or memory data checksum failure.— Power supply system fault: battery voltage below 9V or above 16V; poor contact at the SRS dedicated fuse (usually 10A or 15A); loose connection in the ECU constant power (B+) or ignition power (IG) circuit; ground terminal corrosion causing reference voltage drift.— CAN network communication fault: A short circuit or open circuit in the powertrain CAN or comfort CAN bus prevents the ECU from communicating normally with the Vehicle Control Module (VCM) and Instrument Cluster Module (ICM), triggering a watchdog reset.+2 more →
Actions
— Use the BYD VDS2000/3000 diagnostic tool to perform a deep scan. Record all fault codes and freeze frame data. Check specifically for accompanying B16XX series sensor faults or U-class communication faults.— Perform power integrity check: measure battery static voltage (must be ≥12.4V); check continuity and terminal fit of the SRS fuse in the instrument panel fuse box (F1/16 or F2/08, depending on model); measure voltage to ground at ECU connector B01-1 (B+) and B01-2 (IG); measure resistance to ground at B01-3 (GND) (must be <1Ω).+3 more →
B16A0-00›
DTC B16A0-00 indicates the airbag control unit (SRS ECU/ACM) detected a severe fault during its internal self-test. This indicates a hardware-level anomaly in the ECU internal processor, memory, power regulation circuit, or safety monitoring circuit, rather than an external sensor or actuator fault. The SRS ECU integrates crash discrimination algorithms, firing decision logic, and fault diagnostic functions. This safety-critical fault means the ECU cannot guarantee reliable airbag and pretensioner deployment during a collision. The root cause may be internal EEPROM data corruption, CPU calculation errors, abnormal internal voltage monitoring, or watchdog circuit triggering. This fault typically requires ECU assembly replacement rather than repair.
Causes
— Internal ECU electronic component failure: Aged internal energy storage capacitor, damaged main control chip (MCU), or corrupted memory (EEPROM/Flash) data causing self-test failure.— Power supply system fault: Battery voltage too low (<9V) or too high (>16V), momentary voltage drop during ignition ON, or poor ground wire contact (oxidation at ground points G201/G301), causing abnormal operation of the ECU internal power management module.— Water ingress or corrosion: Vehicle wading, A/C condensate leakage, or improper engine bay cleaning causes corrosion and short circuits on the internal circuit board of the SRS ECU located in the centre tunnel (beneath the gear selector on Qin series).+2 more →
Actions
— Diagnostic confirmation: Use the BYD VDS2000/VDS6000 diagnostic tool to read fault codes. Confirm if only B16A0-00 is present or if accompanied by other communication faults (such as U0146). Record freeze frame data (vehicle speed, voltage, etc. at the time of the fault).— Basic circuit check: Measure the pins at SRS ECU connectors G09/G10 — constant power (B+) should be 12V ± 0.5V, IGN power should be 12V in the ON position, ground resistance <1Ω, CAN-H (2.6V) / CAN-L (2.4V) terminal resistance approximately 60Ω.+6 more →
B16A0›
DTC B16A0 indicates a fault in the passenger-side Occupant Classification System (OCS) rather than a purely SRS_ECU hardware fault. The system uses a pressure sensor matrix integrated into the front passenger seat cushion and the OCS control module to monitor front passenger seat occupancy and weight category (adult/child/empty) in real time, and sends commands to the SRS_ECU to suppress or allow airbag deployment. The OCS sets DTC B16A0 when it detects an open circuit, short circuit, abnormal signal, or loss of calibration data in the sensor circuit. This fault prevents the SRS_ECU from accurately determining the front passenger status, posing the following risks: 1) Unnecessary airbag deployment when the front passenger seat is empty, increasing repair costs; 2) Airbag suppression during a collision due to incorrectly identifying the passenger as a child, resulting in inadequate occupant protection; 3) Abnormal seat belt pretensioner operating logic. The system uses a 5V reference voltage circuit and is extremely sensitive to changes in circuit resistance and connector contact resistance.
Causes
— Seat occupancy sensor (OCS) wiring harness connector loose, oxidized, or corroded by water ingress, causing increased contact resistance or intermittent signal interruption.— Physical damage to the pressure sensor mat (pressure sensing film) inside the seat cushion, such as punctures from sharp objects, plastic deformation from prolonged heavy loads, or creases.— Seat adjustment slide rail interferes with the OCS wiring harness during movement, causing harness insulation wear, broken copper cores, or a short circuit.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault Confirmation: Use the BYD dedicated diagnostic tool (VDS2000) to read the DTC. Confirm B16A0 is the current fault code. Record freeze frame data (including vehicle speed at the time of the fault, seat status signal voltage, etc.).+6 more →
B16A1›
DTC B16A1 indicates the airbag control unit (SRS ECU) detects an internal fault or abnormal communication with connected left-side safety system components. Specific causes include an SRS ECU internal processor error, memory fault, software anomaly, or a communication interruption with the left side impact sensor (left B-pillar), left seat belt pretensioner, or left seat occupancy detection sensor. This critical airbag system fault indicates the ECU may fail to receive left-side impact signals or execute airbag deployment commands. Consequently, the left side airbag, side curtain airbag, or seat belt pretensioner may fail to deploy during a side impact. This severely degrades vehicle passive safety protection and requires immediate repair.
Causes
— SRS ECU internal circuit board fault, processor crash, or incorrect software version— Left side impact sensor (located in the left B-pillar or left front door) damaged, connector loose, or wiring open/short circuit— Abnormal resistance in the left seat belt pretensioner circuit (open circuit, short circuit, or resistance outside the standard range of 2.0-3.0Ω)+2 more →
Actions
— Use the VDS2000/VDS3000 diagnostic tool to read all fault codes and freeze frame data. Confirm B16A1 is a current fault and check for accompanying left-side safety component fault codes (e.g., B16A0, B16A2).— Check the SRS ECU power supply circuits (including constant power +B and ignition power) and ground circuits. Measure the voltage to verify it remains stable between 11-14V. Check if fuses SB02, SB03, etc. are blown.+4 more →
B16A1-00›
DTC B16A1-00 indicates the Airbag Control Unit (ACU) detected a communication anomaly or internal circuit fault in the Left Side Impact Sensor. The SRS_ECU continuously monitors the supply voltage, signal circuit resistance, and LIN/CAN communication frame rate of each impact sensor. The ECU sets this DTC if it detects an open circuit, short to ground, or short to power in the left sensor wiring, or a sensor data validation error (e.g., capacitance drift, acceleration signal out of range) lasting over 200ms. Once set, the system enters a degraded mode. This mode may disable the left side airbag and curtain airbag deployment, or on certain models, restrict the entire airbag system, posing a severe safety hazard.
Causes
— A damaged internal accelerometer or aged capacitor in the left side impact sensor (located behind the left B-pillar trim panel) causes abnormal signal output.— Wiring harness connector between the SRS ECU and the left side impact sensor (usually located under the left front seat or at the base of the B-pillar) is loose, oxidized from water ingress, has backed-out pins, or has poor contact.— Airbag Control Unit (ACU) internal memory damage, power supply chip failure, or software logic error causing a false sensor fault report.+2 more →
Actions
— Connect the VDS2000 or BYD dedicated diagnostic tool. Enter the SRS system and read the complete DTCs. Confirm whether B16A1-00 is a current (Active) or historical (History) fault, and record the vehicle speed and sensor voltage values from the freeze frame data.— Disconnect the 12V battery negative terminal and wait 90 seconds for the capacitors to discharge. Remove the left B-pillar lower trim panel. Verify the side impact sensor connector (black plug, 2-pin or 3-pin) is locked. Inspect the pins for oxidation or recession. Apply conductive grease if necessary.+4 more →
B16A100›
DTC B16A100 actually indicates an AVAS (Acoustic Vehicle Alerting System) fault, not an SRS airbag system fault. This DTC signifies the Pedestrian Warning Speaker has an open or short circuit, or the AVAS control module detects a speaker circuit fault. AVAS is a mandatory safety feature on new energy vehicles that simulates engine sound to warn pedestrians at low speeds (0-20 km/h). The system triggers this DTC when it detects abnormal speaker circuit resistance (normal range: 4-8 Ω), a wiring short to ground or open circuit, or an internal control module fault. This disables the low-speed warning sound and compromises safety compliance.
Causes
— Pedestrian warning speaker unit damaged: Internal coil burnt out causing a short circuit (resistance close to 0Ω) or coil open circuit (infinite resistance). Common causes include water ingress, aging, or quality defects.— Wiring harness connector fault: loose plug, terminal oxidation or corrosion, poor contact, or water ingress after wading causing an abnormal signal.— Wiring harness mechanical damage: Front compartment wiring harness chafes against sharp edges such as the fender liner and bumper bracket, causing insulation damage, intermittent short to ground, or open circuit.+2 more →
Actions
— Use VDS2000 or an original BYD diagnostic tool to read the fault code. Confirm whether B16A100 is a current or history fault. Record the freeze frame data (vehicle speed, temperature, etc., at the time of occurrence).— Visually inspect the exterior of the pedestrian warning speaker (usually mounted on the front right side of the front compartment or inside the front bumper). Check the AVAS control module (usually located near the front compartment fuse box or inside the cabin dashboard) and all related connectors for signs of water ingress, corrosion, or looseness.+7 more →
B16A2-00›
B16A2-00 indicates an internal fault or performance degradation in the airbag control unit (SRS ECU). This is not an external sensor or actuator issue, but an abnormality in the microprocessor, memory chip, power management module, or internal acceleration sensor on the ECU main board. This fault causes the airbag system to enter a degraded mode or fail completely. Front airbags, side airbags, and pretensioner seatbelts may fail to deploy normally during a collision. It may also trigger a high-voltage interlock cut-off, preventing the vehicle from powering up or causing a loss of high voltage while driving. This DTC is a Hard Fault. Simply disconnecting the power usually cannot clear it. Perform an in-depth diagnosis of the hardware or software status.
Causes
— Aged or damaged SRS ECU internal circuit board components (such as bulging electrolytic capacitors or cold solder joints on the main control chip)— Abnormal power supply (unstable battery voltage, excessive voltage drop in ECU power supply circuit, ground point oxidation causing reference voltage drift)— Uncleared internal ECU trigger record after a vehicle collision, or a short circuit in the crash sensor circuit causing ECU self-protection.+2 more →
Actions
— Use the VDS2000/VDS3000 diagnostic tool to read the complete DTC list, check for accompanying communication or power supply fault codes such as B16A3 and B1650, and record the freeze frame data.— Check the SRS ECU power supply (constant +B, ignition switch IG1) and ground (G10A/G10B) voltages. The standard value is 12V ± 0.5V. Check fuse SB02/FB14 (depending on vehicle model).+5 more →
B16A2›
DTC B16A2 indicates the airbag control unit (SRS ECU) detects an internal fault or system-level communication error. As the core control module of the passive safety system, the SRS ECU monitors crash sensor signals, deploys airbags and seat belt pretensioners, and executes post-collision fuel cut-off protection. This DTC indicates an anomaly in the ECU internal processor, memory, or communication interface. It also triggers upon detecting a power/ground circuit fault, CAN bus communication interruption, or crash data lock (incorrectly reset after a collision). This fault may prevent the airbag system from deploying during an actual collision or cause related functions, such as seat belt pretensioners and seat occupancy detection, to fail. This severe fault compromises driving safety.
Causes
— Abnormal SRS ECU power supply: Includes low battery voltage (<9V), blown dedicated fuse (usually located in the instrument panel fuse box or front compartment power distribution box), or loose connection or corrosion in the power supply circuit.— Ground circuit fault: ECU ground point is loose, oxidized, or has excessive contact resistance (>1Ω), causing unstable control unit operation.— CAN bus communication fault: Lost communication between the SRS ECU and the vehicle network (powertrain CAN or comfort CAN). A wiring short circuit, open circuit, or abnormal terminating resistor may cause this.+2 more →
Actions
— Step 1: Use the BYD dedicated diagnostic tool (VDS2000/6000) to access the SRS system, read all fault codes and freeze frame data, check for accompanying fault codes (such as B16A0, B16A1), and view the 'collision history record' data stream to verify if the vehicle experienced a collision.— Step 2: Check the SRS ECU power supply circuit: Disconnect the negative battery terminal, wait 3 minutes, then unplug the ECU connector. Measure the voltage to ground at the ECU connector power pins (constant power +B, ignition switch IG) and check fuse continuity. The voltage must be 9-16V. Check the resistance to ground at the ground pins. The resistance must be <1Ω.+4 more →
B16A3-00›
DTC B16A3-00 indicates an internal self-check failure or core function fault within the airbag control unit (SRS ECU). Specifically, this code indicates the ECU detects an internal processor fault, EEPROM memory error, abnormal internal power reference voltage, or SRS-CAN (Supplemental Restraint System CAN bus) communication interruption during the startup self-check or operation. In BYD Qin series models, the SRS ECU integrates crash criteria algorithms, high-voltage interlock cut-off control logic, and multi-sensor data fusion functions. This fault causes the airbag system to enter Fail-Safe mode, disabling the deployment of airbags, side curtain airbags, seat belt pretensioners, and the high-voltage system emergency cut-off function, while illuminating the instrument cluster SRS warning lamp. If a collision occurs, the occupant protection system will fail and the high-voltage battery may not disconnect automatically, creating an extremely high safety risk.
Causes
— SRS ECU internal hardware fault (damaged MCU processor, memory data checksum error, or capacitor aging causing excessive internal power supply ripple)— Abnormal vehicle battery voltage (prolonged depletion below 10.5V or charging system fault causing voltage to exceed 16V), resulting in unstable ECU power supply or current surge during startup.— SRS-CAN bus physical layer fault (short circuit between CAN-H and CAN-L, short to ground or power, or terminating resistor drift causing signal reflection interference)+2 more →
Actions
— Use BYD dedicated diagnostic tool VDS2000 or VDS1000 to perform a full vehicle scan. Confirm B16A3-00 is a current (Active) fault, not a history fault. Record the vehicle status in the freeze frame data (vehicle speed, ignition cycle count, battery voltage).— Check the battery state of health (SOH) and static voltage (standard: above 12.6 V). Check the alternator output voltage (13.8–14.8 V) to rule out power supply system fluctuations causing false reports.+5 more →
B16A3›
DTC B16A3 indicates an internal fault in the airbag electronic control unit (SRS ECU, also known as the ACU - Airbag Control Module). This fault points to an abnormality within the ECU processor, memory (EEPROM), power supply monitoring circuit, or safety sensor monitoring circuit, rather than an issue with external airbags, sensors, or wiring harnesses. The ECU internal self-diagnostic program triggers this DTC when it detects key circuit parameters exceeding thresholds (e.g., internal voltage reference deviation, memory checksum failure, or watchdog reset). This fault may prevent the airbag system from deploying normally during a collision or create a risk of unintended deployment. It constitutes a core fault in the passive safety system and requires immediate resolution.
Causes
— SRS ECU internal memory damaged or data verification failed (EEPROM-stored collision algorithm parameters and configuration codes lost or corrupted)— ECU internal power supply monitoring circuit fault (abnormal internal voltage regulator output causes the ECU to incorrectly determine its power supply status)— External power supply system fault (IG1 power supply voltage fluctuation or excessive ground point contact resistance causing an ECU internal low-voltage reset)+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds to fully discharge the capacitors and prevent accidental airbag deployment; read and record all fault codes and freeze frame data.— Basic inspection: Inspect the SRS ECU exterior for physical damage or signs of water ingress; verify fuse F1/15 (IG1 power supply) is intact; inspect ECU connectors G36/G37 for oxidation or backed-out pins.+4 more →
B16A4-00›
DTC B16A4-00 indicates the airbag control unit (SRS ECU) detects an internal or systemic fault. As the core control module of the safety system, the SRS ECU monitors crash sensor status, controls the firing and deployment of airbags and seat belt pretensioners, and communicates with the vehicle CAN network. This fault indicates potential hardware damage, software malfunction, or power/communication interruption in the ECU’s internal microprocessor, memory, power regulation circuit, or communication interface. When this DTC triggers, the SRS system enters fail-safe mode. All airbags (driver, passenger, side, and curtain) and seat belt pretensioners may fail to deploy during a collision. The instrument cluster continuously illuminates the airbag warning light, severely compromising passive safety protection.
Causes
— SRS ECU internal hardware fault: Aging, overheating, or manufacturing defects caused a short or open circuit in the capacitors, resistors, processor chip, or ignition drive circuit on the control unit's internal circuit board.— Abnormal power supply: Unstable constant power (B+) or ignition power (IG) voltage (below 9V or above 16V), excessive contact resistance in the power supply circuit, blown fuse, or loose or corroded ground points G501/G502.— CAN bus communication fault: Short circuit between the H and L lines of the powertrain CAN or body CAN, short to ground or power, open circuit, or abnormal terminating resistance prevents the ECU from communicating normally with the vehicle network.+2 more →
Actions
— Fault confirmation and freeze frame recording: Use the BYD VDS2000 or Launch X-431 diagnostic tool to read all DTCs. Record the freeze frame data (vehicle speed, voltage, and temperature at the time of the fault). Check for related fault codes (such as U0140-00 BCM communication fault and B16A5-00 internal fault).— Power supply and ground circuit inspection: Disconnect the battery negative terminal, wait 3 minutes, then disconnect the SRS ECU connector. Measure the voltage between connector pin 1 (B+ constant power) and ground, and between pin 17 (IG power) and ground (Standard: 12V ± 0.5V). Measure the resistance between the ground pin (e.g., pin 34) and body ground (Standard: < 1Ω). Check fuses SB03/SB08.+5 more →
B16A4›
DTC B16A4 indicates the airbag control unit (SRS ECU) detected an internal system fault or critical support circuit abnormality. As the core of the passive safety system, the ECU processes real-time data from the front and rear crash sensors, side pressure sensors, and accelerometers. It determines airbag deployment, seat belt pretensioner activation, and high-voltage interlock disconnection. This DTC triggers when the ECU self-diagnostic detects an internal CPU processing error, an EEPROM memory checksum failure, a transient voltage drop at the power supply monitoring circuit, or a communication interruption between the master and slave safety chips. In this condition, the system enters fail-safe mode. This mode may disable all airbag deployment functions and fails to guarantee normal protection logic during a collision, creating a severe safety hazard.
Causes
— Poor solder joint on the SRS ECU internal PCB, or hardware fault in the main control chip (e.g., Infineon or Renesas series)— ECU power supply circuit fault: excessive resistance in the constant power (+B) circuit, poor contact at the ignition switch power supply (IG1), or corrosion at ground terminals G301/G302 causing voltage fluctuation.— CAN bus communication fault: Electromagnetic interference affects the power CAN or chassis CAN signals between the SRS ECU, instrument cluster, and VCU, or a terminating resistor mismatch causes data frame loss.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (ED400 or VDS) to read the complete DTC list, check for accompanying fault codes B16A3 (SRS ECU internal fault), U0155 (lost communication with instrument cluster), or B1B00 series sensor fault codes, and record the freeze frame data.— Check battery voltage and body ground points. Measure voltage at SRS ECU connector terminal 1 (+B constant power) and terminal 9 (IG1 power). Verify static voltage is ≥12.4V and dynamic voltage is ≥9V. Verify ground circuit resistance is <1Ω.+5 more →
B16A5›
DTC B16A5 indicates an internal self-diagnostic fault in the airbag control unit (SRS ECU). The SRS ECU is the core control module of the safety system, responsible for monitoring crash sensors and controlling airbag deployment, seat belt pretensioners, and seat occupancy detection. This fault code specifically points to a hardware-level abnormality in the ECU internal processor, memory (EEPROM/Flash), power supply monitoring circuit, or clock circuit, rather than an external wiring or sensor fault. This internal fault can force the airbag system into fail-safe mode, preventing normal airbag deployment during a collision or creating a risk of unintended deployment, making it a severe safety fault. Upon detecting the fault, the ECU illuminates the airbag fault warning light and may disable related functions such as the seat belt pretensioners and child monitoring system.
Causes
— Power supply system fault: Unstable battery voltage (continuously below 9V or above 16V), poor contact or transient overvoltage in the SRS ECU power supply circuit (B+, IGN), damaging the internal power management chip.— Internal memory fault: EEPROM data corruption, Flash memory read/write error, or checksum failure. Typical causes include software bugs, electromagnetic interference, or incomplete software updates.— ECU hardware aging: dry internal PCB solder joints, capacitor aging, processor crystal oscillator failure, or internal chip circuit breakdown (common in high-temperature, high-humidity environments or after driving through water)+2 more →
Actions
— Use a BYD dedicated diagnostic tool (ED400 or VDS) to read the complete DTC information, record freeze frame data (vehicle speed, timestamp, voltage values), and confirm whether B16A5 is a current or history code.— Perform a full vehicle scan and check for U-class communication fault codes (such as U0100, U0151) to rule out false internal faults caused by CAN bus interference.+7 more →
B16AE›
DTC B16AE indicates the Supplemental Restraint System (SRS) detects a squib encryption verification failure or abnormal encrypted communication in the ignition circuit. In BYD vehicles, the airbag ECU uses an encrypted communication mechanism (Ignition Encryption Protocol) with each airbag module and seat belt pretensioner to prevent accidental deployment or malicious interference. The SRS ECU stores this fault code when it cannot verify the squib identity encryption key, or when it detects ignition circuit resistance outside the standard range (typically 2.0-3.0Ω) accompanied by an abnormal encryption signal. This fault may prevent the corresponding airbag from deploying normally during a collision, or trigger the system to enter fail-safe mode (disabling some airbag functions).
Causes
— Airbag ECU internal software error or encryption chip fault prevents correct verification of the igniter ID.— Airbag igniter (driver/passenger/side airbag) wiring harness connector is oxidized, loose, or has excessive contact resistance, disrupting encrypted signal transmission.— Installing a non-genuine airbag assembly or failing to perform encryption matching after accident repairs causes an encryption key mismatch between the new and old components.+2 more →
Actions
— Safety Preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes to allow the SRS ECU capacitor to fully discharge, preventing accidental airbag deployment.— Diagnostic tool check: Use the VDS2000/BYD dedicated diagnostic tool to read the complete fault code. Verify the code is B16AE-00 and record the voltage value and igniter position from the freeze frame data.+5 more →
B16A7-00›
The definition of DTC B16A7-00 varies across BYD vehicle platforms. In early models such as the Qin 100, Qin 80, and Qin EV450, this code indicates an internal fault in the SRS_ECU (airbag control unit). It signifies an abnormality in the main control chip, internal memory, or ignition circuit driver, preventing the airbag system from executing collision detection and airbag deployment logic. DM-i and e-Platform 3.0 models, such as the Qin PLUS, Song Pro, and Tang DM, often reuse this DTC as a hardware fault code for the seat occupancy recognition sensor (SBR) or the ultrasonic radar/blind spot monitoring radar. This indicates the ECU received an invalid or out-of-range sensor signal. Regardless of the definition, this fault causes the airbag system to enter degraded mode and illuminates the instrument cluster SRS warning lamp. It may also cause seat belt pretensioner failure, airbag suppression, or a risk of unintended deployment. Repair immediately.
Causes
— Seat occupancy detection sensor (pressure film) fatigue fracture or open circuit. Prolonged improper sitting posture or frequent seat adjustments commonly break the film wiring (Qin PLUS/Han models).— Water ingress and oxidation in the radar sensor wiring harness connector, especially after wading or washing the vehicle; poor rear bumper wiring harness sealing causes terminal corrosion and open circuits (Song Pro/Tang DM models).— Damaged internal transducer or shorted coil in the ultrasonic/millimetre-wave radar sensor, mostly due to minor impacts, paint overspray, or internal ageing (Yuan Pro/Song Pro models).+2 more →
Actions
— Use BYD dedicated diagnostic tool VDS2000 or Launch X431 to read the complete fault code stream, confirm the B16A7-00 subtype description (e.g., 'left rear radar', 'driver seat sensor', or 'SRS internal'), and record freeze frame data.— Check the waterproof sealing of the SRS system wiring harness connectors (especially under the seats and inside the bumper). Measure the sensor supply voltage (12V ± 0.5V or 5V ± 0.25V, depending on the specific sensor) and the CAN line voltage (CAN-H 2.6V / CAN-L 2.4V).+4 more →
B16A7›
DTC B16A7 indicates the airbag control unit (SRS ECU) internal self-check detected a systemic fault. This fault involves abnormalities in the SRS ECU internal microprocessor, memory (EEPROM/Flash), power management circuit, or watchdog circuit. Specific causes include an internal 5V/3.3V reference voltage regulator fault, an acceleration sensor (Satellite Sensor) communication timeout, an internal algorithm self-check failure, or a non-volatile memory data checksum error. Upon detecting this fault, the SRS ECU enters Fail-Safe Mode. This mode may disable some or all airbag deployment and seat belt pretensioner activation functions, and illuminate the instrument cluster airbag warning light. Because the airbag system is a critical passive safety system, this fault indicates the vehicle may fail to provide the designed occupant protection during a collision, creating a severe safety hazard.
Causes
— SRS ECU internal hardware fault: Includes PCB capacitor aging and leakage, BGA chip cold solder joints, and internal acceleration sensor (MEMS) zero-point drift or damage. Commonly occurs in vehicles operated in high-temperature and high-humidity environments.— Power supply system fault: unstable battery voltage (below 9V or above 16V), oxidized ground point causing excessive contact resistance, excessive voltage drop in the ignition switch power supply (IG1) circuit, especially voltage drop during start-up triggering an ECU reset.— Wiring harness connector fault: Recessed pins, backed-out pins, oxidation, or water ingress at the SRS ECU 16-pin/24-pin connector terminals (common after vehicle wading), causing abnormal power supply, ground, or CAN bus (HS-CAN) communication.+2 more →
Actions
— Use VDS2000 or a BYD dedicated diagnostic tool (such as ED400) to read the complete DTC list. Check for accompanying B16A5 (internal fault), U-prefix communication fault codes, or collision sensor-related faults. Record the freeze frame data.— Perform a key cycle test (Ignition ON 6 seconds → OFF 10 seconds → ON) and observe if the fault code is Current or History. Check if the instrument cluster airbag warning light remains illuminated or flashes a specific fault code.+6 more →
B16AC-00›
DTC B16AC-00 indicates an internal hardware or software fault in the airbag control unit (SRS ECU), specifically a malfunction in the ECU internal processor, memory, power management circuit, or reference voltage circuit. This core control module fault may cause the airbags to fail to deploy during a collision or deploy unintentionally in non-collision situations, severely compromising occupant passive safety. Abnormal ECU internal voltage regulation circuits (5V reference voltage fluctuation), main control chip (e.g., NXP SPC5604) processor errors, crystal oscillator failure, internal memory data corruption, or lost configuration parameters typically cause this fault, rather than external sensor or wiring harness issues.
Causes
— ECU internal water ingress and corrosion: A blocked or restricted A/C drain hose allows condensation to seep under the center console. Poor SRS ECU housing sealing exposes the internal circuit board to moisture, causing a short circuit in the voltage regulator circuit or corrosion of the chip pins.— Power supply system fault: Improper power disconnection when servicing the high-voltage system or 12V battery generates voltage surges that impact the ECU internal power management module, or prolonged low voltage causes abnormal processor operation.— Physical hardware damage: Cold solder joints on the main control chip BGA, stalled 32.768kHz crystal oscillator, resonant capacitor failure, or PCB interlayer short circuit. This typically affects vehicles with no collision history that experienced vibration or severe temperature fluctuations.+2 more →
Actions
— Connect the diagnostic tool (Launch X-431 or BYD VDS) and access the SRS system. Read and record all fault codes. Confirm B16AC-00 is a current fault that fails to clear. Check for accompanying fault codes (such as B1696, B1684, etc.).— Check the ECU power supply system: Measure the voltage at SRS ECU connector terminal B16 (constant power); it should be 12V. Measure the voltage at terminal B1 (IGN power) with the ignition ON; it should be 12V. Verify the ground wiring harness connection is secure, and measure the CAN-H (2.6V) and CAN-L (2.4V) communication voltages to verify they are normal.+5 more →
B16AC›
For BYD new energy models (Qin, Tang, Song, Yuan, and Han series), DTC B16AC indicates an air conditioning evaporator temperature sensor circuit fault (Evaporator Temperature Sensor Circuit Range/Performance), not the SRS_ECU fault stated in the original information. This NTC thermistor mounts on the air conditioning evaporator surface. It monitors the evaporator temperature in real time to prevent surface icing from blocking the air ducts. The controller sets this DTC and triggers the air conditioning system protection strategy (compressor shutdown or restricted cooling) upon detecting an out-of-range sensor signal voltage (close to 5V during an open circuit, close to 0V during a short circuit, or unresponsive to temperature changes), abnormal resistance, or an abnormal sampling frequency. This fault results in a lack of cooling, intermittent A/C operation, or evaporator icing.
Causes
— Evaporator temperature sensor failure: Internal thermistor open circuit, short circuit, or resistance drift fixes the signal voltage at a specific value (such as 4.9V or 0.1V), preventing it from changing with temperature.— Wiring harness open circuit or poor contact: Signal wire, 5V reference wire, or ground wire from the sensor to the air conditioning controller broken at the glove box hinge or firewall pass-through due to repeated bending or interference.— Connector oxidation or looseness: High humidity near the evaporator housing in the front passenger compartment causes verdigris and oxidation on the sensor connector terminals, resulting in contact resistance fluctuations (0.5Ω-50Ω).+2 more →
Actions
— Connect the VDS or X431 diagnostic tool, access the air conditioning system, and read the fault codes. Confirm whether B16AC is a current fault (Active) or a historical fault (History). Record the ambient temperature and evaporator temperature values from the freeze frame data.— Read the data stream and observe the 'Evaporator Temperature Sensor' value. During cooling, this value normally drops gradually from ambient temperature (25-30°C) to 2-5°C. A reading of -40°C, -25°C, 85°C, or a fixed, unchanging value indicates an abnormal signal.+6 more →
B16AC00›
B16AC00 (Config_Error) indicates the internally stored configuration data in the airbag control unit (SRS ECU/ACU) does not match the actual vehicle hardware configuration, or the configuration data checksum failed. In BYD E2, E3, Qin EV, and similar models, this fault typically means the ACU coding data and vehicle configuration parameters (such as airbag quantity, seat belt pretensioner configuration, crash sensor type, and child seat recognition configuration) do not match the actual installed equipment, or data corruption occurred during writing or storage. This fault forces the SRS system into fail-safe mode, potentially disabling airbag deployment or causing complete system failure. This is a critical fault affecting passive safety.
Causes
— Failure to complete the online configuration/coding procedure after replacing the SRS control unit (ACU) causes the default configuration in the new module to mismatch the vehicle's actual hardware.— Severe vehicle battery discharge or prolonged power disconnection erases or corrupts configuration data stored in the ACU internal EEPROM.— Interruption during the SRS software upgrade or flashing process (such as power loss or communication failure) caused incomplete writing of configuration data.+2 more →
Actions
— Use the official BYD diagnostic tool (BYD-EDS or VDS) to read complete fault code information, including freeze frame data and history records. Check for other accompanying communication or hardware fault codes.— Check the power supply, ground, and CAN line connections of the SRS control unit (usually located under the center console or gear selector). Measure the voltage and terminal resistance to verify they are normal (approximately 60Ω between CAN-H and CAN-L).+3 more →
B16AD-00›
DTC B16AD-00 indicates an internal fault or communication error in the Supplemental Restraint System Electronic Control Unit (SRS ECU). As the core module of the airbag system, this control unit monitors vehicle collision acceleration in real time, processes crash sensor signals, determines airbag deployment timing, and drives the ignition circuits. This fault may force the airbag system into Fail-Safe Mode, preventing the front dual airbags, side airbags, and curtain airbags from deploying during a collision. The condition may also cause seat belt pretensioner failure and disrupt the crash fuel cut-off function. The root cause typically involves an ECU internal microprocessor or memory failure, an abnormal 12V power supply (overvoltage/undervoltage), or an ECU malfunction resulting from a CAN network communication disruption, rather than a single sensor fault.
Causes
— SRS ECU internal circuit board fault (e.g., filter capacitor aging, main control chip dry solder joints, or damage)— Abnormal power supply (unstable battery voltage, blown dedicated SRS fuse, poor or corroded ECU ground)— CAN bus communication fault (short circuit, open circuit, abnormal terminating resistor, or signal interference on the powertrain CAN or dedicated airbag CAN)+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS 2000 or VDS 2100) to read all fault codes. Verify B16AD-00 is a Current DTC, not a history DTC, and check for accompanying communication fault codes (codes starting with U).— Check the SRS ECU power supply circuit: Measure the voltage at the ECU connector B+ terminal (constant power) and IGN terminal (ignition switch power). The standard value is 11-14 V. If the voltage is below 10 V or above 16 V, repair the power supply system.+6 more →
B16AD›
DTC B16AD indicates an internal fault or critical communication error in the airbag control unit (SRS ECU). This fault points to a hardware-level failure in the ECU internal microprocessor, non-volatile memory (EEPROM/Flash), power management module, or acceleration sensor interface circuit, rather than an external wiring issue. The ECU sets this code when its self-check detects a failed internal diagnostic test, a calibration data checksum error, a watchdog reset, or a critical circuit voltage deviating from threshold limits. This fault forces the SRS system into fail-safe mode: the system either completely disables the airbags (no deployment during a collision) or enters a degraded mode (only partial circuits operate), and illuminates the airbag warning lamp. Because this fault affects the passive safety system, the vehicle remains drivable but poses a severe safety risk.
Causes
— SRS ECU internal hardware fault: Damage to the ECU main control chip (MCU), memory, or power regulator circuit. Common causes include aging from long-term vehicle use, overheating, or voltage surges (such as reversed polarity during jump-starting).— Power supply system fault: Unstable battery voltage (persistently below 9V or above 16V), poor contact at the dedicated SRS fuse, or ECU ground terminal oxidation causing reference voltage drift, triggering the ECU internal undervoltage/overvoltage protection.— CAN bus communication fault: A short circuit (short between H and L, short to power, or short to ground), open circuit, or abnormal terminating resistance on the Power CAN or dedicated SRS-CAN bus prevents normal ECU communication with the vehicle network, resulting in a timeout.+2 more →
Actions
— Initial Diagnosis and Safety Preparation: Connect the BYD VDS2000/Launch X431 diagnostic tool. Read all DTCs and freeze frame data to confirm whether B16AD is an active or history code. Disconnect the 12V battery negative terminal and wait 3 minutes to allow the capacitors to discharge. Inspect the SRS ECU exterior for physical damage, water stains, or burn marks.— Power and ground circuit inspection: Reconnect the battery, turn the ignition switch to ON (do not start), and measure the voltage to ground at ECU connector pin16 (B+ constant power) and pin15 (IGN power); voltage must be 12V±0.5V. Measure the resistance to ground at pin14 (ground); resistance must be less than 1Ω. Check the connector terminals for backed-out pins or oxidation.+4 more →
B16AE00›
Internal fault in the SRS_ECU (airbag control unit) or systemic power supply/communication fault. This DTC indicates the airbag control module detects a functional fault in its processor, memory, power management circuit, or internal communication bus, preventing the system from guaranteeing accurate crash detection and reliable airbag deployment. Upon triggering, the SRS system enters fail-safe mode, disables all airbag and seat belt pretensioner functions, and continuously illuminates the instrument panel airbag warning light. The system may fail to provide occupant protection during a collision, and other safety systems may experience limited functionality.
Causes
— SRS ECU internal circuit board fault (damaged main control chip, memory, or power management IC, usually resulting from voltage fluctuations or component aging)— Abnormal ECU power supply voltage (battery voltage below 9V or above 16V, dedicated fuse blown, ground terminals G301/G302 loose, oxidized, or corroded)— CAN bus communication fault (HS-CAN line short circuit, open circuit, abnormal terminating resistance, or electromagnetic interference interrupting communication between the ECU and the vehicle network)+2 more →
Actions
— Use the VDS2000/VDS3000 diagnostic tool to read all DTCs. Confirm B16AE00 is a current fault, not a history fault. Record the freeze frame data (including vehicle speed, voltage, etc., at the time of the fault). Clear the fault code and perform a road test to verify if the fault recurs.— Check the SRS ECU power supply system: measure the voltage at the ECU connector B+ terminal (standard 12V ± 0.5V), check the dedicated SRS fuse in the dashboard fuse box (usually F1/15 10A or F2/10 15A), and check ground terminals G301/G302 for tightening torque (standard 9-11 N·m) and oxidation.+4 more →
B16B0›
DTC B16B0 indicates the Airbag Control Unit (SRS ECU) internal self-diagnosis detected a critical function abnormality. This ECU integrates the main control MCU, backup power supply, crash sensors (accelerometers), and ignition driver circuit. An "internal fault" specifically refers to compromised ECU core hardware or firmware integrity, including internal voltage regulator module failure (e.g., 5V/3.3V reference voltage deviation), EEPROM data checksum errors, interrupted communication between the main and backup CPUs, crash sensor signal processing circuit faults, or ignition loop driver chip damage. This fault forces the airbag system into fail-safe mode. During a collision, the system may fail to deploy airbags or activate seat belt pretensioners. It also carries a risk of unintended deployment, classifying it as a highest-level safety-related fault.
Causes
— ECU internal power management chip failure: Long-term battery depletion or voltage surges (such as reversed polarity during jump-starting) cause the ECU internal DC-DC converter or voltage regulator module to burn out and fail to provide stable operating voltage to the main control chip.— Acceleration sensor (MEMS) fault: The ECU-integrated crash sensor experiences zero-point drift, a stuck-high/low signal, or an SPI communication fault, causing the ECU to detect a loss of its sensing capability.— Software/firmware corruption: Electromagnetic interference, interrupted programming, or physical aging of the Flash memory causes calibration data or control algorithm checksum errors.+2 more →
Actions
— Initial diagnosis: Use the BYD VDS2000/VDS1000 diagnostic tool to read all DTCs. Confirm if B16B0 is a current code (Active) and check for accompanying codes (such as B16B1, U0151). Record freeze frame data (vehicle speed, timestamp, battery voltage) and check if the instrument cluster SRS warning light remains illuminated.— External factor inspection: Disconnect the 12V battery negative terminal, wait 3 minutes, and check the SRS ECU wiring harness connector (usually located under the center console or in front of the gear selector) for oxidation or backed-out pins; measure the constant power (B+) and ignition switch power (IG1) voltages, and the ground wire resistance (<1Ω); measure the CAN-H and CAN-L line voltages (approximately 2.5V) and terminal resistance (approximately 60Ω) to rule out false detection caused by external power supply or communication faults.+4 more →
B16B000›
DTC B16B000 indicates the airbag electronic control unit (SRS ECU) detects an internal system fault or a deployment circuit abnormality. This fault may involve an internal ECU processor fault, a power/ground abnormality, a CAN communication fault, or, more commonly, the driver-side airbag deployment circuit resistance falling outside the calibrated range (normal 2.0-3.0 Ω). When the ECU detects high circuit resistance (>5 Ω), an open circuit, low circuit resistance (<1 Ω), or a short circuit, it sets this code and illuminates the instrument cluster airbag warning lamp. The system enters fail-safe mode, and the airbag may fail to deploy during a collision.
Causes
— Broken internal ribbon cable or poor contact within the clock spring (spiral cable): Repeated steering wheel rotation wears the internal flat cable, causing an intermittent or permanent open circuit.— Airbag module ignition circuit fault: Internal clock spring broken after collision, connector oxidation, or internal module open circuit, causing abnormal circuit resistance.— Wiring harness corrosion due to water ingress: Waterproofing failure in the under-seat or floor wiring harness allows water to enter the connector. This produces green corrosion, increasing contact resistance or causing signal interference.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds for the SRS ECU capacitor to fully discharge. Do not work on the airbag system with the ignition switch ON.— Diagnostic scan: Use the BYD VDS2000 or ED400 to read complete fault codes and freeze frame data. Confirm whether the fault is stored or current. Check the 'DAB Resistance' (driver airbag resistance) value in the data stream.+6 more →
B16B9-00›
DTC B16B9-00 indicates an Airbag Control Unit (SRS ECU) internal self-test failure. Specific causes include a microprocessor logic error, internal memory (EEPROM/Flash) data checksum failure, power management module anomaly, or internal accelerometer signal processing circuit fault. This indicates an ECU hardware or low-level software fault, not a peripheral wiring or sensor issue. Upon entering fail-safe mode, the ECU disables all airbags, seat belt pretensioners, and collision unlock functions. The instrument cluster airbag warning light remains illuminated, and the occupant protection system may fail to operate during a collision.
Causes
— Damaged ECU internal microprocessor or memory chip causes CRC check failure during power-on self-test (POST).— Vehicle power supply system fault (such as a voltage surge during jump-starting or overvoltage caused by a generator regulator failure) causes electrical breakdown of the ECU internal power management IC.— Aging and failure of the ECU internal backup power supply (energy storage capacitor/battery) causes data loss or logic errors during power-off.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000/VDS3100) to read fault codes. Confirm B16B9-00 is a current fault (Active) and record the voltage and mileage from the freeze frame data.— Check the SRS ECU power supply and ground: Measure constant power (B+) and ignition power (IG) at connector M11 (or corresponding vehicle connector). Voltage must be 11-14 V. Ground wire resistance must be less than 1 Ω. This rules out misdiagnosis caused by external power supply issues.+6 more →
B16B9›
DTC B16B9 indicates the airbag electronic control unit (SRS_ECU) detects an internal hardware fault or critical communication anomaly. This fault involves a self-test failure of the ECU internal processor, non-volatile memory (NVM), or power management module. It may also indicate a communication interruption or data checksum error between the ECU and the vehicle CAN network (powertrain CAN or body CAN). When this fault triggers, the SRS system typically enters fail-safe mode, disabling airbag and seat belt pretensioner deployment during a collision, and illuminates the instrument cluster airbag warning light. This safety-critical fault requires immediate repair to ensure correct occupant restraint system operation.
Causes
— Abnormal SRS ECU supply voltage: Battery voltage is below 9V or above 16V, or the IGN power supply drops momentarily during ECU operation, triggering the internal reset circuit.— ECU internal memory data corruption: Electromagnetic interference, interrupted software flashing, or prolonged low battery voltage causes calibration data or crash threshold parameter verification failure.— Airbag CAN bus communication fault: short circuit between CAN-H and CAN-L, short to power or ground, or terminating resistor (usually 120Ω) drift degrading signal integrity.+2 more →
Actions
— Connect the BYD VDS2000/3000 diagnostic tool, enter the SRS system, and read the complete DTC freeze frame data. Confirm whether B16B9 is a current fault (Active) or a history fault (History), and record the vehicle status when the fault occurred (vehicle speed, voltage, temperature).— Check the power supply system: Measure battery static voltage (12.4-12.6V) and voltage after startup (13.8-14.8V). Check if the SRS fuse in the instrument panel power distribution box (usually F4/9, 10A/15A) is blown or has poor contact.+5 more →
B16BA-00›
DTC B16BA-00 indicates the Airbag Control Unit (SRS ECU) detected an abnormality during its internal self-check or lost normal function. This fault indicates an SRS ECU hardware failure, software malfunction, power supply or communication interruption, or internal algorithm error, rather than an external sensor or actuator issue. The SRS ECU serves as the core of the safety system and monitors the crash sensors, seat belt pretensioners, airbag ignition circuits, and occupant classification system. This fault forces the entire airbag system into fail-safe mode; the system may fail to deploy the airbags and pretensioners during a collision. The instrument cluster airbag warning light (AIRBAG/SRS light) remains illuminated, and some models trigger a buzzer alarm. Due to the highly integrated SRS ECU in Qin series models (especially 2017-2018 models), related communication or internal fault codes in the B16B0-B16BF range may accompany this fault.
Causes
— SRS ECU internal processor or memory fault: Voltage fluctuations, component aging, or electrostatic breakdown damage the control module's internal circuit board, preventing it from correctly executing the deployment algorithm or storing crash data.— Power supply system fault: Battery voltage too low (<9V) or too high (>16V), blown dedicated SRS fuse (typically in dashboard fuse box IF08 or engine compartment fuse box EF15), or poor contact at ECU ground wires G301/G302, causing ECU reset or unstable operation.— CAN communication bus fault: Short or open circuit in the power CAN or dedicated safety CAN lines between the SRS ECU, BCM, and instrument cluster (the instrument panel wiring harness on Qin series models wears easily at the A-pillar junction), causing the system to detect an ECU communication loss.+2 more →
Actions
— Initial diagnosis: Connect the VDS2000/3000 diagnostic tool to the vehicle OBD port and read all SRS fault codes. Check if B16BA-00 appears alone or with related codes such as U0155 (lost communication with instrument cluster) and B16B1 (abnormal internal voltage). Record the voltage and temperature values from the freeze frame data.— Power and ground check: Disconnect the battery negative terminal and wait 3 minutes. Check the SRS ECU connector (16-pin or 24-pin, located under the center console; remove the passenger glovebox or center armrest box). Measure the voltage to ground at Pin 1 (constant B+) and Pin 8 (IG power); the voltage must be 12V. Measure the resistance to ground at Pin 16/32 (ground); the resistance must be <1Ω. Check if fuse IF08 (10A) is blown.+4 more →
B16BB›
DTC B16BB indicates the Airbag Control Unit (SRS_ECU) detected a severe fault during its internal self-test. This typically points to a hardware-level fault in the ECU internal processor, memory, power regulation circuit, or ignition driver circuit. This means the SRS_ECU cannot execute the crash detection algorithm, cannot drive the airbag ignition circuits, or detected a program memory error during the cyclic redundancy check (CRC). This safety-critical fault forces the entire airbag system into fail-safe mode. During a collision, all airbags (front airbags, side curtain airbags, knee airbags) and seat belt pretensioners may fail to deploy. The fault may also affect the active head restraint and crash fuel cut-off functions.
Causes
— Burnt internal power supply chip or voltage regulator circuit in the SRS ECU, often resulting from reversed polarity during jump-starting, a faulty alternator voltage regulator, or accidental connection to a 24V power supply.— ECU internal EEPROM memory data corruption, possibly resulting from a high-current surge during a vehicle collision, electromagnetic interference (EMI), or interrupted software flashing.— ECU seal failure causes internal PCB corrosion, commonly resulting from driving through water, leaks from a blocked sunroof drain hose, or long-term parking in high-humidity environments.+2 more →
Actions
— Perform a complete SRS system scan using the VDS3000 diagnostic tool. Confirm B16BB is a current fault (Active) and will not clear. Check for accompanying communication fault codes (such as codes starting with U).— Check the SRS ECU power supply: Measure the voltage at connector terminal 30 (constant power +B) and terminal 15 (ignition switch power). The voltage must be 9-16V. Measure the resistance between ground terminal 31 and body ground. The resistance must be less than 0.5Ω.+6 more →
B16BA›
DTC B16BA indicates an internal fault or system-level communication fault in the airbag control unit (SRS ECU). As the core controller of the passive safety system, the SRS ECU monitors crash sensor signals, evaluates crash severity, triggers airbag and seat belt pretensioner deployment, and continuously performs system self-diagnostics. This DTC typically indicates an internal ECU microprocessor fault, an EEPROM data checksum failure, a power supply monitoring circuit abnormality, or a CAN bus communication interruption. The ECU sets this DTC and enters degraded mode when it detects an internal circuit fault, a supply voltage outside the normal 9-16V range, or a loss of communication with the vehicle network exceeding the specified time (typically >500ms). In this state, the vehicle may completely lose crash protection functions (airbags will not deploy) or risk unintended deployment. This constitutes a high-risk safety fault.
Causes
— SRS ECU internal hardware fault: internal capacitor aging and leakage, MCU crash, memory data corruption (EEPROM checksum error); common in 2018–2020 controller batches.— Power supply system fault: battery voltage below 9V or above 16V, excessive contact resistance in the IGN+ power supply circuit (>1Ω), or loose or oxidized ECU ground wire, causing ECU reset or unstable operation.— CAN network communication fault: Short or open circuit in Powertrain CAN (PT-CAN) or Body CAN (Body-CAN) wiring, or terminal resistance deviation (normal 60Ω±5Ω), preventing ECU communication with the vehicle control unit.+2 more →
Actions
— Safety preparation and initial inspection: Disconnect the 12V battery negative terminal and wait 3 minutes to discharge residual voltage. Inspect the SRS ECU for physical damage, water ingress, or burn marks. Inspect the SRS-related fuses in the instrument panel fuse box (usually 10A-15A) and the cabin wiring harness connectors (near the OBD port/GW connector).— Power supply and ground circuit test: Use a multimeter to measure the voltage to ground at ECU connector Pin30 (constant power +B) and Pin15 (IGN power). The standard value is battery voltage ±0.5V. Measure the resistance to ground at ground Pin31; it must be <1Ω. Check the connector terminals for backed-out pins, enlarged sockets, or green oxidation.+4 more →
B16BB-00›
DTC B16BB-00 indicates the Airbag Control Unit (SRS ECU) internal self-check detected a critical fault. This fault involves a hardware-level abnormality in the ECU internal processor, memory module, or power management unit, which may cause the airbag system to fail to deploy during a collision or deploy unintentionally in non-collision situations. This DTC indicates a permanent hardware fault that a simple code clear usually cannot resolve. Thoroughly inspect the ECU power supply stability, CAN communication integrity, and internal circuit board condition. In BYD Qin series vehicles, this ECU integrates crash decision algorithms and multi-point sensor data processing functions. The fault triggers the system to enter safety protection mode, disabling airbag deployment for safety.
Causes
— SRS ECU internal memory or processor hardware damage, typically due to voltage fluctuations, overheating, or component aging causing internal circuit failure.— Abnormal power supply, including excessive contact resistance in the +B power supply circuit, a loose ground terminal, or unstable battery voltage causing an ECU reset.— CAN bus communication fault: a short circuit, open circuit, or electromagnetic interference in the powertrain CAN or dedicated airbag CAN wiring prevents normal ECU communication.+2 more →
Actions
— Use a dedicated BYD diagnostic tool (VDS2000 or ED400) to read the complete fault code stream, record freeze frame data, and check for accompanying communication fault codes (such as codes starting with U).— Check the SRS ECU power supply: Measure the voltage at the ECU connector +B terminal (must be a stable 9-16V), check the ground wiring harness resistance (must be less than 1Ω), and verify the power supply waveform has no abnormal pulses.+5 more →
B16BC-00›
DTC B16BC-00 indicates the airbag control unit (SRS ECU) internal self-check detected a severe fault, causing the system to enter fail-safe mode. This fault involves hardware failures or data checksum errors in core ECU components, including the main control processor (MCU), internal acceleration sensor (G-sensor), power management module, or memory (EEPROM/Flash). When this fault occurs, the SRS ECU may fail to accurately assess collision severity, preventing passive safety devices such as airbags and seat belt pretensioners from deploying correctly during a crash, or creating a risk of unintended deployment. The system illuminates the instrument cluster airbag warning light and disables the entire airbag system. The vehicle remains drivable but loses crash protection functions, constituting a severe fault that affects driving safety.
Causes
— SRS ECU internal power regulation circuit fault (e.g., damaged 12V to 5V/3.3V voltage regulator chip) causes abnormal MCU power supply and triggers an internal watchdog reset.— Internal memory data corrupted (verification failed for collision threshold, VIN, or configuration parameters stored in EEPROM). Commonly occurs after disconnecting vehicle power during repairs or due to unstable voltage.— Built-in acceleration sensor (MEMS chip) signal drift or failure prevents the ECU from obtaining accurate vehicle deceleration data.+2 more →
Actions
— Use the BYD ED400/ED600 diagnostic tool to read all fault codes. Confirm whether B16BC-00 is an Active or History fault and record the freeze frame data (crash sensor values, supply voltage, temperature, etc.).— Check the SRS ECU power supply circuit: measure constant power at the connector terminal (B+, should be 12V battery voltage), ignition switch power (IG, should be 12V in the ON position), and the ground wire (GND, resistance should be less than 1Ω). Check fuse F1/17 (SRS ECU power supply, usually 10A/15A).+5 more →
B16BC›
DTC B16BC indicates the airbag control unit (SRS ECU) detects an internal system fault or critical safety circuit abnormality. Specifically, this fault typically indicates an SRS ECU internal processor self-test failure, corrupted non-volatile memory (NVM) data, a power management module fault, or a communication interruption between the driver-side Occupant Classification System (OCS) and the ECU. BYD e-platform models integrate the SRS ECU near the body control module. The ECU monitors crash sensors, seat belt pretensioners, airbag ignition circuits, and seat occupancy status. This fault may prevent the airbag system from deploying correctly during a collision or trigger a warning without a collision. It constitutes a critical fault affecting passive safety.
Causes
— SRS ECU internal hardware fault: Voltage fluctuations, static electricity, or aging usually damage the control unit's internal processor, memory, or voltage regulator chip.— Driver seat Occupant Classification Sensor (OCS) fault: Damaged seat pressure sensor, or loose wiring harness connector, water ingress, or oxidized pins causing an abnormal signal.— Abnormal power supply: Blown SRS ECU power supply fuse (e.g., SB03/IG1 power in the dashboard fuse box), battery voltage below 9V or above 16V, or poor ground circuit contact.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the negative battery terminal, and wait at least 3 minutes to completely discharge the airbag system and prevent accidental deployment.— Initial diagnosis: Use the BYD VDS2000/VDS6000 diagnostic tool to access the SRS system. Read the complete fault code list and freeze frame data. Check for accompanying B16BB (SRS_ECU internal fault), U-series communication faults, or seat occupancy-related fault codes.+5 more →
B16BD-00›
DTC B16BD-00 indicates a LIN (Local Interconnect Network) bus communication fault between the Body Control Module (BCM) and the left front window motor. Some early documents label this code as SRS-related; however, it actually indicates a loss of communication or abnormal signal voltage at the left front window motor (LHD Driver Door Motor). The LIN bus uses a single-wire circuit (typically green/white) with a normal operating voltage of 9-11V. The BCM sets this DTC if it fails to receive a response signal from the motor within the specified time, or if it detects a bus open, short to ground, or short to power. This fault disables left front window operation and the anti-pinch function. The BCM may also enter protection mode and cut power to the motor.
Causes
— Shorted or burned-out LIN transceiver chip inside the left front window motor, pulling the bus voltage low (commonly 2-3 V)— Poor connection or broken LIN wiring harness at the door hinge (repeated door cycling causes copper wire fatigue and breakage, leaving only a few strands connected).— Aged or failed motor connector waterproof rubber seal allows car wash water or rainwater to seep in, causing connector oxidation and a LIN line short to ground.+2 more →
Actions
— Connect the BYD VDS diagnostic tool and enter the BCM system to read fault codes. Confirm whether B16BD-00 is a current or history fault, and record the freeze frame data.— Verify the left front window motor power supply (constant 12V, connector pin 1) and ground (connector pin 2) are normal to rule out basic circuit faults.+6 more →
B16BD›
SRS ECU (Airbag Electronic Control Unit) internal self-test fault or abnormal external communication/power supply. This DTC indicates the Airbag Control Unit (ACU) detected a functional fault in its processor, memory, power management circuit, or critical sensor interfaces during the self-test. This triggers the system to enter fail-safe mode (disabling all airbags, seat belt pretensioners, and the crash fuel cut-off function). Specific fault conditions include: 1) ECU internal hardware damage (e.g., BGA chip cold solder joints or aging electrolytic capacitors); 2) Abnormal impedance in the 12V power supply or ground circuit causing an ECU reset; 3) CAN network communication interruption (loss of synchronization with the vehicle control unit and instrument cluster); 4) Short or open circuit in the signal links of critical safety sensors (front impact sensor, side impact pressure sensor, seat occupancy sensor) exceeding the calibrated threshold. This fault may prevent airbag deployment during a collision or risk unintended static deployment. Immediately remove the vehicle from service and perform repairs.
Causes
— SRS ECU internal hardware fault: main control chip (such as NXP SPC56 series) memory checksum failure, damaged internal voltage regulator module, or capacitor aging and leakage causing excessive power supply ripple.— Power supply system fault: battery voltage below 9V or above 16V; poor contact in the ECU constant power (B+) or ignition power (IGN) circuit (loose connector, poor fuse connection); ground point oxidation causing increased resistance (>1Ω)— CAN bus communication fault: wiring harness short/open circuit between the SRS and diagnostic CAN (or private CAN), terminating resistor drift (deviating from 60Ω±5Ω), or electromagnetic interference causing message loss.+2 more →
Actions
— Safety preparation and initial inspection: Disconnect the battery negative terminal and wait at least 3 minutes to discharge the residual charge in the energy storage capacitor. Visually inspect the SRS ECU housing for physical damage, signs of water ingress, or burn marks. Check the ECU connector (usually yellow) located under the center console or floor for looseness, backed-out pins, or corrosion.— Power supply and ground diagnosis: Restore power (do not start the vehicle). Use a multimeter to measure the voltage at ECU connector terminal 30 (constant power) and terminal 15 (IGN). Standard: 12V ± 0.5V. Measure the resistance between the ground point and the vehicle body. Resistance must be less than 1Ω. Use an oscilloscope to measure power supply ripple. Peak value must be less than 100mV.+4 more →
B16BE-00›
DTC B16BE-00 indicates the airbag control unit (SRS ECU) detected a critical internal functional fault. This condition represents a functional failure in the ECU internal microprocessor, memory, power regulation circuit, or internal self-test logic, preventing the control unit from executing its safety monitoring algorithms. The ECU sets this DTC during the power-on self-test if it detects an internal data checksum failure, abnormal core circuit operation, or an internal communication bus fault. This fault forces the SRS system into fail-safe mode, potentially preventing the airbags and seat belt pretensioners from deploying correctly during a collision, or in extreme cases, creating a risk of unintended deployment. This is a critical fault affecting occupant passive safety.
Causes
— Internal hardware fault in the SRS ECU processor or memory (e.g., chip damage, cold solder joints, or corrupted memory data)— Fault in the ECU internal power supply voltage regulator module or abnormal voltage monitoring circuit, causing unstable internal operating voltage.— Vehicle electrical system faults (such as jump-starting a discharged battery or a voltage surge from a faulty alternator voltage regulator) cause internal ECU lock-up or memory data corruption.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor. Wear an anti-static wrist strap. Do not use radio equipment near the airbag sensor.— Initial inspection: Check the SRS ECU housing (usually located under the centre console or in front of the gear selector) for physical damage, signs of water ingress, or burn marks. Check the G36 connector for looseness and the terminals for corrosion or backed-out pins.+7 more →
B16BE›
DTC B16BE indicates an internal fault or functional failure of the airbag system electronic control unit (SRS ECU). The SRS ECU is the core module of the safety system. It monitors the crash acceleration sensors in real time, processes the crash algorithm, and controls the deployment strategy for the airbags and seat belt pretensioners. The ECU internal self-check routine detects this hardware abnormality, which may involve: a main processor (MCU) calculation error, a non-volatile memory (NVM) data integrity check failure, abnormal output from the internal power regulation circuit, a safety monitoring watchdog timeout, or a deployment circuit driver chip fault. The ECU immediately enters Fail-Safe mode, disconnects power to all airbag deployment circuits, and disables airbag deployment to prevent unintended triggering, resulting in a loss of occupant protection during a collision. This fault is a Hard Fault. Disconnecting power or clearing the code usually cannot resolve it. Perform a hardware-level repair or replace the unit.
Causes
— ECU internal power management chip fault: Voltage regulator circuit (usually supplying 5V/3.3V reference voltage) failure disrupts processor power supply, triggering an internal reset.— Memory data corruption: Electromagnetic interference or voltage fluctuations corrupt calibration data, crash threshold parameters, or VIN configuration information in Flash or EEPROM, resulting in a CRC check failure.— CAN bus communication fault: Short circuit, open circuit, or abnormal terminating resistance in the diagnostic CAN (CAN-H/CAN-L) wiring harness causes ECU-to-vehicle network communication timeout, triggering safety monitoring.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000/VDS2100) to read the complete DTC list and freeze frame data. Confirm B16BE is a Current fault rather than a History fault, and record the vehicle status when the fault occurred.— Perform a network test: Measure the resistance between diagnostic CAN-H and CAN-L (standard value: 60Ω±5Ω, power off) and the dynamic voltage (CAN-H: 2.5-3.5V, CAN-L: 1.5-2.5V) to rule out false codes caused by communication line faults.+6 more →
B16BF-00›
B16BF-00 indicates the airbag control unit (SRS ECU) detected an internal fault or critical function failure. This DTC represents a core Safety System fault, indicating the SRS ECU cannot execute crash detection algorithms, airbag deployment logic, or communication with other safety modules (such as seat belt pretensioners, crash sensors, and the vehicle CAN network). Specific causes include an ECU internal processor or memory fault, a power management module anomaly, a damaged deployment circuit driver chip, a Safing Sensor self-test failure, or an EEPROM data checksum error. This fault forces the entire airbag system into fail-safe mode. During a collision, the system may fail to deploy the driver airbag, front passenger airbag, side airbags, and seat belt pretensioners, posing a severe safety hazard.
Causes
— Abnormal SRS ECU power supply/ground: Includes poor connection in the battery constant power (+B) circuit, blown fuse in the ignition switch power (IG) circuit, or ground terminal oxidation/corrosion causing unstable voltage, triggering ECU reset or logic errors.— CAN bus communication fault: Short circuit, open circuit, or terminal resistor drift (standard 60Ω) on the power CAN or dedicated safety CAN between the SRS ECU and the vehicle gateway or instrument cluster isolates the ECU from the network.— ECU internal hardware damage: capacitor aging and leakage, cracked PCB solder joints (common on early Qin series models), main control chip (MCU) program crash, or Flash data corruption.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 5 minutes (10 minutes for some models) to fully discharge the SRS ECU internal backup capacitor and prevent accidental airbag deployment. Wear an anti-static wrist strap.— Initial inspection: Check the instrument cluster AIRBAG warning light status. Use a VDS2000/3000 or Launch X431 diagnostic tool to read all DTCs. Check for accompanying B16C0 (passenger airbag fault), U-series communication faults, or specific sensor faults. Inspect the SRS ECU housing and mounting bracket for collision deformation or water ingress.+6 more →
B16BF›
DTC B16BF indicates an internal fault in the airbag electronic control unit (SRS ECU) or a system-level functional failure. This fault involves an ECU internal processor self-check anomaly, memory checksum failure, power management module fault, or CAN communication interface fault. The SRS ECU continuously monitors the internal operating voltage (3.3V/5V regulated output), EEPROM data integrity, watchdog timer status, and communication quality with the vehicle CAN network. The system sets this DTC when the ECU detects an internal circuit fault, supply voltage outside the 9-16V range, excessive ground resistance (>1Ω), or CAN signal distortion. This safety-critical fault may cause complete airbag system failure (airbags fail to deploy during a collision), unintended deployment, or seat belt pretensioner failure.
Causes
— SRS ECU internal hardware fault: Damaged main control chip (such as Infineon or Renesas series), aging and leaking electrolytic capacitors, or PCB interlayer short circuit. These faults typically cause the ECU housing to heat up or prevent the diagnostic tool from establishing communication.— Power supply system fault: Poor contact at the SRS fuse (usually 10A or 15A) in the instrument panel fuse box, loose circuit connections causing voltage to drop below 8V, or a discharged battery or unstable alternator output causing an ECU reset.— Ground circuit fault: Loose, oxidized, or paint-covered G101 ground point (located on the dashboard crossmember or below the A-pillar) causes ground resistance to exceed 5Ω, resulting in ECU operating voltage drift.+2 more →
Actions
— Initial diagnostic scan: Use VDS2000/VDS3000 to access the SRS system. Read the complete fault code list and freeze frame data. Confirm if B16BF is a current fault (Active) and check for accompanying U-class communication fault codes (such as U0140, U0151). Record the vehicle status at the time of the fault (voltage, temperature, vehicle speed).— Power supply and ground measurement: Disconnect the battery negative terminal and wait 90 seconds to discharge the SRS capacitor. Remove the SRS ECU (usually located under the center console or in front of the gear selector). Measure the voltage to ground at connector pin 1 (constant power +B, BATT) and pin 2 (IGN power). Voltage must be 12.0V ± 0.5V. Measure the resistance between the ground pin (GND) and body ground. Resistance must be less than 1Ω. Inspect the connector for green corrosion or pin back-out.+4 more →
B16C0-00›
DTC B16C0-00 indicates the Airbag Electronic Control Unit (SRS ECU) detected an abnormality during its internal self-check. This typically indicates a hardware fault in the ECU internal processor, memory, or power management module, or a communication failure between the ECU and the vehicle CAN network. This fault forces the airbag system into fail-safe mode. In a collision, the system may fail to deploy the airbags and seat belt pretensioners, or activate the high-voltage interlock cut-off function, posing a severe safety risk. This DTC is a hard fault and generally will not clear automatically. Perform a hardware-level repair or replace the ECU.
Causes
— Damaged components on the SRS ECU internal circuit board (e.g., bulging electrolytic capacitor, cold solder joint on the main control chip, or chip breakdown)— ECU power supply circuit fault (unstable voltage at constant power B+ or ignition power IG1, poor fuse contact, or oxidized ground point)— Vehicle CAN network communication fault (short circuit between CAN-H and CAN-L, short to ground, or wiring open circuit prevents the ECU from communicating with the vehicle)+2 more →
Actions
— Use the VDS diagnostic tool to read the complete DTCs and freeze frame data. Confirm the vehicle speed, power supply voltage, temperature, and other environmental parameters at the time of the fault. Attempt to clear the fault code to verify if the fault is intermittent.— Disconnect the battery negative terminal, wait 3 minutes, then remove and inspect the SRS ECU (usually located under the center console or at the bottom of the center armrest box). Check the housing seal and inspect the interior for water stains, burn marks, or physical damage.+4 more →
B16C0›
On BYD vehicles, DTC B16C0 indicates a front passenger Occupant Classification System (OCS) sensor fault, not an internal SRS ECU fault. The system detects seat load status using a capacitive or piezoresistive pressure-sensing membrane inside the front passenger seat cushion. It distinguishes between an adult, a child, or an unoccupied seat to control the front passenger airbag deployment strategy (deployment decision, timing, and force). When the SRS ECU detects an OCS sensor signal open circuit, short circuit, out-of-range value, or incomplete calibration, it sets this DTC and illuminates the airbag warning lamp. This fault creates an extreme safety risk: the system may incorrectly identify the seat as unoccupied and disable airbag deployment, or erroneously deploy the airbag when a child seat is installed. This safety hazard requires immediate repair.
Causes
— Oxidation, looseness, or poor contact at the yellow 2-pin wiring harness connector under the seat, interrupting signal transmission or causing abnormal resistance.— Prolonged interference and chafing between the wiring harness and the seat metal frame damages the insulation layer, causing a short to ground or short to power.— OCS sensor mat cut, folded, or physically damaged during front passenger seat modification (leather retrim, foam replacement).+2 more →
Actions
— Connect the VDS2000 or X431 diagnostic tool. Access the SRS system to read the fault code and freeze frame data. Check the 'Passenger Seat Status' and 'OCS Sensor Resistance' values in the data stream to confirm whether the fault is continuous or intermittent.— Disconnect the yellow connector under the front passenger seat (usually located in front of the seat slide rail). Check for oxidized or backed-out pins. Clean with electrical contact cleaner and apply conductive grease. Measure the resistance between the connector terminals (normal unloaded value is 2.5 kΩ–3.0 kΩ; resistance changes when occupied).+4 more →
B16C1-00›
DTC B16C1-00 indicates an internal fault or functional failure of the airbag system electronic control unit (SRS_ECU). This fault represents a core self-check abnormality of the airbag control module. It typically indicates a hardware-level fault in the ECU internal processor, memory, power management circuit, or safety monitoring circuit. This fault causes the airbag system to enter a degraded mode or complete failure state. During a collision, the system may fail to deploy the airbags, making this a critical fault affecting vehicle passive safety. Upon fault detection, the SRS system typically illuminates the instrument cluster airbag warning light (solid) and logs a non-clearable hard fault code. Some models may also trigger the seat belt pretensioner disable logic.
Causes
— SRS ECU internal circuit board fault: Aging, dry solder joints, or burnout of the control module's internal CPU, capacitors, resistors, or integrated circuits causes the self-check program to fail.— Abnormal power supply: excessive battery voltage fluctuation (above 16V or below 9V), poor contact in the ECU constant power or ignition power circuit, or ground point corrosion causing unstable ECU operating voltage.— CAN communication bus fault: Abnormal communication between the SRS ECU and the vehicle network, including a short circuit, open circuit, or abnormal resistance in the CAN-H or CAN-L lines, preventing the ECU from completing the network communication self-check.+2 more →
Actions
— Diagnostic confirmation: Use the BYD VDS2000 or VDS3100 diagnostic tool to read all fault codes. Confirm only B16C1-00 is present, either alone or with related communication fault codes. Record the fault code freeze-frame data. Check the instrument panel SRS warning light status.— Power supply and ground check: Disconnect the negative battery terminal. Measure the voltage between the SRS ECU connector constant power (B+) terminal and ground (must be battery voltage). Check the continuity of the ignition switch power (IGN). Measure the ground wire resistance (must be less than 1 Ω). Check if fuses F1/15 (10A) and F1/16 (10A) are blown.+6 more →
B16C1›
DTC B16C1 indicates the airbag control unit (SRS ECU) detected an internal system fault or an external power supply or communication abnormality. Specifically, this code points to a functional failure in the ECU power management module, internal memory (EEPROM/Flash) self-check, watchdog timer, or main processor. The SRS ECU triggers this fault code and illuminates the airbag warning lamp if it detects an operating voltage outside the 9-16V range, an internal data verification failure, or a loss of communication with the vehicle CAN network during the ignition cycle self-check. This fault forces the airbag system into a degraded mode. During a collision, the system may fail to deploy the airbags or actuate the seatbelt pretensioners, posing a severe safety hazard.
Causes
— Low-voltage battery discharged or voltage unstable (extended parking causes voltage to drop below 9V, or a charging system fault causes voltage to exceed 16V), exceeding the normal operating voltage range of the SRS ECU.— SRS ECU power supply circuit fault, including a blown dedicated airbag fuse in the instrument panel fuse box (usually 10A or 15A), a backed-out power supply pin, or a poor circuit connection causing excessive voltage drop.— Abnormal ECU ground circuit resistance. Oxidation, excessive paint, or loose fastening bolts at the front bulkhead or instrument panel crossmember ground point cause the ground resistance to exceed 1Ω.+2 more →
Actions
— Pre-inspection and voltage measurement: Check the low-voltage battery voltage. Standard value: 12.5-14.5V (ignition switch ON). If the voltage is abnormal, first rectify the battery or DC-DC fault, clear the DTC, and rerun the self-check.— Fault code reading and freeze frame analysis: Use a VDS or Launch diagnostic tool to read all DTCs. Check for accompanying U-class communication fault codes (such as U0100) or related codes like B16C0/B16C2. Record the freeze frame voltage values and mileage to determine if the fault is historical.+5 more →
B16C2-00›
DTC B16C2-00 indicates the airbag control unit (SRS ECU) detected a critical fault during its internal self-check, forcing the system into fail-safe mode. This fault involves a hardware-level abnormality in the ECU internal microprocessor, non-volatile memory (NVM), power management module, or safety monitoring circuit. The ECU sets this code upon detecting an internal watchdog reset, checksum verification failure, integrated acceleration sensor (MEMS) signal processing circuit abnormality, or safety communication interruption between the main and secondary CPUs. In BYD Qin series vehicles, this fault prevents the entire airbag system (including driver/passenger front airbags, side airbags, curtain airbags, and seat belt pretensioners) from deploying. It may also interrupt communication with the powertrain CAN and body CAN, causing the instrument cluster to illuminate the airbag warning lamp continuously. Unlike sensor or ignition circuit faults, this DTC indicates a functional failure of the ECU itself. Inspect the ECU installation environment (the area beneath the center tunnel is susceptible to water ingress) and verify power supply stability.
Causes
— ECU internal hardware damage: Main control chip (Renesas RH850 or Infineon TriCore safety-grade MCU) failure, EEPROM data block corruption, internal accelerometer (usually Bosch or STMicroelectronics MEMS chip) component failure, or cold solder joints on the sensor.— Abnormal power supply: blown constant power (B+) circuit fuse F1/14 (Qin series SRS dedicated); unstable ignition switch power (IG1) voltage (below 9V or above 16V); internal ECU DC-DC converter module failure causing 5V/3.3V reference voltage drift.— Ground system fault: Loose or oxidized ECU main ground point G101 (located on the instrument panel frame) or broken ground wiring harness causes reference potential drift, affecting analog signal sampling accuracy.+2 more →
Actions
— Safety Preparation and Initial Inspection: Disconnect the 12V battery negative terminal and wait at least 90 seconds (to fully discharge the ECU backup power supply). Use VDS2000 or the latest diagnostic tool to read the complete fault codes and freeze frame data. Inspect the ECU housing for physical damage, water stains, burning, or impact marks.— Wiring harness connector inspection: Inspect ECU wiring harness connector C1 (power/ground), C2 (CAN communication), and C3 (sensor/ignition circuit) terminals for backed-out pins, corrosion, oxidation, or green corrosion. Check specifically for signs of water ingress beneath the center tunnel.+5 more →
B16C4-00›
B16C4-00 indicates the airbag control unit (SRS ECU) detects an internal fault or critical communication anomaly. This fault code indicates the ECU self-diagnostic detected an error in the processor, memory, power supply monitoring circuit, or internal safety logic, or the ECU lost communication with the crash sensors or airbag modules. Because the SRS ECU is the core of the passive safety system, this fault causes the airbag system to enter fail-safe mode. During a collision, the front, side curtain, or knee airbags may fail to deploy, and the seat belt pretensioners may also fail. When this fault triggers, the ECU typically cuts power to the airbag ignition circuits to prevent inadvertent deployment.
Causes
— SRS ECU internal hardware damage (main control chip, EEPROM memory, or power voltage regulator module failure, commonly caused by water ingress or prolonged high-temperature exposure)— Power supply system fault (blown fuse F1/14, poor connection in IG1/IG2 power supply circuit, or ECU protective lockout due to battery voltage below 9V or above 16V)— Ground circuit fault (loose or oxidized G301 ground point, or broken wiring harness, causing ECU reference voltage drift)+2 more →
Actions
— Safety preparation: Disconnect the low-voltage battery negative terminal, wait at least 90 seconds for the SRS capacitor to fully discharge, and wear an anti-static wrist strap.— Diagnostic scan: Use VDS2000 or Launch X431 to read all fault codes, check for B16C4-00 and any accompanying sensor communication fault codes, and record freeze frame data.+7 more →
B16C2›
DTC B16C2 indicates an internal hardware or software self-test failure in the airbag control unit (SRS ECU). This fault signifies a functional failure in the ECU internal microprocessor, EEPROM memory, crash sensor interface circuit, or firing circuit driver. The ECU performs internal diagnostics at each power-up. If the ECU detects a CPU calculation error, memory checksum failure, internal communication bus fault, or firing circuit driver chip abnormality, it sets this DTC and enters fail-safe mode. The airbag system completely disables, and the airbags may fail to deploy during a collision. This condition also affects related systems such as the seat belt pretensioners and airbag warning lamp. This constitutes a hard fault and typically will not clear by simply disconnecting power. Replace the ECU or repair the internal hardware.
Causes
— Hardware damage to the SRS ECU internal processor or memory chip, usually due to voltage surges or component aging.— Abnormal ECU power supply voltage (below 9V or above 16V) causes unstable internal circuit operation or reset.— Poor contact, oxidation, or high resistance in the ECU ground circuit, causing signal reference potential drift.+2 more →
Actions
— Use a dedicated diagnostic tool (such as BYD ED400 or VDS) to read the complete fault codes. Confirm B16C2 is a current fault and the freeze frame data shows it triggered during the ECU self-check phase. Attempt to clear the fault code, power the vehicle on again, and observe if the fault recurs.— Check the SRS ECU housing ground point (usually located on the center tunnel or instrument panel frame). Remove the ground bolt and clean the contact surfaces. Measure the ground resistance; it must be less than 1Ω. Verify the contact area is free from oxidation and paint.+4 more →
B16C3-00›
BYD strictly defines B16C3-00 as an open circuit or excessive resistance fault in the driver airbag (DAB) stage 1 ignition circuit. Although the original description states "SRS_ECU fault", it actually indicates a communication or circuit anomaly between the driver airbag module and the SRS control unit, rather than an ECU hardware failure. This fault indicates the airbag control module (ACM) detects the driver-side airbag ignition circuit resistance falls outside the normal range (standard value 2.0±0.1Ω). This typically presents as infinite resistance (open circuit) or greater than 5Ω (poor connection). When this fault activates, the airbag system enters fail-safe mode, the driver-side airbag will not deploy during a collision, and the instrument cluster SRS warning light remains illuminated.
Causes
— Broken or loose internal flat cable in the clock spring: Long-term steering wheel rotation causes fatigue and breakage of the internal flexible circuit. This is the most common cause.— Poor contact at the airbag wiring harness connector: Includes oxidation or looseness at the yellow connector under the steering wheel, or the shorting bar (short-circuit plate) failing to fully return and causing an open circuit.— Wiring harness mechanical damage: A broken wiring harness retaining clip below the steering wheel causes the harness to rub against the steering column, breaking the internal copper wires; or repair work pinched the harness or cut it on sharp edges.+2 more →
Actions
— Safe power down: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 3 minutes to fully discharge the SRS system energy storage capacitor and prevent accidental airbag deployment.— Fault code reading: Use a VDS2000 or Launch X-431 diagnostic tool to access the SRS system. Read the current fault codes and data stream, and verify the DAB circuit resistance (normal value: 2-3Ω).+7 more →
B16C3›
DTC B16C3 indicates a functional fault in the airbag system electronic control unit (SRS_ECU). The SRS_ECU is the core controller of the safety system. It monitors crash sensor signals in real time, processes crash algorithms, controls the deployment timing of the airbags and seat belt pretensioners, and manages the communication network of the entire passive safety system. This DTC usually indicates an internal processor or memory fault in the ECU, or a loss of communication between the ECU and the vehicle CAN network. An intermittent open circuit in the ECU power supply or ground circuit can also trigger this fault. This fault causes the airbag system to enter fail-safe mode. The airbags may fail to deploy in a collision, creating a serious safety risk.
Causes
— Abnormal SRS ECU power supply circuit: Includes a blown constant power (B+) circuit fuse, poor relay contact, or unstable IGN supply voltage, causing ECU operating voltage to drop below 9V or exceed 16V.— CAN bus communication fault: A short circuit, open circuit, or abnormal terminating resistor in the communication line between the SRS_ECU and the vehicle network (powertrain CAN or dedicated safety CAN) prevents the ECU from communicating normally with the instrument cluster, VCU, and other modules.— ECU internal hardware damage: Control unit internal memory data corruption, abnormal processor clock, or collision detection circuit self-test failure. Electromagnetic interference, overvoltage, or component aging usually causes these faults.+2 more →
Actions
— Safety Preparation and Initial Diagnosis: Disconnect the high-voltage system (for new energy vehicles) and wait 5 minutes to allow the capacitors to discharge. Use the BYD VDS diagnostic tool to read all fault codes. Confirm if B16C3 is an active fault and check for accompanying communication fault codes (such as the U01XX series). Record the freeze frame data and note parameters such as vehicle speed and voltage when the fault occurred.— Power and ground check: Check if the SRS system fuses (F1/15, F2/13, etc.) in the front compartment fuse box are blown. Disconnect the battery negative terminal, wait 90 seconds, and unplug the SRS ECU connector. Measure the voltage between pin 1 (constant power +B) and ground (should equal battery voltage). Measure the resistance between the ground pin and body ground (should be less than 1Ω). Inspect the connector for oxidation or backed-out pins.+3 more →
B16C4›
DTC B16C4 indicates an internal fault or severe communication failure in the airbag control unit (SRS ECU). This fault indicates a functional failure of the microprocessor, memory, or power management module within the SRS ECU, or a communication interruption between the ECU and the vehicle CAN network or sensor array. The SRS ECU serves as the core controller of the passive safety system. It receives crash sensor signals, determines collision severity, and triggers protective devices such as airbags and seat belt pretensioners. This critical fault compromises occupant safety by potentially preventing normal airbag deployment during a collision, or by creating a risk of false alarms and unintended deployment. When this fault occurs, the SRS system typically enters fail-safe mode, cuts off the airbag ignition circuit to prevent unintended deployment, and illuminates the instrument cluster airbag warning light.
Causes
— SRS ECU internal circuit fault: Damaged control unit internal microprocessor, EEPROM memory, or voltage regulator chip. Repeated charging and discharging of a depleted battery after long-term vehicle storage commonly causes ECU power module breakdown.— Power supply and ground circuit fault: Poor contact at the ECU constant power (B+) fuse holder, unstable IGN supply voltage, or an oxidized ECU ground point or loose bolt causing reference voltage drift, triggering an ECU reset or freeze.— CAN network communication fault: An open circuit or short circuit in the communication line between the SRS ECU and the vehicle CAN bus (powertrain network or body network), or abnormal terminating resistance, prevents the ECU from communicating normally with the VDS diagnostic tool or other modules.+2 more →
Actions
— Safety Preparation and Initial Diagnosis: Disconnect the battery negative terminal and wait 3 minutes to discharge residual voltage. Wear an anti-static wrist strap. Connect the BYD VDS diagnostic tool. Read the complete fault code list and freeze frame data. Confirm whether B16C4 is a current fault (Present) or history fault (History). Check for accompanying crash sensor or seat belt fault codes.— Power and ground check: Reconnect the battery. Measure the voltage at the power supply terminals of the SRS ECU connector (usually located under the center console or behind the armrest box). Constant power must be 12V (11-14V range), and IGN power must be 12V with the ignition switch in the ON position. Measure the resistance between the ground terminal and the vehicle body; it must be less than 1Ω. Check fuse F4/9 (if applicable) and the fuse holder for terminal spread or burn damage.+4 more →
B16C5›
DTC B16C5 indicates an internal fault or critical function failure in the airbag control unit (SRS ECU). The SRS ECU is the core controller of the safety system. It monitors vehicle collision acceleration, processes crash signals, and controls the ignition triggering of protective devices such as airbags and seat belt pretensioners. The following conditions trigger this DTC: ECU internal main control chip (MCU) self-test failure, abnormal internal acceleration sensor signal, ignition circuit driver fault, EEPROM read/write error, or persistent ECU power supply voltage or communication bus abnormalities. When this fault occurs, the SRS system may enter fail-safe mode, preventing normal airbag deployment during a collision or, in extreme cases, causing unintended deployment. This critical fault directly compromises occupant safety.
Causes
— SRS ECU internal hardware damage: Aging, overheating, or electromagnetic interference causes functional failure of the main control chip, internal crash sensor, or ignition drive circuit. Common in 2018-2020 batches of Yuan/Song models.— Power supply system fault: excessive contact resistance in the constant power (B+) circuit, unstable IGN supply voltage (below 9V or above 16V), or a poor ground circuit causing abnormal ECU reset, most commonly occurring with a low battery or after installing an aftermarket audio system.— CAN bus communication fault: Lost communication or message timeout between the SRS ECU and the vehicle network. Possible causes include a wiring harness short circuit, connector water ingress (e.g., poor sealing at the wiring harness hole below the A-pillar), or abnormal terminating resistance.+2 more →
Actions
— Use VDS2000 or the latest BYD diagnostic tool to read all DTCs. Check for accompanying fault codes (such as U-series communication faults or B16XX-series sensor faults) and record the freeze frame data (vehicle speed, voltage, and temperature at the time of the fault).— Perform a key cycle test: disconnect the battery negative terminal for 5 minutes, reconnect it, and check if the fault code changes to a history code. If it remains a current code, check the SRS ECU power supply: measure connector pin 1 (B+) for 12V constant power, pin 2 (IGN) for 12V with the ignition switch ON, and pin 3 (GND) for less than 1Ω resistance to ground.+4 more →
B16C6-00›
DTC B16C6-00 indicates the Airbag Control Unit (SRS ECU) detected an internal self-check fault or abnormal communication with the vehicle network. The SRS ECU is the core controller of the passive safety system, monitoring crash sensors, seat occupancy detection, seat belt pretensioners, and individual airbag modules. When this DTC triggers, the ECU may enter fail-safe mode, degrading or completely disabling the entire airbag system. As a result, the front dual airbags, side airbags, and pretensioning seat belts may fail to deploy during a collision. This is a hard fault and will not clear automatically after a vehicle restart. Troubleshooting requires professional diagnostic equipment.
Causes
— Abnormal SRS ECU power supply or ground circuit: including blown FB-10 (10A) airbag system fuse, low battery voltage (<9V), or poor contact at ECU ground points G104/G105, causing unstable ECU operating voltage or reset.— SRS ECU internal hardware fault: Damage to the ECU internal microprocessor, memory (EEPROM), or crash sensor interface circuit. This commonly results from vehicle water ingress, moisture at the ECU mounting location, or component aging (on Qin series models, the ECU mounts in the lower center console, exposing it to air-conditioning condensation).— CAN communication bus fault: Short circuit, open circuit, or abnormal terminating resistor in the Power CAN (CAN-H/CAN-L) lines between the SRS ECU and the gateway (GW), preventing the ECU from communicating normally with the instrument cluster, VTOG, and other modules.+2 more →
Actions
— Preparation and Diagnosis: Access the SRS system using the ED-400 or VDS2000 diagnostic tool. Read the complete fault code list and record the freeze frame data. Confirm if B16C6-00 is a current fault (Active). Disconnect the battery negative terminal for 5 minutes to perform an ECU hard reset. Reconnect power and check if the fault code returns.— Power and ground check: Check if the FB-10 fuse (10A) in the engine compartment fuse box is blown. Measure the voltage to ground at SRS ECU connector terminals B05-1 (constant +B) and B05-2 (IGN power). Standard value: 11-14V. Measure the ground resistance at B05-3 and B05-4. Standard value: <1Ω. Thoroughly inspect the lower center console wiring harness for wear or water ingress.+4 more →
B16C6›
DTC B16C6 (Left Front Seat Belt Pretensioner Deployment Control Circuit Low) indicates a low voltage or open circuit in the left front (driver side) seat belt pretensioner deployment control circuit. This SRS (Supplemental Restraint System) subsystem fault involves the pyrotechnic pretensioner inside the seat belt retractor and its control circuit. The airbag control unit (ACU) sets this DTC when it detects pretensioner circuit resistance outside the standard range (normally 2.0±0.1Ω), an open circuit, a short to ground, or abnormal voltage. This fault forces the airbag system into a degraded mode. During a collision, the left front seat belt pretensioner may fail to deploy and retract, severely compromising driver protection. The instrument panel SRS warning lamp remains illuminated to indicate system failure.
Causes
— Seat belt pretensioner internal open circuit or abnormal resistance: Aging, moisture, or manufacturing defects in the pretensioner igniter or resistance wire cause the resistance value to deviate from the standard range.— Poor connector contact: The yellow dedicated connector between the pretensioner and wiring harness exhibits backed-out terminals, bent pins, oxidation, corrosion, or an incompletely engaged locking tab, causing intermittent or permanent poor contact.— Wiring harness mechanical damage: Frequent fore/aft seat adjustment, modifications, or assembly issues cause broken internal copper wires or damaged insulation in the wiring harness under the seat, in the A-pillar, or in the door sill area.+2 more →
Actions
— Safety preparation and diagnostic confirmation: Use VDS or a dedicated diagnostic tool to read the fault code, confirm B16C6 is a Current fault rather than a History fault, and record the freeze frame data. Turn off the ignition, disconnect the battery negative terminal, and wait at least 3 minutes to fully discharge the SRS capacitor.— Visually inspect the connector: Remove the left front B-pillar lower trim panel and check the connection of the yellow dedicated seat belt pretensioner connector. Confirm the locking tab is fully engaged, with no looseness, water ingress, or foreign matter. Inspect the terminals for bending, oxidation, burning, or push-out. Repair using the dedicated tool if necessary.+4 more →
B16C7-00›
DTC B16C7-00 indicates an internal fault or communication error in the SR8 panoramic image control unit (360° surround-view system ECU). This ECU typically mounts on the right side of the trunk or inside the center console. It processes video signals from the front, rear, left, and right surround-view cameras to enable the bird’s-eye view, dynamic guide lines, dashcam, and reversing camera functions. This DTC triggers when the ECU self-check detects a processor fault, memory error, unstable power supply, or CAN network communication interruption, forcing the system into fail-safe mode. The multifunction display may go black, show a "Panoramic System Fault" warning, or display only a single camera view. Although this fault does not affect the powertrain or driving safety, the vehicle loses parking assistance functions, increasing the risk of a reversing collision. This fault frequently occurs in BYD Song series (Song Pro, Song MAX, Song PLUS) and early Qin EV models. Diagnostic tools often mislabel it as an "SRS_ECU fault"; it is actually an SR8 system fault.
Causes
— SR8 ECU power supply circuit fault: Blown fuse EF20/EF22, poor ACC relay contact, or loose constant power line causing ECU operating voltage to drop below 9V or exceed 16V.— ECU internal hardware damage: Overheating damage to the main processor (typically an NXP or Renesas chip), cold solder joints on the DDR memory chips, or image processing DSP chip failure. Prolonged high-temperature operation or unstable voltage typically causes this damage.— Software error: Corrupted system firmware, lost calibration data, program runaway, or system crash. Common after prolonged vehicle power loss or an interrupted OTA update.+2 more →
Actions
— Preliminary Check: Confirm the fault symptom. Check if the 360-degree surround-view screen is black or the reversing camera image is inoperative. Use VDS2000 or Launch X431 to read all fault codes. Confirm the presence of accompanying fault codes B16C8 (camera fault) or U0140 (communication fault).— Power supply system check: Measure the voltage at pin 1 (constant B+) and pin 24 (ACC) of the SR8 ECU connector; the voltage must be 12V±0.5V. Verify secure connections at ground points G202/G203. Check if fuses EF20 (10A) and EF22 (15A) in the fuse box are blown.+4 more →
B16C7›
DTC B16C7 indicates the airbag control unit (SRS ECU/ACU) detected an internal system fault. This typically points to an abnormality in the ECU internal microprocessor, non-volatile memory (NVM), power supply monitoring circuit, or safety relay drive circuit. As a hard or persistent fault, it can force the airbag system into fail-safe mode and disable airbag deployment. On BYD e-platform and DM models, a gateway communication interruption may accompany this fault, affecting the normal drive logic of the instrument cluster airbag warning lamp. This Safety Level 2 fault requires immediate repair.
Causes
— SRS ECU internal hardware damage (MCU processor fault, EEPROM data corruption, or power management IC failure)— Power supply system fault (battery voltage fluctuation, poor contact in ECU power circuit, poor grounding causing excessive voltage drop)— CAN bus communication fault (communication interruption caused by CAN-H to CAN-L short circuit, short to power or ground, or abnormal terminating resistance)+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal, wait at least 3 minutes to fully discharge the SRS capacitor, and wear an anti-static wrist strap.— Fault confirmation: Connect the diagnostic tool to read all DTCs, record freeze frame data, and check for other SRS fault codes accompanying B16C7 (such as the B16C0-B16C8 series).+5 more →
B16C8-00›
DTC B16C8-00 indicates an internal fault or critical function failure in the airbag control unit (SRS ECU, BYD internal code SR8). As the core of the passive safety system, this ECU monitors front and side impact sensor signals, vehicle deceleration, and seat belt status in real time. Upon detecting a collision, it controls airbag ignition, seat belt pretensioner activation, and high-voltage system power-off protection. This DTC triggers when the ECU self-check detects an internal processor fault, memory checksum error, power supply monitoring abnormality, or safety monitoring circuit failure, forcing the entire airbag system into fail-safe mode. In this state, the airbag system will not deploy regardless of collision severity. The vehicle may also restrict high-voltage power-on or enter limp mode. This severe fault compromises driving safety.
Causes
— SRS ECU internal hardware fault: Damaged CPU, EEPROM memory chip, or power management IC inside the control unit, typically due to component aging or electrostatic breakdown.— Power supply system fault: Poor connection in the SRS ECU constant power (B+) or ignition power (IGN) circuit, blown fuse, or poor relay contact, causing ECU operating voltage to drop below 9V or exceed 16V.— Ground circuit fault: A loose, oxidized, or corroded ECU ground point (usually G101 or G102) increases circuit resistance and affects the signal reference voltage.+2 more →
Actions
— Safety preparation: Turn off the ignition switch, disconnect the low-voltage battery negative terminal, and wait at least 3 minutes (to fully discharge the SRS capacitor) to prevent accidental airbag deployment.— Fault confirmation: Connect the BYD VDS2000 or ED400 diagnostic tool. Read the B16C8-00 current status and freeze frame data. Check for accompanying fault codes (such as a crash sensor communication fault). Confirm the fault is current and not a historical intermittent fault.+6 more →
B16C8›
DTC B16C8 indicates a functional fault or internal self-check abnormality in the airbag control unit (SRS ECU). As the core control module of the passive safety system, this ECU integrates longitudinal/lateral acceleration sensors, safety sensors, and a microprocessor. It monitors real-time vehicle collision status, calculates collision severity, and controls the ignition and deployment timing of protective devices such as airbags, seat belt pretensioners, and knee airbags. The following conditions trigger this DTC: internal ECU processor faults (such as a damaged Freescale/NXP main control chip), EEPROM data checksum failures, power management circuit abnormalities, internal safety monitoring circuit protection events, or communication interruptions between the ECU and the vehicle CAN network. When this fault occurs, the SRS system enters fail-safe mode and the airbag warning lamp illuminates continuously. In extreme cases, the airbags may fail to deploy during a collision or deploy unintentionally while driving due to false detection, posing a severe safety hazard.
Causes
— SRS ECU internal hardware fault: Damaged main control chip (MCU), corrupted internal memory (Flash/EEPROM) data, or failed power management IC (PMIC), causing the ECU to fail the Power-on Self Test.— Power supply system fault: Blown constant power (+B) circuit fuse (usually a dedicated 10A or 15A SRS fuse), excessive relay contact resistance, or ignition switch power (IG1/IG2) voltage fluctuations (below 9V or above 16V), causing ECU power supply instability or reset.— Ground circuit fault: Loose, oxidized, or corroded SRS ECU ground point (usually G101 on the left instrument panel frame or the lower center console ground point), or improperly removed paint at the connection. This causes excessive ground resistance (>1Ω) and affects sensor signal reference voltage stability.+2 more →
Actions
— Use the VDS2000/VDS3000 diagnostic tool to access the SRS system. Read the complete DTC list and freeze frame data. Check for accompanying fault codes, such as B16C7 (SRS_ECU internal fault) and U0140 (lost communication with BCM). Record key information at the time of the fault, such as vehicle speed and ignition cycle count.— Check the SRS ECU power supply system: disconnect the battery negative terminal, wait 3 minutes, then disconnect and reconnect the ECU connector. Measure the voltage to ground at ECU connector terminal 1 (+B constant power) and terminal 2 (IG power). Standard value: 11-14V. Check the engine compartment or instrument panel fuse box for a blown SRS fuse (marked 'SRS' or 'AIR BAG'). Measure the resistance between the ECU ground terminal and body ground. Resistance must be less than 1Ω.+5 more →
B16DF-00›
This fault code indicates the SRS (airbag) control unit detects a communication interruption or no connection with the Left Rear Impact Sensor. This sensor typically mounts in the vehicle’s left rear side panel, C-pillar, or rear door area to monitor side-impact acceleration signals. The SRS ECU triggers this fault if it fails to receive valid data from the sensor within a predetermined time, or if it detects circuit resistance outside the normal range (open or short circuit). This fault disables the vehicle’s side-impact detection function. The system may fail to accurately determine collision severity, suppressing normal deployment of the left rear side airbag/side curtain airbag. In some cases, this creates a risk of unintended airbag deployment in fail-safe mode.
Causes
— Broken or crushed left rear impact sensor wiring harness, particularly copper wire fractures caused by long-term vibration at harness bends routed through the door hinge or inside the sill trim panel.— Loose sensor connector, backed-out pins, or water ingress causing corrosion. Driving through water or poor sealing after a car wash commonly causes terminal oxidation.— Damage or circuit fault in the crash sensor internal accelerometer causes no signal output.+2 more →
Actions
— Connect the BYD dedicated diagnostic tool (VDS or ED400), read the complete fault codes and freeze frame data, and confirm the vehicle speed, timestamp, and other data recorded when the fault occurred.— Switch off the ignition, disconnect the battery negative terminal, and wait at least 90 seconds to fully discharge the SRS system high-voltage capacitor.+7 more →
B16DF›
DTC B16DF indicates the SRS (Supplemental Restraint System) ECU detects a communication interruption or physical disconnection of the Left Rear Impact Sensor. This sensor typically mounts in the vehicle's left rear quarter panel, C-pillar, or rear longitudinal beam area to monitor collision acceleration from the left rear. The ECU sets this fault code if it fails to receive a valid signal (including the sensor ID code, acceleration data, or heartbeat signal) within the preset monitoring period, or if it detects circuit resistance outside the normal range (typically greater than 10 kΩ or less than 1 Ω). This fault disables the left rear collision detection function. During a side impact or rear-end collision, the SRS ECU may fail to accurately assess collision severity, compromising the deployment strategy of the side airbags, curtain airbags, or seat belt pretensioners and posing a severe safety risk.
Causes
— Loose or disconnected wiring harness connector: After accident repairs, interior trim removal/installation, or water exposure, an incompletely locked sensor connector located inside the left rear door sill trim panel (usually a 3-pin or 2-pin waterproof plug) causes poor contact or complete disconnection.— Sensor harness open or short circuit: Long-term vibration wears through the harness insulation where it passes through body sheet metal holes, seat slide rails, or door sill plates; rodents gnaw the wiring, causing an open circuit; or the harness shorts to the vehicle body.— Crash sensor internal fault: A damaged internal accelerometer element, capacitor leakage, or ASIC chip fault prevents the sensor from sending valid data frames to the SRS ECU.+2 more →
Actions
— Safety preparation: Disconnect the low-voltage battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor. Read and record all DTCs and freeze frame data. Confirm B16DF is a current fault, not a history fault.— Physical inspection: Remove the left rear sill trim, lower C-pillar trim, or left side of the rear bumper. Visually inspect the crash sensor connector (part number usually starts with 69C) to confirm it is fully inserted and locked with an audible 'click'. Inspect the connector terminals for backed-out pins, corrosion, or signs of water ingress (green oxidation).+3 more →
B16DF00›
This DTC indicates an interrupted communication link between the airbag control unit (SRS ECU) and the left rear crash sensor. The left rear crash sensor typically utilizes a MEMS capacitive accelerometer and mounts on the left rear side panel (C-pillar area) to monitor left rear collision acceleration. During the ECU initialization self-check or a drive cycle, if the ECU fails to detect the sensor bias voltage (normally a 2.5V reference voltage at a 2-3kΩ equivalent resistance), detects infinite circuit resistance, or reads a continuous high or low signal line voltage exceeding the threshold, it registers a 'not connected' state. This fault may prevent the left rear side airbag and curtain airbag from deploying correctly during a collision. The ECU simultaneously illuminates the airbag warning lamp and enters fail-safe mode (some models disable the entire side airbag circuit).
Causes
— Sensor wiring harness connector loose, terminal backed out, or oxidized due to water ingress (common when improperly seated after rear seat removal/installation or C-pillar trim panel repairs).— Physical damage to the wiring harness causing an open circuit (sill trim panel pinching the wire, or wiring harness retaining clip detaching and rubbing against a sharp body edge, breaking the copper strands)— Internal damage to the crash sensor (cracked piezoelectric element, internal resistance drift outside the standard 1.8-3.5kΩ range)+2 more →
Actions
— Safety Preparation: Disconnect the negative battery terminal and wait at least 3 minutes to discharge residual charge in the SRS capacitor and prevent accidental airbag deployment.— Fault Confirmation: Use the BYD OEM diagnostic tool (ED400/ED600) to read fault codes, confirm B16DF00 is a Current DTC, and record freeze frame data.+7 more →
B16E0-00›
DTC B16E0-00 indicates a short to ground in the Left Rear Impact Sensor signal circuit within the Supplemental Restraint System (SRS). This sensor typically mounts in the left rear quarter panel or C-pillar area to monitor collision acceleration at the left rear of the vehicle. A short to ground indicates abnormal continuity (resistance below the normal range) between the sensor power wire, signal wire, or shield and the vehicle body metal frame. This causes the SRS control module to receive a continuous low-level signal. This fault forces the SRS into fail-safe mode and may cause the following: 1) The left rear side airbag/curtain airbag fails to deploy during an actual collision. 2) The system misinterprets the fault as a collision and inadvertently deploys the airbag. 3) Entire SRS functionality restricts, severely compromising passive safety performance.
Causes
— Wiring harness chafing or crushing inside the left rear quarter panel: Prolonged driving over rough roads causes the wiring harness to rub against metal edges, damaging the insulation and shorting the signal wire to ground.— Sensor connector water ingress and corrosion: Car washing, wading, or poor sealing causes a short circuit between the connector terminals, creating a path to ground.— Rear crash sensor internal fault: Damaged internal electronic components cause a short circuit between the power supply terminal and the ground terminal.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal, wait at least 90 seconds for the SRS system capacitor to discharge, and wear an anti-static wrist strap.— Visual inspection: Remove the left C-pillar trim panel and the left side of the rear bumper. Inspect the left rear crash sensor (usually numbered Y3) for physical damage. Check the connector for looseness, water ingress, or corrosion.+4 more →
B16E0›
DTC B16E0 indicates a short to ground in the Left Rear Impact Sensor signal circuit within the airbag system (SRS). This sensor typically mounts in the left rear C-pillar, the left side of the rear bumper, or the inside of the left rear fender to monitor left rear collision acceleration. A "short to ground" means the insulation resistance between the sensor signal line and body ground (GND) falls below the standard value (typically <1Ω). This causes the SRS control unit (ACU) to detect a continuous low-voltage signal (approaching 0V), preventing it from acquiring normal acceleration change signals. This fault forces the SRS into fail-safe mode, disabling the deployment function of the left rear side airbags (side curtain or rear seat airbags). In extreme cases, this condition causes unintended airbag deployment or failure to deploy during a collision, posing a severe safety hazard.
Causes
— Harness abrasion and insulation damage: Long-term vibration, friction, or compression damages the insulation of the sensor wiring harness inside the left rear sill trim, C-pillar, or rear bumper, causing the copper core to contact the vehicle body metal and create a short to ground.— Sensor internal short circuit: Moisture ingress, aging, or impact damages the piezoelectric element or circuit board inside the crash sensor, causing a short circuit between the signal terminal and the housing (ground).— Connector water ingress and corrosion: Poor sealing of the rear bumper sensor connector allows water to enter during car washing, wading, or wet conditions, causing electrolytic corrosion between the pins and creating a path to ground.+2 more →
Actions
— Safety Preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes to allow the SRS capacitor to fully discharge and prevent accidental airbag deployment during repair. Wear an anti-static wrist strap. Do not use radio equipment near the sensor.— Locate the sensor: According to the vehicle repair manual, remove the left rear C-pillar trim panel or the rear bumper left cover, and locate the left rear impact sensor (usually a black or yellow connector with a locking clip).+4 more →
B16E011›
This DTC indicates an abnormally low-resistance connection (short circuit) between the signal circuit of the left rear side impact sensor (SIS) in the Supplemental Restraint System (SRS) and the vehicle body ground (GND). Under normal operating conditions, the impact sensor sends a specific voltage signal (typically a PWM or resistor divider signal) to the SRS control unit (ACU) to indicate its status. When a short to ground occurs, the ACU detects the circuit voltage remaining at or near 0V and a resistance well below the standard range (typically <1Ω), identifying a short-to-ground fault. This fault causes the SRS to enter fail-safe mode. The system illuminates the airbag fault warning lamp and disables the left rear side airbag and curtain airbag deployment functions to prevent accidental deployment caused by the short circuit. In a severe side-impact collision, the affected airbags may fail to deploy normally, posing a major safety hazard.
Causes
— Worn or damaged left rear crash sensor wiring harness insulation causes the wire to short to vehicle body metal (commonly found inside the sill trim panel where the harness passes sharp edges or retaining clips).— Seal failure of internal electronic components in the crash sensor body allows moisture intrusion, causing a printed circuit board (PCB) short to ground.— Water ingress, corrosion, or bent pins in the sensor connector (usually located near the C-pillar or rear seat) cause a short circuit between the signal and ground terminals.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS system capacitor and prevent accidental airbag deployment.— Visual inspection: Remove the left rear door sill trim and lower C-pillar trim. Inspect the crash sensor (usually located behind the C-pillar interior trim panel or near the left rear longitudinal beam) and wiring harness for obvious damage, crushing, or water ingress.+5 more →
B16E100›
B16E100 is a BYD SRS (Supplemental Restraint System) proprietary fault code indicating an internal circuit fault or abnormal communication signal in the Left Rear Impact Sensor. This sensor typically mounts in the left rear C-pillar, D-pillar, or inside the rear bumper. It operates as a piezoelectric or MEMS accelerometer and communicates with the Airbag Control Unit (ACU) via the LIN bus or a hardwired connection. During this fault, the ACU cannot accurately receive the left rear impact acceleration signal. This failure may prevent the side curtain airbag and left rear seat belt pretensioner from deploying during a collision. In extreme cases, the abnormal signal risks unintended airbag deployment. The following conditions typically trigger this fault code: abnormal sensor supply voltage (below 9V or above 16V), LIN bus communication timeout (no valid data for over 500ms), or internal sensor self-check failure (accelerometer drift or EEPROM checksum error).
Causes
— Sensor body internal circuit fault: Piezoelectric element aging, MEMS chip damage, or internal EEPROM data loss prevents normal acceleration signal output or causes self-test failure.— Wiring harness and connector fault: Loose left rear C-pillar/left luggage compartment wiring harness connector, oxidized or backed-out pins, water ingress corrosion, or LIN line short to ground, short to power, or open circuit.— Installation and mechanical issues: Loose sensor mounting bolts or a deformed mounting bracket (common after accident repairs) prevent the sensor from accurately detecting collision acceleration.+2 more →
Actions
— Diagnostic scan: Use VDS2000/VDS1000 to read the complete fault codes and freeze frame data. Confirm whether B16E100 is a current or history fault. Record the vehicle speed, voltage, and other data from when the fault occurred.— Physical inspection: Remove the left rear C-pillar trim panel or rear bumper. Inspect the left rear impact sensor for external damage or cracks. Verify the installation torque (usually 8-10N·m) and check the bracket for deformation.+4 more →
B16E200›
DTC B16E200 indicates the SRS (Supplemental Restraint System) control module detects a configuration data mismatch for the Left Rear Impact Sensor. Specifically, the sensor calibration parameters, hardware serial number, or installation position coding stored in the control module do not match the physical characteristics of the connected Left Rear Impact Sensor. This is a software/configuration fault, not a hardware open or short circuit. This fault causes the SRS to enter a degraded mode. The left rear impact detection function may fail or operate with abnormal trigger thresholds, affecting the deployment logic of the side curtain airbags and seat belt pretensioners. However, it typically does not disable the entire airbag system.
Causes
— Failure to perform the 'Sensor Online Configuration' or 'Coding' procedure with the VDS diagnostic tool after replacing the left rear crash sensor causes the new sensor hardware ID to mismatch the record stored in the control module.— Outdated SRS control module software version or corrupted configuration data area (e.g., EEPROM data loss due to disconnecting vehicle power during maintenance or battery depletion), preventing the module from correctly identifying original sensor parameters.— Incorrectly installing the right rear crash sensor on the left side during repair, or using a non-genuine part (aftermarket parts lack original configuration coding), causes a position identification conflict.+2 more →
Actions
— Connect the BYD VDS3000 diagnostic tool. Enter the SRS system to read the complete fault codes and freeze frame data. Record the current part number and hardware version of the left rear crash sensor. Check for other accompanying related fault codes (such as B16E100 communication fault or B16E300 hardware fault).— Visually inspect the left rear crash sensor mounting position (usually inside the C-pillar trim panel or on the rear bumper left bracket). Confirm the sensor is not installed backwards, the connector is free of oxidation or corrosion, and the wiring harness shows no crushing or damage. Verify the left/right marking (L/R mark) on the sensor housing matches the installation position.+3 more →
B16E300›
DTC B16E300 indicates a current monitoring anomaly or communication error in the Electronic Parking Brake (EPB) left rear wheel actuator (motor). The EPB control module sets this fault when it detects the left rear parking motor operating current exceeds the calibrated threshold (normal range approximately 8-15 A) or fails to establish valid communication with the left rear motor. Possible causes include an internal motor short or open circuit, mechanical binding, poor wiring connections, or a control module fault. When this fault triggers, the system enters a safety protection mode. This mode may prevent the electronic parking brake from releasing or applying, disable the Auto Hold function, and illuminate an instrument cluster warning. Extreme cases immobilize the vehicle or create a rollaway risk.
Causes
— Excessive carbon brush wear or a burned commutator inside the left rear EPB motor abnormally increases contact resistance, causing the operating current to deviate from the standard value.— Motor wiring harness connector oxidation, corrosion from water ingress, or terminal back-out causes excessive contact resistance or interrupts signal transmission.— Left rear brake caliper mechanical binding or failure to return, causing excessive motor load and triggering overcurrent protection.+2 more →
Actions
— Use the VDS2000/VDS3.0 diagnostic tool to read the complete fault codes and freeze frame data. Confirm whether B16E300 is a current or history fault, and record the specific abnormal current monitoring values.— Raise the vehicle. Visually inspect the condition of the left rear wheel EPB motor wiring harness connector. Check the sealing ring for aging. Measure the supply voltage at the connector (should be constant 12V) and verify a good ground connection.+5 more →
B16E7-00›
DTC B16E7-00 indicates the airbag system (SRS) detected a communication interruption or abnormal signal between the Middle Rear Impact Sensor and the SRS control module. This sensor typically mounts on a structural member in the middle rear of the vehicle (such as the lower C-pillar or rear panel crossmember) and monitors collision acceleration in the middle rear area. The SRS module sets this DTC if it fails to receive a valid signal from the sensor within the specified time, or if it detects an open or short circuit in the wiring. This fault may prevent the side curtain airbags, rear side airbags, or seat belt pretensioners from deploying correctly during a middle rear collision. This severely compromises passive safety protection and continuously illuminates the instrument panel airbag warning light.
Causes
— Sensor harness connector loose, oxidized, or showing water ingress: Because the center rear impact sensor mounts low in the vehicle (typically on either side of the trunk or behind the rear seats), car washing, wading, or damp environments easily oxidize and corrode the connector pins, causing excessive contact resistance or signal interruption.— Crash sensor internal fault: A damaged internal accelerometer or processing chip cannot generate a valid crash signal, or CAN/LIN bus communication is abnormal.— Wiring harness open or short circuit: Incorrect wiring harness connection after rear-end collision repairs, harness chafing, or rodent damage during long-term use, causing power, ground, or signal wire faults.+2 more →
Actions
— Use VDS2000 or a BYD dedicated diagnostic tool to read the complete fault codes and freeze frame data. Confirm if the fault is current (Active) and record the vehicle status when the fault occurred. Check for any other related crash sensor fault codes.— Locate the center rear impact sensor (on Qin series models, this is usually located in the upper middle area behind the rear seat backrest or inside the C-pillar trim panel). Remove the corresponding trim panel. Visually inspect the sensor for impact marks, cracks, or water stains. Verify the connector is fully seated and check the retaining clip for breakage.+4 more →
B16E7›
DTC B16E7 indicates the airbag control unit (SRS ECU) cannot establish normal communication with the Middle Rear Impact Sensor. This sensor typically mounts in the vehicle's central rear area (such as the rear panel, rear floor, or near the C-pillar) and monitors rear collision acceleration. When the ECU detects an open sensor circuit, an internal sensor fault, or a communication interruption, it stores this fault code and illuminates the airbag warning light. Consequently, during a rear-end collision, the airbag system may fail to correctly determine collision severity and deploy the rear airbags or seat belt pretensioners in time, severely compromising passive safety functions.
Causes
— Centre rear crash sensor wiring harness connector loose, disconnected, or making poor contact. Common causes include vehicle wading, corrosion from water ingress, or failing to fully seat the connector after repairs.— Open or short circuit in the sensor power supply line or signal line due to wiring harness aging, wear, crushing, or rodent damage.— Internal fault in the center rear crash sensor, such as a damaged accelerometer, internal circuit fault, or water ingress due to seal failure.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds for the SRS system capacitors to discharge fully, preventing accidental airbag deployment.— Fault Confirmation: Use the BYD dedicated diagnostic tool (VDS2000/VDS2100) to read the fault code, confirm B16E7 is a current fault (not a history fault), and record the freeze frame data.+5 more →
B16E700›
DTC B16E700 indicates the airbag system (SRS) detects a communication interruption or physical disconnection of the Middle Rear Impact Sensor. This sensor, typically located on the inner rear bumper reinforcement or lower C-pillar, monitors rear-end collision acceleration. A "not connected" status means the SRS control unit receives no valid signal from the sensor, typically indicating an open circuit or high-resistance condition. The system determines the sensor circuit is open, the connector is detached, or the sensor has internal damage. This fault causes the SRS to lose accurate rear-end collision monitoring capabilities. It may force the airbag control unit into a degraded protection mode, disable specific airbag functions, or illuminate the airbag warning lamp continuously, severely compromising passive safety system reliability.
Causes
— Rear bumper wiring harness connector loose or disconnected: Driving on rough roads or through water can loosen the crash sensor plug inside the rear bumper due to vibration. Poor sealing can also cause pin corrosion and oxidation, resulting in poor contact.— Open circuit inside the sensor body: Physical impact (such as a minor rear-end or reversing collision) or long-term aging damages the center rear impact sensor's internal piezoelectric element or circuit board, causing an open circuit.— Harness breakage or wear: Repeated bending or friction against other components breaks the copper wires where the wiring harness from the main body harness to the rear bumper passes through the rear panel and floor trim strip, causing an open circuit fault.+2 more →
Actions
— Fault confirmation and freeze frame analysis: Use VDS2000 or a dedicated BYD diagnostic tool to read fault codes. Confirm B16E700 is a current fault (Active). Record freeze frame data (ambient temperature and vehicle status). Check for other accompanying SRS-related fault codes (such as B16E800 short to ground).— Visual and connector inspection: Remove the rear bumper trim panel and locate the center rear impact sensor (usually located in the middle or left side of the rear crash beam). Verify the sensor connector is fully seated, confirm the connector waterproof sealing ring is intact, and inspect the pins for green oxidation, backed-out pins, or deformation.+4 more →
B16E8-00›
This DTC indicates a short to ground in the signal circuit of the Supplemental Restraint System (SRS) Middle Rear Impact Sensor. The sensor mounts in the center of the rear bumper or rear longitudinal rail area. Electrically, the insulation resistance between the sensor signal wire (typically a LIN communication or analog signal line) and body ground drops below the threshold (generally <1Ω). This causes the SRS control unit (ACU) to continuously receive an abnormally low voltage signal. This fault forces the SRS into fail-safe mode. As a result, the system may fail to accurately detect rear impact acceleration, preventing the airbags, curtain airbags, or seat belt pretensioners from deploying in time during a rear-end collision. Furthermore, the ACU may interpret the condition as a wiring fault and completely disable the rear impact monitoring function, illuminate the instrument panel SRS warning lamp, and downgrade the vehicle's passive safety system. BYD Qin series models typically use a dual-axis accelerometer design for this sensor. The ACU continuously registers a short to ground as 'abnormal circuit current' or 'signal voltage below lower limit'.
Causes
— Damaged wiring harness sheath in the rear bumper area allows direct wire contact with the metal body, causing a short to ground (common after reversing collision repairs or underbody scrapes).— Rear center crash sensor body seal failure; internal water ingress or moisture causes the signal terminal to short to the sensor housing (ground).— Sensor connector (usually located inside the rear bumper or near the spare wheel well) is loose, or terminal pins are backed out or corroded, causing the signal pin to short to ground against the connector housing.+2 more →
Actions
— Safety Preparation: Disconnect the battery negative terminal. Wait at least 3 minutes (or the time specified in the repair manual) to fully discharge the SRS energy storage capacitor and prevent accidental airbag deployment.— Fault confirmation: Use VDS or a dedicated diagnostic tool to read all SRS fault codes, record freeze frame data, and confirm the fault is current (Present) rather than historical.+6 more →
B16F0-00›
B16F0-00 indicates a short to body ground in the Supplemental Restraint System (SRS) Right Rear Impact Sensor signal circuit. This sensor typically mounts in the C-pillar or right rear quarter panel area to monitor collision acceleration at the right rear of the vehicle. The SRS ECU logs this fault code when it detects abnormal voltage to ground on the sensor signal wire (continuous low level or excessively low impedance). This fault prevents the SRS ECU from accurately receiving the right rear impact signal. It may cause the airbag system to fail to deploy correctly during a side or rear impact, or to deploy inadvertently under normal conditions. Consequently, the system enters fail-safe mode, illuminates the airbag warning light, and may disable certain airbag functions.
Causes
— Damaged insulation on the right rear impact sensor wiring harness causing a short to the body (commonly due to chafing at the C-pillar wiring hole or the edge of the rear bumper mounting bracket)— Water ingress or corrosion in the sensor connector causing a short circuit between terminals (common after water fording, rear windshield leaks, or spraying high-pressure water directly at the C-pillar during car washes)— Internal electronic component failure in the right rear impact sensor causing a short to ground at the signal terminal (sensor internal short circuit).+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait 3 minutes for the SRS capacitor to discharge to ensure safe operation.— Fault confirmation: Connect the diagnostic tool to read DTCs, confirm B16F0-00 is a current fault (Active), and record the freeze frame data.+8 more →
B16E8›
DTC B16E8 indicates the SRS (Supplemental Restraint System) control unit detects an abnormally low-resistance path (short to ground) between the Center Rear Impact Sensor (typically installed on the rear panel or C-pillar area) signal circuit and body ground. This sensor uses a piezoelectric or capacitive accelerometer. During normal operation, it outputs a 0.5-4.5V analog voltage signal to the SRS control unit to reflect collision acceleration. A short to ground causes the control unit to continuously receive a voltage signal near 0V, triggering the following: 1) The system determines the sensor has failed, enters fail-safe mode, and disables the associated airbags (including side curtain airbags and rear collision protection functions); 2) During an actual rear collision, the system cannot accurately identify collision severity, causing delayed or no airbag deployment; 3) If the short-circuit resistance is unstable, it triggers an intermittent fault, causing the SRS warning lamp to illuminate erratically. This is a hard fault. Upon detection, the control unit stores the DTC and illuminates the instrument cluster airbag warning lamp.
Causes
— Rear wiring harness mechanical damage: Long-term vibration, cargo friction, or a rear-end collision wears through the rear wiring harness insulation where it passes through the boot rear panel, C-pillar sheet metal holes, or retaining clips. The exposed copper conductor directly contacts the vehicle body metal, causing a short to ground.— Internal sensor circuit fault: Failure of the collision sensor internal signal conditioning circuit or piezoelectric element package seal causes insulation breakdown between the signal output terminal and the sensor metal housing (ground), forming an internal short circuit.— Water ingress or seal failure: Ageing boot seal, poor rear windscreen sealing, or water entering the rear wiring harness connectors (usually located on both sides of the rear panel) when wading, causing electrolytic corrosion between terminals or a short to earth.+2 more →
Actions
— Safety preparation: Switch the vehicle to OFF, disconnect the 12V low-voltage battery negative terminal, and wait at least 3 minutes (or as required by the repair manual, usually 5 minutes) to fully discharge the SRS backup power supply capacitor and prevent accidental airbag deployment during repair.— Fault confirmation and freeze frame analysis: Use VDS or a dedicated diagnostic tool to read the fault code status. Confirm B16E8 is a current fault (Current DTC), not a history fault. Record the vehicle status in the freeze frame data (vehicle speed, timestamp, etc.) and analyze the environmental conditions when the fault occurred.+6 more →
B16EF-00›
DTC B16EF-00 indicates the SRS (Supplemental Restraint System) detects an open circuit or high resistance condition (typically exceeding 10kΩ) in the Right Rear Impact Sensor or Driver Seat Belt Pretensioner circuit. The system triggers this Hard DTC when it detects interrupted communication between the component and the airbag ECU, or abnormal resistance in the ignition circuit. In BYD Qin series models, this code typically indicates a LIN bus communication failure or hard-wired connection fault at the side impact acceleration sensor located in the right rear C-pillar or B-pillar. In Song Pro, Tang DM, Han EV, and other models, this code designates an open circuit in the driver-side seat belt pretensioner ignition circuit. Upon triggering, the SRS ECU illuminates the airbag warning light, disables the corresponding airbag deployment and pretensioner functions, and enters fail-safe mode. In extreme cases, this failure may result in a loss of occupant protection during a side impact.
Causes
— Loose connector, backed-out pins, or corrosion at the right rear crash sensor (located inside the right rear fender liner or C-pillar trim panel; susceptible to water ingress or damp conditions)— Repeated bending of the driver's seat belt pretensioner wiring harness at the seat slide rail causes fatigue fracture of the internal copper wire, resulting in an intermittent open circuit.— Damaged crash sensor internal accelerometer element, waterproofing failure, or pretensioner deployed in an accident (internal open circuit in the single-use pyrotechnic device)+2 more →
Actions
— Use a dedicated diagnostic tool (Launch X-431 or BYD ED400) to read complete fault codes and freeze frame data. Confirm whether the fault status is Current or History, and record the vehicle status at the time of occurrence.— Disconnect the 12V battery negative terminal and wait 3 minutes (for capacitor discharge). Locate the target component based on vehicle configuration: for Qin series, check the right rear crash sensor (position B16, usually inside the right rear fender); for other models, check the pretensioner connector under the driver's seat.+6 more →
B16EF›
DTC B16EF indicates the SRS (Supplemental Restraint System) control module detects a communication interruption or missing physical connection with the Right Rear Impact Sensor. This sensor typically mounts in the right C-pillar, rear door frame, or inside the right rear quarter panel to monitor collision acceleration changes on the right rear side of the vehicle. During a side-rear collision, the sensor transmits the acceleration signal to the SRS module to determine whether to deploy the right curtain and side airbags. A "not connected" fault means the SRS module cannot detect the sensor during initialization or periodic communication checks. Causes include an open circuit, disconnected connector, internal sensor open circuit, or abnormal module power supply. This fault disables the right rear collision protection function. As a safety-critical fault, it requires immediate repair.
Causes
— Sensor harness connector loose, terminal backed out, or poor contact: Commonly caused by failing to fully seat the connector after accident repairs, or prolonged rough road vibration loosening the retaining clip.— Wiring harness open or short circuit: The wiring harness in the right rear sill and C-pillar area breaks after vehicle wading, accidents, prolonged bending, or rodent damage. Metal edge chafing causes a short to ground or power.— Internal sensor fault: Damage to the sensor's internal piezoelectric element or processing circuit causes no signal output or a power supply short circuit.+2 more →
Actions
— Safety preparation and fault confirmation: Disconnect the negative battery terminal and wait at least 90 seconds to fully discharge the SRS capacitor. Use VDS2000 or a BYD dedicated diagnostic tool to read fault codes. Confirm B16EF is a current fault (ACTIVE), not a historical fault. Verify the 'Right Rear Impact Sensor Status' in the data stream shows 'Not Connected' or 'Communication Failure'.— Physical connection check: Remove the right C-pillar interior trim panel or rear door sill trim panel and locate the right rear impact sensor (typically a yellow connector). Verify the connector is fully seated, the locking tab is intact, and the terminals are not backed out or corroded. Inspect the sensor mounting bracket for deformation or looseness.+4 more →
B16EF00›
DTC B16EF00 indicates the airbag control unit (SRS ECU) detected a communication interruption or open circuit in the Right Rear Impact Sensor. This sensor, typically installed inside the right rear door, C-pillar, or inner rear fender, monitors collision acceleration in the vehicle's right rear area. The ECU determines a "not connected" state if it fails to receive a valid sensor signal (voltage signal or LIN bus data frame) within the specified period (typically 500ms), or if it detects circuit resistance outside the threshold (typically >10kΩ or <1Ω, depending on specific circuit design). This safety-related fault can prevent the side airbag and side curtain airbag from deploying during a right rear collision. The vehicle remains drivable, but the airbag system enters a degraded mode.
Causes
— Loose sensor harness connector or poor contact: The right rear impact sensor mounts near the door or C-pillar. Frequent door operation or wading can loosen the 2-pin or 3-pin connector or oxidize the terminals, interrupting the signal.— Wiring harness open circuit or chafing: Long-term bending of the right rear sill wiring harness at the seat slide rail, carpet retaining strip, or door hinge breaks the internal copper strands while leaving the insulation intact (hidden open circuit), or wire routing during rear bumper modification accidentally damages the sensor wiring harness.— Internal sensor fault: damaged MEMS accelerometer chip, internal step-down circuit failure preventing operation, or sensor housing seal failure causing water ingress and circuit board corrosion.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal. Wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment. Read and record the DTC freeze frame data. Confirm the vehicle speed, timestamp, and other information at the time of the fault.— Locate the sensor: Refer to the vehicle repair manual (usually inside the right rear C-pillar trim panel for Qin/Qin Pro; inside the right rear fender for E2/E3). Remove the interior trim panel or rear bumper. Visually inspect the right rear impact sensor (small black square with a 2-3 wire harness) and its white/yellow connector for looseness or water ingress.+4 more →
B16F0›
This DTC indicates an abnormally low-resistance connection between the Supplemental Restraint System (SRS) Right Rear Impact Sensor signal circuit and body ground. In the BYD SRS architecture, impact sensors utilize a dual-axis accelerometer design, transmitting a 0-5V analog voltage signal to the Airbag Control Unit (ACU) via hardwire. A short to ground continuously pulls the signal line voltage down to <0.5V (normal static voltage is approximately 2.5V). The ACU sampling circuit detects this abnormal voltage level and triggers the DTC. This fault forces the SRS into fail-safe mode, disabling the right rear side airbag and curtain airbag deployment while illuminating the airbag warning lamp. Because the short circuit can occur anywhere in the wiring harness, excessive short-circuit current (>2A) risks burning out the internal ACU drive circuit. This single-point failure directly compromises the vehicle's side-rear collision detection capability and, in extreme cases, prevents airbag deployment during a collision.
Causes
— Long-term vibration at the C-pillar or rear seat mounting bracket wears the right rear impact sensor wiring harness. Damaged insulation causes the signal wire to contact the body ground. This is common on vehicles with >50,000 km.— An aged sealing ring or loose retaining clip on the sensor connector (usually located inside the right rear quarter panel) allows water ingress after washing the vehicle or driving through water, causing electrolytic corrosion between the pins and creating a short-to-ground path.— External impact or electrical overstress typically causes internal breakdown of the crash sensor ASIC chip, creating an internal short circuit between the signal output terminal and the metal housing (ground).+2 more →
Actions
— Use VDS2000 or a BYD dedicated diagnostic tool to read fault codes. Confirm B16F0 is a Current DTC, not a history fault. Record environmental parameters from the freeze frame data, such as vehicle speed and temperature.— Perform the safe power-down procedure: Disconnect the 12V battery negative terminal and wait at least 90 seconds for the SRS capacitor to fully discharge. Do not operate any electrical equipment during this time.+8 more →
B16F100›
DTC B16F100 indicates an internal electrical fault or signal plausibility error in the right (passenger side) Side Impact Sensor (SIS). This sensor typically mounts inside the right B-pillar trim panel or right front door cavity. It monitors the acceleration change rate (Delta-V) during a side impact and transmits an analog voltage signal (normal range 0.4-4.6V) to the SRS airbag control unit via the LIN bus or a hardwired connection. Fault trigger conditions include internal accelerometer self-test failure, signal voltage continuously outside thresholds (too high/too low), sensor ID verification failure, or communication loss with the SRS module. This fault prevents the right side airbags and side curtain airbags from deploying correctly during a side impact, or forces the airbag system into a degraded protection mode (retaining only the driver's front airbag function). This is a safety-critical fault requiring immediate repair.
Causes
— A damaged piezoelectric accelerometer element or faulty signal processing chip inside the right side impact sensor body causes output signal drift or a fixed voltage.— Water ingress and oxidation in the sensor wiring harness connector (commonly resulting from rainwater entering through a poorly sealed lower right B-pillar or aging window seals), causing a power wire or signal wire short to ground.— Broken internal copper strands in the right front door wiring harness at the hinge bend (due to metal fatigue from frequent door operation) cause an intermittent open circuit in the sensor power supply or communication line.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor. Remove the service disconnect switch (if equipped with a high-voltage system). Use the VDS2000/VDS2100 diagnostic tool to read the complete DTC snapshot. Record the vehicle speed, sensor voltage values, and freeze frame data at the time of the fault.— Physical inspection: Remove the right lower B-pillar trim panel (remove the sill trim panel first). Inspect the crash sensor connector (part number usually starts with 5A or 6A) for looseness, water ingress (look for green oxidation), or backed-out pins. Inspect the sensor mounting bracket for deformation. Verify the fixing bolt torque is 7-9N·m.+4 more →
B16F200›
DTC B16F200 indicates the airbag control unit (SRS ECU) detects abnormal configuration parameters for the right rear side impact sensor (C-pillar/rear quarter panel). This is a configuration fault, not a hardware failure. The sensor ID, installation position parameters, sensitivity calibration data, or hardware identification code stored in the SRS ECU do not match the installed physical sensor. While the sensor still communicates, the ECU cannot correctly interpret its crash signal threshold, potentially causing unintended deployment or failure of the side airbags or curtain airbags. Common triggers include: failing to perform online configuration after replacing the sensor during collision repair, using non-OEM parts causing a hardware ID mismatch, losing configuration data after an SRS software update, or interrupting the programming process resulting in incomplete configuration.
Causes
— Configuration/calibration not performed after replacing the right rear crash sensor: Technician replaced only the hardware and did not use the VDS diagnostic tool to perform the 'crash sensor configuration' or 'coding' procedure, preventing the ECU from recognizing the new sensor's hardware ID.— Sensor hardware model mismatch: Installing a sensor with an incorrect part number (e.g., installing a low-spec sensor on a high-spec vehicle, or swapping left and right sensors) causes the SRS ECU to fail the hardware coding check.— SRS control unit software fault: Corrupted configuration data in the control unit internal EEPROM, an outdated software version incompatible with the new sensor, or a power loss during an upgrade causing configuration area data errors.+2 more →
Actions
— Step 1: Use the BYD VDS diagnostic tool to enter the SRS system. Read all fault codes, check for accompanying faults (such as B16F300 communication fault, U0141 lost communication with BCM, etc.), and record the freeze frame data (supply voltage, temperature, mileage).— Step 2: Remove the right rear C-pillar trim panel. Visually inspect the right rear crash sensor for physical damage. Check the wiring harness connector (usually located above the rear sill beam or in the middle of the C-pillar) for a secure connection. Measure the connector terminal voltages (expect 12V constant power, ground, and CAN-H/CAN-L) and confirm no short or open circuits.+5 more →
B16F300›
DTC B16F300 indicates an abnormal communication link between the airbag control unit (SRS ECU) and the Rear Right Impact Sensor. This sensor typically uses a LIN bus or a dedicated digital communication protocol to exchange data with the SRS ECU to monitor collision acceleration on the rear right side of the vehicle. The ECU sets this communication fault when it fails to receive a valid data frame from the sensor within the specified time or receives data with a checksum error. This fault causes the SRS system to enter a degraded mode and disables the rear right collision detection function. In extreme cases, it may affect the correct deployment timing of the side airbags/side curtain airbags. This is a safety-related fault.
Causes
— Poor contact, loose connection, or oxidized terminals at the right rear crash sensor wiring harness connector, interrupting signal transmission.— Internal sensor circuit fault (e.g., chip damage or corrosion from water ingress) preventing response to ECU communication requests.— Wiring harness open or short circuit (especially after rear-end collision repairs, which may pinch or cut the harness)+2 more →
Actions
— Use VDS2000 or the BYD dedicated diagnostic tool to read all fault codes. Confirm B16F300 is a current fault and cannot be cleared. Check for related historical fault codes.— Visually inspect the right rear crash sensor (usually located at the C-pillar, rear fender liner, or rear body panel). Verify no physical damage, no signs of water ingress, no deformation of the mounting bracket, and that the fixing bolt torque meets the standard (usually 8-10 N·m).+5 more →
B16F511›
DTC B16F511 indicates an abnormally low-resistance connection between the first signal line (low-side reference line/signal return) of an SRS crash sensor (typically a front or side crash sensor) and body ground. This short to ground causes the SRS control unit (ACU) to detect an abnormal voltage near 0V, preventing it from correctly receiving the sensor acceleration signal. The system enters fail-safe mode and disables the corresponding airbag deployment function. In extreme cases, misinterpreting the crash signal may trigger unintended airbag deployment. This critical circuit fault in the active safety system directly affects the normal protective function of the occupant restraint system.
Causes
— Moisture ingress, burn damage, or mechanical damage to the crash sensor internal circuit board causes the signal terminal to short to the sensor housing (ground).— Sensor wiring harness chafes at a body panel hole, harness bracket, or firewall pass-through, damaging the insulation and allowing the wire to directly contact the chassis ground.— Improperly secured wiring harness or missing retaining clips after accident repairs cause the harness to chafe against sharp metal edges over time, resulting in a progressive short circuit.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000/VDS2100) to read all fault codes. Check for accompanying code B16F811 (Circuit 2 short to ground) or other SRS-related fault codes. Record the crash trigger record from the freeze frame data.— Turn off the ignition, disconnect the negative battery terminal, and wait at least 3 minutes for the system to discharge. Based on the fault code location, remove the corresponding front collision sensor (B16 series) or side collision sensor (B17 series).+4 more →
B16F612›
DTC B16F612 indicates a short to vehicle battery positive (B+, usually 12V) in the first signal circuit of an airbag system (SRS) sensor. On the BYD Qin PRO, this typically points to the first signal circuit (pressure sensor signal wire or communication wire) of the front passenger Occupant Classification System (OCS) sensor. During normal operation, this circuit voltage varies between 0-5V. A short to power pulls the voltage to 12V, preventing the SRS control unit (ACU) from correctly identifying the seat occupancy status. This fault triggers the safety system protection mechanism, which may disable the passenger-side airbag or seat belt pretensioner, or illuminate the airbag warning lamp continuously. This creates a risk of the airbag failing to deploy during a collision or deploying unintentionally.
Causes
— Under-seat wiring harness wear: Frequent forward and backward movement of the front seat chafes the harness sleeve, shorting the internal wires to a power wire (such as constant B+ or IGN+).— Internal sensor short circuit: A damaged internal circuit in the seat occupancy sensor (OCS) module shorts the signal terminal to the power supply terminal.— Connector water ingress and corrosion: Vehicle wading, car washing, or a sunroof leak allows water into the under-seat connector, causing a short circuit between terminals.+2 more →
Actions
— Use VDS or a dedicated diagnostic tool to read the complete fault code and freeze frame data. Confirm the fault occurred on the passenger side (B16F6 usually corresponds to the passenger side; B16F5 usually corresponds to the driver side).— Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to ensure the SRS capacitor fully discharges.+6 more →
B16F700›
For BYD Qin PRO (2018–2019) models, DTC B16F700 indicates a "Sensor line 1 configuration error" in the SRS (Supplemental Restraint System/airbag system). "Line 1" typically refers to the main power wire, signal wire, or CAN communication line of a crash sensor (e.g., front or side impact sensor). This fault indicates the ACU (Airbag Control Unit) detects the sensor circuit's electrical configuration does not match the calibration parameters. Possible causes include incorrect pin assignments, incorrect wiring harness connection order, or incorrect coding and matching after sensor replacement. This safety-critical fault disables the related airbag circuit, preventing deployment during a collision.
Causes
— After replacing the crash sensor or airbag control module, failing to perform the 'Sensor Configuration' or 'Coding' procedure using the VDS diagnostic tool caused a configuration parameter mismatch.— Incorrect pin installation in the sensor wiring harness connector during repair (e.g., reversed CAN High and CAN Low wires, or incorrect power and signal pin positions), causing a circuit logic configuration error.— Incorrect sensor part number installed (e.g., high-spec model sensor installed on a low-spec model); hardware pin definition does not match the vehicle wiring harness.+2 more →
Actions
— Connect the VDS2000/VDS1000 diagnostic tool and enter the SRS (airbag) system. Read and record all fault codes. Verify B16F700 is a current fault, not a history fault, and check for other related sensor fault codes.— Use the repair manual to locate the specific sensor corresponding to the 'first circuit' (usually the left front impact sensor or driver-side side impact sensor). Verify the wiring harness connector color and pin positions match the standard configuration. Confirm there are no backed-out or misaligned pins.+4 more →
B16F811›
DTC B16F811 indicates an unintended electrical connection (short circuit) between body ground and the second circuit of a Supplemental Restraint System (SRS) sensor, typically the low-side drive line or signal return line. In BYD’s SRS architecture, this usually indicates a wiring fault in the seat belt pretensioner igniter, side impact sensor, or seat occupancy recognition sensor. The SRS control unit detects an abnormally low circuit resistance (approaching 0Ω) and triggers the safety protection mechanism. This disables airbag and pretensioner deployment to prevent injury from accidental activation. This constitutes a hard fault, indicating a very high probability of physical wiring damage or an internal component short circuit.
Causes
— Seat belt pretensioner squib internal short circuit (component not replaced after a collision, or component aging caused the internal bridge wire to blow or short to ground)— Damaged wiring harness insulation causing a short circuit to body metal (commonly due to harness chafing at the seat rails, B-pillar trim, or under the carpet)— Internal fault in the SRS control unit drive MOSFET or monitoring circuit (especially on accident-repaired vehicles with a repaired rather than replaced control unit)+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS6000 or ED400) to read all DTCs. Check for accompanying code B16F511 (Circuit 1 fault) or other related fault codes. Record freeze frame data to determine the fault location (driver/passenger seat belt pretensioner, left/right crash sensor).— Disconnect the battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.+6 more →
B16F912›
This is an SRS (Supplemental Restraint System / airbag system) DTC. It indicates a short to the vehicle power supply (12V/B+) in a safety-related sensor circuit—typically the second signal/communication line of the seat occupancy sensor, seat belt pretensioner sensor, or side impact sensor. In the BYD DTC structure, "B16F9" designates the second-row Occupant Classification System (OCS) or the seat belt anchorage sensor, and the "12" suffix indicates a short to power. This fault causes the Airbag Control Unit (ACU) to detect an abnormally high signal voltage. The ACU then triggers the safety protection mechanism and places the affected airbag circuit into fail-safe mode. In extreme cases, this prevents correct airbag deployment during a collision or generates false warnings. Consequently, the system illuminates the airbag warning lamp and prevents vehicle operation.
Causes
— Damaged wiring harness insulation causes a short to body power circuits (such as the seat heater power wire or constant power wire). This commonly occurs in areas with frequent seat track adjustment or harness wear inside the door sill trim.— Internal sensor electronic component breakdown or capacitor short circuit causes the signal line to short directly to the sensor internal power terminal.— Connector terminal corrosion from water ingress or misaligned pins (e.g., a bent pin contacting an adjacent power terminal), especially in vehicles with a damp environment under the seat, a history of wading, or interior liquid spills.+2 more →
Actions
— Use BYD dedicated diagnostic tool VDS2000/VDS3000 to read complete fault codes and freeze frame data, record vehicle status at the time of the fault, and perform a system self-test to confirm B16F912 is currently present and is a hard fault.— Refer to the vehicle repair manual wiring diagram to locate the specific sensor (typically the second-row seat occupancy sensor or seat belt buckle sensor). Visually inspect the connector for looseness, water ingress, or obvious burn marks.+4 more →
B16FC12›
DTC B16FC12 indicates the third wire of an SRS sensor (typically the signal or 5V reference wire) shorts to positive (B+ or 12V/5V supply). In the BYD Qin PRO SRS architecture, crash sensors, seat occupancy sensors, and side airbag sensors typically use a three-wire design (power, ground, signal). The "third wire" transmits the sensor status signal to the Airbag Control Unit (ACU) or receives the reference voltage. When this circuit shorts to power, the ACU detects an abnormally high voltage (near battery voltage or above 5V) and determines the sensor signal is unreliable. The ACU immediately illuminates the airbag warning light and sets the airbag system to fail-safe mode (deployment disabled). This prevents unintended deployment or failure to deploy during a collision. This fault compromises a core active safety function and requires immediate repair.
Causes
— Wiring harness insulation worn through: Long-term vibration and friction damage the sensor wiring harness insulation where it passes through sheet metal holes, near seat slide rails, or under the carpet, causing a short circuit to a power wire (such as constant B+ or ignition power).— Internal sensor short circuit: Integrated circuit (IC) breakdown inside the crash sensor or seat occupancy sensor causes internal continuity between the signal pin and the power supply pin. Water ingress, electrostatic breakdown, or aging typically causes this failure.— Connector terminal short circuit: Metallic debris, corrosion, or deformed terminals in the sensor or ACU plug short the signal wire to the power terminal. This commonly occurs after driving through water or cleaning the interior.+2 more →
Actions
— Use the BYD VDS2000/VDS3000 diagnostic tool to read the complete fault code stream. Confirm if B16FC12 is a Current DTC and read the freeze frame data. Record the vehicle status at the time of the fault (vehicle speed, timestamp). Use the diagnostic tool to identify the specific sensor location (e.g., 'driver-side airbag sensor' or 'seat occupancy sensor').— Disconnect the battery negative cable and wait at least 90 seconds (to fully discharge the SRS backup power supply and comply with airbag repair safety specifications). Refer to the corresponding vehicle repair manual wiring diagram and confirm the specific function of the faulty sensor's third wire (usually the signal wire Sig or 5V Ref).+5 more →
B16FD00›
DTC B16FD00 indicates the SRS (airbag system) control module detects a mismatch between the electrical characteristics of a sensor's third wire (typically the sensor identification/configuration wire) and the preset ECU configuration. In BYD Qin PRO models, this usually involves the ID recognition wire for the seat occupancy sensor (SBR) or seat belt pretensioner sensor. The third wire transmits the sensor part number, installation position, or calibration parameters to the SRS ECU, typically via a specific resistance value or voltage range. The ECU logs a configuration error when it detects an open circuit, short circuit, or resistance/voltage outside the calibrated range on this wire. Causes include installing non-genuine parts, misaligned pins, or resistance drift from wiring harness aging. Unlike standard short or open circuits, this fault indicates a hardware identity recognition failure. It can force the SRS into a degraded mode, affecting normal airbag deployment logic.
Causes
— Installation of a non-genuine seat or seat belt assembly: The third-wire identification resistor in an aftermarket or used part does not match the factory calibration value, preventing the ECU from identifying the sensor.— Physical damage to the under-seat wiring harness: Frequent forward and backward seat adjustment on the Qin PRO may cause the third wire (usually a thin-gauge signal wire) to break or make poor contact at the slide rail, resulting in abnormal resistance.— Pin misalignment or backed-out terminal: Disconnecting or reconnecting the sensor connector during repairs leaves the third wire terminal unseated or misaligned with other terminals, causing the ECU to read an incorrect voltage.+2 more →
Actions
— Use the ED400/ED600 diagnostic tool to read the complete fault information. Confirm whether B16FD00 is a current (Active) fault and record any accompanying SRS fault codes to determine the exact sensor location (driver/passenger seat, left/right).— Visually check the airbag warning light status on the instrument cluster to confirm whether the system has entered fail-safe mode (the light usually remains on).+6 more →
B16FE11›
DTC B16FE11 indicates a short to ground in the fourth circuit of the airbag system (SRS) crash sensor. In the BYD SRS architecture, the "fourth circuit" typically refers to the signal return or diagnostic feedback circuit of the right rear side crash sensor (located in the right C-pillar/rear bumper area). This circuit abnormally connects to body ground (GND), causing the SRS control unit to detect an abnormal sensor signal voltage (continuous low level) and fail to receive the crash acceleration signal correctly. This fault triggers the SRS degraded mode, potentially causing complete airbag system failure (non-deployment) or a risk of unintended deployment. This constitutes a safety-critical fault. In this DTC, "B" represents the body system, "16F" identifies the SRS subsystem, and "E11" specifically indicates a short to ground in the right rear sensor circuit.
Causes
— Right C-pillar wiring harness chafed: Prolonged driving on rough roads or bottoming out damages the right rear side impact sensor wiring harness insulation, causing the copper core to contact the vehicle body metal and create a short to ground.— Connector water ingress and oxidation: The right rear crash sensor is located at the lower C-pillar or inside the rear bumper. Car washing, wading, or poor sealing allows moisture to enter the K05 connector, causing a short circuit between pins or a short to ground.— Internal sensor fault: A damaged integrated circuit inside the crash sensor causes the fourth signal wire to short to ground internally. This commonly occurs after a minor collision damages the sensor and it is not replaced promptly.+2 more →
Actions
— Safe power-off and wait: Disconnect the 12V battery negative terminal and wait at least 3 minutes (5 minutes for some models) to fully discharge the SRS backup power supply and prevent accidental airbag deployment during repair.— Fault confirmation and location: Use a VDS2000/Launch X431 diagnostic tool to read the fault code and confirm B16FE11 is a current fault. Consult the wiring diagram to confirm the right rear crash sensor location (Qin EV/E2: below the right C-pillar; E3: on the right rear longitudinal beam).+6 more →
B16FF12›
DTC B16FF12 indicates a short to the vehicle 12V power supply on the fourth circuit (typically the signal or CAN communication line) of an SRS (airbag system) crash sensor (such as the front crash sensor, side crash sensor, or seat occupancy sensor). In the BYD Qin PRO 4-wire sensor architecture, the fourth wire typically transmits sensor signals or diagnostic communications. When this circuit shorts to power, the SRS control unit (ACM) detects an abnormal voltage (continuous high level) and fails to receive the sensor acceleration signal correctly. This triggers the safety protection mechanism, forces the airbag system into fail-safe mode (system disabled), and illuminates the instrument cluster airbag warning lamp. This fault may prevent proper airbag deployment during a collision, posing a severe safety hazard.
Causes
— Wiring harness mechanical damage: Long-term vibration and friction against sharp edges damage the insulation on engine compartment or door wiring harnesses, causing the fourth wire to short to a power wire (such as a constant 12V wire). This commonly occurs where harnesses pass through the firewall or hinges.— Connector water ingress and corrosion: Vehicle wading or poor sealing allows water to enter the sensor connector (usually located inside the front bumper or below the B-pillar), causing an electrolytic short circuit between the pins, specifically creating a conductive path between the fourth wire and the power supply pin.— Internal sensor fault: Breakdown of the signal processing chip or filter capacitor on the collision sensor internal PCB shorts the signal output terminal (fourth wire) to the internal power supply terminal.+2 more →
Actions
— Safety Preparation: Use the BYD VDS2000 or a dedicated diagnostic tool to read the fault code. Confirm B16FF12 is a current fault and the freeze-frame data shows the vehicle status when the fault occurred. Disconnect the battery negative terminal and wait at least 3 minutes to fully discharge the SRS control unit capacitor and ensure repair safety.— Locate the faulty sensor: Refer to the Qin PRO workshop manual wiring diagram. Use the DTC sub-code to identify the specific sensor location (front left/front right crash sensor, side airbag sensor, or seat occupancy sensor). Confirm the function of the fourth wire (usually the signal wire or CAN-L).+5 more →
B170000›
DTC B170000 indicates a configuration error on circuit 4 (typically the configuration identification line, backup signal line, or sensor type identification line) of the Supplemental Restraint System (SRS) crash or acceleration sensor. The SRS control unit detects that the connected sensor hardware model, wiring harness pin assignment, or internal coding data does not match the preset system configuration. Circuit 4 typically handles sensor identification, redundant signal transmission, or address coding. Incorrect circuit connections, incorrect sensor models (e.g., installing a left-side sensor on the right side or using a sensor from an incompatible model year), or incorrect control module software calibration trigger this fault. This prevents the SRS from accurately determining the crash sensor status, potentially causing the airbags to fail to deploy during a collision or to deploy unintentionally. This is a safety-critical fault.
Causes
— Incorrect collision sensor installed: Using a non-OEM part or a sensor for the wrong model year/configuration (e.g., installing a DM version sensor on a petrol version, or swapping the left and right sensors) causes the fourth identification wire signal to mismatch ECU expectations.— Incorrect pin insertion during wiring harness repair or modification: During accident repair or wiring modification, the fourth pin of the sensor connector (usually the configuration or identification wire) swaps positions with an adjacent pin, or the wiring harness has a short or open circuit.— SRS control module software version mismatch: The control unit software lacks the update matching the current hardware configuration, or sensor parameters remain unconfigured/uncoded after replacing the control module.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000/VDS3100) to read the complete fault code stream, confirm if B170000 is a current fault, check for accompanying fault codes (such as B16FF12 or other circuit short faults), and record the freeze frame data.— Visually inspect the physical condition of the relevant crash sensor (front crash sensor, side crash sensor, or central sensor). Confirm no external impact damage. Check the connector for looseness, water ingress, or corrosion. Confirm the wiring harness is not crushed or damaged.+6 more →
B1704-00›
DTC B1704-00 indicates the SRS (Supplemental Restraint System) ECU detects an open circuit fault in the left curtain shield airbag ignition circuit. The SRS ECU continuously monitors the airbag inflator circuit resistance via an internal diagnostic circuit. When the resistance value exceeds the normal threshold (typically >10Ω or approaching infinity), the ECU registers a 'disconnected' state. This fault prevents the left curtain airbag from deploying during a side impact, depriving the occupant's head of lateral impact protection and posing a severe safety hazard. Interrupted electrical connections, damaged wiring harnesses, or a failed inflator within the airbag module can cause this fault.
Causes
— Left curtain airbag connector loose or poor contact: dedicated yellow connector above the B-pillar or C-pillar not fully locked, or pinched after interior trim panel repairs, causing terminal back-out.— Wiring harness broken or worn: Long-term repeated bending at the door hinge breaks the internal copper wires in the harness between the A-pillar and the roof side rail, or the edge of the wiring hole wears through the insulation layer, causing an open circuit.— Internal airbag module fault: Aging, moisture ingress, or manufacturing defects cause abnormal resistance or an open circuit in the igniter (squib) inside the curtain airbag inflator.+2 more →
Actions
— Safety preparation: Turn off the ignition, disconnect the 12V battery negative cable, and wait at least 90 seconds for the SRS backup power capacitor to fully discharge to prevent accidental airbag deployment.— Fault Confirmation: Use BYD VDS or a dedicated diagnostic tool to read the fault code. Confirm B1704-00 is a current fault (Active). Record freeze frame data (crash sensor status, vehicle speed, etc.).+5 more →
B1704›
DTC B1704 indicates the Supplemental Restraint System (SRS) detects a communication circuit abnormality between the left curtain airbag (CAB) and the Airbag Control Unit (ACU). Specifically, the ACU detects the left curtain airbag squib circuit resistance falls outside the standard range (normally 2-3Ω), indicating an open circuit, short circuit, or poor connection. As a safety-critical fault, this condition prevents the left curtain airbag from deploying during a side impact, severely compromising occupant head protection. Potential causes include wiring issues, poor connector contact, or an internal squib failure within the curtain airbag assembly.
Causes
— Left curtain airbag wiring harness connector loose, oxidized, or making poor contact: Commonly occurs at A-pillar and B-pillar connectors, where long-term vibration or damp environments cause terminal oxidation or loose retaining clips.— Hidden open circuit or wiring harness wear: Internal wires in the A-pillar trim panel harness break at bend points or from repeated removal and installation, or the roof harness wears at the firewall pass-through hole.— Left curtain airbag unit fault: Open circuit or abnormal resistance in the internal igniter; usually occurs with curtain airbag aging or previous external impact.+2 more →
Actions
— Safety preparation: Disconnect the negative battery cable and wait at least 3-5 minutes to fully discharge the SRS system capacitor and prevent accidental airbag deployment.— Initial visual inspection: Verify the curtain airbag wiring harness connectors on the left A-pillar, B-pillar, and roof seat securely. Inspect the connectors for oxidation, corrosion, or signs of water ingress. Confirm the locking tabs fully engage.+6 more →
B17041B›
DTC B17041B indicates the SRS (Supplemental Restraint System) ECU detected an open circuit or abnormal resistance in the left curtain shield airbag circuit (typically >4.8Ω or <1.0Ω). This fault indicates an interrupted electrical connection between the left curtain airbag inflator and the SRS control unit. Causes include a disconnected connector, a wiring harness open circuit, or an internal open circuit within the curtain airbag assembly. This condition prevents the left curtain airbag from deploying during a side impact or rollover event, severely compromising occupant head protection. Because the SRS uses a dual-stage deployment circuit, this DTC typically triggers a circuit resistance warning. Read the live data stream with a dedicated diagnostic tool to confirm the exact resistance value.
Causes
— Left-side curtain airbag connector loose or disconnected: Commonly occurs when the yellow airbag connector is not fully locked after removing and installing the headliner, repairing the A/C-pillar trim panels, or removing and installing the seats (listen for the 'click' of the secondary lock).— Wiring harness open circuit or wear: The left curtain airbag wiring harness routes through the B-pillar, C-pillar, and roof edge. Long-term vibration from door operation may break the internal copper core, or trim panel clips may crush the insulation layer, causing a hidden open circuit.— Internal open circuit in the left curtain airbag assembly: Burnt gas generator igniter wire or broken internal bridge wire (typically resulting from component aging or previous external impact). Static resistance measurements usually indicate infinite resistance or deviate significantly from the standard value (2.0 ± 0.3 Ω).+2 more →
Actions
— Safety Preparation: Turn the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor. Wear an anti-static wrist strap to prevent accidental airbag deployment.— Fault confirmation: Connect the VDS2000/Launch X431 diagnostic tool, read the fault code status (Current/History), check the live resistance value of the left curtain airbag (normal range 1.5-3.0Ω), and record the freeze frame data.+5 more →
B1705-00›
This DTC indicates the Supplemental Restraint System (SRS) detects a short to ground in the left curtain airbag deployment circuit. Specifically, during self-diagnostics or monitoring, the SRS control module (ACU) detects insulation resistance between the left curtain airbag igniter circuit and vehicle ground (GND) below the system threshold (typically <2Ω). This causes abnormal current leakage to ground instead of normal flow through the airbag deployment circuit. This fault may result in: 1) the left curtain airbag failing to deploy normally in a collision, compromising head protection for front and rear left occupants; 2) the SRS entering fail-safe mode, disabling related airbag functions, and illuminating the instrument cluster airbag warning light; 3) unintended airbag deployment in extreme cases due to abnormal circuit heating. The fault involves the left curtain airbag module, wiring harness, connectors, or internal SRS control module circuits.
Causes
— Left curtain airbag wiring harness worn or pinched: Inside the A-pillar, B-pillar, or C-pillar trim panels, the wiring harness rubs against the body metal frame, seat mounting bracket, or roof reinforcement, damaging the insulation and causing the conductor to directly contact body ground.— Connector water ingress or corrosion: Vehicle wading, a blocked sunroof drain tube, or poor body sealing causes water to enter the left curtain airbag connector (usually located in the left body side panel, headliner, or C-pillar trim), forming a conductive path between terminals or producing verdigris.— Curtain airbag module internal fault: Abnormal drop in inflator internal igniter resistance (below 1.0Ω) or internal short circuit, causing resistance to ground to fall outside standard specifications (typical standard value: 2.0±0.1Ω).+2 more →
Actions
— Safety preparation and system discharge: Park the vehicle in a safe area, apply the parking brake, turn the ignition switch to OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS system energy storage capacitor and prevent accidental airbag deployment.— Fault Confirmation and Data Recording: Use a BYD VDS2000 or Launch X431 diagnostic tool to read the fault code. Confirm B1705-00 is a Current fault, not a History fault. Record the Freeze Frame Data, including parameters such as vehicle speed and temperature when the fault occurred.+4 more →
B1705›
DTC B1705 indicates the airbag control module (SRS ECU) detects a short to ground in the left curtain shield airbag ignition circuit. During self-diagnostics or real-time monitoring, the ECU detects the insulation resistance between the left curtain airbag ignition line (typically designated as pins FL- or F5) and body ground falls below the threshold (typically <2Ω). This indicates a short-to-ground path in the ignition circuit, which may cause: 1) Curtain airbag fails to deploy during a collision (current shorts to ground and cannot ignite the gas generator). 2) Risk of unintended curtain airbag deployment under abnormal conditions (intermittent poor contact at the short point generates sparks). This constitutes a hard fault in the active safety system. The ECU immediately illuminates the SRS warning light and disables the entire airbag system (including driver, passenger, and side airbags), eliminating side-impact protection.
Causes
— Wiring harness physical damage: The left curtain airbag wiring harness (typically routed along the A-pillar, B-pillar, and roof side rail) rubs against sharp metal body edges, damaging the insulation and causing the copper core to contact the chassis directly. This commonly occurs after vehicle wading, interior trim removal and installation, or accident repairs.— Connector water ingress and corrosion: A poorly sealed airbag wiring harness connector inside the left front door sill trim or below the B-pillar allows water ingress during car washing, wading, or high-humidity conditions. This causes a short circuit between pins or between pins and the housing (ground), forming an oxide layer that creates abnormal resistance to ground.— Internal gas generator fault: Insulation failure of the igniter (squib) inside the left curtain airbag assembly shorts the igniter pins to the curtain airbag metal bracket or vehicle body. Curtain airbag aging, previous impact damage, or manufacturing defects usually cause this.+2 more →
Actions
— Safety Preparation: Move the vehicle to a well-ventilated area, turn off the ignition, disconnect the 12V battery negative terminal, and wait at least 90 seconds (to fully discharge the SRS ECU energy storage capacitor and prevent accidental airbag deployment and personal injury).— Initial visual inspection: Remove the left A-pillar, B-pillar, and left headliner trim panels. Inspect the left curtain airbag wiring harness along its routing (from the SRS ECU to the left C-pillar). Focus on contact points with the metal frame, harness retaining clips, and pass-through holes. Look for insulation damage, burn marks, or signs of crushing.+4 more →
B170511›
This DTC indicates a short to body ground in the Left Curtain Shield Airbag ignition circuit. In the BYD SRS (Supplemental Restraint System) architecture, B170511 constitutes a critical safety fault, indicating an abnormally low-resistance path (typically <1Ω) in the wiring from the Airbag Control Unit (ACU) to the left curtain airbag igniter. The left curtain shield airbag mounts above the driver's side headliner, extending from the A-pillar to the C-pillar. A short to ground results in the following: 1) The curtain airbag fails to deploy normally during a collision (ignition current diverts to the vehicle body); 2) The ACU continuously detects abnormal circuit resistance, illuminates the airbag warning light, and disables the entire SRS; 3) Unintended deployment occurs in extreme cases due to momentary circuit energization. This fault involves a pyrotechnic device ignition circuit (trigger current approx. 1.5-2A, pulse voltage approx. 24-30V). Strictly follow high-voltage safety procedures. Disconnect the battery and wait for the capacitors to discharge before repairing.
Causes
— Mechanical damage to the left A-pillar/B-pillar wiring harness: During removal and installation of the left A-pillar, B-pillar, or C-pillar interior trim panels, or during collision repairs, metal clips or sharp sheet metal edges can cut the insulation of the curtain airbag wiring harness (wrapped in yellow corrugated conduit). This shorts the copper core to body ground. This condition is relatively common on Qin PRO series models.— Connector water ingress and oxidation: An aged sealing ring on the left curtain airbag connector (usually located at the base of the A-pillar or front of the headliner, part number GJ101/GJ102 series) allows water entry. Car washing or wading oxidizes the pins, forming a conductive path and causing a short to ground.— Improper modification damage: When installing left A-pillar ambient lighting, routing dashcam wiring on the left side, or modifying the audio system, fixing screws or harness retaining clips pierce the dedicated SRS wiring harness, or aftermarket wiring harnesses compress the factory curtain airbag harness, damaging the insulation.+2 more →
Actions
— Safe power-down and wait: Turn off the ignition and disconnect the negative battery cable. Wait at least 3 minutes to ensure the ACU capacitor fully discharges. Wear an anti-static wrist strap. Do not use radio equipment in the repair area.— Fault status confirmation: Connect the VDS2000/VDS2100 diagnostic tool. Read DTC B170511 and freeze frame data. Distinguish between current (Current) and history (History) faults. Record environmental parameters such as vehicle speed and temperature at the time the fault occurred.+7 more →
B1706-00›
This DTC indicates the Airbag Control Unit (ACU) detects an abnormal short circuit between the ignition drive circuit of the Left Side Curtain Airbag (located inside the driver-side roof side rail) and the vehicle constant power supply (B+). Under normal conditions, the ACU internal boost circuit supplies a high-voltage pulse to the airbag ignition circuit only at the moment of deployment, and the circuit remains insulated from body ground and power lines. When the diagnostic system detects a continuous 12V battery voltage in this circuit, it identifies a short to power. This fault causes the ACU to trigger primary/secondary safety protection and disable the left curtain airbag circuit to prevent accidental deployment, resulting in a loss of head protection during a side-impact collision. If the short-circuit current reaches the deployment threshold, extreme cases may cause unexpected airbag deployment, constituting a severe safety defect.
Causes
— The left curtain airbag wiring harness chafes against a body constant power wire (such as the reading light, sun visor light, or roof ambient light power wire) inside the A-pillar or C-pillar trim panel, causing insulation damage and a short to positive.— Detached headlining wiring harness retaining clip above the front seats causes the harness to sag and rub against the sharp metal edge of the roof crossmember, exposing the positive wire and causing it to contact the curtain airbag circuit.— Vehicle wading or a blocked sunroof drain hose causes water ingress and corrosion at the left curtain airbag connector (usually located inside the B-pillar or C-pillar), creating a conductive path between the pins.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the 12V battery negative terminal, and wait at least 3 minutes to fully discharge the ACU energy storage capacitor. Do not work on the airbag system with the ignition switch ON.— Fault confirmation: Use the BYD dedicated diagnostic tool (VDS2000 or VDS2100) to read the DTC. Confirm B1706-00 is a current fault, not a history fault. Check the voltage value in the freeze frame data (usually displays as abnormally high voltage B+).+5 more →
B1706›
DTC B1706 indicates the SRS (Supplemental Restraint System) detected abnormal continuity between the left curtain airbag (CAB) driver circuit and the vehicle battery positive (B+). This "short to power" means at least one of the two wires in the CAB deployment circuit (typically the high-side and low-side driver wires) is shorted to the 12V power supply, or the squib inside the CAB module has an internal short circuit. The SRS ECU continuously monitors the CAB circuit resistance (normally 2-3 Ω) via its internal diagnostic circuit. If the ECU detects an abnormally high voltage (approaching battery voltage) or abnormal resistance, it immediately sets this DTC and illuminates the airbag warning lamp. Because a short circuit can cause unintended CAB deployment or prevent deployment during a collision, the system enters fail-safe mode and disables the left CAB. This severely compromises occupant head protection during a side impact.
Causes
— Worn left curtain airbag wiring harness or damaged insulation contacting the A-pillar, roof side rail, or power wires in the wiring channel (such as reading light or sunroof motor power wires), causing a short circuit.— Moisture ingress or aging failure of the internal squib in the left curtain airbag module (inflator) causes an internal short circuit, usually presenting as abnormal resistance (<1Ω or >10Ω) at the curtain airbag connector.— Internal driver circuit fault in the SRS control unit (ACM) falsely reporting a short circuit; or bent or backed-out curtain airbag connector pins contacting an adjacent power supply pin.+2 more →
Actions
— Safety precautions: Disconnect the 12V battery negative terminal and wait at least 90 seconds (some models require 3 minutes) to fully discharge the SRS capacitor and prevent accidental airbag deployment during repair.— Fault confirmation and freeze frame analysis: Use VDS or a dedicated diagnostic tool to read the fault code. Confirm whether B1706 is a current (Active) or history code. Record the vehicle status when the fault occurred (temperature, voltage, vehicle speed, etc.).+5 more →
B170612›
DTC B170612 indicates the Airbag Control Module (ACM) detects abnormal continuity between the left curtain shield airbag squib circuit and the vehicle power supply (B+). In the SRS system, the squib remains isolated from the power supply during normal operation. The ACM provides a brief pulse current only at the moment of deployment. A short to power continuously energizes the circuit, resulting in the following: (1) The curtain airbag fails to deploy during a collision, resulting in a loss of side protection. (2) Short-circuit current may damage the internal ACM driver circuit. (3) The system enters fault protection mode, continuously illuminates the instrument cluster SRS warning light, and may sound a buzzer on some models. This fault constitutes a hard short and typically does not clear automatically. Repair immediately.
Causes
— Worn wiring harness insulation between the left A-pillar and roof side rail causes the curtain airbag power wire to short to the body 12V power wire or a constant live circuit.— Seal failure at the left curtain airbag connector (usually located above the A-pillar or inside the headliner) allows water ingress, causing an electrolytic short circuit between the terminals.— Incorrectly splicing into the curtain airbag wiring during non-professional modifications (such as installing A-pillar ambient lighting or a dash cam), introducing an external power supply.+2 more →
Actions
— Safety preparation: Turn off the ignition switch, disconnect the negative battery terminal, wait at least 90 seconds (to fully discharge the SRS capacitor), and wear an anti-static wrist strap.— Fault confirmation: Connect the diagnostic tool to read the DTC, confirm B170612 is a current fault (Current), and record freeze frame data (crash sensor status, voltage values, etc.).+6 more →
B1708-00›
BYD defines DTC B1708-00 as "Seat Driver Recline Rearward Switch Circuit Short To Ground", a body electrical system fault. This fault indicates the Seat Control Unit (SCU) detects an abnormal 0-ohm resistance (short to ground) in the driver seat recline rearward switch circuit. Possible causes include switch contacts stuck closed, damaged harness insulation causing a short to ground, or connector water ingress. This fault prevents rearward seat adjustment, causes uncontrolled continuous rearward movement, or disables the seat memory function. Some third-party data sources incorrectly label this code as "left curtain airbag resistance is 0". Airbag faults typically use the B10XX-B19XX range or dedicated SRS fault codes, and standard OBD-II assigns B1708 to the seat adjustment circuit.
Causes
— Burnt internal contacts, a deformed spring plate, or water ingress in the driver seat backrest rearward adjustment switch causing a permanently closed short circuit.— Frequent forward and backward seat movement chafes the under-seat wiring harness, wearing through the insulation and exposing the copper wire, resulting in a short to ground.— Poor sealing of the seat wiring harness connector. Water ingress and oxidation after washing the vehicle or wading causes a short circuit between pins or a short to ground.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (BYD-EDS or Launch X-431) to read the fault codes. Confirm if B1708-00 is a current (Active) or historical (History) fault, and check for other accompanying seat fault codes.— Visually inspect the wiring harness under the driver's seat and near the seat rails. Check friction points against the metal frame and areas with an excessively small bend radius for damage, discoloration, or signs of water ingress.+5 more →
B1708›
DTC B1708 indicates the airbag control unit (SRS ECU) detects a 0-ohm resistance in the left side curtain airbag ignition circuit. This typically indicates a short circuit in the ignition circuit (short to ground or short between positive and negative terminals). Under normal operating conditions, the airbag igniter resistance must measure between 2.0 and 3.0 ohms to generate sufficient Joule heat to trigger the gas generator during a collision. A 0-ohm reading means the circuit has virtually no resistance. Potential causes include an internal short circuit in the curtain airbag igniter, wiring harness damage causing direct contact between positive and negative terminals, connector water ingress and corrosion, or a fault in the SRS ECU internal detection circuit. This fault prevents the left side curtain airbag from deploying normally during a side impact (current bypasses the igniter) or, in extreme cases, creates a risk of unintended deployment. This critical fault severely compromises passive safety functions.
Causes
— Internal short circuit in the left side curtain airbag igniter: Damaged insulation on the ignition bridge wire inside the gas generator or moisture in the propellant shorts the internal positive and negative terminals. Measured resistance is close to 0Ω.— Harness wear short circuit: Vehicle vibration, collision crushing, or sharp sheet metal edges damage the insulation on the harness from the SRS ECU to the left curtain airbag (usually routed along the A-pillar, B-pillar, and C-pillar), causing direct contact between the positive and negative wires.— Connector water ingress or corrosion: Poor sealing of the dedicated yellow airbag connector located below the A-pillar, inside the B-pillar trim panel, or at the door sill causes internal pins to short circuit after water exposure, or long-term oxidation causes an abnormal decrease in resistance.+2 more →
Actions
— Safety Preparation and Diagnostic Confirmation: Use the VDS2000/VDS3100 diagnostic tool to read and confirm fault code B1708. Record the freeze frame data (vehicle speed, temperature, etc. at the time of occurrence). Disconnect the negative battery terminal and wait at least 3 minutes to fully discharge the SRS backup power supply capacitor.— Visual and connector inspection: Remove the left A-pillar, B-pillar, and C-pillar trim panels. Inspect the left curtain airbag module for visible damage. Thoroughly inspect the yellow dedicated connector (usually located at the bottom of the A-pillar or middle of the B-pillar) for looseness, water ingress, bent pins, or green corrosion.+4 more →
B17081A›
DTC B17081A indicates the LHS Curtain Shield Airbag ignition circuit resistance is 0 ohms, representing a short circuit. In the BYD SRS (Supplemental Restraint System), normal curtain airbag inflator resistance is 1.8-2.5 Ω. A 0 Ω resistance indicates a short to ground in the ignition wiring between the SRS control unit and the LHS curtain airbag, or an internal short circuit within the inflator. This fault prevents the LHS curtain airbag from deploying during a collision. The control unit disables the shorted circuit to prevent accidental deployment and illuminates the airbag warning lamp. The short circuit can trigger a protective lockout of the SRS control unit, which in severe cases affects the normal operation of the entire airbag system.
Causes
— Internal short circuit in the left side curtain airbag inflator: Moisture, aging, or manufacturing defects cause a short circuit between the positive and negative terminals of the igniter bridge wire inside the curtain airbag assembly.— Wiring harness worn and shorted to ground: Long-term vibration and friction damage the wiring harness insulation in the A-pillar, B-pillar, or headliner, causing a short circuit to the vehicle body metal.— Connector fault: Water ingress, corrosion, or bent pins making contact and causing a short circuit in the curtain airbag connector (usually located in the headliner or C-pillar).+2 more →
Actions
— Safety Preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor; disable the high-voltage system (if applicable).— Initial diagnosis: Use a dedicated diagnostic tool (e.g., VDS2000/3000) to read freeze frame data and confirm environmental conditions when the fault occurred. Clear the fault code, cycle the ignition, and check if it is a current fault (Current DTC).+4 more →
B1709-00›
DTC B1709-00 indicates the resistance of the LH Side Curtain Airbag (also known as the head side airbag) squib circuit falls below the normal threshold set by the SRS ECU (typically below 1.0Ω). The standard airbag squib resistance normally ranges from 1.5Ω to 3.0Ω. Low resistance essentially indicates a short circuit. An internal squib short, a wiring harness short to ground, a short between connector terminals, or a faulty SRS ECU internal detection circuit can cause this condition. This fault causes the airbag control unit to detect an abnormal circuit, illuminate the SRS warning lamp continuously, and potentially activate the system protection mechanism (disabling the LH side curtain airbag and related airbags). In extreme cases, the short circuit can cause unintended airbag deployment in non-collision conditions (though unlikely due to the SRS ECU dual trigger logic). Alternatively, current shunting can prevent proper airbag deployment during a side impact, severely compromising occupant head safety.
Causes
— Moisture ingress or aging inside the left curtain airbag gas generator (inflator) causes a short circuit in the internal resistance wire, dropping resistance below 1.0 Ω.— Prolonged vibration, compression, or wear damages the insulation of the positive and negative wires in the roof side rail or B-pillar trim wiring harness, causing a short circuit between wires or a short to ground.— Vehicle wading, leakage from a blocked sunroof drain tube, or improper car washing causes water ingress in the wiring harness connector near the left A-pillar, B-pillar, or C-pillar (usually a yellow waterproof plug), resulting in an electrolytic short circuit between terminals.+2 more →
Actions
— Safety Preparation: Turn off the vehicle, disconnect the negative battery cable, and wait at least 90 seconds (to fully discharge the SRS backup power supply) to prevent accidental airbag deployment during inspection.— Initial inspection: Remove the left A-pillar trim, left upper B-pillar trim, and left edge of the headliner. Visually inspect the left curtain airbag wiring harness and connector (yellow identifier) for obvious damage, burn marks, water ingress, or terminal back-out.+5 more →
B1709›
DTC B1709 indicates the left side curtain airbag (located at the top left of the vehicle, protecting front and rear occupant heads during side impacts) igniter circuit resistance falls below the SRS control unit threshold. (Standard resistance is typically 2.0–3.0 Ω; "low resistance" generally indicates a measured value below 1.5 Ω or near 0 Ω.) This indicates a short in the igniter circuit. Possible causes include a shorted internal squib, a wiring harness short to ground, a wire-to-wire short, or an internal connector short. This fault forces the SRS system into a degraded mode: during a collision, the left side curtain airbag may fail to deploy (loss of protection), or in extreme cases, deploy unintentionally. The system illuminates the airbag warning lamp to indicate an occupant safety system hazard, requiring immediate repair.
Causes
— Internal short circuit in the left side curtain airbag igniter: Manufacturing defects, aging, or moisture ingress in the igniter charge or bridge wire abnormally lower internal resistance.— Wiring harness physical damage causing short circuit: Improper removal/installation, wear, or crushing damages the wiring harness insulation near the A-pillar trim, headliner, or sunroof frame, resulting in a short to ground or short between wires.— Connector fault: Water ingress (leaking from a blocked sunroof drain), corrosion, bent pins, or backed-out pins at the wiring harness connector above the left B-pillar or in the headliner cause a short circuit between terminals.+2 more →
Actions
— Safety preparation: Power down the vehicle, disconnect the 12V battery negative terminal, and wait at least 3 minutes (to ensure the SRS capacitor fully discharges and prevent accidental airbag deployment). Wear an anti-static wrist strap.— Initial diagnosis: Use VDS or a dedicated diagnostic tool to read the complete fault codes and freeze frame data. Confirm whether B1709 is a Current or History fault. Record the vehicle status at the time of the fault.+6 more →
B17091A›
DTC B17091A indicates the airbag control unit (SRS ECU) detects the resistance of the left-hand curtain shield airbag igniter circuit is below the system calibration threshold (typically below 1.5Ω; standard operating range is 1.5-3.0Ω). An internal short circuit in the curtain airbag igniter, a wiring harness short to ground, or shorted connector terminals can cause this low-resistance fault in the igniter circuit. After the SRS system enters fail-safe mode, the left-hand curtain shield airbag may fail to deploy during a side impact, posing a severe safety risk.
Causes
— Internal short circuit in left side curtain airbag igniter (airbag module aging, moisture ingress, or mechanical impact damages the internal igniter coil insulation, causing a short circuit)— Wiring harness short to ground (harness chafing inside the A-pillar, C-pillar, or headliner trim panel damages the insulation, causing a short to body ground)— Connector fault (water ingress and corrosion in the connector between the SRSECU and curtain airbag, deformed terminals causing a short circuit, or loose terminals causing poor contact)+2 more →
Actions
— Safety preparation: Turn the ignition switch to OFF, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS backup power supply capacitor.— Fault confirmation: Use the BYD VDS diagnostic tool to read the fault codes. Confirm B17091A is a current DTC, not a history code. Record the resistance value from the freeze frame data.+7 more →
B170A-00›
DTC B170A-00 indicates the Supplemental Restraint System (SRS) detected the resistance in the left curtain shield airbag igniter circuit exceeds the calibrated threshold (normal range is typically 2.0-3.0Ω; fault threshold is generally >3.5Ω or open circuit). The SRS ECU continuously monitors the circuit impedance of each airbag igniter using a low-current detection circuit. Excessive resistance indicates a high-resistance condition in the circuit. Potential causes include poor connector contact, a partially broken wiring harness, or increased internal resistance from igniter aging. This fault prevents the left curtain shield airbag from deploying normally during a collision and constitutes a critical failure in the passive safety system.
Causes
— Loose or oxidized left curtain airbag igniter connector: Moisture or vibration increases contact resistance at the connector located inside the left C-pillar trim panel or on the left roof side rail.— Wiring harness wear or breakage: Long-term bending from opening and closing the door partially breaks the copper wires where the left curtain airbag harness passes through the left front door hinge, A-pillar, or B-pillar routing holes (common failure area on Qin series models).— Clock spring (spiral cable) internal fault: If the vehicle's steering wheel-to-body wiring harness includes the curtain airbag circuit, wear on the clock spring's internal slip ring increases resistance.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal. Wait at least 90 seconds to fully discharge the SRS backup power supply and prevent accidental airbag deployment.— Initial inspection: Use BYD VDS or Launch X431 to read the DTC freeze frame, confirm vehicle status and ambient temperature at the time of the fault, and rule out intermittent interference.+5 more →
B170A›
DTC B170A indicates the Left Side Curtain Airbag ignition circuit resistance exceeds the normal threshold set by the SRS control unit (typically >3.0 Ω, standard range 1.5–2.5 Ω). This Level 2 airbag system fault means the Left Side Curtain Airbag may fail to deploy normally or experience delayed deployment during a collision, severely compromising side-impact occupant protection. High resistance typically indicates a high-impedance point in the circuit, such as a partially broken wire, increased connector contact resistance, oxidation, corrosion, or an internal open circuit in the airbag inflator. The SRS control unit continuously monitors this circuit. Upon detecting abnormal resistance, the unit illuminates the airbag fault warning lamp and may disable the entire airbag system to prevent accidental deployment.
Causes
— Aging or poor contact of the internal resistance wire in the left curtain airbag module (gas generator) causes increased internal resistance.— Loose connection, oxidation, or water corrosion at the roof wiring harness connector (usually located inside the A-pillar or B-pillar trim), causing increased contact resistance.— Repeated door opening and closing wears and breaks the roof crossmember wiring harness, reducing the conductor cross-sectional area.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Initial inspection: Remove the left A-pillar and B-pillar trim panels, and visually inspect the curtain airbag wiring harness connector (usually a yellow plug) for looseness, backed-out pins, oxidation, or signs of water ingress.+4 more →
B170A1B›
This DTC indicates the Supplemental Restraint System (SRS) detected the igniter (squib) circuit resistance of the left curtain shield airbag (located above the driver-side window between the B-pillar and C-pillar) exceeds the calibrated threshold (typically >3.6Ω, normal range 1.5-3.0Ω). Excessive resistance usually indicates a high-resistance connection, a partial open circuit, poor connector contact, or an internal open circuit in the igniter. This fault may prevent the left curtain shield airbag from deploying during a side impact and continuously illuminates the SRS warning light. This is a critical fault affecting passive safety.
Causes
— Loose connection, backed-out pins, or oxidized terminals at the left lower A-pillar curtain airbag wiring harness connector (yellow plug), causing increased contact resistance.— Internal open circuit or poor contact in the spiral cable (clock spring) affecting signal transmission in the curtain airbag circuit (on some models, the curtain airbag circuit routes near the steering column).— Internal open circuit or aging failure of the curtain airbag igniter causes infinite or abnormally high circuit resistance.+2 more →
Actions
— Safety preparation: Turn the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation: Use the BYD VDS diagnostic tool to read freeze frame data, confirm the exact current resistance value of the left curtain airbag (e.g., 3.8Ω or OL open circuit), and check for intermittent faults.+5 more →
B170D-00›
This DTC indicates the SRS (Supplemental Restraint System) control module detects a disconnected right side curtain airbag or interrupted communication. When the ignition switch is ON, the SRS module monitors the airbag inflator circuit resistance (normal range: 2.0-4.0 Ω) to verify the airbag module's presence. If the SRS module detects an open circuit (infinite resistance), a resistance value exceeding the threshold (>10 Ω), or a loss of communication, it flags the airbag as "not connected". Potential causes include an open airbag wiring harness, a loose connector, oxidized or corroded terminals, an internal open circuit in the airbag module, or a failed internal diagnostic circuit in the SRS control module. This fault eliminates right-side head protection during a side impact or rollover. As a critical passive safety system fault, it requires immediate repair.
Causes
— Right C-pillar and headliner curtain airbag wiring harness connector loose, not fully seated, or locking mechanism failed (common due to improper reassembly after headliner repair or windshield replacement).— Airbag wiring harness chafed or broken inside the A-pillar, C-pillar, or headliner trim (repeated door operation or vibration causes harness bending fatigue and insulation damage).— Open circuit in right curtain airbag module internal igniter (airbag aging, moisture, or previous impact disconnected the internal circuit)+2 more →
Actions
— Safety preparation: Turn the vehicle OFF. Disconnect the low-voltage battery negative terminal and wait at least 90 seconds to fully discharge the SRS energy storage capacitor. Wear an anti-static wrist strap to prevent airbag deployment.— Visual inspection: Remove the right A-pillar upper trim, C-pillar trim, and right edge of the headliner. Verify the yellow dedicated curtain airbag connector (usually located at the junction of the C-pillar and headliner) is fully seated, the locking tab is fully engaged, and the wiring harness shows no obvious damage.+4 more →
B170D›
DTC B170D indicates the SRS (Supplemental Restraint System) control unit detects an open circuit or disconnection in the right-hand (RH) curtain airbag circuit. Specifically, during the self-test, the control unit fails to detect the load signal from the RH curtain airbag inflator within the specified time (typically under 6 seconds). Normal resistance is 1.6-2.4Ω. This fault prevents the RH curtain airbag from deploying during a side impact or rollover accident, severely compromising occupant head protection, and continuously illuminates the instrument panel SRS warning light. Determine whether the cause is a loose harness connector, an open circuit in the wiring, or a faulty curtain airbag module.
Causes
— Curtain airbag wiring harness connector (usually a yellow or white 2-pin connector) not fully locked or terminal backed out after removing and installing the right A-pillar or C-pillar interior trim panel. Common after window tinting, audio modifications, or accident repairs.— Roof wiring harness retaining clip failure causes the harness to rub against sharp body edges during driving vibration, resulting in an open circuit. This commonly affects models such as the Yuan and Song MAX.— Water or moisture ingress into the connector during vehicle wading or high-pressure washing causes copper pin oxidation and corrosion, resulting in high resistance or an open circuit.+2 more →
Actions
— Safety preparation: Turn off the ignition, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment during repair.— Fault status confirmation: Use VDS2000 or a dedicated BYD diagnostic tool to read the fault code, confirm B170D is a current (Active) fault rather than a historical (History) fault, and record the freeze frame data.+4 more →
B170D1B›
This DTC indicates the SRS (Supplemental Restraint System) control module detects an open circuit in the Curtain Shield Airbag RH ignition circuit. Specifically, the ACU (Airbag Control Unit) continuously monitors the circuit resistance of each airbag inflator. When the Curtain Shield Airbag RH resistance exceeds the normal range (typically >10Ω or infinite), the ACU registers a 'disconnected' state. This fault prevents the Curtain Shield Airbag RH from deploying during a side impact or rollover, severely compromising occupant head protection, and continuously illuminates the instrument cluster airbag fault warning lamp.
Causes
— Right-side curtain airbag wiring harness connector loose or poor contact (commonly the yellow plug on the right side of the headliner or B-pillar)— Right curtain airbag module internal igniter open circuit (broken internal spiral coil or propellant failure causing abnormal resistance)— Physical damage to the wiring harness (frequent door operation causing fatigue fracture inside the B-pillar, or accidental damage during headliner repairs)+2 more →
Actions
— Safety preparation: Disconnect the low-voltage battery negative terminal and wait at least 3 minutes to fully discharge the SRS backup power supply and prevent accidental airbag deployment.— Visual inspection: Remove the right A-pillar, B-pillar, and right roof trim panel. Verify the yellow connector (usually marked 'CSAB RH' or similar) is fully locked. Inspect the terminals for oxidation, burn marks, or water ingress.+3 more →
B170E-00›
DTC B170E-00 indicates an abnormally low-resistance connection between the Right Side Curtain Airbag squib circuit and body ground (GND). In the SRS (Supplemental Restraint System) architecture, two independent wires connect each airbag inflator to the ACU (Airbag Control Unit). Normal resistance typically ranges from 1.5 to 3.0 Ω. The ECU identifies a short to ground when it detects circuit resistance below the threshold (typically <1.0 Ω) or abnormal voltage to ground. This fault causes: 1) The Right Side Curtain Airbag to fail to deploy properly in a collision, resulting in loss of side-impact protection. 2) The SRS to enter fail-safe mode, keeping the instrument cluster airbag warning lamp illuminated and degrading the vehicle safety rating. 3) A risk of unintended deployment in extreme cases due to intermittent wiring contact. This is a passive safety system hard fault and requires immediate resolution.
Causes
— Wiring harness wear inside A-pillar/C-pillar trim panels: Frequent door operation or vehicle vibration wears through the insulation of the right curtain airbag wiring harness inside the corrugated conduit at the A-pillar upper trim panel, roof side rail, or C-pillar. This causes the wire to directly contact the body metal frame, creating a short to ground.— Connector water ingress and corrosion: Poor sealing of the right curtain airbag connector (usually located inside the B-pillar or C-pillar trim) allows water to enter during car washing, wading, or in high-humidity environments. This decreases insulation resistance between the pins or to ground, creating a short circuit.— Internal airbag module fault: The bridgewire inside the right curtain airbag inflator shorts to the metal housing, or chemical degradation inside the igniter charge increases conductivity. This condition typically presents with abnormally low resistance (<0.5Ω).+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds for the SRS backup power supply to fully discharge. For high-voltage models, remove the Manual Service Disconnect (MSD). Wear an anti-static wrist strap and place a 'Do Not Touch' warning sign on the steering wheel and airbag area.— Fault Confirmation and Freeze Frame Analysis: Use a VDS2000 or Launch X431 diagnostic tool to read the fault code. Confirm B170E-00 is a current code (Active) and not a history code. Check the crash sensor data, vehicle speed, and short-circuit resistance values in the Freeze Frame data. Record the ECU software version.+5 more →
B170E›
DTC B170E indicates the SRS (Supplemental Restraint System) control unit detects a short to body ground in the right curtain shield airbag ignition circuit. Specifically, the ACU detects the resistance between the right curtain airbag deployment circuit (typically marked R CSA+ and R CSA-) and ground falls below the threshold (generally <2Ω). Damaged wiring harness insulation, connector water ingress and corrosion, a shorted inflator inside the curtain airbag module, or a driver transistor breakdown inside the SRS control unit can cause this fault. Under this fault condition, the circuit protection mechanism may disable the curtain airbag (preventing deployment). In extreme cases, short-circuit current can trigger unintended deployment, posing a severe safety hazard.
Causes
— Right A-pillar/C-pillar wiring harness wear: Long-term vehicle use or repeated interior trim removal and installation wears the right curtain airbag wiring harness insulation where it passes through sheet metal holes or retaining clips, causing the copper core to directly contact the vehicle body metal.— Connector short circuit due to water ingress: A blocked sunroof drain hose or poor sealing allows rainwater to leak into the right roof side rail area, causing the curtain airbag wiring harness connector (usually located above the B-pillar or near the C-pillar) to short between terminals or short to ground.— Internal fault in the curtain airbag module: A manufacturing defect or aging causes insulation breakdown between the two terminals of the squib inside the right curtain airbag assembly, resulting in a short to ground.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the 12V battery negative terminal, wait at least 3 minutes (to fully discharge the SRS capacitor), and wear an anti-static wrist strap.— Fault confirmation: Use VDS or a dedicated BYD diagnostic tool to read the DTC, confirm B170E is an active fault (Active DTC), and record the freeze frame data.+6 more →
B170E11›
B170E11 indicates a short to ground in the ignition circuit of the right side curtain airbag. In the BYD SRS (Supplemental Restraint System) architecture, this fault code indicates the airbag control unit (ACU) detects an abnormally low-resistance path between the right side curtain airbag squib wiring and vehicle body ground (typically below the 1.5-2.0 ohm threshold). This short circuit causes the ACU to determine the curtain airbag cannot deploy normally, triggering fail-safe mode. The instrument panel airbag warning light illuminates continuously, and the system suspends deployment control for this curtain airbag. Consequently, the right side curtain airbag may fail to activate during a side collision, severely compromising crash protection for right-side occupants, particularly head protection. Potential causes include damaged wiring harness insulation, connector water ingress and corrosion, an internal short circuit in the clock spring, or a squib failure within the curtain airbag module itself.
Causes
— Right curtain airbag wiring harness wear: Loose wiring harness retaining clips inside the A-pillar, B-pillar, or C-pillar trim panels cause the harness to rub against sharp metal body edges over time, damaging the insulation and shorting the wire to ground.— Connector water ingress and corrosion: A degraded sealing ring on the right curtain airbag connector (usually located above the B-pillar or roof side rail) allows water intrusion during heavy rain, car washes, or leaks from a blocked sunroof drain tube. This corrodes the internal terminals and causes a short to ground.— Clock spring or spiral cable fault: If the right curtain airbag circuit on this model routes through the B-pillar wiring harness spiral cable (clock spring), a broken internal flat cable or abnormal winding may short the wire core to ground.+2 more →
Actions
— Safety Preparation and Power Isolation: For new energy vehicles, first disconnect the high-voltage service disconnect. For all models, disconnect the 12V battery negative terminal and wait at least 90 seconds (3 minutes for some models) to allow the SRS capacitor to fully discharge and prevent accidental airbag deployment.— Visual and physical inspection: Remove the right A-pillar and B-pillar upper trim panels and the roof side trim panel. Check the curtain airbag wiring harness for obvious wear, pinching, damage, or signs of water ingress. Focus on the contact points between the wiring harness and the vehicle body metal.+5 more →
B170F-00›
DTC B170F-00 indicates a short to power fault in the driver seat Occupant Sensing System (OSS). Integrated into the driver seat cushion, the sensor uses a pressure sensing mat and an electronic control module to detect seat occupancy. It sends a 0.4-4.6V analog voltage signal to the SRS airbag control unit (approximately 0.5V when unoccupied and 4.2V when occupied). The SRS module sets this DTC when it detects a continuous voltage above 4.8V or near battery voltage. This occurs if the signal circuit shorts to the 12V power supply line (B+), the internal sensor circuit breaks down, or the control module fails. This fault forces the SRS system into fail-safe mode: the driver airbag may fail to deploy, the seat belt reminder function may malfunction (false or missing warnings), and the instrument cluster airbag warning light remains illuminated. Because this fault affects the passive safety system, do not drive the vehicle until repaired.
Causes
— Damaged seat occupancy sensor harness insulation causes a short to the power wire, commonly due to the seat fore-aft adjustment rail rubbing against the harness.— Water ingress, oxidation, or misaligned pins in the under-seat wiring harness connector (usually 4-pin) cause a short circuit between the power pin (PIN1/12V) and the signal pin (PIN2).— Fault in the seat occupancy sensor internal pressure sensing mat or control module circuit (such as protection capacitor breakdown or voltage regulator chip damage) causing a short circuit to power.+2 more →
Actions
— Connect a BYD VDS or professional diagnostic tool (such as Launch X-431 or Autel), read the DTC to confirm B170F-00 is a current fault (Active), and record the freeze frame data (Fault Frame).— Visually inspect the wiring harness connector under the driver's seat (black 4-pin connector) for looseness, backed-out terminals, water ingress, or corrosion. Measure the connector terminal voltages: power (PIN1) should be 12V, signal (PIN2) 0.4-4.6V, and ground (PIN4) 0V. If the signal wire voltage is 12V, confirm a short to power.+5 more →
B170F›
DTC B170F indicates a short to power (B+) in the right-hand curtain airbag (SRS Curtain Shield Airbag - RH) ignition circuit. In the BYD SRS system, the curtain airbag uses an electrically ignited gas generator. During normal operation, the control unit supplies a momentary high current to trigger ignition. The diagnostic system triggers this fault when it detects abnormal continuity (resistance below the threshold, typically <10Ω) between the curtain airbag ignition circuit and the vehicle power supply (12V battery positive terminal), or when the circuit voltage remains above the set value (approximately 5V). This is a hard fault. The SRS control unit immediately disables the right-hand curtain airbag function and illuminates the instrument cluster airbag warning lamp. Potential risks include: 1) The right-hand curtain airbag fails to deploy in a collision, resulting in a loss of occupant head protection. 2) In extreme cases, if the short circuit contact resistance fluctuates, vehicle jolts can generate a momentary current, creating a minimal risk of unintended curtain airbag deployment. Therefore, the system classifies this as a severe fault and prohibits continued vehicle operation.
Causes
— Wiring harness insulation wear inside the right A-pillar or C-pillar trim panel: During long-term vehicle use, the right roof curtain airbag wiring harness rubs against sharp metal body edges (such as the roof crossmember mounting bracket). This damages the insulation between the positive and negative wires, or between the power and ignition wires, causing a short circuit to the constant power wire.— Curtain airbag connector water ingress and oxidation: A blocked sunroof drain tube or poor seal causes rainwater to seep into the right headliner. Water accumulates between the pins of the curtain airbag connector (typically located at the right D-pillar or right side of the headliner). The electrolyte forms a conductive path, causing a short to power.— Incorrect wiring harness connection after accident repair: After a right-side collision or roof headliner removal and installation, technicians mistakenly connect the curtain airbag igniter wire (normally a high-resistance circuit) to a constant power wire (such as the reading light or sun visor light power supply), or missing harness retaining clips cause the harness to shift and contact the power supply.+2 more →
Actions
— Safety pre-check and fault confirmation: Use the VDS2000/3000 diagnostic tool to read the complete SRS fault codes. Confirm B170F is a current fault (Present) rather than a history fault (History). Disconnect the battery negative terminal and wait at least 90 seconds to allow the SRS backup power supply to fully discharge and prevent accidental airbag deployment.— Right curtain airbag wiring harness visual inspection: Remove the right A-pillar, B-pillar, and C-pillar interior trim panels and the right headliner trim panel. Inspect the orange curtain airbag module wiring harness (usually marked RCurtain or R CSA) along the roof side rail (BYD SRS harness standard color is orange or yellow). Check the harness retaining clips for detachment, the insulation for wear, and the connectors for water stains or corrosion.+6 more →
B170F12›
DTC B170F12 indicates a short to power in the right side curtain airbag ignition circuit. In the BYD SRS (Supplemental Restraint System) architecture, this fault indicates the airbag control unit (ACU) detects an abnormally low-impedance connection between the right side curtain airbag igniter circuit (typically two wires: high-side driver and low-side driver) and the vehicle power supply (+12V or +B). This hardware short-to-battery fault may cause: 1) risk of unintended airbag deployment (in extreme cases); 2) airbag failure to deploy during a collision; 3) the SRS entering protection mode, disabling related airbag functions. The '12' suffix in the BYD diagnostic protocol typically designates the specific 'short to power' subtype.
Causes
— Right curtain airbag wiring harness insulation damage: Long-term vibration, compression, or external impact damages the harness insulation inside the A-pillar, B-pillar, or roof side rail, shorting the harness to the body power supply wire.— Curtain airbag connector fault: Water ingress, oxidation, or deformed pins in the curtain airbag connector located inside the B-pillar trim cause a short circuit between pins (especially between the high-side drive pin and constant power pin).— Damage from modifications or added equipment: Fixing screws or harness clips pierced the factory curtain airbag wiring harness during the installation of a dash cam, roof ambient lighting, or aftermarket audio system.+2 more →
Actions
— Safety preparation: Switch the vehicle OFF, disconnect the 12V battery negative terminal, wait at least 90 seconds (to fully discharge the SRS capacitor), and wear an anti-static wrist strap.— Visual inspection: Remove the right A-pillar, B-pillar, and headliner trim panels. Inspect the curtain airbag wiring harness for damage or burn marks. Focus on the sill trim and roof side rail retaining clips.+6 more →
B1712-00›
This DTC indicates the RH Curtain Shield Airbag igniter circuit resistance measures 0 Ω, indicating a typical short circuit. Normal airbag igniter resistance is 2.0-5.0 Ω. A 0 Ω resistance typically indicates a short to ground in the igniter circuit (damaged harness insulation), a short to power (contact with constant power), or a shorted driver transistor inside the airbag control module (SRS ECU). This fault forces the SRS system into fail-safe mode: the affected airbag will not deploy during a collision (the short circuit diverts the deployment current), and the airbag warning lamp illuminates continuously. Some models simultaneously disable the front seat belt pretensioners and the corresponding side airbag. The short circuit also carries a minimal risk of unintended deployment. Immediately remove the vehicle from service for repair.
Causes
— Wear or pinching of the right curtain airbag wiring harness at the C-pillar trim panel or roof lining retaining strip causes the wire to short to body ground.— Airbag connector (usually located at the right C-pillar or front of the headliner): fused internal terminals, electrolytic corrosion from water ingress, or short circuit caused by metal foreign objects.— Internal short circuit in the right curtain airbag igniter (gas generator bridge wire insulation breakdown). Commonly occurs after vehicle wading or exceeding the airbag service life.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to ensure the SRS backup power capacitor fully discharges; remove the smart key and place it 3 meters away.— Initial inspection: Remove the right C-pillar trim panel and the right roof trim panel. Visually inspect the curtain airbag wiring harness (yellow sleeve) for wear, cuts, or crush marks. Focus on the C-pillar hinge area and the roof wiring harness retaining clip locations.+5 more →
B1712›
DTC B1712 indicates the SRS (Supplemental Restraint System) detects a 0 ohm resistance in the right curtain airbag firing circuit (located in the roof side rail, protecting front and rear occupant heads). This indicates a hard short circuit in the firing circuit (short to ground or short to power), not an open circuit. Normal airbag inflator resistance ranges from 2.0-3.0 ohms (typical value approx. 2.3Ω). A 0 ohm resistance allows current to bypass the inflator bridge wire. This prevents proper airbag deployment during a collision or creates a major safety risk of unintended deployment. The SRS ECU continuously monitors all firing circuit impedances in real time using a highly sensitive Wheatstone bridge circuit. If the ECU detects a resistance below the safety threshold (typically <0.8Ω), it sets this DTC, illuminates the airbag warning light, immediately disables the right curtain airbag and related coordinated protection strategies, and enters safety protection mode.
Causes
— Internal short circuit in the right curtain airbag inflator: Manufacturing defects, prolonged moisture exposure, electrolytic corrosion, or abnormal current surges cause insulation breakdown and a short circuit between the positive and negative terminals of the igniter bridge wire inside the airbag module.— Wiring harness short to ground or power: Wear, crushing, rodent bites, or improper accident repairs damaged the insulation on the yellow dedicated wiring harness connecting the SRS ECU to the right curtain airbag (typically routed along the A-pillar, roof side rail, and C-pillar), causing a short to body metal or a power wire.— Connector pin short circuit: Bent pins, backed-out pins, corrosion from water ingress, metallic debris, or incorrect terminal spacing at the curtain airbag connector (located inside the headliner or C-pillar trim) cause direct contact between the positive and negative terminals.+2 more →
Actions
— Safety preparation and power disconnection: Set the vehicle to OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds (some newer models require 3-5 minutes) to fully discharge the SRS backup power capacitor and prevent accidental airbag deployment and personal injury.— Fault confirmation and freeze frame analysis: Connect VDS or a dedicated diagnostic tool, read DTC B17112 status (current/history), review the freeze frame data for the recorded resistance value and vehicle status at the time of occurrence, and check for accompanying DTCs (e.g., B1711 left curtain airbag, B1600 series crash sensors).+6 more →
B17121A›
DTC B17121A indicates the Supplemental Restraint System (SRS) detects a 0-ohm resistance in the right curtain airbag ignition circuit. Under normal operating conditions, the curtain airbag squib requires a specific resistance (typically 2.0–3.0 ohms, depending on the vehicle model). A 0-ohm resistance indicates a short circuit. Possible causes include an internal short in the curtain airbag module, a short between the positive and negative harness wires, or a short between connector terminals. This fault causes the SRS control unit to determine the curtain airbag has deployed or has a circuit fault. Consequently, the right curtain airbag fails to deploy during a collision. This severely compromises side impact protection and constitutes a high-risk safety fault.
Causes
— Right curtain airbag igniter internal short circuit: A short circuit in the igniter bridge wire or pyrotechnic charge inside the curtain airbag module drops the resistance to 0 ohms.— Damaged wiring harness insulation causing short circuit: The right roof wiring harness (A-pillar to C-pillar section) wears during vehicle operation, modification, or accidents, causing direct contact between the positive and negative conductors.— Connector water ingress and corrosion: Vehicle wading or a blocked sunroof drain tube allows water to enter the right curtain airbag connector (usually located on the roof side rail or above the A-pillar), causing a short circuit between terminals.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the low-voltage battery negative terminal, and wait at least 3-5 minutes (some models require more than 5 minutes) to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation: Connect the diagnostic tool and read the freeze frame data. Confirm B17121A is a current fault (Present), not a history fault (History). Record the vehicle status when the fault occurred.+6 more →
B1713-00›
DTC B1713-00 indicates the airbag control unit (SRS ECU) detects the right curtain shield airbag ignition circuit resistance falls below the system-calibrated minimum threshold (typically below 1.0Ω; normal range is 1.5-3.0Ω). Low resistance usually indicates an abnormally low-resistance path in the ignition circuit. Possible causes include an internal inflator short circuit within the curtain airbag module, a wiring harness short to ground, grounded internal connector pins, or a wire-to-wire short. This fault prevents normal airbag deployment (failure to inflate during a collision) or, in extreme cases, creates a risk of unintended deployment. This critical occupant safety fault requires immediate repair.
Causes
— Right curtain airbag module internal igniter short circuit (due to manufacturing defect or aging)— Harness insulation damaged, causing a short to ground (harness in the A-pillar, C-pillar, or roof side rail chafes to ground due to vibration or water ingress).— Connector short circuit (water ingress and corrosion at the SRSCM and wiring harness connector, or bent and deformed pins contacting each other)+2 more →
Actions
— Safety preparation: Disconnect the negative battery terminal and wait at least 3 minutes to discharge residual charge from the SRS system capacitor and prevent accidental deployment.— Visual inspection: Remove the right C-pillar trim panel and headliner edge. Check the curtain airbag wiring harness connector for looseness, water ingress, corrosion, or bent pins.+6 more →
B1713›
DTC B1713 indicates the right curtain airbag igniter circuit resistance falls below the normal threshold set by the SRS control unit (typically 2.0-5.0Ω). Low resistance (<2Ω or close to 0Ω) indicates a short circuit risk in the igniter circuit. Potential causes include an internal short circuit in the curtain airbag, a wiring harness short to ground, or an abnormal internal driver circuit in the SRS ECU. This fault forces the SRS system into fail-safe mode. During a collision, the right curtain airbag may fail to deploy, or it may deploy unintentionally. This constitutes a high-level safety fault.
Causes
— Internal short circuit in the right curtain airbag igniter: Aging, moisture ingress, or manufacturing defects in the squib reduce insulation between the terminals, dropping resistance below 2Ω.— Wiring harness short to ground: A-pillar, B-pillar, or roof wiring harness worn from accident repairs, modifications, or long-term use, causing the igniter circuit to short to body ground.— Connector terminal short circuit: Water ingress, oxidation, or improper connection causes a short circuit between terminals at the right curtain airbag connector (usually located near the roof side rail or C-pillar).+2 more →
Actions
— Use VDS or a dedicated diagnostic tool to read the fault code, verify B1713 is a current (Active) fault rather than a history fault, and record the freeze frame data.— Perform the safe power-down procedure: Turn off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.+8 more →
B17141B›
DTC B17141B indicates the right curtain airbag ignition circuit resistance exceeds the normal threshold set by the SRS control module (typically 3.0-5.0Ω, depending on vehicle calibration). This active SRS system fault means the right curtain airbag may fail to deploy or experience delayed deployment during a collision. Excessive resistance usually indicates a high-resistance point in the ignition circuit. Potential causes include poor wiring contact, connector oxidation or corrosion, a partially broken wiring harness, or an internal open circuit in the curtain airbag module. This fault illuminates the SRS warning light continuously and forces the system into degraded mode. Extreme cases may compromise side-impact protection.
Causes
— Loose or oxidized right C-pillar/D-pillar curtain airbag connector: Long-term vehicle vibration loosens the connector, or pin oxidation after wading increases contact resistance.— Roof side rail wiring harness chafed and broken: Prolonged flexing of the curtain airbag wiring harness at the door seal or A-pillar/C-pillar routing hole partially breaks the copper strands, causing high resistance.— Right curtain airbag module internal open circuit: A broken bridge wire inside the curtain airbag inflator or damp propellant causes abnormally high resistance.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (some models require 180 seconds) to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Read data stream: Use VDS or Launch X-431 to read the SRS system data stream. Record the current curtain airbag resistance value and historical freeze frame data. Confirm whether the fault is intermittent.+6 more →
B17131A›
DTC B17131A indicates the RHS Curtain Shield Airbag squib circuit resistance falls below the normal threshold calibrated by the SRS control module (typical standard value: 2.0 ± 0.5 Ω). This fault signifies a partial circuit short, an internal component short, or a wiring insulation failure to ground, dropping circuit resistance below approximately 1.5 Ω. This condition triggers the airbag system fail-safe mechanism. Low resistance can prevent proper curtain airbag deployment during a collision, as the short circuit diverts ignition energy. Furthermore, a severe short circuit increases the risk of unintended deployment. The SRS typically disables the affected curtain airbag circuit, eliminating occupant head protection during a side impact. This safety hazard requires immediate repair.
Causes
— Internal inter-turn short circuit in the right curtain airbag igniter, or moisture inside the gas generator, causing an abnormal resistance drop.— Worn or damaged wiring harness insulation inside the A-pillar or C-pillar trim panel contacts the vehicle body metal, causing a short to ground.— Curtain airbag module connector (usually inside the right roof trim panel): water ingress, pin corrosion, pin back-out, or short circuit between terminals.+2 more →
Actions
— Use the BYD VDS2000/VDS3000 diagnostic tool to read all fault codes and freeze frame data. Confirm whether B17131A is a current or intermittent history fault, and record the vehicle status parameters at the time of the fault.— Perform the SRS system safety procedure: disconnect the negative battery terminal and wait at least 90 seconds to ensure the SRS capacitor fully discharges to prevent accidental airbag deployment during repair.+5 more →
B1714-00›
DTC B1714-00 indicates the airbag control unit (SRS ECU) detects the circuit resistance of the RH Curtain Shield Airbag inflator (gas generator) exceeds the calibrated threshold. The normal range is typically 1.5Ω–2.5Ω; an excessive value generally indicates >3.5Ω or a near open circuit. The SRS ECU periodically measures this resistance using a low-current signal. Increased resistance indicates poor circuit contact, wiring oxidation, a partially broken wiring harness, or an aging/broken bridge wire inside the inflator. This fault may prevent the RH Curtain Shield Airbag from deploying properly during a collision, degrading passive safety system function. The SRS warning lamp illuminates continuously and the system enters fail-safe mode (which may disable this circuit's trigger function to prevent unintended deployment).
Causes
— Right-side curtain airbag inflator internal resistance increased due to aging, or bridge wire nearly broken (precursor to internal open circuit).— Oxidation, loose connection, or terminal back-out at the yellow airbag connector in the B-pillar or headliner (usually located at the junction of the A-pillar upper trim and headliner), increasing contact resistance.— Vehicle modification work (such as installing a dashcam or removing/installing the roof trim) pinches, chafes, or partially breaks the roof wiring harness, increasing circuit resistance.+2 more →
Actions
— Use the BYD VDS2000 or Launch X-431 diagnostic tool to read the complete fault codes and freeze frame data. Record the ambient temperature and voltage at the time of the fault, and confirm if the fault is intermittent.— Perform the safe power-down procedure: turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds (to ensure the SRS capacitor fully discharges). Do not operate any electrical equipment during this time.+5 more →
B1714›
DTC B1714 indicates the SRS (Supplemental Restraint System) control unit detects the right curtain airbag (head protection curtain/side curtain) inflator circuit resistance remains above the calibrated threshold (normal range typically 1.5-3.5 Ω, depending on vehicle calibration). The SRS ECU periodically monitors each airbag inflator's resistance via an internal Wheatstone bridge or constant-current source circuit. Excessive resistance indicates a high-impedance point in the inflator circuit. Potential causes include poor connector contact, a partial open circuit in the wiring harness, or an aging inflator. This constitutes a hard or intermittent fault. During a side impact, the right curtain airbag may fail to deploy within the specified time (delayed deployment) or fail to deploy entirely. The system illuminates the airbag warning light, and the front side airbags and seat belt pretensioners may enter fail-safe mode.
Causes
— Right curtain airbag connector (usually located inside the C-pillar trim or at the rear of the roof side rail) is loose, has backed-out terminals, or is oxidized or corroded, causing increased contact resistance (common in vehicles exposed to water or high humidity).— Internal copper wires in the airbag wiring harness at the A-pillar/C-pillar trim panel transition area partially break from repeated removal and installation or tension during seat adjustment, creating a high-resistance intermittent connection.— Aging or a batch defect of the right curtain airbag inflator internal squib causes its internal resistance to increase abnormally as temperature rises.+2 more →
Actions
— Safety Preparation: Disconnect the low-voltage battery negative terminal and wait at least 90 seconds (to fully discharge the SRS capacitor). Never measure the airbag circuit while energized.— Initial diagnosis: Use VDS or a dedicated diagnostic tool to read complete DTC information and freeze frame data. Confirm whether B1714 is a current or history fault. Record the ambient temperature at the time of occurrence (low temperatures may affect contact resistance).+5 more →
B1717-00›
This DTC indicates the SRS (Supplemental Restraint System) ECU detected an open circuit or disconnected condition in the left knee airbag module (Driver Knee Airbag Module) during self-diagnosis. Specifically, when the SRS ECU sends a test signal to the left knee airbag igniter circuit, it fails to receive a normal circuit response or detects a circuit resistance exceeding the normal threshold (typically infinite or extremely high resistance). Consequently, the left knee airbag may fail to deploy during a collision, resulting in a loss of lower limb protection for the driver. Additionally, the SRS enters fail-safe mode and continuously illuminates the instrument cluster airbag warning light. The system may also lock the deployment function of the entire airbag system, severely compromising passive safety performance.
Causes
— Knee airbag module connector loose, not fully seated, or locking tab damaged, causing poor pin contact or complete open circuit.— Open circuit, short to ground, or short to power in the wiring harness between the SRS ECU and the left knee airbag module— Left knee airbag module internal igniter open circuit or abnormal resistance (resistance too high or too low)+2 more →
Actions
— Safety preparation: Turn the power mode to OFF, disconnect the battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor.— Visual inspection: Remove the driver-side knee trim panel and verify the left knee airbag module connector is fully seated. Confirm the locking tab is intact and secure.+5 more →
B1717›
DTC B1717 indicates a loss of communication or an open circuit between the driver-side knee airbag and the SRS (Supplemental Restraint System) control unit. Specifically, this fault indicates an incorrect connection at the knee airbag module located under the left side of the dashboard, an open circuit in the wiring, or an internal open circuit in the airbag squib. The knee airbag, a critical component of the frontal impact protection system, limits the forward movement of the driver's lower limbs and distributes crash forces. When this fault occurs, the SRS control unit illuminates the airbag warning light and may enter fail-safe mode, disabling the related airbag circuit to prevent accidental deployment. Consequently, the knee airbag will fail to deploy during a collision, increasing the risk of lower limb injury to the driver.
Causes
— Knee airbag module connector loose, not fully seated, or locking mechanism failure (commonly caused by failing to reconnect after dashboard repairs, A/C filter replacement, or carpet removal and installation)— Knee airbag wiring harness open circuit, chafing, or crush damage (especially at harness bends under the steering column and along the instrument panel frame edge)— Knee airbag assembly inflator igniter open circuit (abnormal resistance; normal range approx. 2.0-3.0 Ω)+2 more →
Actions
— Use the BYD VDS or a dedicated diagnostic tool to read and confirm DTC B1717, check for other accompanying SRS fault codes, and record the freeze frame data.— Turn the ignition switch to OFF, disconnect the negative battery terminal, and wait at least 90 seconds to allow the SRS capacitor to discharge fully and prevent accidental airbag deployment.+6 more →
B17171B›
DTC B17171B indicates the SRS (Supplemental Restraint System) control module detects an open circuit in the left knee airbag (Driver Knee Airbag) igniter circuit. The resistance value falls outside the normal range (normal: approx. 2-3Ω; open circuit: >10Ω or infinite). This fault indicates a physical break in the wiring or connector between the airbag ECU and the left knee airbag assembly, or an internal open circuit within the airbag igniter itself. The knee airbag protects the driver's lower limbs from dashboard intrusion during a frontal collision. This fault prevents the airbag from deploying during a crash and may trigger the SRS secondary protection mechanism (e.g., disabling the associated airbag group), posing a severe safety hazard. In the BYD diagnostic protocol, the '1B' suffix specifically denotes an 'open circuit/high resistance' condition.
Causes
— Loose or disconnected knee airbag wiring harness connector: Water intrusion, vehicle modifications, or failing to fully seat the connector after repairs can cause poor contact at the dedicated yellow SRS connector located under the dashboard near the steering column.— Airbag igniter internal open circuit: Broken or aged igniter coil inside the knee airbag assembly, usually accompanied by damage to the airbag module itself. This commonly results from failing to replace the airbag after a collision or the airbag exceeding its service life (vehicles over 10 years old).— Wiring harness physical damage: Pedal operation, floor mat compression, or accident repairs strain the wiring harness under the dashboard, breaking the wire; or repeated bending in the door sill harness transition area breaks the internal copper strands while leaving the insulation intact.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the negative battery terminal, and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment during repair.— Fault confirmation and freeze frame retrieval: Use a diagnostic tool (such as VDS2000 or Launch PAD) to read the complete fault codes and freeze frame data. Confirm whether the fault is current (Active) or historical (Historic). Record the vehicle status when the fault occurred.+6 more →
B1718-00›
B1718-00 indicates a short to ground in the driver-side knee airbag ignition circuit. In the BYD SRS (Supplemental Restraint System) architecture, this fault code indicates the airbag control module (ACM) detects the left knee airbag inflator circuit resistance is below the threshold (typically < 1.0Ω), identifying a short to ground. This fault forces the entire airbag system into fail-safe mode and continuously illuminates the instrument cluster SRS warning lamp. During a collision, the knee airbag may fail to deploy, and the fault may affect the deployment strategy for other front airbags. This constitutes a hard fault. Once confirmed, it remains active; cycling the ignition does not clear it.
Causes
— A worn or crushed knee airbag wiring harness damages the insulation layer, causing contact with the metal body frame and creating a short to ground. This commonly occurs after driving through water or modifying the chassis.— Oxidation due to water ingress or bent pins in the knee airbag connector (located under the driver-side instrument panel, left of the steering column) cause a short circuit between the ignition circuit terminal and the ground terminal.— Internal short circuit in the knee airbag module igniter, usually due to the internal bridgewire shorting to the housing or a manufacturing batch defect.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF. Disconnect the 12V battery negative terminal and wait at least 90 seconds for the SRS capacitor to fully discharge. Wear an anti-static wrist strap to prevent accidental airbag deployment.— Fault Confirmation: Use the BYD dedicated diagnostic tool (VDS2000/ED400) to read the fault code. Confirm B1718-00 is a current fault (Active). Record the resistance value in the freeze frame data (typically 0Ω or extremely low).+5 more →
B1718›
B1718 is a BYD-specific SRS (Supplemental Restraint System / airbag system) fault code indicating an unintended low-resistance path (short to ground) between the driver-side knee airbag (Left Knee Airbag) ignition circuit and vehicle ground (GND). The knee airbag contains an igniter (squib). Under normal conditions, both igniter terminals must show an open circuit (infinite resistance) to ground. A short to ground indicates current may bypass the igniter and flow directly to ground, causing the airbag control unit (ACU) to register a fault in that airbag circuit. This fault poses a severe safety risk. The short circuit can prevent the airbag from deploying during a collision or, in extreme cases, trigger unintended deployment. The system classifies this fault as severity level 3, illuminates the SRS warning lamp continuously, and may force the entire airbag system into fail-safe mode (disabling all airbags).
Causes
— Damaged knee airbag wiring harness insulation: Long-term friction or compression (such as driver knee impacts or improper aftermarket pedal installation) damages the wiring harness below the steering wheel or inside the instrument panel, tearing the outer sheath and allowing the copper wire to contact the vehicle body metal.— Connector water ingress or corrosion: During vehicle wading, A/C condensate leakage, or car washing, water enters the knee airbag connector (usually located under the left side of the dashboard), causing a terminal-to-terminal or terminal-to-housing short circuit.— Airbag Control Unit (ACU) internal fault: A damaged ACU internal driver circuit or monitoring circuit causes a false short-to-ground fault (actual wiring is normal).+2 more →
Actions
— Safety preparation: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 90 seconds (to fully discharge the SRS capacitor and prevent accidental airbag deployment).— Visual inspection: Remove the driver-side knee bolster (Under Cover). Inspect the knee airbag wiring harness (yellow sleeve marking) for crushing, cuts, or abrasion. Focus on contact points with the steering column and metal brackets.+5 more →
B1719-00›
DTC B1719-00 indicates the SRS (Supplemental Restraint System) control unit detects an abnormally low-resistance connection (short circuit) between the Driver Knee Airbag squib circuit and the vehicle power supply (B+). Under normal operating conditions, the airbag squib circuit exhibits high resistance (2-5 Ω) and lacks continuity to power or ground. A short to power causes the SRS ECU to detect an abnormally high circuit voltage (close to 12 V) and register a severe fault. This condition may prevent the airbag from deploying correctly during a collision (as the short circuit bypasses the current) or, in extreme cases, cause unintended deployment (though a short circuit typically prevents rather than triggers ignition). Repair this critical safety fault immediately.
Causes
— Worn or aged knee airbag wiring harness insulation contacts the dashboard metal frame or power wiring harness, causing a short circuit. This commonly occurs after driving through water, scraping the underbody, or prolonged driving on rough roads.— Misaligned pins, backed-out pins, or water ingress due to poor sealing inside the yellow airbag connector (usually located under the driver side dashboard or left of the steering column) cause a short circuit between the power pin and the airbag signal wire.— Vehicle modifications (such as installing a dash cam, floor mat retaining clips, or audio system upgrades) pierce or crush the knee airbag wiring harness, causing insulation damage and a short to power.+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 90 seconds (to completely discharge the SRS backup capacitor). Do not connect or disconnect the airbag connector while powered on.— Inspection procedure: Remove the driver-side knee trim panel (Lower Panel) and locate the left knee airbag module (below the left side of the steering column) and the dedicated yellow connector. Visually inspect the wiring harness for signs of abrasion, crushing, or modification, and the connector for water ingress, corrosion, or exposed pins.+5 more →
B171811›
DTC B171811 indicates an abnormally low-resistance connection (typically <1.5Ω) between the Driver Knee Airbag squib circuit and the vehicle chassis ground (GND). In the SRS (Supplemental Restraint System), the squib circuit must maintain a high-impedance state (normally 2-3Ω). The airbag control unit (ACU) logs a short to ground when it detects circuit resistance continuously below the threshold or abnormal current flow to ground. This fault forces the ACU into an immediate fail-safe mode, disabling the knee airbag and potentially related airbag systems, and illuminates the instrument cluster airbag warning light. Potential causes for this short to ground include contact between the internal squib bridge wire and the housing, damaged harness insulation shorting to the chassis, bent connector terminals touching metal components, or a breakdown of the internal ACU driver circuit. This creates a dual safety risk of unintended airbag deployment (premature deployment) or failure to deploy during a collision. Technicians must repair this hard fault immediately.
Causes
— Internal short circuit in knee airbag module: Airbag internal bridge wire contacts the metal housing, or moisture in the pyrotechnic element causes insulation failure, creating a path to ground.— Physical damage to the wiring harness: Long-term vibration, friction, or compression damaged the insulation of the yellow SRS wiring harness under the dashboard, near the steering column, or in the pedal area, causing contact with the vehicle body metal.— Connector fault: Water ingress, oxidation/corrosion, or terminal back-out at the knee airbag connector (usually under the driver's side dashboard, marked yellow), causing the pin to short to body ground.+2 more →
Actions
— Safety preparation: Switch the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds (120 seconds for some models) to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault Confirmation and Freeze Frame Analysis: Use BYD dedicated diagnostic tool VDS2000 or X431 to read the fault code. Confirm B171811 is a current fault (Active, not History). Record the resistance value (usually 0Ω or <1Ω) and the vehicle status at the time of occurrence from the freeze frame data.+5 more →
B1719›
DTC B1719 indicates a short to B+ in the Driver Side Knee Airbag squib circuit. In the SRS (Supplemental Restraint System) architecture, the knee airbag squib is a low-value resistor (standard value 2.0 ± 0.3 Ω). Under normal conditions, the airbag ECU triggers the squib by controlling the ground circuit. When the diagnostic system detects the circuit voltage continuously exceeding the threshold (typically above 4.5V, approaching the 12V battery voltage), it identifies a short to power. This fault results in the following: 1) The ECU actively disables the airbag circuit, preventing deployment during a collision and resulting in a loss of driver leg protection. 2) A potential safety risk exists; in extreme cases, circuit abnormalities may cause unintended airbag deployment. 3) The SRS enters fail-safe mode and continuously illuminates the instrument cluster airbag warning light. Inspect for damaged wiring harness insulation, misaligned connector terminals, electrolytic short circuits caused by fluid ingress, and internal short circuits within the airbag module squib.
Causes
— Prolonged friction between the knee airbag wiring harness and the dashboard metal frame or steering column edge damages the insulation, causing a short to the constant power supply wire.— Internal short circuit in the knee airbag assembly squib due to a manufacturing defect, moisture ingress, or aging, resulting in abnormally low resistance.— Terminals in the dedicated yellow SRS connector under the driver's dashboard are bent, backed out, or not fully seated, contacting an adjacent power pin (such as constant 12V).+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the negative battery cable, and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Remove the driver-side lower dashboard trim panel (knee bolster). Inspect the yellow 2-pin knee airbag connector and wiring harness for damage, burn marks, water ingress, or modification crimp marks.+6 more →
B171912›
DTC B171912 indicates a short to the 12V power supply in the driver-side knee airbag igniter circuit. In the BYD SRS system, the normal resistance of the airbag igniter is 2.0 ± 0.3 Ω. The Airbag Control Unit (ACU) continuously monitors this resistance through a low-current diagnostic circuit. A "short to power" means the signal wire or return wire in the igniter circuit shorts to the vehicle constant power (B+), causing circuit resistance to rise abnormally (approaching infinity or exhibiting short-circuit characteristics). This fault is extremely dangerous. It can cause the airbag to deploy unexpectedly while driving, injuring occupants. Alternatively, during a collision, the ACU may detect the circuit fault and fail to trigger the airbag, disabling the protection function. Upon detecting this fault, the ACU immediately illuminates the instrument cluster SRS warning light and locks the airbag system into fail-safe mode.
Causes
— The knee airbag wiring harness chafes beneath the steering column or instrument panel frame, damaging the insulation and causing a short circuit to the body power wiring harness.— Knee airbag connector (usually located under the dashboard near the center console): bent pins, backed-out pins, or water ingress causing a short circuit between the power and signal pins.— During non-standard modifications (such as installing a dash cam, full-coverage floor mats, or scuff plates), fixing screws or clips pierce the wiring harness, causing a short circuit between multi-core wires.+2 more →
Actions
— Safe power-down: Switch off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds for the ACU energy storage capacitor to fully discharge, preventing accidental airbag deployment during repair.— Visual inspection: Check the wiring harness below the driver's knee and under the instrument panel for abrasion, scorching, or crushing marks. Focus on the contact areas between the wiring harness and the steering column or metal brackets.+7 more →
B2AB049›
DTC B2AB049 indicates a malfunction in the current sampling circuit of the electric compressor drive controller in the thermal management system. This circuit typically uses a Hall effect sensor or a precision shunt resistor to monitor the compressor motor operating current in real time, enabling overcurrent protection, closed-loop torque control, and stall detection. The controller sets this fault when it detects a sampled value outside the valid range (e.g., signal line open circuit, short to ground or power, sampled value continuously at zero or saturated, or an abnormal three-phase current vector sum). When this fault occurs, the compressor initiates a protective shutdown, disabling the air conditioning cooling and heating functions. If the vehicle uses a heat pump system or relies on the air conditioning system for battery cooling, prolonged operation may overheat the battery or motor, but generally does not directly affect driving safety.
Causes
— Damage or cracked solder joints on the internal Hall current sensor of the electric compressor controller cause sampling signal drift or interruption.— Backed-out pins, water ingress, or oxidation in the compressor low-voltage wiring harness connector (usually an 8-pin or 12-pin plug) causing excessive contact resistance in the sampling signal wire.— Inter-turn short circuit or three-phase imbalance in the compressor motor winding distorts the actual current waveform, triggering abnormal sampling protection.+2 more →
Actions
— Use VDS2000 or the BYD dedicated diagnostic tool to read complete fault codes and freeze frame data. Check for accompanying codes B2AA000 (compressor communication fault) or B2AB149 (compressor drive fault). Check if 'compressor phase current' and 'bus current' in the data stream display 0, 65535, or abnormal fluctuations.— Check that the front compartment electric compressor controller low-voltage connector locking mechanism is intact. Visually inspect the pins for green copper corrosion, burn marks, or backed-out pins. Measure the current sampling signal wire voltage to ground (typically a thin wire of a specific colour; refer to the Qin EV wiring diagram). Normal static voltage is approximately a 2.5V bias or 0V; compare this against the repair manual standard value.+4 more →
B171C-00›
DTC B171C-00 indicates the driver's knee airbag circuit resistance is 0 Ω, representing a hard short. In the SRS (Supplemental Restraint System), normal airbag squib resistance is 2.0-3.0 Ω. A 0 Ω reading indicates a line short to ground between the SRS ECU and the knee airbag, an internal short in the airbag squib, or a short caused by abnormal connector terminal contact. This fault triggers the SRS fail-safe mode. The airbag may fail to deploy during a collision, or in extreme cases, the wiring fault could cause unintended deployment (a low-probability theoretical risk). Because the knee airbag sits in front of the driver's knees (beneath the dashboard), water ingress, physical impacts, or aftermarket modifications easily affect this area. Consequently, it is one of the SRS components most prone to short circuits.
Causes
— Loose knee airbag connector (yellow plug), backed-out terminal, or water ingress corrosion, causing a short circuit between terminals or a short to ground. Commonly occurs after vehicle wading or improper cabin cleaning.— Internal short-circuit failure of the knee airbag igniter (generator). This internal component fault typically accompanies airbag assembly aging or previous external impact (such as a forceful knee strike).— Damaged wiring harness insulation causes a short to ground, especially below the steering column or near the instrument panel frame, where vibration and chafing wear through the harness and cause contact with the vehicle body metal.+2 more →
Actions
— Safety preparation: Switch the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Locate component: Remove the driver-side lower dashboard trim panel (knee bolster). Find the left knee airbag module (usually below the steering column) and the yellow 2-pin connector.+6 more →
B171C›
DTC B171C indicates the Airbag Control Unit (ACU) detects 0 ohms in the Driver Side Knee Airbag igniter circuit. This points to a short to ground in the circuit or an internal short in the igniter. In the BYD SRS system, normal airbag igniter resistance is 2.0-5.0Ω. When the ACU detects circuit resistance below the threshold (typically <0.8Ω), it registers a short circuit fault, illuminates the airbag warning lamp, and disables the airbag to prevent accidental deployment. During a frontal collision, the driver loses knee airbag protection, risking severe lower limb injury. This fault does not cause unintended airbag deployment.
Causes
— Left knee airbag igniter internal short circuit (damaged internal squib coil insulation causing an inter-turn short circuit)— Airbag wiring harness short to ground (wiring harness under dashboard chafed against body metal bracket, causing a short to ground)— Short circuit between airbag connector terminals (water ingress and corrosion after wading, metal swarf bridging, or terminal deformation causing contact)+2 more →
Actions
— Use the BYD VDS2000 or a dedicated diagnostic tool to read the DTC. Confirm B171C is a current fault (Active) that will not clear. Record the freeze frame data.— Visually inspect the lower left knee area of the dashboard for signs of impact, water ingress, or unauthorized modifications (such as added metal pedals).+7 more →
B171C1A›
DTC B171C1A indicates the Supplemental Restraint System (SRS) detects a 0Ω resistance in the Driver Knee Airbag ignition circuit, representing a typical short circuit fault. Normal airbag inflator resistance measures between 2.0 and 3.0Ω. A 0Ω resistance indicates a Line Short to Ground in the ignition circuit. Possible causes include an internal short circuit in the airbag module, damaged wiring harness insulation grounding to the chassis, or a short circuit between connector terminals. This fault causes the SRS control unit to flag the left knee airbag as unavailable, preventing deployment during a collision. The control unit also illuminates the airbag warning light continuously. The knee airbag is a critical restraint system component that protects the driver's lower limbs from dashboard intrusion. Consequently, this fault significantly reduces protection performance during a frontal collision.
Causes
— Left knee airbag module igniter short circuit: Moisture, aging, or manufacturing defects cause a short circuit between the positive and negative terminals of the heating wire or bridge wire inside the airbag.— Wiring harness short to ground: Wear, crushing, or water ingress damages the insulation on the wiring harness under the driver's side dashboard (typically routed along the steering column or carpet), causing a short to the vehicle body metal.— Connector fault: The SRS-specific yellow connector (usually located under the dashboard or center tunnel) has bent pins, corrosion from water ingress, or shorted terminals, resulting in 0 resistance.+2 more →
Actions
— Safety preparation: Switch off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS backup power supply and prevent accidental airbag deployment.— Visual inspection: Remove the driver's side lower dashboard trim panel (knee bolster). Check the left knee airbag module for damage, water stains, or burn marks. Check the wiring harness for obvious wear, crushing, or corrosion.+6 more →
B171D-00›
DTC B171D-00 indicates the resistance of the driver-side left knee airbag ignition circuit is below the normal threshold set by the SRS control unit (typically below 1.5Ω; the standard value is 1.6-2.4Ω). This fault indicates a short circuit in the knee airbag ignition circuit. Potential causes include an internal short in the airbag igniter coil, damaged wiring insulation causing a short between positive and negative circuits, or a short between connector terminals. The SRS system identifies the airbag circuit as abnormal. The knee airbag may fail to deploy during a collision or, in extreme cases, deploy unintentionally. Consequently, the system illuminates the airbag warning light and logs this fault code.
Causes
— Internal short circuit in left knee airbag igniter: Manufacturing defects or prolonged exposure to high temperatures damage the inter-turn insulation of the igniter coil inside the airbag module, reducing resistance to below 1Ω.— Wiring harness chafing and short circuit: Long-term vibration causes the knee airbag wiring to chafe against a metal bracket where it passes under the instrument panel near the steering column. This damages the insulation and causes direct contact between the positive and negative wires.— Connector water ingress and oxidation: When driving through water or cleaning the interior, moisture enters the knee airbag connector (usually located low under the dashboard), decreasing insulation resistance between terminals or causing electrolytic corrosion.+2 more →
Actions
— Safety preparation: Disconnect the negative battery terminal and wait at least 90 seconds to fully discharge the SRS system capacitors and prevent accidental airbag deployment.— Fault code confirmation: Use the BYD VDS diagnostic tool to read fault codes. Confirm if B171D-00 appears alone or with other SRS fault codes. Check the real-time knee airbag resistance value in the data stream.+5 more →
B171D›
DTC B171D indicates the driver-side knee airbag igniter circuit resistance falls below the lower threshold calibrated by the SRS control unit (ACU), typically under 2.0 Ω. In the BYD SRS system, the knee airbag serves as a critical restraint system component, with a standard igniter resistance range of 2.0–3.0 Ω. A low resistance value indicates a short circuit risk. Potential causes include an internal short in the igniter assembly, a short between wiring harness connector pins, or a wiring harness short to ground or power. This fault causes the ACU to classify the airbag circuit as unsafe. During a collision, the knee airbag may fail to deploy, or in extreme cases, deploy unintentionally. Consequently, the SRS system illuminates the airbag fault warning lamp and may disable the entire airbag system.
Causes
— Knee airbag squib internal coil short circuit: Manufacturing defects or prolonged vibration cause an inter-turn short circuit in the airbag igniter internal coil, decreasing the resistance value.— Airbag wiring harness connector short circuit: Water ingress and corrosion from wading or improper vehicle washing, or foreign objects bridging the pins, caused a short circuit in the knee airbag connector located on the left side beneath the dashboard (usually a yellow plug).— SRS wiring harness damage and short circuit: Long-term friction or compression damages the insulation where the harness passes through the dashboard frame or near the steering column, causing a short circuit to body ground or the 12V power line.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes (to ensure complete SRS capacitor discharge). Read and record all fault codes. Check for accompanying fault codes such as B171C (resistance too high) and B171E (short to ground).— Visual inspection: Remove the driver-side knee panel. Inspect the knee airbag connector for looseness, water ingress, pin corrosion, or foreign object intrusion. Inspect the wiring harness near the steering column for wear or crush marks.+4 more →
B171D1A›
This DTC indicates the driver-side knee airbag module squib resistance falls below the SRS control unit (ACU) threshold (typically below 1.5Ω). The knee airbag mounts on the left side of the dashboard below the steering wheel to protect the driver's knees and lower limbs during a frontal collision. Low resistance typically indicates a short circuit in the squib circuit (short between wires, short to ground, or internal short within the airbag module), causing the ACU to detect abnormally low circuit resistance. This fault forces the SRS system into degraded mode. During a collision, the knee airbag may fail to deploy or deploy inadvertently. Simultaneously, the instrument cluster airbag warning light remains illuminated, severely compromising passive safety functions.
Causes
— Internal short circuit in the knee airbag module igniter: Moisture, manufacturing defects, or aging causes insulation failure between the positive and negative terminals of the igniter bridge wire inside the airbag module, dropping resistance below 1Ω.— Wiring harness chafing and short circuit: Vibration, friction, or crushing damages the insulation on the wiring harness from the ACU to the knee airbag (typically routed along the instrument panel frame or floor harness), causing a short circuit between the conductors or to the vehicle body.— Connector terminal short circuit: Deformed internal terminals, corrosion from water ingress, or metallic foreign objects inside the knee airbag connector (yellow, located under the left side of the dashboard) cause a short circuit between the positive and negative terminals.+2 more →
Actions
— Safety preparation and fault confirmation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (to discharge the SRS capacitor). Read all fault codes using VDS or a dedicated diagnostic tool. Confirm if only B171D1A is present or if other airbag circuit faults accompany it.— Visual inspection and connector check: Inspect the knee airbag area under the dashboard for signs of impact, water stains, or removal/installation marks. Disconnect the knee airbag connector (yellow locking tab) and check the terminals for corrosion, deformation, or foreign objects.+4 more →
B171E-00›
DTC B171E-00 indicates the driver-side knee airbag ignition circuit resistance exceeds the normal threshold range (typically 1.5Ω-3.5Ω, depending on vehicle calibration) established by the SRS control module (ACU), registering as excessively high resistance. Potential causes include increased internal resistance in the airbag inflator, poor wiring harness connector contact, a wiring harness open or short circuit, or a faulty internal sampling circuit within the control module. This fault forces the SRS system into a degraded mode and illuminates the instrument panel airbag warning light. During a collision, the knee airbag may fail to deploy, compromising lower limb protection for the driver.
Causes
— Aging or moisture ingress causes the knee airbag igniter internal resistance to drift beyond the normal range.— Airbag wiring harness connector (usually located under the left side of the dashboard, yellow plug) pins oxidized, loose, backed out, or corroded by water ingress— Worn, broken, or pinched knee airbag wiring harness inside the instrument panel reduces the effective conductive cross-sectional area.+2 more →
Actions
— Use BYD VDS or a dedicated diagnostic tool to read and confirm DTC B171E-00, record freeze frame data, and check the instrument panel airbag warning light status.— Disconnect the 12V battery negative terminal and wait at least 3 minutes for the SRS system to fully discharge to prevent accidental airbag deployment.+6 more →
B171E›
DTC B171E indicates the driver-side knee airbag (Left Knee Airbag Module) firing circuit resistance exceeds the ACU (Airbag Control Unit) calibrated threshold (typically >3.0Ω, standard value 2.0-3.0Ω). Located under the left side of the dashboard, this airbag protects the driver's lower limbs from secondary impact during a frontal collision. High resistance essentially indicates an open circuit or high-impedance state. Causes include poor airbag connector contact, an open wiring harness inside the dashboard, an internal open circuit in the airbag inflator, or an ACU detection circuit fault. This fault forces the SRS system into fail-safe mode. It can prevent the knee airbag from deploying during a collision, continuously illuminate the instrument panel airbag warning light, and compromise the vehicle's passive safety system.
Causes
— Loose or oxidized knee airbag wiring harness connector: Water ingress, damp conditions, or prolonged vibration causes terminal oxidation and increases contact resistance in the yellow dedicated airbag connector under the dashboard, creating a high-resistance state.— Dashboard internal wiring harness wear or open circuit: Dashboard removal and installation, cabin air filter replacement, or aftermarket equipment installation crushes, cuts, or causes a fatigue break in the knee airbag wiring harness near the steering column.— Knee airbag inflator fault: Aging, batch defects, or prolonged exposure to high temperatures cause an internal open circuit in the airbag inflator coil, resulting in infinite resistance.+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment and personal injury.— Initial inspection: Inspect the yellow dedicated connector for the left knee airbag under the dashboard (usually a 2-pin yellow housing). Verify the connector is securely seated, and check for broken locking tabs or obvious signs of water ingress, oxidation, burning, or terminal back-out.+5 more →
B171E1B›
This fault code indicates the airbag control unit (SRS ECU) detects the left knee airbag (Driver Knee Airbag) igniter circuit resistance exceeds the calibrated upper limit (typically >3.5Ω; normal range is 2.0-3.0Ω). Excessive resistance indicates a high-resistance point in the igniter circuit. Potential causes include poor connector contact, a partially broken wiring harness, oxidation, or an aging spiral resistance wire inside the airbag module. This fault forces the SRS system into a degraded protection mode, and the left knee airbag may fail to deploy during a collision (this airbag protects the driver’s lower limbs from rearward steering column movement or instrument panel intrusion). The airbag warning light remains illuminated on the instrument panel, and some models trigger a warning buzzer. Because this fault affects a core passive safety system function, it presents a safety risk and requires immediate inspection.
Causes
— The knee airbag wiring harness connector (yellow plug, usually located behind the driver-side knee trim panel) is loose, has backed-out terminals, or has oxidized pins, causing increased contact resistance.— Broken spiral resistance wire or poor solder joint in the airbag module internal igniter (component aging or production batch defect)— Physical damage to the wiring harness: Foot contact abrades the wiring harness in the driver's footwell, or the wiring harness below the steering column rubs against a metal bracket, causing partial breakage of the copper wires.+2 more →
Actions
— Safe power-off: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS backup power supply and prevent accidental airbag deployment during repair.— Visual inspection: Remove the driver-side lower trim panel (knee bolster). Verify the yellow airbag connector is fully inserted and the locking tab is engaged. Inspect for water ingress or green oxidation on the terminals.+4 more →
B1721-00›
B1721-00 is a BYD SRS (Supplemental Restraint System) fault code indicating a communication interruption or open circuit between the front passenger (right) knee airbag and the Airbag Control Unit (ACU). The fault triggers when the ACU detects the right knee airbag deployment circuit resistance falls outside the normal range (typically 2.0Ω-3.0Ω), causing the system to register a 'not connected' state. During a collision, the right knee airbag may fail to deploy, leaving the front passenger's knees and lower limbs unprotected. Additionally, the SRS fail-safe mechanism may force the entire airbag system into a degraded mode, affecting the normal operating logic of other airbags.
Causes
— Right knee airbag connector loose or disconnected: Previous maintenance (such as replacing the A/C filter or removing and installing the dashboard) failed to fully lock the yellow dedicated connector under the passenger side dashboard, or prolonged driving on rough roads loosened it.— Wiring harness wear or breakage: The knee airbag wiring harness routes behind the passenger glove box and through the floor wiring channel. Excessive pressure from the glove box, or detached harness retaining clips causing prolonged chafing against metal edges, can cause a short or open circuit.— Knee airbag module internal fault: Airbag internal squib open circuit or abnormal resistance. Common causes include airbag aging, poor internal solder joints, or moisture ingress.+2 more →
Actions
— Safety preparation: Disconnect the 12 V battery negative terminal. Wait at least 90 seconds for the SRS capacitor to discharge completely to prevent accidental airbag deployment. Wear an anti-static wrist strap.— Fault code confirmation: Use a VDS2000 or VDS3100 diagnostic tool to access the SRS system. Read and record the freeze frame data (Freeze Data) for B1721-00. Check if the fault is current (Present) or historical (History), and check for accompanying fault codes (such as B1720-00 left knee airbag fault).+5 more →
B17211B›
DTC B17211B indicates the Supplemental Restraint System (SRS) detects a communication loss or abnormal resistance between the right knee airbag (typically located under the passenger-side dashboard) and the SRS control module. Specifically, this fault indicates an open airbag igniter circuit (resistance too high, typically >10Ω), which the system registers as a "not connected" state. This condition prevents the right knee airbag from deploying during a collision and continuously illuminates the airbag fault warning lamp. This constitutes a hard fault or intermittent open circuit requiring immediate repair to ensure passive safety system integrity.
Causes
— Knee airbag wiring harness connector loose or disconnected: Following vehicle repair, modification, or collision repair, the yellow SRS connector under the instrument panel does not fully lock, or a damaged locking mechanism causes poor contact.— Airbag igniter internal open circuit: Broken internal heating wire in the right knee airbag inflator (due to aging, moisture, or minor impact damage), resulting in infinite circuit resistance.— Harness wear or breakage: Vibration and friction during long-term use damage the insulation and break the copper core of the wiring harness under the dashboard, especially where it passes over metal bracket edges.+2 more →
Actions
— Safety preparation: Park the vehicle on a level surface, turn the ignition switch to the OFF position, disconnect the negative battery cable, and wait at least 90 seconds to completely discharge the SRS system backup power supply and prevent accidental airbag deployment.— Fault Confirmation: Use the BYD dedicated diagnostic tool (VDS or ED400) to read the fault code. Confirm B17211B is a current fault (Current), not a history fault (History). Read the data stream to check the airbag resistance value.+5 more →
B1722-00›
DTC B1722-00 indicates the SRS (Supplemental Restraint System) control unit detects an abnormally low-resistance connection to body ground (short to ground) in the right knee airbag (front passenger side knee airbag) squib circuit. The knee airbag contains a gas generator electrothermal igniter (typical resistance 2 ± 0.5 Ω). The SRS module determines circuit integrity by monitoring circuit current and resistance. If damaged wiring harness insulation contacts vehicle body metal, water enters the connector causing a short between terminals, or the internal airbag module igniter shorts, circuit resistance drops to nearly 0 Ω. The control unit immediately cuts power to the circuit and illuminates the airbag fault warning lamp to prevent unintended airbag deployment or insufficient ignition energy. In this condition, the right knee airbag fails to deploy during a collision, and the entire SRS system may enter a degraded protection mode.
Causes
— Wiring harness mechanical damage: Detached or improperly installed retaining clips allow the right knee airbag harness to rub against sharp metal edges when passing through the instrument panel frame or firewall. Prolonged friction damages the insulation, causing the copper core wire to directly contact the vehicle body ground.— Connector water ingress and corrosion: Water entering the right knee airbag connector (located low under the center console) during vehicle wading, A/C condensate leakage, or high-pressure washing causes electrolytic corrosion between the terminals, creating a short-circuit path.— Improper removal and installation of the center console: Pinching the wiring harness between the dashboard and the body when removing or installing the center console to repair the air conditioning system or central control components. Failing to fully seat the connector bends the terminals, causing them to contact the metal frame.+2 more →
Actions
— Safety preparation: Switch the vehicle OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds for the SRS system energy storage capacitor to discharge completely. Place 'Airbag Under Repair' warning signs on the steering wheel and instrument panel.— Fault confirmation: Connect the BYD VDS or Launch X-431 diagnostic tool. Enter the SRS system to read fault codes. Confirm B1722-00 is a current fault (Active), not a history fault. Check the right knee airbag circuit resistance value in the data stream (should display <1Ω or short circuit).+6 more →
B172211›
DTC B172211 indicates the Supplemental Restraint System (SRS) detects an abnormally low-resistance path (short circuit) to body ground in the right knee airbag (passenger-side knee airbag) ignition circuit. Under normal conditions, the airbag igniter circuit resistance should be between 2.0 and 3.0 Ω. The ECU determines a short to ground when it detects circuit resistance below 1.0 Ω or voltage to ground near 0 V. This fault prevents proper airbag deployment during a collision (as the ECU disables the circuit to protect the power supply) or, in extreme cases, causes unintended deployment. Simultaneously, the SRS enters fail-safe mode, illuminates the airbag warning light, and may lock the entire airbag system, severely compromising passive safety performance.
Causes
— Prolonged chafing of the right knee airbag wiring harness against the instrument panel crossmember or glove box bracket damages the insulation, shorting the wire directly to the metal body.— Water ingress and oxidation at the airbag connector (yellow double-locking plug) on the lower right side of the center console, especially after vehicle wading or a blocked A/C drain, creating a short-to-ground path between the pins.— Airbag module aging or previous external impact causes bridge wire insulation breakdown in the knee airbag module internal squib, resulting in an internal short to ground.+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS backup capacitor and prevent accidental airbag deployment.— Fault confirmation: Use the BYD VDS diagnostic tool to read the fault code. Confirm B172211 is a current (Active) fault, not a historical fault, and record the freeze frame data.+6 more →
B1723-00›
B1723-00 indicates the Supplemental Restraint System (SRS) detected a short to vehicle power (B+, 12V) in the ignition circuit (squib circuit) of the right knee airbag (passenger-side knee airbag, typically located below the right side of the dashboard). Under normal conditions, the SRS control unit (ACU) maintains a specific voltage across the airbag inflator terminals (typically a 5V or 12V pulse diagnostic voltage), and circuit resistance measures between 2.0 and 3.0 Ω. When the ACU detects the circuit voltage remains at or near battery voltage (>10V), it identifies a short to power. This fault can cause: 1) the right knee airbag to fail to deploy properly during a collision; 2) the SRS to enter fail-safe mode, disabling all airbag functions; 3) a potential risk of unintended airbag deployment. This severe-level fault requires immediate repair.
Causes
— Damaged right knee airbag wiring harness or aged insulation contacts vehicle power wiring (such as a constant 12V circuit), causing a short circuit. This commonly occurs at the wiring harness pass-through hole under the dashboard or near the steering column.— Water ingress, corrosion, or terminal deformation at the airbag connector (usually a yellow plug) causes a short circuit between terminals, particularly after vehicle wading or A/C condensate leakage.— During instrument panel (IP) removal and installation, a pinched wiring harness, damaged retaining clips, or worn harness protective sleeve exposes copper wire, causing contact with the metal frame or power wire.+2 more →
Actions
— Safety preparation: Power down the vehicle, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS backup capacitor and prevent accidental airbag deployment.— Fault confirmation: Use a dedicated BYD diagnostic tool (VDS or ED400) to read fault codes. Confirm B1723-00 is a current fault (Active) and check for accompanying fault codes (e.g., B1722, B1724).+6 more →
B1723›
This DTC indicates a short to vehicle power (B+) in the SRS (Supplemental Restraint System) Right Knee Airbag ignition circuit. Under normal operating conditions, the airbag ignition circuit remains isolated from the power supply. The SRS ECU triggers the circuit with a specific current only during a collision. When the control unit detects a short to power in this circuit, it logs a severe fault, immediately illuminates the airbag warning lamp, and enters fail-safe mode. This mode may disable the entire airbag system to prevent accidental deployment or system failure. During a frontal collision, the knee airbag limits the forward movement of the occupant's lower limbs, preventing femur and hip injuries caused by the knees striking the instrument panel. Therefore, this fault directly compromises occupant passive safety protection.
Causes
— A worn or crushed right knee airbag wiring harness causes a short circuit to the power supply harness. Common causes include tight harness routing under the dashboard or metal edge burrs cutting the insulation.— Water ingress, oxidation, or deformed terminals at the airbag connector (usually located behind the glove box or on the right side of the dashboard), shorting the power terminal to the signal terminal.— Internal short circuit between layers in the clock spring (spiral cable). Although knee airbag wiring typically does not route through the steering wheel clock spring, some models use an intermediate connector.+2 more →
Actions
— Use a dedicated BYD diagnostic tool (VDS or ED400) to read fault codes. Confirm B1723 is a Current fault, not a History fault, and check for accompanying SRS fault codes.— Disconnect the battery negative cable and wait at least 90 seconds (120 seconds for some models) to fully discharge the SRS capacitor and prevent accidental airbag deployment during repair.+7 more →
B172312›
DTC B172312 indicates the Supplemental Restraint System (SRS) detects an abnormally low-resistance path between the right knee airbag (Knee Airbag - Passenger Side) ignition circuit and the vehicle positive power supply (+B, usually 12V). In the SRS, normal airbag squib resistance is typically 2-3Ω. The ECU supplies a low-voltage detection signal. When the circuit shorts to power, the ECU detects an abnormally high voltage or a constant 12V and logs a Short to B+ fault. This severe active safety system fault may cause: 1) the airbag to fail to deploy during a collision (the short circuit diverts ignition energy); 2) unexpected airbag deployment in extreme cases due to short-circuit current; 3) the SRS to enter fail-safe mode, restricting all airbag functions. The '12' in the DTC is the sub-code specifically indicating a short-to-power fault.
Causes
— Damaged right knee airbag wiring harness insulation contacts the instrument panel frame or power wiring harness (e.g., IGN+, constant power +B), causing a short circuit. Commonly occurs after water ingress, underbody impact, or rodent chewing.— Water ingress, corrosion, or bent pins in the right knee airbag connector (typically located under the right side of the dashboard, near the rear of the glove box) causing continuity between the power supply pin and the airbag igniter pin.— Insulation failure of the internal squib in the knee airbag assembly causes an internal short to power, usually due to airbag module aging or previous external impact.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation: Use VDS or a BYD dedicated diagnostic tool to read the fault code. Confirm B172312 is a current (Active) fault, not a historical fault. Record freeze frame data (ambient temperature, vehicle speed, etc.).+6 more →
B1726-00›
DTC B1726-00 indicates the Airbag Control Module (ACM) detects an abnormal resistance of 0 ohms (or below 0.8 Ω) in the Passenger Knee Airbag igniter circuit, evaluating it as a wiring short to ground or an internal short circuit within the airbag module. In BYD Qin series and similar models, this DTC strictly corresponds to the right knee airbag circuit. However, the SRS systems in other models (such as Song Pro, Tang DM-i, and Qin Plus) define this code as a front passenger seat Occupant Classification Sensor (OCS) circuit fault. Regardless of the specific definition, the SRS system detects abnormal circuit impedance in the passenger-side lower safety protection device. This causes the system to enter fault protection mode, disable the airbag deployment function, and illuminate the instrument cluster airbag warning light. A 0-ohm resistance typically indicates a short circuit risk; prevent accidental deployment or complete failure.
Causes
— Right knee airbag module internal igniter short circuit: Moisture ingress, aging, or manufacturing defects in the airbag assembly cause a short circuit in the internal heating wire.— Harness short to ground: The harness from the ACM to the right knee airbag has chafed or damaged insulation inside the dashboard, behind the glove box, or in the floor wiring channel, grounding to body metal.— Connector fault: Bent pins, oxidation, water ingress, or loose connections at the airbag wiring harness plug (usually located under the passenger-side dashboard) causing a short circuit between the positive and negative terminals.+2 more →
Actions
— Safety preparation and initial inspection: Disconnect the battery negative terminal and wait 3 minutes to discharge the SRS capacitor. Use VDS2000 or Launch X431 to read the complete fault codes. Confirm B1726-00 is a current fault. Check for accompanying communication fault codes (e.g., U0151).— Connector and visual inspection: Remove the passenger-side lower dashboard trim panel. Inspect the white/yellow 2-pin right knee airbag connector (located under the glove box or on the lower right side of the dashboard) for looseness, water ingress, or oxidation. Measure the resistance between the wiring harness terminals at the plug (normal: open circuit, must not be 0).+4 more →
B1726›
DTC B1726 indicates the SRS (Supplemental Restraint System) control unit detects a Right Knee Airbag circuit resistance of 0Ω or near 0Ω. Normal airbag inflator resistance is 1.5-3.0Ω. A resistance of 0Ω indicates a short circuit in the airbag circuit. Potential causes include an internal short in the airbag inflator, a wiring harness short to ground, or a short between connector terminals. This fault causes the SRS to enter protection mode. During a collision, the Right Knee Airbag may fail to deploy normally. The system also illuminates the airbag warning light and may disable the entire airbag system to protect occupants.
Causes
— Internal short circuit in right knee airbag igniter: Moisture, aging, or manufacturing defects cause the igniter bridge wire inside the airbag module to short circuit between the positive and negative terminals.— Harness short to ground: Wear, crushing, or rodent bites damaged the insulation on the yellow dedicated harness connecting the SRS ECU to the right knee airbag (typically located under the dashboard, right of the center console), causing a short to body ground.— Connector fault: Knee airbag connector (usually located behind the glove box or on the dashboard crossmember) improperly locked, bent terminals causing a short circuit, or shorting bar failing to disengage, resulting in a continuous short circuit.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (to fully discharge the SRS capacitor). Use a multimeter to confirm the system has no residual high voltage.— Fault Confirmation: Connect the diagnostic tool, read the DTC, and record the freeze frame data. Confirm B1726 is a current fault (Active), not a history fault. Attempt to clear the fault code. If it reappears immediately, confirm the fault is persistent.+7 more →
B17261A›
DTC B17261A indicates the front passenger seat Occupant Classification System (OCS) sensor detects a circuit resistance of 0 or an open circuit. This sensor integrates into the front passenger seat cushion and uses pressure-sensing elements to monitor seat occupancy status in real time (empty/child/adult classification). A resistance of 0 typically indicates a short to ground in the sensor power or signal wire, an internal open circuit, or a disconnected connector. This fault causes the airbag control unit (SDM) to enter degraded mode, preventing it from accurately determining the front passenger type during a collision. The SDM may incorrectly suppress the front passenger frontal and knee airbags, or cause unintended airbag deployment, severely compromising the passive safety system protection strategy.
Causes
— Ruptured pressure-sensing diaphragm inside the OCS sensor body or burnt circuit board causing abnormal resistance (normal range: 50-200 Ω).— Loose, oxidized, backed-out pins, or poor contact at the white 4-6 pin wiring harness connector under the seat, causing signal interruption.— Excessive pulling of the seat wiring harness during vehicle modifications (such as fitting leather upholstery or installing seat cushions) or repairs, causing internal wire breakage.+2 more →
Actions
— Use the BYD dedicated diagnostic tool VDS to read the fault codes, confirm the B17261A current status and freeze frame data, and check for related fault codes such as 'Lost communication with front passenger seat occupancy sensor'.— Visually inspect the OCS sensor wiring harness connector under the front passenger seat (usually located in front of the seat slide rail) for looseness, backed-out pins, or oxidation, and check the wiring harness for pinching or damage.+5 more →
B1727-00›
This DTC indicates the Airbag Control Unit (ACU) detects the right knee airbag (front passenger knee airbag) squib circuit resistance is below the system calibration threshold (typically <1.0Ω; normal range: 2.0-3.0Ω). Low resistance indicates an abnormally low-resistance path in the circuit. A short to ground, a wire-to-wire short, or an internal short in the airbag squib typically causes this condition. This fault presents two severe risks: first, short-circuit current can trigger unintended airbag deployment, injuring occupants; second, excessive circuit current during a collision can burn the contacts, preventing airbag deployment. This fault constitutes an active safety system failure. The vehicle remains drivable, but the airbag system enters degraded protection mode. During a collision, the right knee airbag and any other airbags with related faults will fail to deploy.
Causes
— Internal short circuit in the knee airbag inflator: Manufacturing defects or moisture ingress damage the igniter bridge wire insulation inside the airbag assembly, causing an internal short circuit.— Physical damage to the wiring harness: During dashboard removal and installation, carpet replacement, or front passenger glove box repair, the metal frame crushes or cuts the knee airbag wiring harness (usually in a yellow sleeve), causing a short to ground.— Connector water ingress and corrosion: Water from vehicle wading, A/C condensate leaks, or floor cleaning enters the airbag connector under the front passenger floor (usually located under the lower center console or front passenger seat), causing an electrolytic short circuit between the terminals.+2 more →
Actions
— Safety preparation and diagnostic confirmation: Use the BYD ED400/ED600 diagnostic tool to read the DTC. Confirm B1727-00 is a current fault and the freeze frame data shows abnormal resistance (usually <0.5Ω). Disconnect the battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor.— Visual inspection and location: Remove the passenger-side lower dashboard trim panel (knee bolster). Inspect the yellow connector on the right knee airbag module (located on the frame beneath the glovebox) for looseness, water ingress, or obvious corrosion. Check the wiring harness for signs of frame edge crush damage or screw punctures.+5 more →
B1727›
DTC B1727 indicates the SRS (Supplemental Restraint System) ECU detects Passenger Knee Airbag squib circuit resistance below the calibrated threshold (typically <1.0Ω or <1.5Ω, depending on vehicle calibration). This fault represents an abnormally low impedance in the squib circuit. Potential causes include an internal short circuit in the squib coil, a wiring harness short to ground, a short between connector terminals, or a faulty internal sampling circuit within the SRS ECU. Low resistance typically indicates an abnormal current path, causing the SRS system to identify a risk of unintended deployment or monitoring failure. The system subsequently illuminates the airbag warning light and may disable the entire airbag system. This results in the loss of knee protection during a collision and disrupts the normal deployment logic of other airbags.
Causes
— Internal inter-turn short circuit in the right knee airbag igniter: Damaged insulation on the internal airbag ignition coil reduces the effective number of turns and lowers resistance. Airbag aging, moisture ingress, or manufacturing defects usually cause this fault.— Harness short to ground: The harness from the SRS ECU to the right knee airbag (usually with yellow sleeving) has damaged insulation and contacts vehicle body metal, causing current shunting and abnormally low resistance.— Connector terminal short circuit or bridging: Bent pins, metal foreign objects bridging the terminals, or water ingress corrosion in the front passenger knee area airbag connector (usually under the dashboard) reduce impedance between the terminals.+2 more →
Actions
— Safety precautions and initial checks: Disconnect the 12V battery negative terminal and wait at least 90 seconds to discharge the SRS capacitor. Use a megohmmeter to verify the system has no residual high voltage. Read the SRS data stream and record the specific current resistance value of the right knee airbag (e.g., 0.3Ω, 0.8Ω) to determine if the fault is intermittent or continuous.— Visual inspection and connector check: Inspect the yellow SRS connector in the front passenger knee airbag area (lower right dashboard) for looseness, water ingress, or foreign objects. Disconnect the airbag connector. Use a dedicated probe to measure the resistance between the airbag-side terminals (do not insert probes directly into the terminals to prevent damage). Standard value: 1.5-3.5Ω. If the resistance is normal, the fault lies in the wiring harness or ECU. If the resistance remains low, replace the airbag module.+3 more →
B17271A›
BYD's diagnostic system assigns two definitions to DTC B17271A depending on the vehicle platform. On early ICE platforms like the Qin PRO, the code indicates the right passenger knee airbag ignition circuit resistance falls below the standard threshold (normal range 1.5–3.0 Ω, measured value <1.0 Ω). This indicates a hard short in the circuit, an internal short in the airbag module, or damaged wiring insulation, which may prevent normal airbag deployment or cause unintended deployment without a collision. On newer platforms like e-Platform 3.0 and DM-i, the code indicates a left rear blind spot detection (BSD/BSDA) radar sensor fault. Causes include hardware damage, CAN communication interruption, a power supply short circuit, or loss of system calibration data. Both scenarios constitute a safety-related system failure. The vehicle remains drivable with caution, but safety protection functions operate with limitations. Repair the vehicle immediately.
Causes
— Internal circuit short or breakdown in the left rear BSD radar sensor unit (e.g., damaged voltage regulator module causing a power supply short to ground)— Water ingress and oxidation at the radar wiring harness connector, loose terminals, or poor contact (common after car washing, driving through water, or in rainy, high-humidity conditions).— Radar mounting bracket deformed, loose, or misaligned, causing signal interference or calibration failure (common after accident repairs).+2 more →
Actions
— Use the VDS2000 diagnostic tool to read all fault codes and freeze frame data. Confirm the B17271A status (current/history/intermittent) and any accompanying fault codes (such as U015487 communication fault).— Visually inspect the left rear bumper radar sensor for physical damage. Check the bracket installation tightness and the fit gap between the bracket and the bumper (gap must be zero).+5 more →
B1728-00›
DTC B1728-00 indicates the Airbag Control Unit (ACU) detects the squib circuit resistance of the right knee airbag (usually located beneath the passenger-side dashboard) exceeds the calibrated threshold. The normal range is typically 1.5-3.0 Ω, varying by vehicle calibration. High resistance generally means >3.5 Ω or a near open-circuit condition. This is an actively monitored SRS fault. The ACU continuously monitors the airbag squib circuit current and resistance to determine circuit integrity. High resistance indicates a high-resistance connection in the squib circuit. This may result in insufficient ignition energy during a collision, preventing proper airbag deployment. In extreme cases, the system detects an open-circuit fault and triggers a secondary lockout, compromising the entire airbag system operation. This fault illuminates the instrument cluster SRS warning lamp and forces the vehicle passive safety system into a degraded protection mode.
Causes
— Poor contact at the right knee airbag wiring harness connector: Long-term vibration causes backed-out pins, oxidation, corrosion, or looseness at the airbag connector under the passenger-side dashboard, increasing contact resistance (common in vehicles driven through water or operated in high-humidity environments).— Knee airbag module internal igniter fault: Oxidation, moisture ingress, or manufacturing defects in the airbag igniter internal bridge wire cause the resistance value to drift higher, indicating a faulty airbag module.— Partial open circuit or hidden high resistance in wiring harness: The harness connecting the ACU to the right knee airbag has partially broken internal copper wires or loose crimp points where it passes through the instrument panel frame, floor, or hinge, creating a high-resistance path instead of a complete open circuit.+2 more →
Actions
— Connect the BYD VDS2000 or a dedicated diagnostic tool. Read DTC B1728-00 and freeze frame data. Record the ambient temperature, voltage, and vehicle status at the time of the fault. Confirm whether the fault is intermittent.— Run the airbag system self-diagnosis and check for accompanying fault codes (if B1728-00 occurs with communication fault codes, inspect the CAN wiring harness first).+6 more →
B1728›
DTC B1728 indicates the SRS (Supplemental Restraint System) ECU detects the right knee airbag squib circuit resistance exceeds the calibrated threshold (the normal range is typically 1.5-3.0Ω; actual thresholds vary by vehicle software version, generally triggering this code at >3.5Ω). Electrically, excessive resistance indicates a high-impedance point in the circuit, resulting from increased contact resistance, a partial open circuit, or squib aging. This hard or intermittent fault causes the SRS to enter a degraded mode. During a collision, the airbag may fail to inflate, experience delayed inflation, or deploy with insufficient energy, failing to effectively protect the occupant's knees and lower limbs. Simultaneously, the instrument cluster airbag warning light remains illuminated, and the system may lock other airbag circuits.
Causes
— Pin oxidation, terminal back-out, or insufficient contact pressure at the right knee airbag module connector (usually located below the steering wheel or inside the right side of the instrument panel), causing increased contact resistance.— Corroded or deformed shorting bar in the clock spring or knee airbag wiring harness fails to fully disengage or makes poor contact, introducing additional resistance.— Microscopic fractures or carbonization of the internal igniter wire in the right knee airbag igniter (squib), causing resistance to drift upward (common in older vehicles or vehicles involved in minor collisions without airbag deployment).+2 more →
Actions
— Safety Preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes (5 minutes for some models) to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Diagnostic confirmation: Use VDS or a dedicated diagnostic tool to read the fault code, check the resistance value in the freeze frame data (Freeze Data), and confirm the fault is current (Current) rather than history (History).+6 more →
B17281B›
DTC B17281B indicates the Supplemental Restraint System (SRS) detects the right knee airbag (front passenger knee airbag) igniter circuit resistance exceeds the normal threshold (typically >3.5Ω; normal range 1.5-3.0Ω). This open-circuit fault indicates high resistance or an open circuit in the airbag igniter circuit. When the SRS control module detects continuously high resistance, it flags the airbag as abnormal, illuminates the airbag warning light, and disables deployment of the affected airbag. During a collision, the right knee airbag may fail to deploy, disabling lower limb and pelvic protection for the front passenger and increasing the risk of injury.
Causes
— Loose knee airbag module connector, backed-out pin, or oxidized terminal: Located under the front passenger dashboard. Cabin humidity or vibration causes increased contact resistance.— Airbag igniter internal open circuit or aging: The igniter bridge wire inside the airbag module breaks or the resistance wire oxidizes, increasing resistance.— Wiring harness open circuit or localized damage: Poor connection, break, or water corrosion in the wiring harness from the SRS ECU to the right knee airbag, either inside the instrument panel or at the floor harness junction.+2 more →
Actions
— Use the BYD VDS diagnostic tool to read the DTC freeze frame data. Confirm the DTC status is Active, note the specific resistance value, and record the environmental data.— Disconnect the battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment.+5 more →
B172B›
DTC B172B indicates the SRS (airbag) control unit detects an open circuit or disconnected condition in the left middle-row side airbag module (typically located inside the left B-pillar trim or on the side of the left rear seat). An abnormal resistance value in the circuit between the control unit and the airbag squib (typically infinite or outside the normal 2-3Ω range) causes the system to determine the airbag module is physically disconnected or internally open. This fault prevents the left middle-row side airbag from deploying during a side-impact collision. The SRS system may also enter a degraded protection mode, continuously illuminate the instrument panel airbag warning light, and restrict seat belt pretensioner function on some models.
Causes
— Loose connector, backed-out pins, or poor contact at the left middle-row side airbag module (commonly due to connector oxidation after vehicle wading, or an unseated connector following B-pillar trim removal and installation)— Open or short circuit in the airbag wiring harness due to wear (especially the yellow SRS harness under the seat or at the B-pillar, where frequent fore/aft seat adjustment or door operation causes fatigue breakage).— Internal open circuit in the left middle-row side airbag module (gas generator igniter tube aging or detached internal solder joint, causing abnormal resistance)+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the battery negative terminal, and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment during repair.— Visual inspection: Remove the left B-pillar lower trim panel or the left rear seat side cover. Check the left middle-row side airbag module (yellow connector) for looseness, water ingress, corrosion, or recessed pins. Clean the connector and reconnect it securely. Confirm the locking tab engages fully.+5 more →
B172B1B›
DTC B172B1B indicates the Supplemental Restraint System (SRS) detected a communication loss between the left middle-row (second-row left-side) side airbag module and the SRS control unit (ACU). This fault indicates an open airbag module circuit with resistance exceeding the threshold (typically >10Ω), preventing the control unit from detecting the module. Possible causes include a disconnected physical connector, broken wiring harness, faulty internal spiral cable (clock spring), or an open circuit within the module itself. Because the SRS uses a dual-stage deployment circuit, this fault prevents the left middle-row side airbag from deploying during a collision. It may also trigger a system self-check lockout, affecting the entire side airbag system.
Causes
— Airbag wiring harness connector under the seat or inside the B-pillar trim panel is loose, disconnected, or has poor contact, commonly resulting from frequent seat adjustment or failing to securely clip the B-pillar trim after removal and installation.— Wiring harness fatigue fracture, especially in harnesses routed through the seat frame or near the door hinge, where long-term bending and pinching break the internal copper strands while the outer insulation remains intact.— Internal airbag module open circuit; abnormal internal squib resistance (open circuit or excessive resistance). Module aging, previous moisture exposure, or electrostatic discharge usually causes this fault.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Locate the module: Remove the left middle-row seat side trim panel or lower B-pillar trim panel, and locate the side airbag module (usually marked 'SIDE AIRBAG') and its dedicated yellow connector.+4 more →
B172C›
DTC B172C indicates the Airbag Control Unit (ACU) detects an abnormally low-resistance path (typically <1Ω) between the left second-row side airbag squib circuit and body ground. In the SRS system, normal airbag squib resistance is approximately 2.0-3.0Ω. When the ACU detects a short to ground in the circuit, it registers a severe fault and triggers protection mode: immediately disconnecting power to the airbag circuit, illuminating the SRS warning lamp, and disabling left second-row side airbag deployment. This fault prevents the side airbag from inflating normally to protect the occupant during a collision, or in extreme cases, risks unintended deployment due to intermittent wiring contact.
Causes
— Mechanical damage to the under-seat wiring harness: During fore/aft adjustment of the left middle-row seat, the seat frame rubs against the floor wiring harness, damaging the insulation and causing the wire to contact the metal seat rail.— Airbag connector water ingress and corrosion: Poor sealing of the under-seat airbag wiring harness connector (usually a yellow plug) allows water entry during vehicle wading or interior cleaning, oxidizing the internal terminals and causing a short to ground.— Airbag module internal igniter short circuit: Igniter resistance wire insulation inside the airbag gas generator fails, shorting directly to the metal housing.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Diagnostic confirmation: Use the BYD dedicated diagnostic tool (VDS2000/ED400) to read the DTC freeze frame data. Record the vehicle status at the time of the fault (mileage, temperature, voltage) and confirm B172C is a current DTC, not a history DTC.+5 more →
B172C11›
DTC B172C11 indicates the SRS (Supplemental Restraint System) detected an abnormally low-resistance path from the left second-row side airbag ignition circuit (usually the left B-pillar side airbag or seat side airbag) to body ground (GND), with a resistance typically <1Ω. The airbag system ignition circuit features a dual-circuit redundant design (high side and low side). Under normal conditions, resistance to ground should be >100kΩ. Upon detecting a short to ground, the SRS ECU identifies a risk of unintended deployment or failure to deploy. The ECU immediately illuminates the airbag fault warning lamp and disables that side airbag and any linked restraint systems (such as the seatbelt pretensioner). This is a hard short circuit, not an intermittent fault. Repair immediately for occupant safety.
Causes
— Wiring harness wear inside the left B-pillar trim panel: Long-term driving on rough roads or repeated removal and installation of the B-pillar trim panel causes the side airbag wiring harness (usually wrapped in yellow corrugated conduit) to rub against sharp metal body edges. This damages the insulation and causes the copper core to directly contact the body ground.— Under-seat harness pinched and shorted: On vehicles equipped with seat side airbags, dynamic movement between the seat fore-aft adjustment mechanism and the floor harness fixing point causes the seat slide rail to pinch or wear through the harness sheath, resulting in a short to ground.— Connector water ingress and corrosion: An aging left front door seal or leaking window allows water to enter the airbag wiring harness connector at the A/B-pillar junction (usually located inside the sill trim panel). This creates an electrolytic conductive path between the terminals, causing a short to ground.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds (to fully discharge the SRS capacitor). Wear an anti-static wrist strap and prepare a dedicated diagnostic tool (such as BYD VDS 3000 or Launch X-431) and a multimeter.— Freeze frame analysis: Connect the diagnostic tool to read the DTC freeze frame data. Record information such as vehicle speed, temperature, and voltage at the time of the fault to determine whether it is a continuous fault (current DTC) or a historical fault.+5 more →
B172D›
DTC B172D indicates the Supplemental Restraint System (SRS) detects a short to vehicle power (B+) in the Left Second Row Side Airbag Module ignition circuit. During self-diagnostics or continuous monitoring, the Airbag Control Unit (ACU) detects an abnormally high voltage (near 12V battery voltage) in the left second row side airbag deployment circuit. This exceeds the normal monitoring range (typically a low voltage or specific resistance value). This short to power forces the airbag system into fail-safe mode, disables the affected airbag to prevent accidental deployment, and illuminates the airbag fault warning lamp. As the second row side airbag is part of the passenger restraint system, this fault constitutes a severe safety risk. The short circuit can prevent the airbag from deploying during a collision or, in extreme cases, trigger unintended deployment.
Causes
— Under-seat harness worn or pinched: Frequent fore-and-aft adjustment of the left middle-row seat or passengers stepping on the harness damages the side airbag harness insulation, causing contact with the power wire.— Airbag module internal short circuit: The igniter bridge wire inside the left middle-row side airbag assembly shorts to the housing or power terminal, usually due to manufacturing defects or water ingress.— Connector terminal misalignment: A backed-out or bridged terminal in the yellow airbag connector under the seat (usually near the seat rail) shorts the ignition circuit terminal to the power terminal.+2 more →
Actions
— Safety Preparation: Disconnect the 12V battery negative terminal, wait at least 90 seconds to fully discharge the SRS system capacitors, wear an anti-static wrist strap, and disable the vehicle high-voltage system (for hybrid/EV models).— Fault Confirmation and Freeze Frame Analysis: Use a dedicated BYD diagnostic tool (VDS or ED400) to read the fault code, confirm B172D is a current fault (Active), and record the freeze frame voltage values and vehicle status at the time of the fault.+6 more →
B172D12›
In DTC B172D12, "B" indicates the Body/Safety system, "172D" identifies the Left Middle Row Side Airbag, and "12" indicates a Short to B+. This fault indicates the airbag control unit (SRS ECU) detects abnormal continuity between the Left Middle Row Side Airbag squib circuit and the vehicle power supply (12V). Under normal conditions, the airbag squib resistance is approximately 1.5-3.0Ω. The SRS ECU monitors circuit current and voltage through the low-side or high-side driver circuit. When the ECU detects circuit voltage continuously exceeding the threshold (typically >5V and approaching battery voltage), it identifies a short to B+. This fault prevents normal airbag deployment (causing failure to deploy or unintended deployment during a collision). As a hard fault, it triggers a continuous SRS warning light, forces the system into fail-safe mode, and disables the affected airbag function.
Causes
— Wiring harness wear near the seat slide rail: Forward and backward adjustment of the left middle-row seat causes the airbag wiring harness to rub against the seat frame or slide rail edge. Prolonged friction damages the insulation, allowing internal wires to contact a power wire (such as the seat heating supply or a constant power wire) and cause a short circuit.— Airbag module connector fault: Backed-out connector terminals, oxidation from water ingress, or bent pins shorting the squib terminal to the power supply terminal. Common after vehicle wading or washing.— Airbag squib internal short circuit: Insulation breakdown of the gas generator squib inside the airbag module shorts the resistance wire to the housing (excluding ground) or power supply. Internal module quality issues or previous impact damage usually cause this.+2 more →
Actions
— Safety preparation: Turn off the ignition, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault Confirmation: Connect the BYD VDS diagnostic tool. Read the complete DTC information and freeze frame data (record vehicle speed, temperature, etc., at the time of the fault). Confirm B172D12 is a current fault (Active), not a history fault.+6 more →
B1730›
DTC B1730 indicates the airbag control unit (SRS ECU) detects a resistance of 0 ohms in the left second-row side airbag firing circuit (typically located inside the left B-pillar trim or on the side of the left second-row seat). This indicates a short to ground in the firing circuit, damaged wiring harness insulation shorting to ground, or an internal short circuit in the airbag module inflator. This fault forces the SRS system into fail-safe mode, preventing the left second-row side airbag from deploying during a side impact, and continuously illuminates the instrument cluster airbag warning light. Unlike high resistance (open circuit), a 0-ohm resistance typically means current flows directly to ground without passing through the inflator. This is a hard short circuit fault and requires immediate repair.
Causes
— Internal igniter short circuit failure in the left centre row side airbag module (manufacturing defect, moisture ingress, or ageing causing an internal bridge wire short circuit)— Water ingress or bent pins at the airbag wiring harness connector (poor B-pillar trim panel sealing commonly allows rainwater to seep in, causing a short circuit between connector terminals or to ground).— Wiring harness wear causing a short to body ground (frequent seat adjustment, B-pillar trim removal/installation, or modifications pinch the harness and wear through the insulation)+2 more →
Actions
— Safety preparation: Power down the vehicle, disconnect the battery negative terminal, and wait at least 90 seconds to fully discharge the SRS backup power supply and prevent accidental airbag deployment.— Fault confirmation: Use VDS or a dedicated diagnostic tool to read the fault code. Confirm B1730 is a current fault and will not clear. Record freeze frame data to check vehicle status at the time of the fault.+5 more →
B17301A›
DTC B17301A indicates the Supplemental Restraint System (SRS) detected a resistance of 0 ohms in the left middle-row (second-row left-side) side airbag module firing circuit, indicating a hard short circuit. Normal airbag squib resistance is between 2.0 Ω and 4.0 Ω. A resistance of 0 ohms indicates current passes directly through the circuit without load. Possible causes include an internal short circuit in the airbag ignition wire, a wiring harness short to ground, a short circuit between connector terminals, or a fault in the SRS control unit (ACU) internal detection circuit. Upon detecting this fault, the ACU immediately illuminates the airbag warning lamp and disables the left middle-row side airbag to prevent accidental deployment from the short circuit. Consequently, the airbag will fail to deploy during a collision, posing a severe safety hazard.
Causes
— Left middle-row side airbag module internal igniter short circuit: Moisture, aging, overload, or manufacturing defects break down the insulation between the positive and negative terminals of the airbag igniter wire, creating a short circuit.— Seat wiring harness chafed and shorted to ground: During middle-row seat fore/aft sliding or backrest angle adjustment, the airbag wiring harness chafes against the seat frame, slide rail, or spring, damaging the insulation and shorting to the vehicle body ground.— Connector fault: Water ingress, bent pins, dislodged terminals, foreign object ingress, or oxidation in the yellow airbag-specific connector (usually fitted with a shorting bar) located under the seat or inside the C-pillar trim panel causes a short circuit between terminals.+2 more →
Actions
— Safety preparation: Switch the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS system energy storage capacitor to prevent accidental airbag deployment and personal injury.— Fault confirmation: Use the VDS2000 or Launch X431 diagnostic tool to read the fault code. Confirm B17301A is a current (Active) fault, not a history fault. Record the resistance value and ambient temperature from the freeze frame data.+8 more →
B1731›
DTC B1731 indicates the Supplemental Restraint System (SRS) control unit detects the igniter circuit resistance for the left second-row side airbag module (typically located inside the left B-pillar trim panel or on the side of the left rear seat) falls below the normal threshold (BYD models typically specify 1.5-2.5Ω; refer to the workshop manual for exact specifications). Low resistance indicates an abnormal low-resistance path in the circuit. Potential causes include an internal short circuit in the igniter, a wiring harness short to ground, a short between connector terminals, or a faulty internal sampling circuit in the SRS ECU. This fault forces the SRS into fail-safe mode. During a side impact, the airbag may fail to deploy, or in extreme cases, trigger inadvertently. The instrument panel airbag warning light remains illuminated, indicating limited occupant protection system functionality.
Causes
— Left middle-row side airbag module internal igniter short circuit (component aging or impact damage)— Damaged wiring harness insulation causing a short to ground or a short between positive and negative wires (often due to movement friction at the seat adjustment mechanism or B-pillar hinge).— Water ingress, corrosion, or terminal deformation in the airbag connector causes abnormal continuity between terminals (common after vehicle wading or due to poor sealing).+2 more →
Actions
— Use the BYD VDS diagnostic tool to read the complete fault codes and freeze frame data. Confirm B1731 is a current fault, not a history fault. Record the environmental conditions when the fault occurred.— Perform the airbag system safe power-down procedure: Turn off the ignition, disconnect the battery negative terminal, and wait at least 90 seconds (allowing the SRS capacitor to fully discharge). Before disconnecting the airbag module connector, short the wiring harness terminals on the SRS ECU side to prevent accidental deployment.+7 more →
B1732›
DTC B1732 indicates the Airbag Control Unit (ACU) detects the Left Middle Row Side Airbag Module squib circuit resistance falls outside the manufacturer's normal threshold (BYD standard is typically 1.6-2.0Ω, with a ±0.3Ω tolerance). "Resistance too high" usually means the resistance exceeds the upper limit (e.g., >2.5Ω or approaching an open circuit), indicating a high-impedance connection in the circuit. Connector oxidation, poor wiring harness connections, an internal open circuit in the airbag module, or increased partial winding resistance can cause this condition. Essentially, the SRS self-check detects reduced reliability in the secondary protection circuit. This condition can prevent the airbag from deploying fully within the specified time (typically <10ms) or with sufficient energy during a side-impact collision, degrading or disabling side-impact protection for the left middle-row occupant.
Causes
— Airbag wiring harness connector under the left middle-row seat (usually near the seat rail or inside the lower C-pillar trim panel) is loose, has backed-out terminals, or is oxidized/corroded, especially common after vehicle wading or interior cleaning.— Poor contact, partially broken copper strands, or pinched wiring in the harness between the airbag module and the ACU (commonly at flex points from frequent fore-and-aft seat adjustment, or at the body-to-seat connector)— Increased internal igniter resistance in the left middle-row side airbag module (generator winding aging, internal solder joint oxidation, or intermittent open circuit), indicating component end-of-life failure.+2 more →
Actions
— Safety preparation: Turn the ignition switch to OFF, disconnect the negative battery terminal, wait at least 90 seconds to fully discharge the SRS capacitor, and wear an anti-static wrist strap.— Fault confirmation: Use a BYD VDS2000 or equivalent diagnostic tool to read freeze frame data. Record the ambient temperature and voltage at the time the fault occurred. Confirm whether the fault is 'Active' or 'Stored'.+6 more →
B1735›
DTC B1735 indicates the airbag control unit (SRS ECU) detects a communication loss or abnormal circuit resistance in the second-row right side airbag module (typically located in the side of the second-row right seat or inside the C-pillar/door trim panel). Specifically, the inflator circuit of this airbag assembly is open (infinite resistance), or the communication line between the module and the SRS ECU is open. This is an active safety system fault. During a side collision, this airbag may fail to deploy, leaving the second-row right occupant without side impact protection. Disconnected physical connections, damaged wiring harnesses, an open inflator inside the airbag module, or poor terminal contact at the SRS ECU typically cause this fault. Use the dedicated diagnostic tool (VDS2000/VDS3000) and the wiring diagram to pinpoint the fault.
Causes
— The yellow dedicated wiring harness connector under the seat or at the B-pillar is loose, disconnected, or the locking tab is not fully engaged (commonly resulting from frequent fore-and-aft sliding adjustment of the second-row seat or passenger kicks).— Open circuit in the right middle-row side airbag module internal igniter, or module communication circuit fault (airbag assembly damaged)— The wiring harness connecting the airbag module to the SRS ECU is worn or broken, or the seat rail crushed or sheared the harness over time, breaking the copper wire.+2 more →
Actions
— Safety preparation: Turn the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds (to ensure the SRS backup power capacitor fully discharges). Never use a standard multimeter to directly measure the airbag inflator resistance to prevent accidental deployment.— Visual inspection: Remove the second-row right seat side trim panel or lower C-pillar trim panel. Verify the yellow dedicated airbag module connector (usually equipped with a double-locking mechanism) is fully inserted. Confirm the locking tab (CPA) is in the locked position with no looseness or terminal back-out.+4 more →
B17351B›
DTC B17351B indicates the SRS (Supplemental Restraint System) control unit detects a communication interruption or open electrical connection between the right second-row side airbag module (typically located on the right rear seat side or C-pillar) and the main control unit. Specifically, this open circuit fault indicates the airbag ignition circuit resistance falls outside the normal range (typically >10Ω or reading infinite). This fault prevents the affected side airbag from deploying normally during a collision. It may also deactivate the entire airbag system (entering fail-safe mode) and retain only the driver airbag function, severely compromising occupant side-impact protection.
Causes
— Airbag wiring harness connector under the seat or inside the C-pillar trim panel is loose, disconnected, or making poor contact, especially near the adjustable seat slide rail where frequent adjustment causes the connector to loosen.— Open circuit in the right middle-row side airbag assembly internal igniter or module failure. Airbag module aging or an internal open circuit usually causes this.— Physical damage to the wiring harness, especially in the harness between the seat frame and body, where long-term bending and compression fracture the copper core (common in vehicles with frequent fore-and-aft seat adjustment).+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS or ED-400) to read the fault code, confirm whether B17351B is a current fault (Active) or a history fault (History), and record freeze frame data.— Switch off the ignition, disconnect the negative battery terminal and wait at least 90 seconds (to fully discharge the SRS capacitor). Remove the right middle-row seat or C-pillar trim panel and locate the side airbag module connector (usually yellow or orange, with a shorting bar).+5 more →
B1736›
DTC B1736 indicates the Supplemental Restraint System (SRS) detects a short to body ground in the igniter circuit of the right second-row seat side airbag (Side Airbag Module, located on the side of the right second-row seat). Under BYD DTC coding rules, B1736 serves as the general identifier for this fault type. A specific short to ground typically corresponds to B173611 (hexadecimal 11 indicates a short to ground). This fault means the resistance between the two airbag igniter terminals, or between a terminal and the vehicle body, drops abnormally low (typically below 1.0 Ω). The SRS ECU determines this is a short circuit. This fault causes the airbag warning lamp to remain illuminated. The system automatically cuts off the affected airbag circuit to prevent accidental deployment. In a collision, the airbag may fail to deploy normally, severely compromising occupant safety. Applicable models primarily include the Tang, Song MAX, and other 6-seat or 7-seat vehicles equipped with second-row side airbags.
Causes
— Wiring harness wear at the seat slide rail: Frequent forward and backward adjustment of the right middle-row seat rubs the underlying yellow airbag wiring harness (typically located inside the seat rail) against the metal bracket. This friction damages the insulation and shorts the copper wire to body ground.— Connector water ingress and oxidation: During vehicle wading or interior cleaning, the under-seat airbag connector (yellow waterproof connector) fails to seal properly. Moisture enters, causing a short circuit between terminals or to ground. This is especially common in humid southern regions.— Improper seat removal and installation: Pulling the wiring harness during seat removal for repairs or when installing floor mats or seat covers causes the airbag connector to loosen, pins to bend and contact the vehicle body, or metal clips to pierce the harness insulation.+2 more →
Actions
— Safe power isolation and waiting: Turn off the ignition switch, disconnect the negative battery cable, and wait at least 3 minutes (or 5 minutes per the repair manual) to fully discharge the internal SRS ECU capacitor and prevent accidental airbag deployment.— Preliminary visual inspection: Remove the right middle-row seat (second row, right side). Inspect the yellow wiring harness corrugated conduit under the seat, inside the seat rail, and on the side of the backrest for wear, cuts, or crush marks. Inspect the connector for looseness, water ingress, or green corrosion.+4 more →
B173611›
DTC B173611 indicates the SRS (Supplemental Restraint System) control unit detects an abnormal short to body ground in the firing circuit of the right second-row side airbag module (typically located on the side of the right second-row seat or the lower B-pillar). The airbag module contains an electric squib (igniter) controlled by the airbag ECU, with a normal resistance between 1.5 and 2.5 Ω. The diagnostic system logs a short to ground when the circuit-to-ground resistance drops below the threshold (typically under 1 Ω or a specific calibrated value). This fault produces the following consequences: 1) The side airbag fails to deploy during a collision, resulting in a loss of side-impact protection; 2) In extreme cases, short-circuit current triggers unintended airbag deployment, causing occupant injury; 3) The SRS enters fail-safe mode, disabling the entire vehicle airbag system. This constitutes a highest-severity electrical safety fault requiring immediate repair.
Causes
— Airbag module internal igniter coil short circuit: Moisture, aging, or manufacturing defects in the squib inside the right middle-row side airbag module damage the internal coil insulation, causing direct continuity to the module metal housing (ground).— Physical wiring harness damage: Frequent seat adjustment, foreign object pinching, or vehicle vibration wears the wiring harness insulation near the seat rail, inside the B-pillar trim panel, or under the floor, causing the signal wire to directly contact the body metal.— Connector water ingress and corrosion: Vehicle wading, a blocked sunroof drain tube, or interior cleaning allows moisture to enter the right middle-row side airbag connector, causing pin oxidation and creating a short-to-ground path.+2 more →
Actions
— Safety pre-operation: Set the vehicle to OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds (to fully discharge the SRS capacitor and prevent accidental airbag deployment).— Initial visual inspection: Remove the right middle-row seat side trim panel or lower B-pillar trim panel. Inspect the airbag module for external damage, the wiring harness for obvious damage or burn marks, and the connector for looseness or water ingress.+4 more →
B1737›
DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.
Causes
— Right middle-row seat side airbag wiring harness worn or insulation damaged, causing a short circuit to a body permanent live circuit (such as seat heater or adjustment motor power supply wires).— Water ingress, corrosion, or deformed terminals in the yellow airbag connector under the seat or inside the B-pillar trim, causing a short circuit between the power terminal and the airbag circuit terminal.— Internal igniter in the right middle-row side airbag assembly (curtain or seat airbag) shorted to power. Internal airbag module manufacturing defects or previous external impacts typically cause this.+2 more →
Actions
— Safety preparation: Switch the vehicle to OFF, disconnect the 12V battery negative terminal and wait at least 90 seconds (to fully discharge the SRS backup power capacitor). Do not measure airbag terminals directly with a multimeter.— Fault confirmation: Use VDS or the BYD dedicated diagnostic tool to read DTC B1737 and freeze frame data. Record parameters such as vehicle speed and temperature when the fault occurred. Confirm the current fault is not a historical fault.+6 more →
B173712›
DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Causes
— A damaged right middle-row side airbag wiring harness or aged insulation causes interference and chafing against the body power wiring harness, resulting in a short circuit. Common causes include driving through water, chassis scraping, or improper wiring harness routing during modification.— Airbag connector (usually located under the seat or inside the B-pillar trim panel) with bent pins, backed-out pins, or water corrosion, causing a short circuit between the ignition circuit terminal and the power supply terminal.— Internal short circuit in the SRS clock spring or insulation failure between coil windings causes the steering wheel or seat side airbag circuit to short to power.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment and personal injury.— Visual inspection: Remove the right B-pillar lower trim panel or seat side trim panel. Check the right middle row side airbag connector (usually a yellow plug) for looseness, water ingress, corrosion, or foreign objects. Check the wiring harness for obvious damage or crush marks.+5 more →
B173A1A›
DTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.
Causes
— Airbag module internal igniter short circuit: Manufacturing defects, aging, or prior electrostatic discharge caused the igniter resistance wire to blow or short-circuit.— Seat wiring harness mechanical damage: The right middle-row side airbag wiring harness typically routes through the seat frame or moves during seat adjustment. Prolonged friction damages the insulation, shorting the core wire to ground.— Connector fault: Bent or backed-out internal terminals in the yellow dedicated airbag connector, or a pin-to-pin short circuit caused by water or cleaning fluid ingress.+2 more →
Actions
— Safe power-down: Turn off the ignition, disconnect the 12V battery negative terminal, and wait at least 90 seconds for the SRS capacitor to fully discharge.— Fault confirmation: Use the dedicated diagnostic tool to read freeze frame data, record vehicle status when the fault occurred, and confirm whether the fault is current or historical.+5 more →
B173B›
DTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Causes
— Damage to the compressor controller (IPM module) internal drive circuit or speed detection circuit prevents the module from interpreting the speed sensor Hall signal.— Compressor internal Hall speed sensor fault (sensor chip damage, magnet demagnetization, increased installation gap due to vibration)— Open circuit, short to ground, or poor connector contact in the speed feedback wiring harness between the controller and compressor (pin corrosion, backed-out pins, or water seal failure)+2 more →
Actions
— Connect the BYD dedicated diagnostic tool (VDS2000 or X431). Enter the air conditioning system to read all DTCs and freeze frame data. Verify B173B is an Active fault, not a History fault. Record the compressor speed, current, and voltage data at the time of the fault.— Visually inspect the electric compressor exterior and the high- and low-pressure pipe connections. Verify there is no refrigerant leakage or physical damage. Inspect the controller heat sink for overheating and discoloration.+8 more →
C102A00›
DTC C102A00 indicates the IPB (Integrated Power Brake) control unit detects an invalid or abnormal reverse gear signal. In BYD DM-i and e-Platform 3.0 models, the gearshift controller (or TCU) typically sends the reverse gear signal to the IPB system via the CAN bus. This signal activates reverse-related brake control strategies, such as reverse automatic hold release logic, reverse misapplication prevention (R-AEB), and hill reverse assist control. The IPB triggers this fault code if it fails to receive a valid reverse gear signal within a predetermined time, if the received signal contradicts actual vehicle state logic (e.g., vehicle speed conflicts with the reverse gear signal), or if the signal voltage or message format falls outside the valid range. This fault may prevent the automatic hold system from releasing normally during reverse maneuvers, cause abnormal brake pedal feel, or trigger the brake system degraded protection mode, compromising reversing safety.
Causes
— Defective IPB control unit software version or abnormal calibration data (signal parsing algorithm error)— CAN communication fault between gearshift actuator controller (or TCU) and IPB (wiring open circuit, short circuit, or abnormal terminal resistance)— Reverse gear signal hardwire connection fault (for some early models or specific configurations, including wiring open circuit, short to ground, or short to power)+2 more →
Actions
— Use the BYD VDS diagnostic tool to read the complete fault information, including freeze frame data (recording vehicle speed, gear status, power supply voltage, etc., at the time of the fault), and confirm the specific operating conditions when the fault occurred.— Check the IPB system software version against the BYD Technical Service Bulletin (TSB) to determine if a software defect exists regarding reverse gear signal monitoring. If necessary, upgrade the IPB control unit software or refresh the calibration.+5 more →
B173C›
DTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Causes
— Airbag module connector loose or terminals oxidized: Vehicle vibration, water ingress, or long-term oxidation increases contact resistance at the plug under the seat or inside the C-pillar trim. This is the most common cause.— Wiring harness worn or partially broken: The right middle-row side airbag wiring harness routes through the seat slide rail or B/C-pillar area. Long-term bending and friction partially break the copper strands, reducing the effective conductive cross-sectional area.— Internal airbag module fault: Igniter bridge wire aging, cold solder joints, or manufacturing defects cause internal resistance to drift outside the normal 2.0-3.0Ω range.+2 more →
Actions
— Safe power-down: Turn off the ignition, disconnect the 12V battery negative terminal, and wait at least 3 minutes (or the time specified in the workshop manual) to fully discharge the SRS capacitor and prevent accidental deployment.— Locate the component: Confirm the physical location of the right middle-row side airbag (on Song MAX, Tang, and similar MPV/SUV models, this typically mounts on the side of the right second-row seat backrest or inside the C-pillar trim panel). Remove the relevant trim panels or seat components to expose the yellow SRS connector.+5 more →
B1740-00›
This DTC indicates that during the self-check, the SRS (Supplemental Restraint System) control module detects, through its internal diagnostic circuit, an open circuit in the left rear side airbag (left curtain airbag or seat side airbag) communication line, or the airbag module initialization resistance falls outside the normal range (typically 2.0-3.0 ohms). Consequently, the SRS module cannot confirm the physical presence or electrical connection integrity of the airbag, and the system registers the airbag as "not present". In a collision, this airbag may fail to deploy, disabling side impact protection for the left rear passenger. Additionally, the SRS system enters fail-safe mode, which may alter the deployment logic of the entire airbag system and illuminate the instrument cluster airbag fault warning lamp.
Causes
— Loose, disconnected, or poor contact at the left rear side airbag wiring harness connector (common after seat adjustment, B-pillar trim removal/installation, or rear passenger kicks)— Airbag module internal inflator squib open circuit or abnormal resistance (internal airbag fault or aging)— Open circuit, short circuit due to chafing, or short to ground in the wiring harness from the SRS module to the left rear airbag (long-term flexing at the seat rail or B-pillar sill breaks the copper wires).+2 more →
Actions
— Use the BYD VDS or a dedicated diagnostic tool to read the fault code. Confirm B1740-00 is a Current DTC, not a history fault. Check the voltage and ambient temperature in the freeze frame data.— Disconnect the battery negative terminal and wait at least 90 seconds to discharge the residual charge in the SRS capacitor to ensure safe operation and prevent accidental airbag deployment.+6 more →
B1740›
DTC B1740 indicates the Airbag Control Unit (ACU) detects an open circuit in the Left Rear Side Airbag during the self-check, or the system configuration marks the airbag module as 'not present'. Hardware causes typically include an open circuit between the ACU and the left rear side airbag (resistance exceeds the threshold, typically >6Ω) or an internal open circuit within the airbag module itself. Software configuration issues occur when the vehicle configuration code (VCU configuration) mismatches the actual hardware. Examples include configuring a low-spec vehicle with high-spec parameters or installing a seat assembly without a side airbag. This fault prevents the side airbag from deploying during a collision, severely compromising side-impact protection. The SRS system also illuminates the instrument cluster airbag warning lamp and may disable the entire airbag system to enter safety mode.
Causes
— Loose, disconnected, or poor contact at the left rear seat side airbag wiring harness connector: frequent fore-and-aft seat adjustment or folding can loosen the yellow airbag connector under the seat, or pin oxidation can cause high resistance.— Airbag module fault: Left rear side airbag internal igniter open circuit. Common causes include airbag aging, moisture ingress, or failure to replace a previously deployed airbag.— Physical damage to the wiring harness: Seat frame crushing, rodent chewing, or seat modification damaged the airbag wiring harness inside the seat, causing an open circuit.+2 more →
Actions
— Safety Check and Preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds for the SRS capacitor to discharge to prevent accidental airbag deployment. Remove the left rear seat assembly to access the airbag assembly.— Visual inspection and connection check: Verify the yellow airbag connector under the seat (usually marked 'SRS' or 'AIRBAG') is fully locked. Inspect the plug for signs of water ingress, corrosion, or recessed pins. Disconnect and reconnect the connector; listen for a 'click' to confirm locking.+5 more →
B1741-00›
DTC B1741-00 indicates the airbag system (SRS) control module detected a short to ground in the Left Rear Side Airbag deployment circuit. The SRS ECU continuously monitors the airbag inflator resistance via its internal diagnostic circuit (normal range: 2.0-3.0 ohms). When the system detects an abnormally low circuit resistance (near 0 ohms) or a short-to-ground path, it logs a short-to-ground fault. This fault prevents the affected airbag from deploying during a collision or, in extreme cases, risks unintended deployment due to wiring faults. Consequently, the SRS immediately illuminates the airbag warning lamp and disables the entire airbag system to protect occupants.
Causes
— Damaged or worn left rear seat side airbag wiring harness: Frequent fore/aft seat adjustment or passenger entry/exit wears through the harness insulation at seat frame friction points, causing the wire to contact vehicle body metal and create a short to ground.— Water ingress or corrosion in the under-seat wiring harness connector: Liquid seeping into the yellow SRS connector under the left rear seat during interior cleaning causes a short circuit between terminals or a short to ground.— Airbag igniter internal fault: Short circuit in the igniter element inside the left rear side airbag module, possibly due to a manufacturing defect or hidden damage from an unreplaced module following a vehicle accident.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes to discharge the residual charge in the SRS capacitor to prevent accidental airbag deployment.— Visual inspection: Remove the left rear seat and side trim panel. Check the yellow SRS wiring harness for obvious damage or crush marks. Focus on the harness fixing points and bends near the seat rail.+5 more →
B1741›
DTC B1741 indicates the Airbag Control Module (ACM) detected a short to ground in the Left Rear Side Airbag squib circuit. In the SRS system, two wires (high side and low side) connect each airbag inflator to the ACM. These circuits normally maintain a high-impedance state. The ACM logs a short to ground when it detects an abnormally low circuit resistance (close to 0Ω) or a voltage drop to ground potential. This condition causes the following: 1) The airbag system enters fail-safe mode, disabling this airbag and related airbags. 2) The airbag warning light (SRS light) remains illuminated. 3) The airbag fails to deploy during a collision, severely compromising occupant safety. 4) The system may store related fault codes, such as B1740 (airbag not present). Different vehicle models or model years may define B1741 as a left front window lift switch signal fault in the Left Body Domain Controller (LBDC) system, reflecting the evolution of BYD fault codes across electrical architectures.
Causes
— Wiring harness mechanical damage: Continuous flexing of the left rear door wiring harness at the door hinge wears and cracks the insulation. The internal wire contacts the metal door frame, creating a short to ground.— Connector water ingress and corrosion: Poor sealing of the airbag connector inside the left rear door trim panel allows an electrolyte path to form between the pins or to ground after car washing, wading, or rainwater leakage, causing a short circuit.— Airbag module internal fault: Short circuit in the airbag assembly internal igniter (squib), or internal wiring shorted to the metal housing. Manufacturing defects or long-term high-temperature aging typically cause this.+2 more →
Actions
— Safety preparation and power disconnection: Set the vehicle to OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds (120 seconds for some models) to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual and physical inspection: Remove the left rear door trim panel. Inspect the yellow SRS wiring harness sleeve at the door hinge for damage. Inspect the airbag connector (typically located at the door-to-body joint or under the seat) for water ingress, corrosion, or deformed pins.+4 more →
B174111›
DTC B174111 indicates a short to ground in the Left Rear Side Airbag ignition circuit. In the SRS (Supplemental Restraint System), this means the wiring between the Airbag Control Unit (ACU) and the left rear side airbag module (typically the low-side drive wire or high-side power wire) has an abnormal electrical connection to vehicle ground (GND). This drops the circuit resistance abnormally, typically below 1-2 ohms. This fault causes the ACU to detect a short-circuit risk in the airbag circuit. To prevent accidental deployment or insufficient ignition energy, the system disables the airbag and illuminates the instrument cluster airbag warning light. The left rear side airbag typically mounts inside the C-pillar trim panel or on the side of the rear seat. The wiring harness routes through crush-prone areas, such as the sill trim panel and seat rails, making mechanical damage a frequent cause of this fault.
Causes
— Wiring harness mechanical damage: A loose or detached wiring harness retaining clip inside the left rear door sill trim causes the harness to rub against the seat slide rail or sharp body edges over time. This friction damages the insulation, causing a short circuit to the metal body.— Improper seat modification/repair: During rear seat removal/installation or leather wrapping, retaining screws or clips pierce the side airbag wiring harness, causing the core wire to short to ground.— Connector water ingress and corrosion: Vehicle wading or poor floor sealing allows water to enter the airbag connector below the left B/C pillar (usually a yellow waterproof plug), causing electrolytic corrosion between the terminals and a short to ground.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault Confirmation and Data Recording: Use a VDS2000 or Launch X431 diagnostic tool to read complete fault codes and freeze frame data. Record vehicle speed, temperature, voltage, and other parameters at the time of the fault. Confirm B174111 is a current fault (Present), not a history fault.+6 more →
B1742-00›
DTC B1742-00 indicates the SRS (airbag) control module detects an abnormally low-resistance short circuit between the Left Rear Side Airbag squib circuit and the vehicle positive power supply (+B, typically 12V battery voltage). Under normal conditions, high resistance isolates the airbag squib circuit from both power and ground. The SRS module internal capacitor releases current only at the moment of deployment. A short to power causes: 1) airbag deployment failure (the power supply bypasses the trigger current); 2) a risk of unintended deployment (if short circuit resistance changes or voltage fluctuates); 3) the SRS system to enter fail-safe mode, disabling all airbag functions. This fault is a continuous, non-intermittent hard short.
Causes
— Mechanical wear of the rear seat wiring harness: Long-term friction between the left rear seat fore-and-aft slide rail adjustment mechanism and the floor wiring harness damages the yellow airbag wire insulation. The exposed copper core contacts and short-circuits to body power wires (e.g., seat heating power wire, 12V permanent live wire).— Connector water ingress causing electrolytic corrosion: Water ingress in the rear footwell from wading, high-pressure washing, or a blocked air conditioning drain hose causes water to seep under the seat. Water accumulates between the pins of the airbag wiring harness connector (typically located under the seat or below the C-pillar). This creates an electrolytic conductive path, causing a short circuit between the power and signal terminals.— Modification damage: Clips, screws, or other fasteners used to install aftermarket full-cover seat covers, leather seats, or rear seat heating pads directly pierce or crush the airbag wiring harness, causing the internal wires to short to the power wire.+2 more →
Actions
— Safe power-off and discharge: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds (3 minutes on some models) to fully discharge the SRS control module internal backup capacitor and prevent accidental airbag deployment.— Removal and visual inspection: Remove the left rear seat assembly (cushion and backrest) and the lower C-pillar trim panel to expose the left rear side airbag module (usually located on the side of the seat backrest or inside the C-pillar trim panel) and wiring harness connector. Inspect the wiring harness insulation for damage, scorch marks, or punctures. Check the connector for water ingress, oxidation, or deformed pins.+4 more →
B1742›
DTC B1742 indicates an abnormal short circuit between the left rear side airbag ignition loop (typically installed in the left rear seat backrest or C-pillar) and the vehicle power supply positive (B+). In the Supplemental Restraint System (SRS), the airbag module connects to the Airbag Control Unit (ACU) via two wires. Normal wiring harness resistance measures approximately 2-3 ohms. The diagnostic system triggers this fault code upon detecting a short to power in this circuit (voltage approaching 12V battery voltage instead of the normal low-voltage signal). This fault is extremely dangerous. The short circuit can cause unexpected airbag deployment while driving, severely injuring occupants. Furthermore, the system enters protection mode and disables the airbag, preventing inflation during a collision and eliminating side-impact protection. Additionally, the SRS illuminates the instrument cluster airbag warning light and may lock the entire airbag system, disabling all airbags.
Causes
— Wiring harness insulation wear under the seat or inside the B-pillar/C-pillar: Frequent fore/aft seat adjustment or friction during passenger entry/exit damages the airbag wiring harness insulation, causing the wire core to directly contact the metal vehicle frame or power circuits.— Water ingress or corrosion in the under-seat connector: Spilled drinks, water seepage during car washing, or vehicle wading creates a conductive path or electrolytic corrosion between the airbag connector terminals, causing a short circuit between the pins.— Airbag module internal fault: Insulation failure of the igniter (Squib) inside the airbag inflator causing a short circuit between the bridgewire and housing, or an internal circuit board fault.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (some models require 3 minutes) to fully discharge the SRS backup power supply and prevent accidental airbag deployment during repair.— Fault confirmation and freeze frame retrieval: Use a dedicated diagnostic tool (such as BYD VDS2000/3000) to read the complete fault codes and freeze frame data. Record the vehicle status when the fault occurred (vehicle speed, temperature, etc.) and confirm whether the fault is intermittent.+5 more →
B174212›
DTC B174212 indicates the SRS (Supplemental Restraint System) electronic control unit detects an abnormally low-resistance connection between the left rear side airbag squib circuit (typically installed in the left rear C-pillar or left rear door frame side panel) and the vehicle power supply positive terminal (B+). Under normal conditions, the airbag squib circuit remains in a high-resistance open state. The SRS ECU momentarily closes the circuit only during a collision to release current and ignite the gas generator. A short to power causes: 1) The airbag to fail to deploy during a collision (the power supply bypasses the current, preventing sufficient heat generation to ignite the squib). 2) A potential risk of unintended airbag deployment in extreme cases due to the circuit fault (although modern SRS systems typically feature shorting bars and dual-stage trigger protection). Affected components include the left rear side airbag module, C-pillar/floor wiring harness, seat wiring harness (if the seat integrates the airbag), and the SRS ECU. As a Level 3 fault (the highest safety classification), the system immediately illuminates the instrument cluster airbag warning lamp and disables the entire airbag system.
Causes
— Wiring harness wear under the left rear seat or inside the C-pillar trim panel: During long-term vehicle use, fore-and-aft seat adjustment or friction from C-pillar trim clips damages the airbag wiring harness insulation, causing the copper core to directly contact the vehicle body metal frame or a power wire.— Left rear side airbag module internal igniter short circuit: Moisture in the gas generator ignition charge or a manufacturing defect causes the ignition resistance wire to short to the housing.— Connector water ingress or terminal corrosion: Vehicle wading, vehicle washing, or poor window seals cause water ingress into the left rear airbag wiring harness connector (usually yellow), creating an electrolytic conductive path between the terminals.+2 more →
Actions
— Safety preparation: Switch the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS ECU internal capacitor and prevent accidental airbag deployment.— Fault confirmation: Use the genuine BYD VDS diagnostic tool to read all DTCs. Check for accompanying fault codes such as B1742-11 (short to ground) and B1742-13 (open circuit). Confirm the fault is Active, not a historical fault.+5 more →
B174400›
The BYD Qin PRO series defines DTC B174400 as "Crash Output Fault", a critical safety fault in the SRS airbag system. This indicates the airbag control unit (ACU) detects a circuit abnormality when attempting to output a crash trigger signal to other vehicle systems. In BYD new energy vehicles, this specifically refers to a crash signal interaction fault between the ACU, the high-voltage system manager (BMS/VCU), and the body control module (BCM), including: 1) A short to power/ground or an open circuit in the crash output signal line; 2) Damage to the ACU internal crash output driver MOSFET circuit; 3) Abnormal feedback signals from receiving actuators (e.g., high-voltage power cut-off relay, fuel pump cut-off relay, and door unlock relay). During a collision, this fault prevents high-voltage system disconnection (electric shock risk), fuel pump shutoff (fire risk), and automatic door unlocking (hindering escape and rescue). This significantly increases the risk of secondary accidents. Hyundai/Kia vehicles typically define this DTC as "Front Passenger Side Pressure-Type Side Impact Sensor ID Error", indicating cross-brand definition differences. For BYD systems, prioritize diagnosing the crash output signal circuit and ACU driver circuit faults.
Causes
— Damaged internal crash output drive circuit in the SRS control unit (ACU), or an outdated software version causing a false DTC.— Collision output signal wiring harness (connected to the high-voltage system manager, BCM, fuel pump relay, etc.) worn at the door hinge, shorted to power/ground, or open circuit.— Internal short circuit at the High-Voltage System Manager or BCM crash signal receiving port, causing abnormal feedback voltage.+2 more →
Actions
— Use a BYD VDS2000 or the latest diagnostic tool to read the complete SRS fault codes and freeze frame data. Confirm whether B174400 is a current or historical fault code. Record key information such as vehicle speed and time of occurrence.— Visually inspect the front and sides of the vehicle for signs of collision. Check the SRS control unit (located under the center console or gear selector) for exterior condition, secure mounting, and water ingress at the plug connections.+4 more →
B174A-00›
This fault code indicates the measured resistance of the left rear side airbag (Side Airbag, Left Rear) firing circuit is 0 ohms, confirming a short circuit. In the BYD SRS (Supplemental Restraint System), normal airbag squib resistance ranges from 1.5 to 3.5 ohms. A 0-ohm reading indicates a direct short circuit between the firing circuit power wire (Squib+) and ground wire (Squib-), or the airbag module detects abnormally low internal resistance. This condition causes the SRS control unit to identify an unintended deployment risk, illuminate the airbag warning light, and disable the left rear side airbag. Unlike a "resistance too high/open circuit" fault (infinite resistance), damaged wiring insulation, connector water ingress, or mechanical damage typically causes short circuits. Inspect the circuit immediately to prevent potential overheating.
Causes
— Water ingress, moisture, or oxidation in the left rear seat side airbag connector (usually located under the seat or inside the C-pillar trim) causing a short circuit between metal terminals.— The rear seat adjustment mechanism, seat belt mechanism, or a foreign object chafes the airbag wiring harness under the seat or inside the B/C-pillar trim panel, damaging the insulation and causing the positive and negative conductors to contact and short circuit.— Rear passengers stepping on the side of the seat, heavy objects compressing the seat, or fixing clips piercing the wiring harness during seat modifications (leather retrimming or installing seat covers) cause an internal short circuit in the wiring harness.+2 more →
Actions
— Use the BYD VDS2000/2100 diagnostic tool to read the fault code. Confirm B174A-00 is 'Active' and record the voltage and ambient temperature from the freeze frame data.— Perform the safety procedure: turn off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds (to fully discharge the SRS capacitor and prevent accidental airbag deployment).+6 more →
B174A›
DTC B174A indicates the measured resistance of the Left Rear Side Airbag ignition circuit is 0 ohms, representing a short circuit fault in the airbag system. Normal airbag igniter resistance ranges from 1.5 to 3.5 ohms. A 0-ohm reading indicates a short to ground or short to power in the ignition wiring, allowing current to directly bypass the igniter. This causes the SRS control unit to identify the airbag circuit as faulty, illuminate the airbag warning light, and disable deployment of the Left Rear Side Airbag. In a side collision, this airbag may fail to inflate normally, severely compromising side impact protection for rear passengers. This fault represents a loss of airbag ignition circuit integrity. Repair the system immediately to ensure correct operation of the passive safety system.
Causes
— Left rear side airbag module internal igniter short circuit (airbag internal bridge wire short circuit or moisture ingress)— Airbag wiring harness short to body ground (seat slide rail wears through harness insulation, seat frame pinches harness)— Water ingress, oxidation, or bent pins in the airbag connector under the seat or in the C-pillar causing a short circuit between the positive and negative terminals.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds to discharge residual power in the SRS system and prevent accidental airbag deployment.— Fault confirmation: Use BYD VDS or a dedicated diagnostic tool to read the DTC and confirm B174A is a current fault (Present), not a history fault.+7 more →
B174B-00›
This DTC indicates the firing circuit resistance of the left rear side airbag (typically integrated into the left rear door C-pillar trim panel or the side of the left rear seat backrest) falls below the SRS control module threshold (normal range 2.0-3.0Ω; fault threshold typically <1.0Ω or near 0Ω). Low resistance indicates an abnormal low-resistance path in the circuit. Causes include a short to ground, damaged wiring harness insulation, shorted connector pins, or an internal short in the airbag inflator bridge wire. This fault forces the SRS system into a degraded mode and illuminates the airbag warning light. During a collision, the affected airbag may fail to deploy (as the control module detects a short and disables the firing circuit) or, in extreme cases, deploy unintentionally.
Causes
— Water ingress and oxidation in the left rear door sill or C-pillar wiring harness connector: Vehicle wading, car washing, or poor sealing forms a conductive water film between the connector pins, creating parallel resistance.— Wiring harness mechanical damage: Improper removal/installation of the rear seat or door sill trim causes the seat rail to crush and chafe the wiring harness, resulting in a short to body ground.— Airbag module internal fault: Short circuit in the igniter bridge wire or damp propellant causes an abnormal drop in resistance.+2 more →
Actions
— Safe power-down: Disconnect the 12V battery negative terminal and wait at least 3-5 minutes to fully discharge the SRS energy storage capacitor and prevent accidental deployment.— Inspection procedure: Remove the left rear C-pillar trim panel and door sill trim panel. Check the connection status of the white/yellow side airbag connector (usually marked 'Side Airbag').+6 more →
B174B›
This DTC indicates the SRS (Supplemental Restraint System) ECU detects that the igniter circuit resistance for the left rear side airbag (typically located in the left rear seat backrest side or C-pillar trim panel) is below the calibrated threshold (typically < 1.5Ω; standard value 2.0 ± 0.3Ω). Electrically, low resistance usually indicates a parallel resistance path in the circuit. Possible causes include an inter-turn short circuit in the internal igniter coil, damaged wiring harness insulation shorting to body ground, or conductive contamination between connector terminals. This fault forces the SRS into a degraded mode. During a collision, the ECU may disable deployment of the affected airbag due to the circuit anomaly (fail-safe). Furthermore, if the resistance drops near 0Ω, the system risks inadvertent deployment. This safety-critical fault requires immediate repair.
Causes
— Internal short circuit in the left rear side airbag squib: Aging, moisture ingress, or manufacturing defects cause an inter-turn short circuit in the gas generator ignition coil inside the airbag module, reducing total resistance.— Harness chafed and shorted to ground: Damage to the harness sleeve at the seat frame, slide rail, or hinge causes the igniter harness (usually yellow) to contact the vehicle body metal, creating a parallel resistance path to ground.— Connector water ingress or corrosion: An aging left rear door frame seal or driving through water allows moisture to enter the seat side airbag connector, causing electrolytic corrosion between the terminals or forming a conductive water film, which reduces circuit resistance.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the low-voltage battery negative terminal, and wait at least 3 minutes to fully discharge the SRS ECU capacitor and prevent accidental airbag deployment.— Fault confirmation: Connect the VDS or dedicated diagnostic tool, read the fault code, confirm B174B is active, and record the freeze frame data (vehicle speed, temperature, etc. at the time of occurrence).+5 more →
B174C-00›
DTC B174C-00 indicates the Airbag Control Unit (ACU) detects the left rear side airbag (typically located on the outboard side of the left rear seat backrest or inside the C-pillar trim panel) igniter resistance exceeds the calibrated threshold (normal range: 1.5-3.0 Ω, typically calibrated around 2.0 Ω). This SRS continuity monitoring fault indicates a high-resistance condition in the circuit between the ACU and the airbag igniter. Potential causes include an open circuit, poor contact, or an internal open circuit within the airbag assembly. This fault prevents the affected airbag from deploying during a collision. The system illuminates the airbag warning light and disables the associated airbag function.
Causes
— Airbag wiring harness connector (usually yellow) under the left rear seat or at the C-pillar is loose, not fully seated, or making poor contact due to a broken locking clip.— The seat adjustment mechanism interferes with the airbag wiring harness, causing prolonged friction between the harness and the seat slide rail or frame. This damages the insulation, resulting in a partial wire break or complete open circuit.— Open circuit or abnormally high resistance in the left rear side airbag assembly igniter (squib), common after a vehicle collision (even without airbag deployment) or due to component aging.+2 more →
Actions
— Safety preparation: Turn the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 3 minutes to discharge the SRS system capacitor to prevent accidental airbag deployment.— Fault confirmation: Connect a diagnostic tool (such as Launch X-431 or BYD VDS), read the DTC to confirm B174C-00 is a current fault, and check the live data for the airbag's real-time resistance value (usually >5Ω or open circuit).+5 more →
B174C1B›
This fault code indicates the Airbag Control Module (ACM) detects the squib circuit resistance of the left rear side airbag (typically integrated into the left rear seat backrest side or C-pillar trim panel) exceeds the calibrated upper limit. Normal airbag squib resistance ranges from 1.5Ω to 3.0Ω. The ACM logs a 'high resistance' fault when it detects the value continuously exceeding the threshold (typically above 4.5Ω). This active safety system functional fault means the airbag may deploy abnormally, deploy late, or fail to deploy completely during a side-impact collision, disabling side protection for the left rear passenger. An abnormal drop in squib circuit conductivity causes this fault. Increased contact resistance, a partial open circuit, or an aging internal squib spiral coil can trigger this condition.
Causes
— Loose, oxidized, or water-corroded airbag wiring harness connector under the left rear seat or at the B-pillar, causing increased contact resistance.— Frequent seat adjustment causes the wiring harness to chafe at the slide rail mounting point, resulting in partially broken copper strands (poor contact) and a high-resistance condition.— Aging, open circuit, or manufacturing defect in the left rear side airbag module internal igniter.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds to fully discharge the SRS energy storage capacitor. Use the diagnostic tool to read the freeze frame data and confirm B174C1B is a current fault code (Current DTC), not a history fault.— Visual inspection: Remove the left rear seat assembly (or lower C-pillar trim panel), locate the left rear side airbag wiring harness connector (usually a yellow plug), and check for looseness, signs of water ingress, green oxidation, or backed-out pins; check the wiring harness sleeve at the seat slide rail for damage.+5 more →
B174C›
DTC B174C indicates the SRS (Supplemental Restraint System) detects the inflator resistance of the left rear side airbag (usually located inside the left rear C-pillar trim panel or on the side of the left rear seat) exceeds the system-calibrated threshold (typically above 3.0Ω; normal range is 1.5Ω-3.0Ω). This fault indicates a high-resistance condition or open circuit in the airbag inflator circuit. Inflator aging, poor wiring harness contact, or a broken wire can cause this condition. This fault prevents the airbag from deploying correctly during a side-impact collision and continuously illuminates the dashboard airbag warning light (SRS light). The system enters fail-safe mode, and some models may limit the seat belt pretensioner function.
Causes
— Left rear C-pillar airbag connector loose, pin backed out, or terminal oxidized/corroded, causing increased contact resistance.— Moisture ingress or aging of the igniter charge in the left rear side airbag module, or an open circuit in the squib coil, causing abnormally high resistance.— Long-term bending and wear of the wiring harness at the rear seat folding mechanism or C-pillar trim panel edge causes internal wire breakage or shielding layer damage.+2 more →
Actions
— Safety Preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes to discharge the SRS capacitor residual charge and prevent accidental airbag deployment.— Fault confirmation: Use the BYD dedicated diagnostic tool (VDS3000) to read the DTC and confirm B174C is a current fault (Active), not a history fault (History).+6 more →
B1750-00›
This DTC indicates the SRS (Supplemental Restraint System) ECU cannot establish valid communication with the right rear side airbag module and detects an open circuit in the airbag circuit (resistance exceeds the normal 2-3Ω range, typically reading as infinite or >10Ω). This failure disables protection for the right rear occupant during a side impact and may trigger an SRS downgrade mode, affecting the coordinated deployment strategy of other airbags. On certain vehicle configurations, incorrect vehicle coding (flashing high-spec software to a low-spec vehicle) can cause a false DTC.
Causes
— Right rear seat side airbag connector loose or disconnected, or terminals oxidized (common after frequent seat adjustment or failing to reconnect after cleaning).— Airbag module internal open circuit or abnormal resistance (module aging, moisture ingress, or electrostatic damage)— Wiring harness open circuit or wear causing a short to ground or short to power (long-term bending and wear of the harness inside the seat slide rail, B-pillar, or sill trim panel).+2 more →
Actions
— Safe power down: Turn the power switch to OFF, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS system capacitor and prevent accidental airbag deployment during repair.— Visual inspection: Remove the right rear seat and side trim panel, locate the airbag module connector (usually on the side of the seat backrest or below the B-pillar), and check for looseness, disconnection, water ingress, or terminal oxidation. Disconnect and reconnect the connector, and confirm the locking tab locks securely in place.+4 more →
B1750›
DTC B1750 indicates the SRS (Supplemental Restraint System) control unit detects an open circuit, abnormal resistance, or a physically missing Right Rear Side Airbag module. This level 2 airbag system fault (a non-fatal hardware fault affecting passive safety functions) indicates the SRS control unit cannot establish normal communication with the right rear side airbag or detects infinite resistance in the airbag igniter circuit. This fault prevents the right rear side airbag from deploying during a collision, severely compromising side-impact protection. The instrument cluster continuously illuminates the airbag warning light. Possible causes include an open circuit in the airbag module wiring harness, a loose connector, an open circuit in the internal airbag igniter, or incorrect airbag assembly installation following vehicle modification or repair.
Causes
— Right rear side airbag wiring harness connector loose, oxidized, or making poor contact (commonly the yellow connector inside the C-pillar trim panel or under the seat)— Open circuit in the internal airbag module initiator, or resistance outside the standard range (Normal: 1.8-2.5 Ω; excessively high or low values trigger a fault).— Wiring harness chafed or pinched at the door hinge, seat track, or body sheet metal opening, causing an open circuit (especially on vehicles with frequent seat adjustment or door operation).+2 more →
Actions
— Safety preparation: Turn the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 3 minutes for the SRS system capacitors to fully discharge to prevent accidental airbag deployment.— Fault confirmation: Use the BYD VDS2000 or VDS1000 diagnostic tool to read all fault codes. Confirm only B1750 or related sub-codes (such as B1750-00) are present, and record the freeze frame data.+6 more →
B1751-00›
B1751-00 is a Supplemental Restraint System (SRS) hard fault code indicating a short circuit to body ground (GND) in the right rear seat side airbag squib circuit (typically integrated into the seat backrest or C-pillar trim). The SRS ECU internal detection circuit continuously monitors the airbag squib circuit resistance (normal range: 2.0-3.0 Ω; 1.6-2.1 Ω on some models). The ECU registers a short to ground when it detects circuit resistance to ground below 1.0 Ω (near 0 Ω). This fault causes the following: 1) The affected airbag fails to deploy during a collision, losing its protective function. 2) The SRS enters fail-safe mode, which may restrict seat belt pretensioner operation. 3) The instrument panel airbag warning light remains illuminated, indicating a critical safety hazard. This is a level 3 severe fault requiring immediate repair.
Causes
— Mechanical wear of the under-seat wiring harness: Frequent right rear seat movement or folding causes long-term friction between the seat frame and the wiring harness sleeve. Damaged insulation allows the wire to directly contact the metal vehicle body frame, creating a short to ground (most common cause, approx. 60% of cases).— Airbag module internal short circuit: The bridge wire inside the airbag inflator shorts to the housing. Airbag module aging, moisture ingress (water entering through open windows), or improper previous repairs usually cause this fault (approximately 25% of cases).— Connector corrosion or water ingress: Poor sealing of the wiring harness connector under the right rear seat (usually designated KJ10 or similar) allows water entry after vehicle washing or wading, causing a short circuit between terminals or to ground (approximately 10% of cases).+2 more →
Actions
— Safety preparation: Turn the vehicle power mode to OFF, disconnect the negative battery cable, and wait at least 90 seconds to fully discharge the SRS backup power supply and prevent accidental airbag deployment during repair.— Fault confirmation: Connect a genuine BYD diagnostic tool (such as VDS or ED400). Read the fault codes to confirm B1751-00 is present. Record the freeze frame data (ambient temperature and voltage). Attempt to clear the fault code, cycle the power, and observe if the fault returns.+6 more →
B1751›
DTC B1751 indicates the SRS (Supplemental Restraint System) control module detects a short to ground in the right rear side airbag deployment circuit. Specifically, an abnormally low resistance path (typically less than 1 ohm) exists between the vehicle body ground and the igniter wiring for the right rear side curtain airbag (C-pillar side curtain airbag) or the right rear seat side airbag. The standard igniter resistance is 2.0 ± 0.3 ohms. When the ECU detects a circuit short to ground, it immediately sets this DTC and cuts off the airbag deployment circuit to prevent accidental deployment while driving or failure to deploy during a collision. This safety-critical fault causes the airbag warning light to remain illuminated and may fail to protect the right rear passenger during a crash.
Causes
— Right rear side curtain airbag (C-pillar curtain airbag) module internal igniter is shorted or damaged, causing abnormally low resistance.— The wiring harness from the SRS ECU to the right rear airbag chafes in the sill trim panel or C-pillar area, damaging the insulation and shorting to the vehicle body metal.— Failed seal on the right rear seat airbag connector (if equipped with seat side airbag) allows water ingress or moisture, causing a short circuit between terminals or a short to ground.+2 more →
Actions
— Connect the BYD dedicated diagnostic tool (VDS or ED400), enter the SRS system, and read the data stream. Verify the right rear side airbag resistance reads 0 ohms or close to 0 ohms, and confirm the fault is currently present.— Disconnect the battery negative terminal and wait at least 3 minutes for the SRS capacitor to fully discharge to ensure safe operation.+6 more →
B1752-00›
DTC B1752-00 indicates the right rear side airbag igniter circuit is shorted to vehicle power (B+). In the SRS (Supplemental Restraint System) circuit architecture, the airbag igniter is a low-impedance (nominal 2-5Ω) resistance wire. Normally, the SRS control unit uses an internal boost circuit to supply a momentary high current (approx. 1-3A) to deploy the airbag during a collision. Detecting a short to the 12V power supply in the igniter harness indicates an abnormal high-potential path in the circuit. This creates two risks: first, continuous power supply may cause accidental airbag deployment without a collision (although modern SRS controllers typically feature short-circuit protection); second, during an actual collision, the external power short prevents the control unit from forming an effective current loop to deploy the airbag, disabling the safety function. Consequently, the SRS control unit immediately illuminates the airbag warning lamp, stores this DTC, disables the right rear side airbag and related linked protection functions, and enters fail-safe mode.
Causes
— Long-term bending and wear at the seat frame hinge damages the right rear seat side airbag wiring harness insulation, causing a short circuit to the seat heating or adjustment motor power wire.— Frequent folding or lowering of the rear seat, or modifying seat covers, causes the seat rails or metal frame to pinch the wiring harness, damaging the wire insulation and causing a short to power.— Water ingress and corrosion at the airbag connector (yellow plug) at the right rear C-pillar or under the seat (commonly due to aged sunroof drain tube leaks or vehicle wading) causes electrolyte conduction between terminals, creating a short circuit.+2 more →
Actions
— Safety preparation: Turn the power switch to OFF, disconnect the negative battery terminal, and wait at least 3 minutes (to fully discharge the SRS energy storage capacitor). Never measure the airbag circuit while energized.— Visual inspection: Remove the right rear seat and lower C-pillar trim panel. Check the right rear side airbag module connector (usually located on the side of the seat back or below the C-pillar) for looseness, water ingress, corrosion, or foreign objects. If necessary, clean with electrical contact cleaner and blow dry.+5 more →
B175111›
This DTC indicates the Supplemental Restraint System (SRS) detected an abnormally low-resistance connection (short to ground) between the right rear side airbag squib circuit (typically located on the outer side of the right rear seat or inside the C-pillar trim panel) and vehicle chassis ground (GND). Under normal conditions, the airbag squib circuit maintains a specific resistance (approximately 2-3Ω). When the ACU (Airbag Control Unit) detects circuit resistance near 0Ω, it registers a short to ground. This constitutes a critical safety fault. The system immediately illuminates the SRS warning lamp and disables the right rear side airbag and related coordinated protection functions to prevent accidental deployment while driving or deployment failure during a collision.
Causes
— Right rear side airbag wiring harness insulation wear: Long-term friction against the seat frame, C-pillar trim panel retaining clips, or door sill trim edges wears through the harness insulation. The exposed internal wires directly contact the vehicle body metal and short to ground.— Water ingress and oxidation at the connector under the seat or B/C pillar: A blocked rear sunroof drain tube, poor rear windshield sealing, or water entering the right rear door sill during a car wash causes the internal pins of the yellow SRS connector to short circuit or short to ground.— Wiring harness fatigue caused by frequent seat adjustment: Frequent forward and backward sliding of the right rear seat compresses and excessively bends the airbag wiring harness at the seat rail, breaking the internal copper wire and causing a short to ground.+2 more →
Actions
— Safe power-off: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Locate the component: Confirm the right rear side airbag installation position (on Qin Pro series, typically inside the right rear seat outer backrest or C-pillar). Remove the right rear seat or lower C-pillar trim panel to expose the yellow SRS wiring harness connector.+5 more →
B1752›
DTC B1752 indicates a short circuit to battery positive (B+) in the RHS Rear Side Airbag squib circuit. In the Supplemental Restraint System (SRS), normal airbag inflator resistance is 2-3 ohms. The control unit determines circuit status by monitoring circuit current and voltage drop. When wiring harness insulation damage causes a short to the 12V power supply wire, the control unit detects an abnormally high potential (near battery voltage) and triggers DTC B1752. This fault causes the system to disable the affected airbag (fail-safe mode), preventing deployment during a collision. Additionally, continuous current creates a risk of unintended airbag deployment. The system classifies this as a level 3 severe fault.
Causes
— Wiring harness wear inside the right B-pillar trim panel: Frequent rear passenger entry and exit or seat adjustment wears the harness sleeve between the B-pillar and the seat, shorting the copper wire to the body power supply wire.— Water ingress into under-seat connector: Water seeps into the airbag wiring harness connector under the right rear seat during vehicle wading or interior cleaning, causing a short circuit or conductive corrosion between terminals.— Airbag module internal fault: Abnormally low igniter resistance or an internal short circuit in the right rear side airbag assembly causes abnormal circuit resistance.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor. Wear an anti-static wrist strap. Do not use radio equipment near the airbag assembly.— Initial diagnosis: Use a Launch X-431 or BYD dedicated diagnostic tool to read all SRS fault codes, check for B1752 and accompanying fault codes (such as B1751 short to ground), and record the freeze frame data.+6 more →
B175212›
DTC B175212 indicates the Supplemental Restraint System (SRS) detects abnormal continuity between the ignition circuit of the right rear side airbag (Side Airbag Module, typically installed inside the C-pillar trim panel or on the side of the seat backrest) and the vehicle power supply positive (B+). In the SRS architecture, the airbag squib circuit must maintain high-resistance isolation from both power and ground. When the ECU detects that the circuit voltage continuously exceeds the threshold (typically over 80% of supply voltage) and the resistance falls below the specified value (<1kΩ), it identifies a short to power. This fault may cause: 1) Airbag deployment failure during a collision (ECU triggers protective cut-off). 2) Accidental airbag deployment in extreme cases due to false triggering. 3) SRS fail-safe mode activation, limiting overall vehicle airbag functions.
Causes
— Mechanical damage to the wiring harness under the seat: The right rear seat fore-and-aft adjustment mechanism interferes with the wiring harness mounting point. Prolonged chafing damages the insulation, exposing the power wire and causing a short circuit to the vehicle body metal.— Connector water ingress and corrosion: Driving through water, a blocked sunroof drain tube, or spilled drinks in the rear cause a short circuit between the terminals of the airbag wiring harness connector at the C-pillar or under the seat (usually at the junction of the floor and seat wiring harnesses).— Airbag module internal fault: High-temperature aging or manufacturing defects damage the inflator igniter coil insulation, causing a short circuit between the two terminals or to the housing.+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 90 seconds (120 seconds for some models) to fully discharge the SRS backup capacitor and prevent accidental airbag deployment.— Fault confirmation and freeze frame analysis: Use the BYD VDS diagnostic tool to read the complete fault codes and freeze frame data. Record parameters such as vehicle speed, temperature, and voltage at the time of the fault to confirm whether the fault is intermittent.+6 more →
B175A-00›
DTC B175A-00 indicates the Airbag Control Module (ACM) detects 0 ohms resistance in the igniter (inflator) circuit of the right rear side airbag, typically located in the right rear seat side or C-pillar trim panel. Normal igniter resistance is 2.0-3.0 ohms. A resistance of 0 indicates a short circuit. Possible causes include an internal igniter short, a wiring harness short to ground, a short between connector terminals, or a control module internal driver circuit fault. This fault forces the SRS system into fail-safe mode. The right rear side airbag may fail to deploy during a collision, and the airbag warning lamp (SRS lamp) may illuminate continuously.
Causes
— Airbag igniter internal short circuit: Moisture, manufacturing defects, or aging causes an internal short circuit in the igniter bridgewire or pyrotechnic charge inside the airbag module.— Wiring harness short circuit: Seat adjustment wear, pinching, water ingress, or rodent chewing damaged the wiring harness insulation under the right rear seat or in the C-pillar area, causing a short to ground or a short between twisted pair wires.— Connector fault: Airbag connector (usually yellow) has bent or backed-out terminals, or the shorting bar did not separate correctly during mating, causing a short circuit between terminals.+2 more →
Actions
— Safety preparation: Turn the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Locate the component: Confirm the position of the right rear side airbag (Qin series models typically mount this on the side of the right rear seat backrest or inside the lower C-pillar trim panel). Visually inspect the yellow dedicated connector and wiring harness for damage, water stains, or crush marks.+4 more →
B175A›
DTC B175A indicates the Right Rear Side Airbag ignition circuit resistance measures 0Ω, indicating a short to ground in the airbag circuit or an internal short circuit in the airbag module. Normal airbag inflator resistance ranges between 1.5 and 3.5 ohms (typically 2.0-2.8Ω). When the SRS control module detects a resistance of 0Ω, it identifies a circuit short fault, immediately disables airbag deployment, and illuminates the instrument panel airbag fault warning lamp. Due to this fault, the Right Rear Side Airbag may fail to inflate and deploy during a side impact, severely compromising occupant protection. Common causes include wiring harness wear, connector water ingress, or an internal short circuit in the airbag module.
Causes
— Short circuit to ground caused by worn SRS wiring harness insulation under the right rear seat: Sliding the seat forward and backward or adjusting the height rubs the yellow SRS wiring harness under the seat against the metal slide rail and springs. Damaged insulation allows the copper wire to directly contact the vehicle body ground.— Airbag connector water ingress or bent pin short circuit: The right rear side airbag connector is located on the side of the seat backrest or inside the C-pillar trim panel. Vehicle wading, improper car washing, or rainy weather easily causes water ingress, resulting in a short circuit between the pins. Alternatively, disconnecting and reconnecting the connector during seat repairs can bend the pins, causing them to make contact.— Internal short circuit in the airbag module (gas generator): Short circuit in the airbag igniter bridge wire, or damp propellant causing an abnormal resistance drop. This condition is rare, but requires replacing the entire airbag module.+2 more →
Actions
— Safety preparation and fault confirmation: Disconnect the negative battery terminal and wait at least 3 minutes. Use the BYD VDS dedicated diagnostic tool or Launch X431 to confirm DTC B175A. Check the resistance value in the freeze frame data (should display 0.0Ω). Check for accompanying SRS fault codes (such as B175B left rear side airbag fault).— Visually inspect the connector: Remove the right rear seat backrest side trim panel or lower C-pillar trim panel. Locate the yellow SRS wiring harness connector (usually with a double-locking mechanism). Inspect inside the connector for water stains, oxidation, corrosion, or bent or deformed pins. Clean with electrical contact cleaner and blow dry.+5 more →
B175B-00›
DTC B175B-00 indicates the SRS (Supplemental Restraint System) control unit detects the right rear side airbag igniter circuit resistance (typically located in the right rear seat side or C-pillar trim panel) falls below the manufacturer threshold (normal range: 1.8–3.0 Ω; fault condition: below 1.0 Ω or near 0 Ω). This constitutes a low-resistance airbag circuit fault, meaning the control unit identifies a short circuit risk (wiring harness short to ground, wire-to-wire short, or internal short within the airbag module). Consequently, the affected side airbag may fail to deploy during a collision (as the ECU interrupts the trigger signal due to the circuit anomaly) or, in extreme cases, deploy unintentionally. Simultaneously, the SRS system illuminates the instrument cluster airbag warning light and may disable the entire airbag system to protect occupants.
Causes
— Right rear side airbag module internal igniter short circuit: Airbag internal igniter wire resistance is abnormally low due to manufacturing defects, aging, or moisture ingress.— Wiring harness chafed and shorted to ground: Seat adjustment mechanism, seat belt anchor, or sheet metal edge wears through the wiring harness insulation, shorting the wire to the vehicle body.— Connector water ingress and corrosion: Vehicle wading, a blocked sunroof drain tube, or aging seals cause water ingress into the lower right B/C-pillar airbag connector (typically located under the seat or at the base of the C-pillar). Electrolytic corrosion between the pins creates a low-resistance path.+2 more →
Actions
— Safety preparation: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 3 minutes (or follow the workshop manual to ensure the SRS capacitor fully discharges) to prevent accidental airbag deployment during repair.— Data confirmation: Connect the VDS2000/DiLink diagnostic tool. Enter the SRS system and read the live data stream. Verify the right rear side airbag resistance is below the standard value (record the specific resistance value, such as 0.3Ω or 0.0Ω).+6 more →
B175B›
DTC B175B indicates the Airbag Control Unit (ACU) detects the igniter (squib) circuit resistance for the right rear side airbag (typically the right C-pillar curtain airbag or right rear seat side airbag) falls below the system threshold (generally <1.5 Ω). Normal airbag igniter resistance is 2.0-3.0 Ω. Low resistance indicates a circuit short to ground, a wire-to-wire short, or an internal short within the airbag module igniter. The ACU consequently registers the airbag as deployed or the circuit as faulty, disabling the airbag deployment function. During a side impact, the right rear side airbag fails to inflate and protect the occupant. This condition may trigger a continuous airbag warning lamp and constitutes a critical fault compromising passive safety.
Causes
— Wear or crushing of the right rear side airbag wiring harness damages the insulation, causing a short to ground (commonly due to improper removal or installation of the C-pillar trim panel or the seat slide rail pinching the wiring).— Water ingress, oxidation, or deformed pins at the airbag wiring harness connector (usually located inside the right rear door sill trim panel or below the C-pillar), causing a short circuit between terminals.— Airbag gas generator (igniter) internal short circuit failure; resistance permanently low.+2 more →
Actions
— Read the fault code using the BYD VDS2000 or ED400 diagnostic tool. Confirm B175B is an active fault. Record the freeze frame data and check the specific resistance value displayed in the data stream (typically <1.0Ω).— Disconnect the battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment.+7 more →
B175B1A›
DTC B175B1A indicates the right rear side airbag igniter circuit resistance falls below the normal ECU threshold (typically below 1.0 Ω). In the BYD SRS (Supplemental Restraint System), standard airbag igniter resistance is generally 2.0–3.0 Ω. If the ECU continuously detects abnormally low circuit resistance, it logs a short circuit fault (indicating a possible short to ground or internal igniter short circuit). This fault causes the following: 1) The airbag may fail to deploy during a collision, resulting in a loss of side protection. 2) The airbag may deploy unexpectedly in extreme cases. 3) The SRS enters fail-safe mode and illuminates the airbag warning light. Common causes include wiring harness wear, connector water ingress, or an internal airbag module short circuit.
Causes
— Right rear side airbag module internal igniter short circuit (internal bridge wire short circuit or moisture ingress)— Wiring harness wear causing a short to ground (commonly chafed near the seat track or pinched inside the C-pillar trim)— Water ingress into the connector or terminal corrosion (vehicle wading, rear floor water ingress, or moisture intrusion into the connector after a car wash)+2 more →
Actions
— Use the BYD VDS diagnostic tool to read fault codes, confirm B175B1A is a current fault, record freeze frame data, and check for accompanying SRS fault codes (such as B175C).— Perform the safe power-off procedure: disconnect the battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment.+6 more →
B175C-00›
DTC B175C-00 indicates the airbag control unit (SRS ECU) detects resistance in the Right Rear Side Airbag ignition circuit above the calibrated threshold. Normal airbag igniter resistance ranges from 1.6Ω to 2.4Ω (standard value approximately 2.0Ω). The ECU sets this fault when it detects resistance exceeding approximately 2.8Ω or a high-resistance state in the circuit. This fault indicates poor contact or a partial open in the ignition circuit, or abnormal internal resistance in the airbag module. As a functional fault in the passive safety system, it may prevent the side airbag from deploying during a collision. Because the SRS uses a two-stage diagnostic mechanism, this fault code continuously illuminates the airbag warning lamp and may force the entire airbag system into a downgraded protection mode, even if the vehicle remains drivable.
Causes
— Loose or oxidized right rear seat side airbag wiring harness connector: Frequent seat movement or damp environments increase contact resistance at the connector pins. This is the most common cause of the fault.— Airbag wiring harness wear or internal breakage: Repeated harness bending at the seat rail, B-pillar, or sill trim panel partially breaks the copper wire without creating a complete open circuit, resulting in abnormally high resistance.— Airbag igniter internal fault: Igniter resistance wire inside the airbag module is aged or poorly connected, causing the resistance value to fall outside the normal range.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes to discharge the residual charge in the SRS capacitor to prevent accidental airbag deployment. Wear an anti-static wrist strap. Do not measure the airbag directly with a standard multimeter (use a dedicated airbag tester or limit the multimeter current to below 10mA).— Visual inspection: Remove the right rear door sill trim panel and seat side trim panel. Inspect the airbag wiring harness for wear, crushing, or water stains. Specifically check the connector under the seat for looseness or a broken locking tab.+5 more →
B175C›
DTC B175C indicates the airbag control unit (SRS ECU) detects that the igniter (squib) resistance for the right rear side airbag (typically located in the right rear seat backrest side or C-pillar area) exceeds the upper normal threshold. The SRS system continuously monitors each airbag igniter's resistance via a low-current circuit; the normal range is typically 1.5-3.0 ohms. If the resistance remains above approximately 3.5-4.5 ohms (specific thresholds vary by model), the system flags a 'resistance too high' condition. This fault indicates a high-resistance state in the airbag circuit. Possible causes include poor connector contact, a partially broken wiring harness, igniter degradation, or a faulty ECU internal sampling circuit. Safety Impact: Insufficient current may prevent this airbag from deploying during a collision, or the system may trigger a safety strategy disabling the entire airbag system, degrading occupant protection.
Causes
— Loose right rear side airbag connector, water ingress causing oxidation, or backed-out terminals (commonly affects connectors under the seat or inside the C-pillar trim panel, where frequent seat adjustment or damp environments increase contact resistance).— Internal aging or a partial open circuit within the airbag igniter causes abnormally high internal resistance (common in older vehicles or vehicles exposed to high temperatures).— Worn wiring harness or broken strands, especially in the under-seat harness. Long-term bending and friction partially break the copper strands, reducing the effective conductive cross-sectional area (the seat harness protective sleeve design on some BYD models has a wear risk).+2 more →
Actions
— Use the VDS diagnostic tool to read the DTC freeze-frame data, confirm the environmental conditions (temperature, voltage) when the fault occurred, and check for history DTCs or related DTCs (such as sub-code B175C-00).— Perform the safe power-down procedure: Disconnect the battery negative terminal and wait at least 3 minutes for the SRS capacitor to fully discharge to prevent accidental airbag deployment.+5 more →
B175C1B›
DTC B175C1B indicates the SRS (Supplemental Restraint System) detects the right rear side airbag ignition circuit resistance exceeds the normal upper limit (typically > 10Ω; standard value 2.0-5.0Ω). This fault represents a high-resistance or open-circuit condition in the airbag ignition circuit. During a collision, the airbag control unit (ACU) may fail to supply sufficient current to ignite the gas generator. Consequently, the right rear side airbag will not deploy properly, severely compromising occupant side-impact protection. The manufacturer-specific '1B' sub-code typically indicates high resistance or an intermittent circuit.
Causes
— Poor contact at the airbag wiring harness plug: Long-term vibration, oxidation, or water ingress increases terminal contact resistance at the right rear side airbag connector (usually located inside the C-pillar trim panel or under the seat).— Wiring harness wear or open circuit: Forward and backward seat movement causes mechanical wear on the harness between the seat frame and vehicle body, breaking the internal copper strands without complete separation (high-resistance state).— Airbag assembly internal fault: An open circuit or poor connection in the gas generator igniter coil causes an abnormal increase in circuit resistance.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes for the airbag system to discharge completely. Verify zero system voltage using a multimeter.— Fault confirmation: Connect the VDS2000/Launch X431 diagnostic tool, read and record the DTC B175C1B status (current/history), and check the specific value of 'right rear side airbag resistance' in the data stream (usually displays as above 10Ω or open circuit).+5 more →
B175D›
This fault code indicates the SRS (Supplemental Restraint System) control module detects a resistance of 0 Ω (or below 0.5 Ω) in the Left Front Side Curtain Airbag squib circuit. Under normal conditions, standard airbag squib resistance is 2.0 to 3.0 Ω (typical BYD specification is 1.5 to 4.0 Ω). A 0 Ω resistance indicates a short circuit in the squib circuit. Possible causes include a wiring harness short to ground, a wire-to-wire short (power wire shorted to ground wire), or an internal short in the squib bridge wire. This fault causes the SRS control module to identify the airbag circuit as abnormal, illuminate the airbag warning light, and disable Left Front Side Curtain Airbag deployment. In a collision, this side curtain airbag will fail to inflate and deploy, severely compromising side impact protection. Additionally, the short circuit creates a potential risk of unintended airbag deployment.
Causes
— Airbag igniter internal short circuit: The igniter bridge wire inside the left front side curtain airbag module melts and welds together due to a manufacturing defect, aging, or impact, causing direct continuity between the two terminals and resulting in a resistance of 0.— Harness short to ground: The harness from the SRS control unit to the left front side curtain airbag (typically running along the left A-pillar, B-pillar, C-pillar, and roof side rail) has damaged insulation and contacts the vehicle body metal frame, causing a short to ground.— Connector terminal short circuit: Water ingress, oxidation, corrosion, bent or deformed terminals, or foreign metal objects inside the wiring harness connector (located below the A-pillar or near the B-pillar, typically connecting to the body harness) cause a short circuit between the power terminal and the ground terminal.+2 more →
Actions
— Safety preparation: Park the vehicle on level ground, apply the parking brake, turn the ignition switch to OFF, disconnect the 12V battery negative cable, and wait at least 90 seconds (to fully discharge the SRS backup power capacitor and prevent accidental airbag deployment).— DTC Confirmation: Reconnect the battery, turn the ignition switch to ON, and access the SRS system using the BYD dedicated diagnostic tool (VDS2000 or VDS6000). Read the DTCs to confirm B175D is a current fault (Active), and record the ambient temperature and vehicle status from the freeze frame data.+6 more →
B175E›
DTC B175E indicates the Left Front Side Curtain Airbag ignition circuit resistance is below the normal threshold established by the SRS control unit (ACU) (typically 1.0–3.0 Ω, depending on model year). Low resistance indicates a short circuit, either complete (near 0 Ω) or partial. This fault causes the SRS system to flag the circuit as abnormal. During a collision, the airbag may fail to deploy or may deploy unintentionally. Consequently, the ACU illuminates the airbag warning light, stores the fault code, and may disable the entire airbag system to protect occupants.
Causes
— Airbag wiring harness wear or crushing causes a short circuit between the positive and negative wires: The side curtain airbag wiring harness routes along the A-pillar and roof side rail. Long-term vibration may damage the harness insulation, especially near the door hinge or harness retaining clips.— Airbag connector water ingress or terminal corrosion: The left front side curtain airbag connector sits below the A-pillar or inside the sill trim panel. Car washing, wading, or poor sealing allows water ingress, causing terminal short circuits or reduced resistance.— Side curtain airbag inflator internal short circuit: A short circuit in the internal igniter bridge wire or damp propellant causes an abnormal drop in resistance, indicating a faulty airbag assembly.+2 more →
Actions
— Safe power-down and wait: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds (to fully discharge the SRS capacitor). Do not measure the airbag circuit while powered on.— Read freeze frame and data stream: Connect the diagnostic tool to read the B175E freeze frame data, and record the vehicle speed, temperature, and other information at the time of the fault; read the SRS data stream to check the real-time resistance value of the left front side curtain airbag (normal: approx. 2.0-3.0Ω; faulty: typically <1.0Ω or displays as 0.0Ω).+4 more →
B175D1A›
DTC B175D1A indicates the SRS (Supplemental Restraint System) ECU detects a resistance of 0 ohms or near 0 ohms in the left front side curtain airbag (head protection airbag) igniter circuit. Normal igniter resistance typically ranges between 2.0 and 3.0 ohms. A resistance of 0 ohms indicates a short circuit (short to ground or short between wires), not an open circuit. This short circuit prevents the SRS ECU from deploying the side airbag during a collision, or in extreme cases, abnormal current causes unintended airbag deployment. The ECU continuously monitors this hard fault and illuminates the airbag warning light. The system enters fail-safe mode, potentially limiting overall airbag system functionality.
Causes
— Airbag module internal igniter short circuit: A broken igniter bridge wire inside the curtain airbag or damp pyrotechnic charge causes a short circuit between the two terminals, reducing resistance to 0.— Wiring harness short to ground: The A-pillar, B-pillar, or roof wiring harness rubs against the metal body during vehicle vibration, damaging the insulation and shorting the wire directly to ground.— Connector terminal short circuit: Water ingress, oxidation, or terminal deformation in the yellow SRS connector below the A-pillar causes direct contact between the positive and negative terminals.+2 more →
Actions
— Safe power-down and discharge: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Check the yellow SRS wiring harness sleeve inside the left A-pillar, B-pillar, and headliner trim panels for wear or compression marks. Check the connectors for water ingress, corrosion, or looseness.+5 more →
B175F›
DTC B175F indicates the SRS (Supplemental Restraint System) control unit detects the left front curtain airbag (CAB) ignition circuit resistance falls outside the normal range (normal value: 2.0–3.0 Ω; fault threshold: >6 Ω or open circuit). This Level 2 airbag system fault means the affected curtain airbag may fail to deploy or deploy late during a collision, severely compromising occupant side-impact protection. The SRS ECU continuously monitors each airbag inflator circuit resistance using a Wheatstone bridge. Excessive resistance typically indicates poor circuit contact, high wiring impedance, or an open circuit within the inflator. On BYD new energy vehicles, check for potential electromagnetic interference from the high-voltage interlock circuit affecting the SRS.
Causes
— Poor contact, oxidation, or corrosion at the left front curtain airbag connector (especially the dedicated yellow connector near the B-pillar and C-pillar, where prolonged moisture exposure oxidizes the terminals).— Airbag wiring harness worn or partially broken (frequent door operation causes fatigue fracture of the roof side rail wiring harness at the hinge, creating a high-resistance connection)— Internal open circuit in the clock spring (spiral cable) (poor contact in the internal flat cable if the curtain airbag circuit on this model passes through the clock spring under the steering wheel)+2 more →
Actions
— Safety preparation: Disconnect the low-voltage battery negative terminal and wait at least 3 minutes to allow the SRS backup capacitor to fully discharge. Wear an anti-static wrist strap. Disable the high-voltage system (perform the high-voltage power-down procedure for new energy vehicles).— Visual inspection: Check the left front side curtain airbag module connector (usually located inside the A-pillar/B-pillar trim) for looseness, water ingress, or corrosion. Check the wiring harness at the door hinge for wear or pinch marks.+5 more →
B1760›
DTC B1760 indicates the SRS (Supplemental Restraint System) control unit detects the Left Front Side Curtain Airbag in a "not present" state. This means the ECU cannot identify the airbag electrical circuit during the self-check, or detects an open circuit or abnormal resistance (normal resistance is approximately 2-5Ω). The side curtain airbag (CAB) mounts inside the roof side rail and protects occupant heads during a side impact or rollover. This level 2 safety system fault prevents the left front side curtain airbag from deploying during a collision and continuously illuminates the instrument cluster airbag warning light. On certain BYD models (such as the Song MAX and Qin petrol version), this fault code may also indicate a driver seat position sensor circuit fault. The SRS uses seat position data to determine the airbag deployment strategy; a failed sensor can cause the system to log a similar code.
Causes
— Open or short circuit in left front side curtain airbag wiring harness (commonly at A-pillar or B-pillar harness connectors, or wear on harness routed under the seat)— Airbag connector loose, terminal backed out, oxidized, or water ingress (especially inline connectors below the A-pillar, inside the headliner, or under the seats)— Open circuit or abnormal resistance in the airbag module internal squib circuit (normal resistance: 2-5 Ω; values outside this range report as not present).+2 more →
Actions
— Use a BYD VDS or Launch X-431 diagnostic tool to read freeze frame data and confirm vehicle status, ambient temperature, and voltage conditions when the fault occurred.— Switch off the ignition, disconnect the battery negative terminal, and wait at least 90 seconds to fully discharge the SRS system and prevent accidental airbag deployment.+7 more →
B17601B›
DTC B17601B indicates the airbag control unit (SRS ECU) detects a disconnected left front curtain airbag (located inside the driver-side roof rail), a communication interruption, or an abnormal resistance value. This is an airbag system hard fault, meaning the left curtain airbag may fail to deploy during a side impact, resulting in a loss of occupant head protection. The SRS ECU typically triggers this fault upon detecting infinite airbag inflator circuit resistance (open circuit) or resistance exceeding the normal threshold (standard value approximately 2.0-3.0 Ω) for longer than the specified time. Possible causes include physical wiring disconnections, module damage, or incorrect configuration. Inspect and repair immediately.
Causes
— Left front side curtain airbag module connector loose or poor contact (located above the left A-pillar or front of the headliner; common after water ingress or interior trim removal and installation)— Airbag igniter internal open circuit or abnormal resistance (broken internal module clock spring causing resistance >10Ω or infinite)— Open circuit in the roof wiring harness or A-pillar wiring harness (frequent bending and wear at the A-pillar pass-through hole breaks the copper core, or a detached retaining clip strains the harness)+2 more →
Actions
— Safety preparation: Switch the vehicle OFF, disconnect the battery negative terminal, wait at least 90 seconds (to ensure the SRS capacitor fully discharges), and wear an anti-static wrist strap.— Initial diagnosis: Connect the BYD dedicated diagnostic tool (VDS or ED400). Read the B17601B freeze frame data (record vehicle speed, temperature, and voltage at the time of the fault) and confirm whether the current fault is a hard fault (Present) or an intermittent fault (History).+5 more →
B1761›
DTC B1761 indicates the Left Front Side Curtain Airbag ignition drive circuit shorted to the vehicle power supply positive (B+). In the SRS system, normal airbag igniter resistance is approximately 2.0-3.0Ω. The control module determines circuit condition by monitoring voltage and resistance. If wiring harness insulation damage, misaligned connector terminals, or an internal airbag module fault causes the ignition circuit to contact a power wire, the control module detects an abnormally high voltage (near battery voltage). The module immediately sets DTC B1761 and enters fail-safe mode. This disables the Left Front Side Curtain Airbag and potentially related airbag functions, preventing deployment during a side impact and creating a severe safety hazard.
Causes
— Harness insulation damage: Chafing, pinching, or rodent bites at the A-pillar, roof side rail, or B-pillar damage the left front curtain airbag harness insulation, causing a short circuit to the body power wire.— Connector fault: Water ingress, corrosion, or a detached terminal at the airbag connector below the A-pillar (usually marked DAB or SAB) causes a short circuit between the ignition circuit terminal and the power supply terminal.— Airbag module internal short circuit: Insulation failure of the side curtain airbag inflator internal igniter causes a short circuit between the terminals or to power.+2 more →
Actions
— Safety preparation: Park the vehicle on a level surface, turn off all electrical equipment, and disconnect the battery negative terminal. Wait at least 90 seconds to fully discharge the SRS capacitors and prevent accidental airbag deployment.— Fault confirmation: Use VDS2000 or the BYD dedicated diagnostic tool to read fault codes. Confirm B1761 is a current fault (Active). Record freeze frame data. Check for accompanying fault codes (e.g., B1762, U0151).+6 more →
B176112›
DTC B176112 indicates a short to power in the left front wiper motor control circuit (although some documents incorrectly label this as an airbag fault, the BYD DTC system designates B17 for the wiper system). This occurs when the Body Control Module (BCM) detects an abnormally low-resistance connection between the left front wiper motor power or control line and battery positive (B+), causing an abnormal increase in circuit current. Symptoms include unintended wiper operation, inability to turn off the wipers, continuous high-speed operation, or complete failure. Severe cases risk wiring harness overheating, blown fuses, or electrical fire. Damaged wiring insulation, internal motor winding breakdown, or sticking relay contacts typically cause this short to power.
Causes
— Damaged insulation on the left front wiper motor wiring harness contacts the body metal frame or power supply wiring, causing a short circuit. Long-term chafing at the firewall pass-through or front compartment hinge commonly causes this.— Damaged insulation on the wiper motor internal armature winding or a shorted carbon brush holder, causing continuity between the motor terminal and the housing.— Wiper motor relay contacts stuck closed or relay internal short circuit, continuously supplying power to the motor.+2 more →
Actions
— Connect the VDS diagnostic tool to read the fault codes and record freeze frame data. Confirm B176112 is currently present and is a hard fault. Check for accompanying related fault codes (such as B176113 short to ground).— Check the condition of the left front wiper motor fuse (usually 30A or 40A) in the dashboard power distribution box or engine compartment fuse box. If blown, identify the cause of the short circuit before replacing the fuse.+6 more →
B1762›
DTC B1762 indicates the SRS (Supplemental Restraint System) detected a short to ground in the Left Front Side Curtain Airbag deployment circuit. Electrically, the side curtain airbag squib is a resistive load (typically 2-5 Ω). The SRS ECU controls it via a twisted pair. The ECU sets this code when it detects the circuit's insulation resistance to body ground falls below the threshold (typically <1 Ω) or when it detects abnormal ground voltage. This fault indicates: 1) Positive or negative squib wiring shorted to body metal within the A-pillar, B-pillar, or C-pillar trim, or in the headliner harness; 2) Igniter bridge wire insulation failure inside the airbag module; 3) Driver MOSFET breakdown inside the SRS ECU. This fault prevents the airbag from deploying during a collision (open-circuit protection mode) or, in extreme cases, creates a risk of unintended deployment. Consequently, the ECU illuminates the airbag warning light and disables the system.
Causes
— Harness wear inside the sill trim panel: The left front curtain airbag harness routes from the SRS ECU along the floor sill to the roof. After removing and installing the sill trim panel, or driving the vehicle through water, a damaged harness protective sleeve causes the copper wire to contact the vehicle body metal.— Water ingress at the A-pillar/B-pillar connector: The side curtain airbag connector is inside the A-pillar upper trim panel or B-pillar interior trim panel. Water leaking from a blocked sunroof drain tube or entering during a car wash causes a short circuit between the connector terminals or to ground.— Airbag module internal fault: Aging of the side curtain airbag igniter internal bridge wire insulation or a manufacturing defect causes a short to ground, typically occurring in vehicles with a history of high-humidity operation.+2 more →
Actions
— Safe power-off and system discharge: Turn off the ignition, disconnect the low-voltage battery negative terminal, and wait at least 5 minutes (10 minutes for some models) to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Locate the physical connection point: Remove the left A-pillar upper trim panel, left B-pillar interior trim panel, and the front edge of the headliner. Find the dedicated yellow connector for the side curtain airbag (usually located above the A-pillar or B-pillar). Inspect the connector for oxidation, water ingress, or foreign objects.+4 more →
C1101›
DTC C1101 indicates the ABS (Anti-lock Braking System) ECU detected its 12V low-voltage supply exceeds the system safety threshold (typically >16V-18V, depending on vehicle calibration). In BYD new energy vehicles, the DC-DC converter converts high-voltage traction battery power to supply 12V to the ABS. When the ECU detects an abnormally high supply voltage, it triggers the overvoltage protection mechanism. This may cause ABS, ESP, EBD, HHC (Hill Hold Control), and Automatic Emergency Braking functions to fail or enter a degraded mode. Unlike a high-voltage insulation fault, this indicates a power management abnormality in the 12V low-voltage system, which directly affects braking safety performance.
Causes
— DC-DC converter fault: The internal voltage regulation circuit of the DC-DC module, which converts high voltage to 12V, fails. The output voltage exceeds 15V-16V, causing ABS ECU power supply overvoltage.— 12V battery aged or damaged: Increased internal resistance or battery plate sulfation causes terminal voltage to surge during charging, resulting in abnormally high system voltage.— ABS module internal power supply monitoring circuit fault: ECU internal voltage sampling circuit or A/D converter fault generates an incorrect overvoltage signal (false alarm).+2 more →
Actions
— Use a diagnostic tool to read fault codes and record freeze frame data. Confirm the specific voltage, vehicle speed, and operating conditions when the fault occurred. Check for accompanying power-related fault codes (such as Type U communication faults or Type B body faults).— Measure the 12V battery status: static voltage should be 12.4-12.8V. After starting the vehicle or powering on, measure the DC-DC output terminal voltage. Normal voltage is 13.5-14.5V. If the voltage remains >15V, diagnose a DC-DC fault.+5 more →
B176211›
DTC B176211 indicates the SRS (Supplemental Restraint System) ECU detected a short to ground in the left front side curtain airbag deployment circuit. Specifically, the SRS ECU continuously monitors the airbag inflator circuit voltage and resistance through its internal diagnostic circuit. When the ECU detects the circuit voltage remaining below the threshold (near 0V) or an abnormally low resistance (well below the normal 2.0-3.0Ω range), it identifies a short to ground. This fault prevents the side curtain airbag from deploying normally during a collision and may disable the entire SRS system (entering fail-safe mode), posing a severe safety hazard.
Causes
— Wiring harness chafing inside the left A-pillar, B-pillar, or C-pillar trim panels: The side curtain airbag wiring harness routes along the left roof side rail and runs down through the A-pillar and B-pillar to connect to the SRS ECU. Prolonged vehicle vibration or previous trim removal and installation can damage the harness insulation, causing the copper wire to contact the body metal and create a short circuit.— Water ingress or corrosion in the upper seat side airbag connector: On some models, the curtain airbag connector is below the left B-pillar or near the C-pillar. Driving through water, a clogged and leaking sunroof drain tube, or improper washing can oxidize and short-circuit the connector pins.— Side curtain airbag module internal igniter fault: Damaged insulation on the igniter bridge wire inside the airbag inflator causes a short circuit to the housing (ground). Damage or aging of the airbag inflator housing usually accompanies this condition.+2 more →
Actions
— Safety Preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (to fully discharge the SRS capacitor). Wear an anti-static wrist strap. Use the BYD VDS2000/VDS2100 diagnostic tool to read the complete fault information and record the freeze frame data (DTC status [current/history], vehicle speed, temperature, etc. at the time of the fault).— Visual inspection and wiring harness check: Remove the left A-pillar trim, left upper B-pillar trim, and front section of the headliner. Inspect the side curtain airbag wiring harness (typically a yellow conduit) for obvious damage, crushing, or burn marks. Focus on sheet metal holes where the harness passes through and retaining clips. Check the connector below the left B-pillar (if equipped) for looseness, water ingress, or pin corrosion.+3 more →
B1763›
DTC B1763 indicates the airbag control unit (SRS ECU) detects a 0 Ω (or near 0 Ω) resistance in the right front curtain shield airbag igniter circuit. Normal airbag igniter resistance is 2.0-5.0 Ω. A 0 Ω resistance indicates a short in the igniter circuit. Possible causes include an internal igniter short, a wiring harness short to ground (GND) or power (B+), or a faulty SRS ECU internal drive circuit. This fault causes the SRS system to enter fail-safe mode. During a collision, the affected curtain shield airbag may fail to deploy. The instrument panel SRS warning light illuminates continuously to indicate limited occupant protection system functionality.
Causes
— Internal short circuit in the right front curtain airbag igniter: Manufacturing defects, aging, or prolonged vibration cause the igniter bridge wire inside the airbag module to break and short together.— Physical damage to the wiring harness: The wiring harness behind the A-pillar trim panel, the headliner wiring harness, or the floor wiring harness wears during accident repairs, modifications (e.g., routing dashcam wiring), or long-term use. This damages the wire insulation, causing a short to ground or short to power.— Connector fault: Water ingress, oxidation, corrosion, or terminal deformation in the airbag wiring harness connector located inside the right front door sill trim panel or below the A-pillar, causing a short circuit between pins.+2 more →
Actions
— Safety Preparation: Turn the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS ECU backup power and prevent accidental airbag deployment during repair.— Fault confirmation and freeze frame analysis: Connect the diagnostic tool to read the freeze frame data for DTC B1763. Record the vehicle speed, temperature, voltage, and other environmental conditions when the fault occurred to determine whether the fault is intermittent or continuous.+5 more →
B17631A›
DTC B17631A indicates the Right Front Side Curtain Airbag ignition circuit resistance is 0 ohms. This means the control module detects a short circuit (short to ground or short to power) in the airbag circuit. In the airbag system (SRS), normal inflator resistance ranges from 1.5Ω to 3.0Ω. A 0-ohm resistance indicates abnormal circuit continuity, presenting the following risks: 1) The side curtain airbag fails to deploy during a collision, resulting in a loss of side impact protection. 2) The wiring short circuit causes unintended airbag deployment in extreme cases. This constitutes a hard fault in the SRS and typically illuminates the SRS warning light continuously. The system enters fail-safe mode and disables the Right Front Side Curtain Airbag.
Causes
— Airbag wiring harness short to ground: The right front side curtain airbag wiring harness chafes inside the A-pillar, C-pillar, or headliner. Damaged insulation causes the wire to ground to the vehicle body, resulting in 0 resistance.— Airbag connector fault: Water ingress, oxidation, or bent pins at the headliner or door frame airbag connector cause a short circuit, resulting in continuity between the signal wire and ground.— Internal short circuit in the airbag unit: The curtain airbag inflator igniter has an internal short circuit (very rare, but a manufacturing defect may cause this).+2 more →
Actions
— Safety preparation: Disconnect the negative battery terminal and wait at least 90 seconds (some models require 3 minutes) to fully discharge the SRS capacitor and prevent accidental airbag deployment during repair.— Visual inspection: Remove the right A-pillar trim, headliner edge, and right front door seal. Inspect the curtain airbag wiring harness for wear, crushing, or signs of water ingress. Focus on contact points between the harness and sharp metal edges on the vehicle body.+5 more →
B1764›
DTC B1764 indicates the Right Front Side Curtain Airbag igniter circuit resistance falls below the SRS control unit (ACU) threshold (typically <1.0Ω or below 70% of the nominal 2.0Ω). This fault suggests an internal inter-turn short circuit in the airbag squib, or a short to ground or power in the wiring harness or connector, causing an abnormal drop in total circuit resistance. This critical safety fault causes the SRS system to detect a short-circuit risk in the airbag circuit, potentially triggering unintended deployment or failure during a collision. Consequently, the system illuminates the airbag warning light and disables the airbag's deployment function, severely compromising side-impact protection.
Causes
— Airbag igniter internal short circuit: Moisture, aging, or manufacturing defects in the bridge wire or ignition charge inside the gas generator reduce internal resistance.— Harness short to ground: Worn airbag harness insulation in the A-pillar, B-pillar, or roof side rail contacts vehicle body metal, causing a short circuit.— Connector fault: Water ingress, oxidation, bent pins, or foreign objects in the airbag connector (usually located below the A-pillar or roof) cause abnormal continuity.+2 more →
Actions
— Safety Preparation: Shift the vehicle into P, apply the parking brake, turn off the ignition, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor.— Fault confirmation: Connect the VDS diagnostic tool, read DTCs to confirm B1764 is a current fault (Active), record freeze frame data, and check for accompanying fault codes such as B1763 (resistance is 0) or B1765 (resistance too high).+8 more →
B1765›
DTC B1765 indicates the resistance in the right front side curtain airbag (RH Side Curtain Airbag) ignition circuit exceeds the normal threshold calibrated by the SRS ECU (typically 2.0-3.0Ω, with an upper limit of approximately 5-6Ω). This constitutes an airbag system loop integrity fault, indicating a high-resistance condition (approaching an open circuit) in the circuit between the SRS control unit and the right front side curtain airbag inflator. This fault causes the SRS ECU to determine the airbag cannot deploy normally, potentially failing to provide lateral head protection during a collision. The system illuminates the airbag warning light and may disable the entire airbag system. Although some OBD-II standards define B1765 as a seat circuit fault, the BYD SRS system (specifically in models like the Song MAX and Qin) defines this code as abnormal right curtain airbag resistance.
Causes
— Internal open circuit or aging of the right front side curtain airbag igniter causes internal resistance to exceed 6Ω.— Airbag wiring harness connector at the A-pillar or roof side rail is loose, oxidized, or has poor contact, causing contact resistance.— Internal copper wire breakage (partial breakage) in the airbag wiring harness where it passes through the door hinge or body bend, causing increased resistance.+2 more →
Actions
— Use BYD dedicated diagnostic tool VDS2000/VDS2100 to read the complete fault codes and freeze frame data. Check for related fault codes such as B1764 (resistance too low) or B1766 (not present).— Perform the safe power-down procedure: turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor.+4 more →
B17661B›
DTC B17661B indicates the airbag control unit (SRS ECU) failed to detect a valid electrical connection or the physical presence of the right front side curtain airbag during the system self-check. This "module missing/configuration error" fault signifies a complete communication loss between the ECU and the airbag module, rather than a simple igniter resistance anomaly. Root causes typically include missing airbag module power supply (12V constant or IG power), poor ground circuit, open or short circuits in the LIN/CAN communication lines, internal airbag module MCU fault, loose connections, backed-out pins, or oxidation at the wiring harness connector, or incorrect vehicle configuration data (e.g., failing to perform online coding after replacing the airbag module). This fault prevents the right front side curtain airbag from deploying during a collision, severely compromising occupant side impact protection. In certain repair scenarios and specific model years, this DTC also indicates a communication loss between the battery management system (BMS) and the vehicle control unit (VCU). Differentiate the diagnosis based on specific symptoms (airbag warning indicator illuminated vs. powertrain fault) and accompanying DTCs.
Causes
— Right front curtain airbag module wiring harness connector (located above the right A-pillar or along the headliner edge) is loose, oxidized, corroded, has backed-out terminals, or makes poor contact, interrupting power supply or communication.— Open circuit, short to power, or short to ground in the communication line (LIN bus or CAN bus) between the airbag module and the SRS ECU, particularly at the A-pillar and headliner wiring harness bends where pinching or chafing causes intermittent faults.— Internal circuit fault in the right front curtain airbag module (damaged power management chip, failed communication chip) or open circuit in the igniter loop causing no module response.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000/3000) to read the complete fault code stream and freeze frame data. Record the vehicle status at the time of the fault (vehicle speed, voltage, temperature). Check for accompanying U-class communication fault codes or related B1766 series fault codes.— Switch off the ignition and wait at least 90 seconds (for capacitor discharge). Remove the right A-pillar trim panel. Visually inspect the right front curtain airbag module connector (usually yellow) for looseness, backed-out terminals, oxidation, or corrosion. If necessary, clean with electrical contact cleaner, apply conductive grease, and reconnect.+4 more →
B1766›
DTC B1766 indicates the SRS (Supplemental Restraint System) control unit cannot identify or establish communication with the Right Front Curtain Shield Airbag. This fault constitutes an "airbag not present" condition; the ECU detects no load signal from the airbag module during the system self-check. This typically indicates an open airbag circuit (infinite resistance). Potential causes include a disconnected airbag connector, broken wiring harness, internal open circuit in the airbag module, or poor contact at the ECU terminal. This safety-critical fault prevents the right front curtain airbag from deploying during a collision, severely compromising side-impact protection.
Causes
— Right front curtain airbag module connector loose, disconnected, or making poor contact (common if not fully seated after A-pillar trim removal and installation)— Airbag wiring harness open circuit or wear (especially where the harness passes the A-pillar and roof side rail, as vibration or removal/installation breaks the copper core)— Internal open circuit in the airbag module (airbag igniter open circuit or internal module circuit fault)+2 more →
Actions
— Step 1: Safety preparation - Disconnect the battery negative terminal and wait at least 90 seconds to fully discharge the SRS system and prevent accidental airbag deployment.— Step 2: Visual inspection - Remove the right front A-pillar trim panel and right roof trim panel. Verify the curtain airbag module connector is fully seated, and inspect the wiring harness for damage, crushing, or water stains.+5 more →
B1767›
DTC B1767 indicates an abnormally low-resistance connection between the right front side curtain airbag inflator circuit and the vehicle positive power supply terminal (B+), resulting in a short to power. Under normal conditions, the airbag inflator circuit maintains high impedance (open-circuit state, with resistance typically between 2-5Ω) and conducts only momentarily when the Airbag Control Unit (ACU) triggers it. This fault indicates the airbag circuit may remain continuously energized even if the ACU does not issue a deployment command, causing two serious consequences: 1) The airbag may deploy unexpectedly during vehicle operation, causing serious occupant injury. 2) The system detects the abnormal voltage and enters protection mode, disabling the entire SRS system and preventing airbag deployment during a collision. This hard short-circuit fault typically causes the SRS warning lamp to illuminate continuously. Clearing the fault code will not resolve the issue.
Causes
— Right front curtain airbag wiring harness insulation worn or broken: Long-term vibration, temperature changes, or interior trim removal and installation damages the wiring harness located inside the headliner trim panel from the right A-pillar to the C-pillar. This shorts the ignition wire (usually the positive trigger wire) to a constant power circuit (such as the reading light or ambient light power wire).— Water ingress or corrosion in the airbag connector: Water leaks from a blocked sunroof drain hose, car washing, or wading cause a short circuit between terminals in the right front side airbag connector (usually located inside the B-pillar or C-pillar trim). Specifically, electrolytic corrosion creates continuity between the igniter pin and the power supply pin.— Internal short circuit in the airbag module: Manufacturing defects or moisture ingress cause an internal short circuit in the curtain airbag inflator igniter tube (squib), creating abnormal continuity between the ignition terminals and the module metal housing (ground) or internal power supply circuit.+2 more →
Actions
— Safety Preparation and Fault Confirmation: Shift the vehicle into P or Neutral, apply the parking brake, disconnect the 12V battery negative terminal, and wait at least 90 seconds (to ensure the SRS capacitor fully discharges). Connect the diagnostic tool to confirm B1767 is an active fault, record the freeze frame data, and check for accompanying airbag circuit fault codes.— Visual inspection and wiring harness check: Remove the right A-pillar, B-pillar, and C-pillar interior trim panels. Inspect the right front curtain airbag wiring harness (wrapped in yellow corrugated conduit) for wear, cuts, or burn marks. Focus on contact points between the wiring harness and body metal edges, trim clips, and the sunroof drain hose. Use a multimeter to measure the resistance between the ignition wire and body ground, and between the ignition wire and constant power (normal value: infinite).+5 more →
B176712›
This DTC indicates the Airbag Control Unit (ACU) detects a short to positive (+B) in the RH front side curtain airbag ignition circuit. Under normal conditions, the airbag ignition circuit remains in a high-resistance state (infinite) or exhibits a specific resistance (typically >2Ω) only during circuit diagnostics. When the ACU detects continuous battery voltage (12V) or a resistance near 0Ω on this circuit, it logs a short to power. This hardwire short circuit causes the following: 1) Airbag fails to deploy during a collision (power supply clamps the circuit); 2) Unintended airbag deployment in extreme cases (if the ACU drive circuit and the shorted point form a complete circuit); 3) The ACU enters fail-safe mode, cuts power to this circuit, illuminates the SRS warning light, and degrades overall airbag system functionality.
Causes
— Worn harness insulation: The right front curtain airbag harness routes along the A-pillar and roof side rail. Long-term vibration or door seal aging causes the harness to rub against body metal edges. Damaged insulation allows the harness to contact a power supply wire (e.g., reading light or sunroof motor power supply wire).— Connector water ingress and oxidation: An aging seal on the airbag connector (usually yellow) located in the headliner or below the A-pillar allows water entry from car washes or sunroof leaks. This forms an electrolytic bridge between the pins, short-circuiting the ignition pin to the power supply pin.— Airbag Control Unit (ACU) internal fault: ACU internal ignition drive transistor breakdown or filter capacitor short circuit causes this channel to continuously output a high level.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to ensure the ACU backup power supply discharges completely. Wear an anti-static wrist strap. Never use a multimeter resistance setting to directly measure the airbag inflator.— Visual inspection: Remove the right A-pillar trim, rear section of the headliner, and right rear C-pillar trim. Inspect the curtain airbag wiring harness (yellow corrugated conduit) for abrasion, crushing, or punctures. Carefully check the rubber grommet where the harness passes through the opening.+4 more →
B1768›
DTC B1768 on models such as the 2019 BYD Song MAX and 2020 Qin ICE indicates a short to ground in the right front side curtain airbag ignition circuit. The SRS ECU detects abnormally low resistance in the airbag inflator circuit (usually <2Ω), indicating damaged wiring insulation causing a short to body ground, or an internal short circuit in the airbag module. This fault prevents the affected airbag from deploying during a collision (fail-safe state) or, in very rare cases, creates a risk of unintended deployment due to circuit interference. This constitutes a highest-level safety fault. Note: Other BYD models (such as the Song Pro, Qin PLUS, and Han EV) may define B1768 as an abnormal left front door lock status signal. Verify the specific vehicle model and year.
Causes
— Wear or crushing inside the A-pillar/B-pillar trim damages the right front curtain airbag wiring harness, causing the wire to short to the vehicle body metal.— Airbag connector (usually located near the right roof grab handle or C-pillar) shorted to ground due to water ingress, oxidation, or bent pins.— Airbag module internal igniter resistance wire short circuit (internal fault); resistance measures close to 0 Ω.+2 more →
Actions
— Safety preparation: Power down the vehicle, disconnect the battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitors and prevent accidental airbag deployment.— Fault Confirmation: Use VDS or a dedicated diagnostic tool to read fault codes, confirm B1768 is a current fault (Active), and record freeze frame data.+5 more →
B176811›
DTC B176811 indicates an abnormally low-resistance connection between the Right Front Side Curtain Airbag ignition drive circuit and vehicle ground (GND). In the BYD Supplemental Restraint System (SRS) architecture, the airbag igniter operates as a low-resistance inductive load (nominal resistance 2.0–3.0 Ω). The Airbag Control Unit (ACU) continuously monitors circuit current and voltage drop through the high-side/low-side drive circuits. When the ACU detects the insulation resistance between the ignition circuit and vehicle ground falls below the threshold (typically <200 Ω), the system registers a short to ground. This fault causes: 1) possible unintended airbag deployment from accidental grounding, risking occupant injury; 2) failure to deploy during a collision due to current bypass; 3) the SRS to enter fail-safe mode, disabling the affected circuit. Subtype identifier '11' indicates a continuous hard short (non-intermittent).
Causes
— Wiring harness chafing inside the right front A-pillar or roof side rail: Long-term vibration and friction damage the insulation where the side curtain airbag harness passes through the A-pillar sheet metal hole or retaining clips, allowing the copper core to directly contact the body metal and create a short to ground.— Airbag connector water ingress and oxidation: The sealing ring on the airbag wiring harness connector (usually yellow) inside the roof trim panel degrades. Car washing or sunroof leaks cause electrolytic corrosion on the internal pins, creating a low-resistance path between the pins or between the pins and the housing.— Improper wiring harness securing after accident repairs: After side impact or roof repairs, failing to seat the wiring harness correctly in the harness channel allows interior trim clips or metal edges to pinch the harness, damaging the insulation.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the 12V battery negative terminal, wait at least 90 seconds (to fully discharge the SRS backup capacitor), and wear an anti-static wrist strap.— Fault freeze-frame analysis: Connect the VDS or Launch diagnostic tool and confirm B176811 is a current fault (Active). Record environmental data at the time of the fault, such as vehicle speed and temperature, and determine if the fault is vibration-related.+6 more →
B176A-00›
This DTC indicates the airbag control unit (SRS ECU) detects a 0-ohm resistance in the left rear seatbelt pretensioner circuit, indicating a Short to Ground fault. As a pyrotechnic actuator, the pretensioner normally has a resistance of 2.0Ω-3.0Ω (depending on the vehicle model, typically 2.2Ω±0.3Ω). A 0-ohm resistance means current returns directly to ground without passing through the load. The SRS system identifies the pretensioner circuit as faulty. During a collision, the pretensioner may fail to activate and tighten the seatbelt, severely compromising occupant protection. This is a hard fault. Once confirmed, the system continuously illuminates the airbag warning light. Disconnecting the power usually fails to clear this fault.
Causes
— Pretensioner internal short circuit: Moisture, aging, or manufacturing defects cause an internal short circuit between the two terminals of the squib inside the seat belt pretensioner.— Physical damage to the wiring harness: The seat slide rail pinches or chafes the left rear floor wiring harness or under-seat wiring harness, damaging the wire insulation and causing contact with the vehicle body metal.— Connector water ingress and corrosion: Vehicle wading, improper interior cleaning, or poor sealing allows water to enter the pretensioner connector (usually located under the seat or lower B-pillar), creating a short circuit between the pins.+2 more →
Actions
— Safety preparation: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental deployment.— Initial visual inspection: Check the pretensioner connectors (yellow markings) under the left rear seat and lower B-pillar for looseness, water ingress, corrosion, or obvious burn marks.+5 more →
B176A›
DTC B176A indicates the SRS (Supplemental Restraint System) detects a resistance of 0 ohms in the left rear seat belt pretensioner circuit. Normally, as a pyrotechnic device, the pretensioner resistance ranges from 1.5–3.0 Ω (depending on vehicle configuration). A resistance of 0 indicates a short in the circuit, typically a short to ground or an internal short within the pretensioner. This causes the Airbag Control Unit (ACU) to identify a pretensioner circuit fault. During a collision, the left rear seat belt pretensioner may fail to deploy, severely compromising rear occupant restraint protection. This fault also illuminates the instrument cluster SRS warning light and may lock the entire airbag system, preventing other airbags from deploying normally.
Causes
— Left rear seat belt pretensioner wiring harness short to ground (long-term friction from seat adjustment damaged the wiring harness insulation inside the B-pillar trim).— Short circuit in the pretensioner connector (usually a yellow waterproof connector) due to an internal short, corrosion from water ingress, or poor terminal contact.— Internal short circuit in the seat belt pretensioner assembly (internal igniter bridge wire short circuit or pyrotechnic component fault)+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds for the SRS capacitor to fully discharge to prevent accidental airbag deployment.— Locate the component: Remove the left rear B-pillar lower trim panel to access the left rear seat belt pretensioner (usually integrated into the base of the seat belt retractor) and its yellow connector.+6 more →
B176A1A›
DTC B176A1A indicates the Airbag Control Unit (ACU) detects a 0-ohm resistance in the left rear seat belt pretensioner. The SRS seat belt pretensioner contains a squib with a standard resistance of 1.5-2.5 ohms. A 0-ohm reading indicates a hard short circuit (short to ground, short to power, or internal short in the pretensioner squib). This fault causes the ACU to identify the pretensioner circuit as abnormal. During a collision, the pretensioner may fail to deploy and tighten the seat belt, or in extreme cases, deploy unintentionally. Because the SRS is a critical passive safety system, this fault illuminates the airbag warning lamp and may disable related airbag functions.
Causes
— Left rear seat belt pretensioner wiring harness chafes at the seat rail or B-pillar area, causing the conductor to short to body ground.— Water ingress, moisture, or corrosion in the pretensioner connector (usually located below the B-pillar or under the seat) causing a short circuit between terminals.— Short circuit damage to the internal igniter of the pretensioner assembly (possibly due to failure to replace after a previous collision or component aging)+2 more →
Actions
— Use the dedicated diagnostic tool to read the fault code, confirm whether B176A1A is a Current or History fault, and record the freeze frame data.— Disconnect the 12V battery negative terminal and wait at least 90 seconds for the SRS backup power supply to completely discharge, preventing accidental airbag deployment.+7 more →
B176B-00›
This DTC indicates the SRS (Supplemental Restraint System) control unit detects the left rear seat belt pretensioner ignition circuit resistance is below the normal system-calibrated threshold (the standard value is typically 2.0Ω±0.3Ω; values below 1.0Ω trigger this code). The pretensioner uses a pyrotechnic igniter to tighten the seat belt during a collision, removing slack between the webbing and the occupant. Low resistance indicates a potential short circuit. Possible causes include a wiring harness short to ground, bridged connector pins, an internal short in the pretensioner igniter, or a faulty internal sampling circuit in the SRS control unit. This fault forces the airbag system into a degraded mode. The left rear pretensioner may fail to deploy during a collision or deploy unintentionally without a collision, severely compromising passive safety.
Causes
— Water ingress, oxidation, or bent pins in the left rear seat belt pretensioner connector (usually located inside the lower B-pillar trim panel or under the seat) causing a short circuit.— Damaged wiring harness insulation between the pretensioner and the SRS control unit contacts vehicle body metal, causing a short to ground. Chafing is especially common at the seat slide rails or B-pillar routing holes.— Aging or damage to the internal pretensioner squib causes an internal short circuit, resulting in permanently low resistance.+2 more →
Actions
— Use a dedicated diagnostic tool (such as BYD ED400 or Launch X431) to read the complete SRS fault codes, confirm whether B176B-00 is a Current or History code, and record the freeze frame data.— Perform the safe power-down procedure: turn off the ignition, disconnect the negative battery terminal, and wait at least 3 minutes to fully discharge the SRS system capacitors and prevent accidental deployment.+6 more →
B176B›
This fault code indicates the airbag control unit (SRS ECU) detects the left rear seat belt pretensioner resistance is below the system threshold (typically below 2.0 Ω; standard value: 2.0–3.0 Ω). As a pyrotechnic safety device, the pretensioner contains a squib and a gas generator. Resistance must remain within a strict range to ensure reliable deployment. Low resistance indicates a short circuit risk, abnormally low resistance in the internal squib, or damaged wiring harness insulation reducing resistance between the positive and negative terminals. This causes two severe consequences: first, during a collision, the pretensioner may fail to ignite and deploy, eliminating safety restraint protection for the left rear passenger; second, the system may misidentify the condition as a short circuit and disable the trigger circuit. In extreme cases, the system activates fault protection mode, affecting the entire SRS operation. This fault illuminates the airbag warning light continuously and requires immediate repair.
Causes
— Moisture ingress, aging, or an internal short circuit in the pretensioner internal squib causes the resistance value to fall below the standard range (<2.0Ω).— Friction from long-term fore-and-aft seat adjustment damages the under-seat wiring harness insulation, causing a short circuit between wires.— Water ingress, oxidation, corrosion, or bent terminals making contact at the left rear seat belt pretensioner connector (usually located under the seat or lower B-pillar) cause abnormal continuity.+2 more →
Actions
— Safety preparation: Turn the power switch to OFF, disconnect the battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Check the left rear seat belt pretensioner connector (located under the seat or inside the B-pillar trim panel) for looseness, water ingress, corrosion, deformed pins, or green rust.+5 more →
B176B1A›
DTC B176B1A indicates the left rear seat belt pretensioner circuit resistance falls below the standard threshold set by the SRS control unit (ACU) (typically 1.5–3.0 Ω; the fault triggers below the lower limit). This is an SRS hard fault, indicating a potential or actual short circuit in the pretensioner igniter circuit. As a key passive safety system actuator, the pretensioner uses electrical current to trigger the igniter. This ignites the gas generator to tighten the seat belt during a collision (within approximately 15–20 ms). Low resistance may cause: 1) Unintended deployment (static electricity or electromagnetic interference causing accidental ignition); 2) The ACU to disable this trigger circuit in fail-safe mode, preventing seat belt pretensioning during a collision; 3) The ACU to lock out the entire SRS system if resistance drops near 0 Ω, disrupting the multi-airbag coordinated deployment strategy.
Causes
— Pretensioner igniter internal short circuit: Moisture ingress, electrolyte corrosion, or manufacturing defects cause the insulation between the igniter bridge wire and the housing to break down, forming a low-resistance path.— Harness short to ground: Seat adjustment, pressure from objects, or water ingress damages the left rear sill harness (B-pillar to C-pillar section) insulation, causing the wire to short to the vehicle body.— Connector terminal fault: Short circuit between terminals in the yellow SRS connector under the seat (usually near the left rear seat rail) due to water ingress, oxidation, or mechanical damage.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes to fully discharge the ACU capacitor. Remove the left rear seat for access.— Visual inspection: Check the left rear seat belt pretensioner connector (yellow) for looseness, water ingress, or corrosion. Check the wiring harness inside the B-pillar trim for pinching or damage.+6 more →
B176C-00›
This DTC indicates the airbag control unit (SRS ECU) detects the left rear seat belt pretensioner igniter resistance exceeds the calibrated threshold (normal range is typically 1.6-2.4Ω; the DTC triggers when detected resistance is >3.0Ω or an open circuit occurs). As a key actuator in the passive safety system, the pretensioner uses the igniter to detonate the gas generator during a collision, instantly tightening the seat belt to eliminate slack between the belt and the occupant. Excessive resistance indicates high impedance or a potential open circuit in the igniter circuit. This condition can prevent pretensioner deployment during a collision, severely compromising occupant restraint protection. This is a hard DTC. While the fault remains active, the system triggers a continuous warning and illuminates the airbag warning lamp. Some models may also limit power output or disable specific assistance functions.
Causes
— Poor pretensioner connector contact: Vibration, oxidation, or loosening increases contact resistance at the left rear pretensioner connector (usually located inside the C-pillar trim panel or under the seat). This is the most common cause of the fault, especially after wading or in damp environments.— Mechanical damage to the under-seat wiring harness: On foldable rear seats, frequent folding can break internal copper strands or damage insulation at the bend point of the pretensioner harness (usually yellow), causing high resistance or an intermittent open circuit.— Pretensioner unit aging: Oxidation of the igniter internal bridge wire or moisture ingress into the pyrotechnic charge causes resistance to drift beyond the normal range over time. This typically affects vehicles over 5 years old or those previously exposed to high-temperature, high-humidity environments.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (or wait for the capacitors to fully discharge as required by the workshop manual). Ensure the SRS system is completely powered down to prevent accidental pretensioner deployment during inspection.— Locate the pretensioner: Remove the left rear seat and lower C-pillar trim panel. Find the left rear seat belt pretensioner assembly (usually integrated with the seat belt retractor) and identify the yellow dedicated wiring harness connector.+6 more →
B176C›
DTC B176C indicates the left rear seat belt pretensioner circuit resistance exceeds the normal threshold set by the SRS ECU (typically >3.5-4.0Ω; normal value is 2.0-3.0Ω). The pretensioner is a pyrotechnic safety device containing an igniter and a gas generator. Excessive resistance indicates a high resistance or open circuit condition within the circuit. Consequently, during a collision, the SRS ECU may fail to ignite the pretensioner charge. This failure prevents the seat belt from tightening, increases occupant forward displacement, and severely reduces crash protection. Additionally, the SRS system enters degraded mode, illuminates the airbag warning lamp continuously, and may disable the related side airbag function on certain models.
Causes
— Left rear seat belt pretensioner internal igniter aging or open circuit: Prolonged inactivity or moisture exposure oxidizes the internal bridge wire, gradually increasing resistance until it exceeds the threshold.— Poor connector contact: The pretensioner connector near the B-pillar or C-pillar (usually marked SR11 or P11) is loose, has backed-out pins, oxidation, or water ingress corrosion, causing increased contact resistance.— Wiring harness damage: Frequent opening and closing of the left rear door partially breaks the internal copper strands of the wiring harness at the hinge, or B-pillar trim panel removal and installation pinches the harness, creating a high-resistance path.+2 more →
Actions
— Safety Preparation: Disconnect the negative battery terminal and wait at least 3 minutes to allow the SRS system capacitor to fully discharge and prevent accidental airbag deployment.— Fault confirmation: Connect the diagnostic tool to read the DTC. Confirm B176C is a current (Active) fault, not a history fault. Record the resistance value in the freeze frame data.+6 more →
B176C1B›
DTC B176C1B indicates the airbag control module (SRS ECU) detects the left rear seat belt pretensioner circuit resistance exceeds the calibrated upper limit (typically >5.0Ω, normal range 2.0-3.5Ω). The pretensioner is a pyrotechnic safety device containing an internal resistance wire and propellant. The ECU determines its readiness by continuously monitoring the circuit current. Excessive resistance usually indicates a high-resistance connection in the circuit, a partial open circuit, or aging of the internal pretensioner coil. This condition can prevent the pretensioner from deploying correctly during a collision, seriously reducing the effectiveness of the occupant restraint system. This fault is a hard fault in the passive safety system. It generally illuminates the instrument cluster SRS warning light continuously and triggers a warning chime on some models.
Causes
— Oxidation or partial open circuit of the pretensioner internal resistance wire: Long-term use causes micro-cracks or oxidation at the pretensioner internal coil weld points, causing the resistance value to drift higher.— Poor contact at the yellow SRS connector under the seat: Water ingress, oxidation, or frequent disconnection and reconnection increases terminal contact resistance at the dedicated airbag connector under the left rear seat (usually located on the inner side of the seat rail).— Seat slide rail wiring harness fatigue fracture: On Qin PRO models, folding or fore/aft adjustment of the left rear seat repeatedly bends the wiring harness at the slide rail. This partially breaks the copper wire without completely severing it, creating a high-resistance condition.+2 more →
Actions
— Safety preparation: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Remove the left rear seat cushion and inspect the yellow dedicated SRS connector under the seat (usually marked AIRBAG) for looseness, water ingress, or green oxidation. If necessary, use a special probe to check terminal tension.+5 more →
B176D›
DTC B176D indicates the SRS (Supplemental Restraint System) ECU detects an open circuit in the left rear seat belt pretensioner circuit (infinite resistance), meaning the ECU cannot detect the pretensioner. This typically indicates a broken circuit connection between the pretensioner and the ECU, or an internal open circuit within the pretensioner. As a key passive safety actuator, the pretensioner rapidly tightens the seat belt via pyrotechnic deployment or motor operation during a collision, removing slack between the webbing and the occupant. This fault disables the left rear seat pretensioner during a collision, increasing occupant injury risk. The ECU continuously monitors the pretensioner circuit resistance (normal range: approx. 2.0-3.0Ω). It sets a 'not present' fault when it detects a resistance >10Ω or a complete open circuit.
Causes
— Left rear seat belt pretensioner wiring harness connector loose or making poor contact (commonly results from failing to fully seat the connector after rear seat removal, or a broken connector locking tab causing an intermittent connection).— Internal open circuit in the pretensioner unit (broken pretensioner squib wire or internal circuit board failure prevents the ECU from establishing a valid circuit)— Physical damage to the wiring harness (seat slide rail compressing the harness over time, or seat folding mechanism wearing through the harness insulation, causing internal copper strands to break)+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS system capacitors and prevent accidental airbag deployment.— Initial visual inspection: Remove the left rear seat (usually requires removing the seat cushion retaining bolts), verify the pretensioner connector (usually located inside the C-pillar trim panel or under the seat) is fully connected, and inspect the wiring harness for obvious damage or crush marks.+6 more →
B176D-00›
DTC B176D-00 indicates the airbag control unit (SRS ECU) detects an open circuit or missing load in the left rear seatbelt pretensioner circuit during the system self-check. The SRS ECU verifies pretensioner presence by monitoring the resistance across the pretensioner squib (normal value: 1.5-3.0 Ω). The ECU determines the pretensioner is "not present" if this resistance falls outside the threshold (open circuit >10 Ω or short circuit <0.5 Ω) or if it fails to receive the pretensioner LIN bus response signal. This safety-critical fault prevents the left rear seatbelt pretensioner from deploying and tightening during a collision, causing a loss of restraint protection for the rear passenger. It also continuously illuminates the instrument cluster airbag warning light. Some models may enter fail-safe mode, limiting vehicle power output.
Causes
— Left rear seat belt pretensioner squib internal open circuit or burnout, causing abnormal resistance (usually >10Ω or infinite).— Pretensioner wiring harness connector (located below the B-pillar or under the left side of the seat) loose, backed-out terminals, oxidized from water ingress, or making poor contact; common in vehicles driven through water or due to mechanical stress from frequent seat adjustment.— Wiring harness physical damage: Fore/aft seat movement wears through the harness insulation, causing a short circuit, or improper B-pillar trim panel installation pinches and severs the harness, causing an open circuit.+2 more →
Actions
— Connect VDS2000 or an equivalent diagnostic tool. Read the complete DTCs and freeze frame data. Confirm whether B176D-00 is a current (Active) or history (History) fault. Check for other accompanying SRS fault codes (such as B176E-00 right rear pretensioner fault).— Perform the safe power-down procedure: turn off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitors and prevent accidental pretensioner deployment during repair.+6 more →
B176D1B›
DTC B176D1B indicates the front passenger Occupant Classification System (OCS) detects an abnormal signal or missing sensor. The system uses pressure/capacitive sensors integrated into the front passenger seat cushion to detect seat occupancy and weight category. It transmits signals to the SRS airbag control unit to determine front passenger airbag deployment and deployment force during a collision. This fault indicates the airbag control unit cannot receive a valid occupancy status signal (typically indicating an open circuit, out-of-range resistance, or signal plausibility error). The system enters a fail-safe mode and defaults the front passenger seat status to "unoccupied". This may prevent the front passenger airbag from deploying during a collision, severely compromising passive safety performance.
Causes
— Repeated adjustment of the seat track causes wear and breakage of the underlying wiring harness, especially an open circuit in the power or signal wire.— Occupant sensor assembly failure (internal open or short circuit). Defective sensor waterproofing commonly causes moisture damage.— Poor contact, oxidized pins, or a loose retaining clip at the dedicated yellow connector under the seat, causing intermittent signal interruption.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000/VDS2100) to read the fault code and view the data stream. Confirm if the 'Passenger Detection Sensor Status' displays 'open circuit', '255', or a fixed value that does not change with pressure.— Check the wiring harness routing under the front passenger seat, focusing on the interference area between the seat slide rail and the frame. Open the corrugated conduit and check the wires for breaks or wear.+5 more →
B176E-00›
DTC B176E-00 is an SRS (Supplemental Restraint System) fault code indicating a short to body ground (GND) in the left rear seat belt pretensioner drive circuit. The pretensioner is a pyrotechnic actuator containing an igniter and gas generant. During a collision, the SRS ECU triggers the pretensioner. The resulting explosive force rapidly tightens the seat belt, removing slack between the occupant and the belt. This fault code indicates a short to ground (resistance below the threshold, typically <2Ω) in the wiring harness between the SRS ECU and the left rear pretensioner, or within the pretensioner itself. This causes the ECU to detect an abnormal current path. Upon detecting this fault, the SRS system illuminates the airbag warning lamp and enters fail-safe mode. This disables the left rear pretensioner and any linked side airbag functions, severely compromising crash safety performance.
Causes
— Wiring harness chafing inside the left rear sill trim: After prolonged vehicle use, the seat belt pretensioner wiring harness (typically routed along the B-pillar or sill) rubs against metal body edges. This damages the insulation and causes the core wire to contact the body ground.— Water ingress in connector under left rear seat: Interior cleaning, wading, or a blocked sunroof drain causes water to accumulate in the left rear carpet. Water enters and corrodes the pretensioner wiring harness connector (usually located under the seat or near the C-pillar), causing a short circuit between pins or between a pin and the housing.— Pretensioner assembly internal fault: Internal igniter insulation breakdown, or the internal bridge wire contacts the housing, causing an abnormal drop in resistance to ground on either wire.+2 more →
Actions
— Safety preparation: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 90 seconds (to ensure the SRS capacitor discharges completely). Wear an anti-static wrist strap. Do not take direct measurements near the airbag/pretensioner using a standard multimeter resistance setting.— Visual inspection: Remove the left rear sill trim panel, lower B-pillar trim panel, and left rear seat. Check the pretensioner wiring harness (yellow harness, usually with a shorting clip) for obvious damage, crushing, water stains, or burn marks. Focus on the seat slide rail fixing bolts and the wiring harness pass-through grommet.+5 more →
B176E›
DTC B176E indicates the SRS (Supplemental Restraint System) control unit detects an abnormally low-resistance path between the Left Rear Seat Belt Pretensioner drive circuit and the vehicle power supply (+B), indicating a short to power. The pretensioner contains a squib controlled by the SRS ECU, with a normal operating resistance of approximately 2.0-3.0 Ω. If the wiring harness or connector shorts to a 12V power wire, the ECU detects an abnormally high voltage or resistance value, immediately sets this DTC, and enters fail-safe mode. This fault presents two risks: first, during a collision, circuit protection may prevent the left rear pretensioner from deploying, causing occupant restraint failure; second, the short-circuit current may accidentally trigger the squib, causing the seat belt to retract suddenly and injure the occupant. Consequently, the SRS system immediately cuts power to this circuit and illuminates the airbag warning lamp, potentially disabling the entire airbag system.
Causes
— Worn wiring harness or damaged insulation inside the left rear B-pillar shorting to body power lines (e.g., constant power or ignition power). Commonly caused by driving through water or prolonged friction from a detached harness retaining clip.— Left rear seat belt pretensioner connector (usually located under the seat or inside the B-pillar trim): terminal misalignment, backed-out pins, or corrosion from water ingress causing terminal bridging, especially water intrusion after car washes or during the rainy season.— During vehicle modifications (such as adding seat heating, floor sound insulation, or a rear entertainment system), technicians accidentally pierce the pretensioner wiring harness or pinch it between the metal frame and the power cable.+2 more →
Actions
— Safety preparation: Switch the vehicle to OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental deployment.— Fault confirmation: Use the VDS2000/BYD dedicated diagnostic tool to read freeze frame data, confirm vehicle status at the time of the fault (voltage, temperature, vehicle speed), and attempt to clear the fault code. If the code persists, it is a current fault.+5 more →
B176E12›
DTC B176E12 indicates abnormal continuity between the left rear seat belt pretensioner circuit and the vehicle power supply (B+), representing a "short to power". In the Supplemental Restraint System (SRS), the seat belt pretensioner is a pyrotechnic actuator. Under normal conditions, its circuit must remain isolated from the power supply; the SRS ECU supplies a momentary high-current ignition signal only during a collision. A short to power indicates: 1) continuous battery voltage across the pretensioner terminals risks accidental deployment (extremely dangerous); 2) the SRS ECU detects circuit voltage above the threshold (typically >5V or near 12V) and registers a severe fault; 3) the system immediately illuminates the airbag warning light and disables the entire airbag system (including front and side airbags), leaving the vehicle without collision protection. This fault involves the left rear seat belt pretensioner (typically located at the lower B-pillar or on the seat frame). The circuit comprises the ignition loop routing from the SRS ECU through the floor harness to the left rear seat.
Causes
— Damaged wiring harness insulation causing contact with a power wire: Frequent fore-and-aft adjustment of the left rear seat or pressure from objects chafes the wiring harness against the seat track or inside the B-pillar trim, exposing the copper wire and causing contact with a constant power wire (such as the seat heating or reading light power supply).— Connector water ingress or terminal corrosion: Vehicle wading, a leaking blocked sunroof drain tube, or spilled drinks cause moisture inside the pretensioner connector (usually yellow) in the left rear B-pillar or under the seat, creating a conductive path between the ignition terminal and the power supply terminal.— Improper modification or repair: When installing a rear entertainment, seat ventilation, or audio system, screws pierce the wiring harness or retaining clips clamp it too tightly, damaging the insulation; or failing to fully lock the connector after accident repairs allows a backed-out terminal to contact an adjacent power terminal.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds (to fully discharge the SRS capacitor). Hang a warning sign to prevent unintended operation.— Visual inspection: Remove the left rear lower B-pillar trim panel and seat side trim panel. Inspect the yellow SRS connector for looseness, water ingress, corrosion, or obvious burn marks. Inspect the wiring harness for pinching or wear at the seat slide rail and hinge.+6 more →
B176F-00›
DTC B176F-00 indicates the SRS (Supplemental Restraint System) ECU detects an abnormal electrical connection between the left rear seat belt pretensioner drive circuit and the vehicle power supply (B+). The pretensioner consists of an igniter and a gas generator, with a normal resistance of 2.0-3.0Ω. Damaged wiring harness insulation, misaligned connector pins, or an internal pretensioner short circuit cause the ECU to detect an abnormally high circuit voltage (approaching 12V battery voltage) and trigger this DTC. This fault may result in: 1) Failure of the left rear pretensioner to deploy during a collision, compromising occupant protection. 2) Unintended pretensioner deployment in extreme cases, causing occupant injury. 3) The SRS entering fail-safe mode, disabling all vehicle airbags.
Causes
— Worn insulation on the pretensioner wiring harness under the left rear seat or near the B-pillar contacts a body power wire (constant or ignition power), causing a short circuit.— Water ingress, oxidation, or bent pins in the pretensioner connector (usually located under the seat or inside the B-pillar trim), causing a short circuit between the power and signal terminals.— Igniter coil insulation failure inside the left rear seat belt pretensioner assembly causes an internal short to power.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Remove the left rear seat and lower B-pillar trim panel. Check the pretensioner wiring harness (usually in a yellow sleeve) for wear, crushing, or burn marks. Focus on the harness within the seat slide rail travel range.+5 more →
B176F›
This fault code indicates an abnormally low-resistance connection to body ground (GND) in the left rear seat belt pretensioner drive circuit. As a key actuator in the SRS (Supplemental Restraint System), the pretensioner typically uses a pyrotechnic or motor-driven design. During a collision, it rapidly retracts the seat belt webbing by igniting a gas generator or driving a motor, eliminating slack between the occupant and the seat belt. A short to ground means the positive circuit between the SRS ECU and the pretensioner (typically high-level triggered) shorts to the vehicle chassis ground, with resistance falling below the calibrated threshold (generally <2Ω). Upon detecting this fault, the SRS ECU immediately enters fail-safe mode, cuts power to the circuit to prevent accidental deployment or wiring overheating, and illuminates the airbag warning lamp. Consequently, the left rear seat loses pretensioner protection during a collision, and the occupant risks secondary impact injuries due to seat belt slack. The short-circuit current may also overheat and damage the SRS ECU driver chip, compromising the normal operation of the entire airbag system.
Causes
— Long-term friction and pinching from fore-aft seat movement damages the wiring harness insulation under the left rear seat or at the B-pillar, causing the copper core to directly contact the vehicle body metal and short to ground.— Internal fault in the seat belt pretensioner unit. The squib resistance wire shorts to the metal housing. Moisture ingress, aging, or manufacturing defects in the pretensioner usually cause this fault.— After vehicle wading, flooding, or floor washing, water enters and corrodes the pretensioner connector (usually located under the seat or at the base of the B-pillar), forming an electrolytic conductive path between the terminals.+2 more →
Actions
— Safe power-down: Turn off the ignition, disconnect the negative terminal of the 12V low-voltage battery, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment during repair.— Fault confirmation and freeze frame analysis: Connect the BYD dedicated diagnostic tool (VDS2000/3000). Read the freeze frame data for DTC B176F. Record the vehicle speed, ambient temperature, and voltage when the fault occurred. Determine if the fault is intermittent.+6 more →
B176F11›
DTC B176F11 indicates the airbag control unit (SRS ECU) detects an abnormally low-resistance connection between the left rear seat belt pretensioner (squib) circuit and body ground (typically <2Ω). The pretensioner is a pyrotechnic actuator with a normal resistance of approximately 2.0-3.0Ω. A short to ground causes the SRS system to identify a safety risk in this circuit and trigger fail-safe mode. This mode immediately cuts power to the pretensioner circuit, illuminates the airbag warning lamp, and disables left rear pretensioner deployment during a collision. It may also affect the normal deployment logic of the entire airbag system. This is a hard DTC. The SRS ECU continuously logs the code while the short circuit exists. Repair the fault immediately to maintain passive safety system integrity.
Causes
— Wiring harness chafing under the left rear seat: Fore-and-aft seat adjustment or trapped objects damage the pretensioner wiring harness insulation, causing a short circuit to the vehicle metal frame.— Inner B-pillar wiring harness interference: The wiring harness retaining clip inside the left rear B-pillar trim panel detached, causing the harness to rub against a sharp sheet metal edge and short to ground.— Connector water ingress and corrosion: Rear floor water exposure or interior cleaning allows water to enter the pretensioner connector (usually located under the seat or at the base of the B-pillar). Electrolytic corrosion between the pins causes a short to ground.+2 more →
Actions
— Safety Preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Read freeze frame: Use the VDS2000/VDS3000 diagnostic tool to read environmental data (temperature, vehicle speed, voltage) at the time of the fault to confirm if it is an intermittent fault.+5 more →
B1770-00›
DTC B1770-00 indicates the SRS (airbag) control module detects the right rear seat belt pretensioner circuit resistance is 0 Ω or close to 0 Ω. Normally, the seat belt pretensioner acts as a pyrotechnic actuator with a standard squib resistance between 2.0-5.0 ohms. A resistance of 0 indicates a hard short in the circuit. Possible causes include an internal short in the pretensioner squib, a wiring harness short to body ground or power, or an internal short in the connector. This fault causes the SRS system to determine the pretensioner has failed. During a collision, the right rear seat belt pretensioner will not deploy, severely compromising the occupant restraint system's effectiveness. The fault also illuminates the instrument cluster airbag warning lamp and may inhibit the entire airbag system.
Causes
— Right rear seat belt pretensioner internal igniter short circuit: Aging, moisture ingress, or manufacturing defects cause insulation failure between the internal squib terminals, resulting in a short circuit.— Wiring harness short to ground or power: Long-term bending, wear, or accident crushing damages the B-pillar wiring harness insulation, causing a short to the vehicle body metal or power wire.— Connector fault: Water ingress, corrosion, deformed pins, or foreign objects in the right rear seat belt pretensioner connector (usually located below the B-pillar or under the seat), causing a short circuit between terminals.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the 12V low-voltage battery negative terminal, and wait at least 90 seconds (2 minutes for some models) to fully discharge the SRS capacitor and prevent accidental deployment.— Locate the component: Remove the right rear B-pillar lower trim panel. Find the right rear seat belt pretensioner and its yellow dedicated connector (usually featuring a short-circuit protection tab).+6 more →
B1770›
This DTC indicates the SRS control module detects an abnormal 0 Ω resistance in the right rear seat belt pretensioner circuit. As a pyrotechnic device, normal pretensioner resistance ranges from 1.5 to 3.0 Ω. A 0 Ω reading typically indicates a short circuit. Possible causes include damaged wiring harness insulation shorting the positive and negative terminals, an internal connector short, a shorted internal resistance wire within the pretensioner body, or an SRS ECU internal drive circuit fault. This fault prevents the pretensioner from deploying during a collision. The SRS system may also disable airbag functions in the affected area, posing a severe safety hazard.
Causes
— Harness wear short circuit: Long-term bending and friction damaged the wiring harness insulation inside the right rear B-pillar or sill panel, shorting the positive and negative wires.— Connector water ingress and corrosion: Poor sealing of the right rear seat belt pretensioner connector (usually located under the seat or at the base of the B-pillar) allows water ingress, causing a short circuit between pins.— Pretensioner unit fault: Internal resistance wire short circuit (rare but possible, usually resulting from a manufacturing defect or overcurrent)+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Check the right rear seat belt pretensioner connector (located at the bottom of the B-pillar or on the outboard side of the seat) for water ingress, corrosion, deformed pins, or foreign matter.+5 more →
B17701A›
This DTC indicates the Airbag Control Unit (ACU) detects a 0-ohm resistance in the right rear seatbelt pretensioner circuit. As a key actuator in the passive safety system, the pretensioner contains an internal squib with a normal resistance of 1.5-3.0 Ω for circuit integrity monitoring. A resistance of 0 indicates a hard short in the circuit. Possible causes include a burned internal coil causing an inter-turn short, a wiring harness short to ground (vehicle body), or shorted connector pins. This fault prevents the ACU from sending a firing command to the pretensioner during a collision or triggers a system protection strategy that disables the entire right-side airbag circuit, severely compromising restraint protection for the right rear passenger during an accident.
Causes
— Right rear seat belt pretensioner internal igniter burned out or coil inter-turn short circuit (typically due to seal failure after water ingress or pretensioner aging).— Worn insulation on the pretensioner wiring harness under the seat or inside the B-pillar causes the positive and negative wires to short to ground (common from frequent seat movement or unsecured harnesses during modifications).— Poor sealing of the yellow dedicated connector (usually located under the seat or inside the B-pillar trim) allows water ingress, causing electrolytic corrosion and a short circuit between pins.+2 more →
Actions
— Safe power-down: Switch off the ignition and disconnect the 12V battery negative terminal. Wait at least 5 minutes to fully discharge the SRS backup power capacitor and prevent accidental airbag deployment.— Fault confirmation: Use a dedicated BYD diagnostic tool (such as ED400 or VDS) to read freeze frame data. Confirm B17701A is a current fault (Active) rather than a history fault (History). Record the vehicle status when the fault occurred.+6 more →
B1771-00›
This fault code indicates the right rear seatbelt pretensioner circuit resistance falls below the normal threshold set by the SRS control unit (typically below 1.5Ω; standard value is approximately 2.0-3.0Ω). As a pyrotechnic safety device, the pretensioner contains an igniter and a gas generator. A low resistance value indicates an abnormally low-resistance path in the circuit. Potential causes include an internal pretensioner short circuit, a wiring harness short to ground, or connector pins shorted to ground. This fault forces the SRS system into a degraded mode. Consequently, the right rear pretensioner may fail to deploy during a collision, and the fault lamp remains illuminated to indicate system failure, severely compromising passive safety protection.
Causes
— Short circuit, moisture ingress, or aging of the right rear seat belt pretensioner internal igniter, causing abnormally low internal resistance.— The seat rail pinches and wears the under-seat wiring harness, damaging the insulation and causing a short circuit between the power and ground wires.— Right rear seat belt pretensioner connector (usually located in the C-pillar or under the seat): bent pins, corrosion from water ingress, or foreign debris causing a short circuit between pins.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds (3 minutes for some models) to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Remove the right rear C-pillar trim panel and seat. Inspect the pretensioner wiring harness for wear, crushing, or water ingress. Inspect the connector for oxidation and the terminals for deformation.+5 more →
B1771›
DTC B1771 indicates the SRS (Supplemental Restraint System) control module detects the right rear seat belt pretensioner resistance is below the system-calibrated lower threshold (typically <1.0Ω or near a short-circuit value). The pretensioner is a pyrotechnic actuator containing an electric squib with a normal resistance of approximately 2.0±0.3Ω. Low resistance indicates a pretensioner internal short circuit, a wiring harness short to ground, connector water ingress causing electrochemical corrosion, or an SRS module internal sampling circuit fault. This fault triggers the airbag system fail-safe strategy. The affected seat pretensioner may fail to deploy in a collision, the AIRBAG warning lamp remains illuminated, and some models trigger a system buzzer alarm.
Causes
— Right rear seat belt pretensioner internal short circuit: Internal igniter bridge wire breaks and shorts to ground, or moisture in the pyrotechnic charge causes an abnormal drop in resistance.— Wiring harness wear causing short to ground: The wiring harness below the B-pillar or the floor harness chafes against the metal body frame, damaging the insulation and causing a short circuit between the positive and negative terminals or a short to ground.— Connector water ingress and oxidation: Rear floor flooding, degraded seals, or water seepage during car washes introduces water into the pretensioner connector (usually located below the B-pillar or on the seat side), leading to electrochemical corrosion of the terminals and creating a low-resistance path.+2 more →
Actions
— Safety Preparation and Diagnostic Confirmation: Use BYD VDS2000 or Launch X431 to read all DTCs. Confirm B1771 is an active fault, not a history fault. Record freeze frame data (vehicle status, mileage, voltage). Disconnect the battery negative terminal and wait at least 90 seconds to fully discharge the SRS energy storage capacitor.— Visual inspection and connector check: Remove the right rear lower B-pillar trim panel and sill trim panel. Inspect the pretensioner connector (typically a yellow connector with a shorting bar) for looseness, water ingress, corrosion, or backed-out pins. Inspect the wiring harness covering for abrasion, burn marks, or rodent bite marks.+5 more →
B1771A›
DTC B1771A indicates the SRS (Supplemental Restraint System) ECU detects the RH rear seatbelt pretensioner circuit resistance is below the calibrated threshold. (The standard value is typically 2.0 ± 0.5 Ω; a measured value below 1.2 Ω or near 0 Ω triggers this code). As a key passive safety system actuator, the pretensioner contains a pyrotechnic combustion chamber and a resistance wire. Low resistance indicates a short circuit risk (harness chafing to ground, water ingress at the connector, or an internal short from a melted resistance wire). To prevent accidental deployment or upon determining actuator failure, the SRS ECU illuminates the airbag warning light and may disable the RH rear side airbag and pretensioner deployment. This disables active tensioning protection for that seat during a collision, increasing occupant injury risk.
Causes
— Wiring harness wear under the right rear seat or inside the B-pillar trim panel: Frequent fore-and-aft seat movement or passengers stepping on the harness damages the insulation, shorting the positive and negative wires and causing abnormally low resistance.— Pretensioner connector water ingress and oxidation: Vehicle wading, a blocked sunroof drain hose, or liquid intrusion during deep interior cleaning causes a short circuit between the connector terminals or abnormal resistance.— Pretensioner unit internal fault: Aging, moisture ingress, or manufacturing defects cause an inter-turn short circuit in the internal resistance wire of the pyrotechnic device, resulting in permanently low resistance.+2 more →
Actions
— Safety preparation: Use the BYD VDS2000 or Launch X431 diagnostic tool to read the fault code. Confirm B1771A is a current fault, not a history fault, and record the freeze frame data. Turn off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor.— Locate the component: Remove the right rear B-pillar lower trim panel (or seat outer trim panel, depending on vehicle structure) and locate the seat belt pretensioner assembly, usually a black cylindrical pyrotechnic device with a yellow two-color connector.+5 more →
B1772-00›
DTC B1772-00 indicates the airbag control unit (SRS ECU) detects the right rear seatbelt pretensioner circuit resistance exceeds the calibrated range (normal range: 1.8–3.0Ω; high resistance typically indicates >5Ω or infinite). As a key passive safety system actuator, the pretensioner features a pyrotechnic design, using propellant gas to instantly tighten the seatbelt during a collision. High resistance indicates a high-impedance connection or open circuit. Causes include poor connector contact, a damaged wiring harness, or an open gas generator coil inside the pretensioner. This fault continuously illuminates the SRS warning light and can trigger a degraded system mode. During a collision, the pretensioner may fail to deploy, and the SRS ECU may suspend the right rear side airbag deployment logic, significantly reducing crash protection for the right rear passenger.
Causes
— Yellow waterproof connector for the right rear seat belt pretensioner (usually located under the seat or inside the C-pillar trim) loose, or pins backed out or oxidized, causing increased contact resistance.— During fore/aft seat adjustment, the seat rail pinches and chafes the pretensioner wiring harness, causing a concealed break in the copper core (insulation intact but internal open circuit) or high resistance.— The pretensioner internal gas generator (squib) heating wire is aged, broken, or open-circuited, resulting in infinite resistance.+2 more →
Actions
— Use BYD VDS or a dedicated diagnostic tool to access the SRS system, read the fault code to confirm B1772-00 is active, and record freeze frame data (e.g., vehicle speed and timestamp at the time of occurrence).— Perform safety procedure: Turn off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.+6 more →
B1772›
DTC B1772 indicates the right rear seatbelt pretensioner ignition circuit resistance exceeds the standard upper limit (typically >3.6Ω or open circuit). The seatbelt pretensioner is a key SRS (Supplemental Restraint System) actuator containing an internal squib. During a collision, the SRS control unit (ACU) sends current to the squib to ignite the propellant, instantly tightening the seatbelt to protect the occupant. Excessive resistance indicates high resistance, poor contact, or a complete open circuit in the ignition circuit, preventing the ACU from activating the pretensioner. During a collision, the rear occupant on that side loses pretensioner protection, significantly increasing safety risks. Typical causes include connector oxidation, wiring harness damage, or internal pretensioner squib failure.
Causes
— Right rear seat belt pretensioner connector (usually located under the seat or inside the C-pillar trim) is loose, oxidized due to water ingress, or has expanded terminals, causing increased contact resistance.— Abnormally high resistance or open circuit in the pretensioner internal igniter (blown internal bridge wire, damp or aged propellant). Standard resistance is usually 2.0-3.0Ω.— Prolonged bending and pinching of the under-seat wiring harness causes broken wires or damaged insulation (common in passenger vehicles with frequent fore-and-aft seat adjustment).+2 more →
Actions
— Safety Preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds for the SRS capacitor to fully discharge. Read and record the DTC freeze frame data. Confirm the fault frequency (current/history).— Visual inspection: Remove the right rear seat and lower C-pillar trim panel. Verify the pretensioner connector (usually yellow) is fully seated and inspect for water ingress, corrosion, or foreign matter. Inspect the wiring harness corrugated conduit under the seat for damage. Check the wires for crush marks from the seat rail.+3 more →
B17721B›
DTC B17721B indicates the airbag system (SRS) detects the right rear seat belt pretensioner circuit resistance exceeds the normal upper threshold. This pretensioner is a pyrotechnic actuator with a typical resistance range of 2.0–3.0 ohms. When the ECU detects resistance >4.0 ohms (or per the calibrated threshold), it determines a High Resistance fault. This fault prevents the seat pretensioner from deploying and retracting normally during a collision. Additionally, the SRS may enter a degraded mode, illuminating the instrument cluster airbag warning light continuously. On some models, other seat airbag functions may also be restricted. The DTC suffix "1B" typically indicates the specific circuit location or fault subtype, pointing to the right rear seat (Third Row/Second Row Right) pretensioner circuit.
Causes
— Poor connector contact: Moisture, oxidation, or vibration increases pin contact resistance at the pretensioner connector (usually marked R2R or SA3) on the right B-pillar or under the seat. This is the most common cause, frequently occurring after wading or car washes.— Harness damage causing high resistance: Crushing the harness during rear seat removal/installation, carpet modification, or child seat installation partially breaks internal copper strands without fully severing them, creating a high-resistance point.— Pretensioner internal fault: Oxidation or breakage of the squib bridge wire, or moisture ingress into the pyrotechnic charge, causes resistance to drift higher over time, indicating actuator aging failure.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds (3 minutes for some models) to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation: Use a dedicated diagnostic tool (such as Launch X431 or BYD VDS) to read the fault code. Confirm B17721B is a current fault (Present) and not a history fault. Record the resistance value from the freeze frame data (usually displays as 4.5-10 ohms or Open).+4 more →
B1773-00›
DTC B1773-00 indicates the airbag control unit (SRS ECU) failed to detect the electrical signal or communication response from the right rear seat belt pretensioner during the system self-check. This passive safety system hardwire/communication fault indicates an abnormality in the squib circuit between the SRS module and the right rear seat belt pretensioner. Causes include an open circuit, a short to ground or power, or the pretensioner internal igniter resistance falling outside the standard range (typically 1.5-3.5Ω). This fault prevents the pretensioner from deploying and tightening the seat belt during a collision, significantly reducing occupant protection. The SRS system also enters fail-safe mode, which may disable other airbags and illuminate the airbag warning light continuously.
Causes
— Loose, disconnected, or poor contact at the right rear seat belt pretensioner connector (usually a yellow waterproof plug). Common causes include frequent fore/aft seat movement, incomplete insertion after removal, or a broken locking tab.— Open circuit or abnormal resistance in the pretensioner internal squib (aging, moisture ingress, previous deployment, or manufacturing defect), preventing the SRS module from detecting the standard resistance circuit.— Physical damage to the wiring harness causing an open or short circuit, especially wiring pinched by the seat rail, wear points at bends inside the B-pillar trim panel, or fatigue fractures at the door hinge wiring pass-through.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds to ensure the SRS capacitor discharges fully, preventing accidental airbag deployment. Wear an anti-static wrist strap and prepare the BYD dedicated diagnostic tool (VDS2000/ED400).— Fault confirmation: Connect the diagnostic tool and read DTCs. Confirm B1773-00 is a current fault (Active), not a historical fault. Record freeze frame data. Check for accompanying communication fault codes (such as B1772 and B1774).+4 more →
P25C700›
This DTC indicates the brake booster (BLM/Booster) temperature sensor signal circuit voltage in the IPB (Intelligent Integrated Braking System) exceeds the normal range (0.5-4.5V). The ECU detects a voltage signal continuously exceeding the threshold (typically >4.8V). This condition usually indicates the temperature sensor signal wire shorts to the 12V power supply line (B+), or the internal thermistor fails due to a short circuit. Due to temperature monitoring failure, the IPB enters a safety degraded mode and limits the brake assist function. This limitation may cause a hard brake pedal and extended braking distance, constituting a severe fault that affects driving safety.
Causes
— The engine compartment wiring harness chafes against body metal edges or sharp edges, damaging the temperature sensor signal wire insulation and causing a short circuit to the 12V power wire.— A short circuit in the brake booster internal temperature sensor thermistor causes the signal voltage to abnormally rise to the 5V reference voltage.— Water ingress, submersion, or moisture corrosion in the IPB wiring harness connector (usually located near the front compartment firewall) creates a low-resistance path between the signal and power terminals.+2 more →
Actions
— Use the VDS diagnostic tool to read all fault codes and freeze frame data. Record the voltage, temperature, and vehicle status at the time of the fault. Confirm DTC P25C700 is current and cannot be cleared.— Open the engine compartment and visually inspect the wiring harness routing between the IPB and the Vehicle Control Unit (VCU). Check the firewall pass-through, harness retaining clips, and metal bracket contact points for wear, insulation damage, or burn marks.+6 more →
B1773›
On BYD new energy vehicles, DTC B1773 indicates a Cell Supervision Circuit (CSC) fault. This represents a Battery Management System (BMS) subsystem communication or sampling abnormality, rather than the seat belt pretensioner issue in the original description (the latter belongs to the SRS system, indicating a possible mix-up in fault code definitions). The CSC module continuously monitors key parameters within the power battery module, including individual cell voltage and temperature, and communicates with the main BMS via the internal CAN bus. The BMS sets DTC B1773 when it fails to detect a response signal from a CSC within the specified timeframe (communication timeout), receives out-of-range data (e.g., a -40°C open-circuit temperature reading), or detects a CSC address conflict or duplication. This fault activates the system safety protection strategy, limiting vehicle power output, disabling pure EV driving, or interrupting the charge/discharge process. It severely compromises power battery thermal management and safety monitoring functions and requires immediate repair.
Causes
— Collector wiring harness connector oxidation, corrosion, terminal back-out, or poor contact (common after water ingress due to battery pack seal failure).— Internal short circuit in the battery information collector (CSC module), PCB cold or broken solder joints, or damaged sampling chip.— Collector low-voltage power supply circuit fault (blown power supply fuse or open circuit causing loss of 12V power)+2 more →
Actions
— Use the VDS diagnostic tool to access the BMS and read the complete fault codes and live data stream. Confirm the specific faulty collector number (CSC Group X) and the fault type (communication fault/sampling abnormality).— Perform the high-voltage safety power-down procedure: disconnect the low-voltage battery negative terminal, remove the Manual Service Disconnect (MSD), wait at least 5 minutes to ensure the high-voltage system powers down completely, and perform an insulation test.+5 more →
B17731B›
This DTC indicates the SRS (Supplemental Restraint System) control module detects a missing signal or communication interruption from the right rear seat belt pretensioner during self-check or real-time monitoring. Specifically, the control module cannot identify the pretensioner’s electronic identification (resistance signature code or LIN/CAN node ID) or detects an open circuit, short to ground, or short to power. This prevents the seat belt at this position from tightening automatically during a frontal collision, increasing passenger forward displacement and significantly reducing restraint system effectiveness. The SRS system also illuminates the airbag fault warning lamp and may disable the related collision trigger logic. This is a critical fault affecting passive safety.
Causes
— Right rear seat belt pretensioner connector (located below the B-pillar or under the seat) loose, terminals backed out, or oxidized/corroded, causing excessive contact resistance or signal interruption.— Open circuit in the pretensioner body internal squib or resistance drift beyond the calibrated range (normal: 2.0-5.0 Ω), failing the SRS module safety check.— Long-term wear or pinching at the sill trim panel bend breaks the floor or B-pillar wiring harness, causing an open circuit between the pretensioner and the SRS module.+2 more →
Actions
— Safety preparation: Turn off the ignition, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to allow the SRS capacitor to discharge fully. Wear an anti-static wrist strap. Never use a standard multimeter resistance setting to directly measure a pretensioner connected to the control module.— Visual inspection: Remove the right rear door sill trim panel and lower B-pillar trim panel. Check the pretensioner connector for looseness, water ingress, or deformed pins. Disconnect and reconnect the connector, and apply conductive grease to ensure good contact.+5 more →
B1774-00›
This DTC indicates a short to vehicle power positive (B+) in the right rear seat belt pretensioner ignition circuit. In the BYD SRS (Supplemental Restraint System) architecture, the seat belt pretensioner is a pyrotechnic actuator. Its normal operating resistance is 2.0-3.0 Ω, and the circuit must remain isolated from the vehicle power supply. When the SRS ECU detects an abnormal resistance drop (near 0 Ω) or a short to power in this circuit, it triggers DTC B1774-00 and enters fail-safe mode. This fault prevents the right rear seat belt pretensioner from tensioning normally during a collision. In extreme cases, short-circuit current may cause the pretensioner to deploy unintentionally, presenting a severe safety hazard. The system illuminates the airbag warning lamp and may disable the entire right-side airbag system.
Causes
— Worn insulation on the pretensioner wiring harness inside the right rear C-pillar trim panel contacts the body power wiring harness (such as constant +B or IGN power), causing a short circuit.— Poor sealing of the seat belt pretensioner connector (usually located under the seat or at the C-pillar) allows water ingress, causing electrolytic corrosion and a short circuit between terminals.— Damaged igniter insulation inside the pretensioner body shorts the coil to the housing (short to vehicle power).+2 more →
Actions
— Safe power-off: Switch off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds (to fully discharge the SRS capacitor and prevent accidental deployment).— Fault Confirmation: Use the BYD ED400 or VDS diagnostic tool to read the fault code. Confirm B1774-00 is a current (Active) fault rather than a history fault, and record the freeze frame data.+6 more →
B177412›
DTC B177412 indicates the Supplemental Restraint System (SRS) detects an abnormally low-resistance connection between the right rear seat belt pretensioner drive circuit and the vehicle positive power supply (B+), indicating a short to power. The normal pretensioner igniter resistance is approximately 2.0-3.0Ω. The SRS ECU monitors circuit current and voltage to determine component status. If damaged wiring harness insulation causes the power wire (typically red/yellow) to contact the pretensioner drive wire, the ECU detects an abnormally high voltage (approaching the 12V battery voltage) and triggers this DTC. This fault causes the SRS to disable the right rear seat belt pretensioner circuit. During a collision, the pretensioner may fail to deploy and tighten the seat belt, creating a severe safety hazard. Additionally, the short to power creates a risk of unintended pretensioner deployment under extreme conditions. The system therefore classifies this as a severe fault (Level 3) and prohibits continued vehicle operation. Note: Repair practices for certain vehicle models may define this DTC as a seat ventilation system control circuit fault. Verify the definition against the specific vehicle configuration.
Causes
— Wiring harness mechanical damage: The pretensioner wiring harness inside the right B-pillar trim panel or under the seat rubs against body metal edges or the seat slide rail, damaging the insulation and shorting the power wire to the pretensioner drive wire.— Connector water ingress and corrosion: Driving through water, improper car washing, or aging seals allow water to enter the right rear seat belt pretensioner connector (usually located at the base of the B-pillar or under the seat), causing an electrolytic short circuit between the pins.— Pretensioner unit internal fault: Igniter internal bridge wire shorted to metal housing (usually resulting from manufacturing defects, physical impact, or residual stress following pretensioner deployment in a previous accident).+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 3 minutes to ensure the SRS capacitor discharges fully to prevent accidental airbag deployment. Wear an anti-static wrist strap.— Visual inspection: Remove the right B-pillar lower trim panel and the right rear door sill trim panel. Check the pretensioner connector (usually marked 'R2 Pretensioner' or 'RR SBPT') for looseness, water ingress, corrosion, or signs of burning.+3 more →
B1775-00›
This DTC indicates an abnormally low-resistance connection (typically <1 kΩ) between the right rear seat belt pretensioner squib circuit and vehicle chassis ground (GND). As a pyrotechnic safety device, the pretensioner relies on the SRS ECU to supply a high-current pulse during a collision. A short to ground causes: 1) abnormal circuit resistance, leading the ECU to register a device fault; 2) potential inadvertent deployment if the short-circuit current reaches the ignition threshold; 3) the SRS system to enter fail-safe mode, disabling the right rear pretensioner and associated seat belt reminder function. This is a hard fault in the passive safety system that directly affects the integrity of the occupant restraint system.
Causes
— Wiring harness wear below the right B-pillar: The pretensioner wiring harness routes through the B-pillar trim to the floor. Long-term fore-and-aft seat adjustment or passenger foot movement wears the insulation, causing a short circuit to the metal body.— Connector water ingress and oxidation: Water accumulation on the rear floor (e.g., from a blocked sunroof drain tube or leaking A/C condensate) corrodes the pins of the pretensioner connector (usually located under the seat or at the base of the B-pillar), forming a short-to-ground path.— Pretensioner internal fault: Igniter (squib) internal bridge wire insulation failure or damp, conductive propellant causes continuity between the terminals and the housing.+2 more →
Actions
— Safe power down: Turn the power switch to OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor. Wear an anti-static wrist strap.— Fault code freeze frame analysis: Connect VDS or a dedicated diagnostic tool, record vehicle status when the fault code occurred (temperature, voltage, mileage), and confirm if the fault is intermittent.+6 more →
B1775›
DTC B1775 indicates the SRS (Supplemental Restraint System) detects a short to ground in the right rear seat belt pretensioner circuit. The seat belt pretensioner is a pyrotechnic actuator containing an explosive device and a resistance wire. Normal resistance is approximately 2-3 Ω. When the SRS control module detects circuit resistance below the threshold (typically <1 Ω) or an abnormal voltage drop to ground, it identifies a short to ground. This safety-critical fault causes: 1) the SRS to enter degraded mode, disabling right rear side impact protection; 2) continuous illumination of the airbag warning light; 3) a risk of unintended pretensioner deployment in extreme cases. The pretensioner wiring harness routes through the right rear door sill trim and C-pillar, exposing it to seat movement, liquid ingress, or mechanical damage.
Causes
— Long-term chafing of the wiring harness under the right rear seat: During fore/aft seat adjustment or folding, the pretensioner wiring harness chafes against the seat frame or floor, damaging the insulation and causing a short to body ground.— C-pillar interior trim panel wiring harness clip failure: A loose or missing C-pillar trim retaining clip allows the wiring harness to contact the metal body while driving, causing an intermittent or continuous short to ground.— Pretensioner connector water ingress: An aging right rear door seal or open window allows rainwater to enter, forming an electrolyte at the pretensioner connector (usually located under the seat or at the base of the C-pillar) and causing a short circuit between pins or to ground.+2 more →
Actions
— Safe power-down and wait: Disconnect the low-voltage battery negative terminal and wait at least 90 seconds. This ensures the SRS capacitor discharges completely and prevents pretensioner deployment during diagnosis.— Freeze frame data analysis: Use the VDS2000 diagnostic tool to read freeze frame data at the time of the fault, including vehicle speed, crash signal, and voltage, to determine if the fault is intermittent.+6 more →
B177511›
DTC B177511 indicates a short to ground in the right rear (RR) seat belt pretensioner ignition circuit. In the BYD SRS (Supplemental Restraint System) architecture, the airbag control unit (ACU) sets this DTC when it detects the right rear seat belt pretensioner drive circuit resistance falls below the threshold (typically <1.0Ω, normal range 2.0-3.0Ω) or detects an abnormal drop in the circuit insulation resistance to body ground. A short to ground prevents normal pretensioner deployment (failing to ignite the gas generator to tighten the seat belt during a collision). Simultaneously, the ACU illuminates the airbag fault warning lamp and may disable the entire side or rear SRS protection strategy, severely compromising occupant passive safety. This is a hard fault; once confirmed, it remains active and does not self-recover.
Causes
— Right rear seat belt pretensioner assembly internal short circuit: Moisture, aging, or manufacturing defects damage the pretensioner squib insulation, causing the ignition wire to short to the metal housing.— Mechanical wear of the B-pillar or seat wiring harness: Long-term bending and compression of the seat belt pretensioner wiring harness at the seat height adjustment mechanism, B-pillar trim panel, or slide rail damages the insulation layer, causing the copper core to contact the vehicle body metal frame.— Connector water ingress and corrosion: A poorly sealed pretensioner connector (usually a multi-pin black plug) located under the seat or at the base of the B-pillar allows water entry if the rear floor floods during wading or vehicle washing, causing a short circuit between terminals or to ground.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal. Wait at least 90 seconds for the SRS capacitor to discharge fully to prevent accidental airbag deployment. Wear an anti-static wrist strap and disable the vehicle smart key system.— Initial visual inspection: Remove the right rear seat and lower B-pillar trim panel. Check the seat belt pretensioner wiring harness (usually wrapped in yellow corrugated conduit) for obvious damage, crushing, or burn marks. Check connector BG08 (or corresponding model pins) for water ingress, corrosion, or looseness.+4 more →
B1777›
This fault code indicates the Airbag Control Module (ACM) detects a 0 ohm circuit resistance in the left middle-row (second-row left) seatbelt pretensioner. In a normal SRS system, the pretensioner functions as a pyrotechnic actuator with a standard resistance typically between 1.8Ω and 3.0Ω (depending on the specific vehicle model). A 0 ohm resistance indicates a hard short in the circuit, usually a short to ground or a short between terminals. This causes the ACM to flag the pretensioner as failed. This condition triggers the airbag system fail-safe mechanism, potentially preventing the corresponding airbag and related restraint systems from deploying during a collision. The instrument cluster SRS warning light remains illuminated, posing a severe safety hazard.
Causes
— Water ingress or moisture in the pretensioner connector causing a short circuit between terminals, commonly resulting from driving through water, leaking interior cleaning fluid, or aging floor sealing strips.— Chafed wiring harness under the seat or inside the B-pillar. Damaged wire insulation allows direct contact with the vehicle body metal, causing a short to ground.— Improper handling during seat removal and installation or interior modification causes an incompletely seated pretensioner connector, deformed terminals, or a broken connector latch resulting in a short circuit to the bracket.+2 more →
Actions
— Use the BYD VDS2000 or a dedicated diagnostic tool to read fault codes. Confirm B1777 is a current (Active) fault, not a history fault. Record freeze frame data and check for related fault codes such as B17771A (resistance below threshold).— Disconnect the battery negative terminal and wait at least 3 minutes to fully discharge the SRS system. Inspect the left second-row seat belt pretensioner connector (usually located under the left side of the seat or at the base of the B-pillar) for signs of water ingress, green corrosion, loose connections, or deformed terminals.+4 more →
B17771A›
DTC B17771A indicates the airbag control unit (SRS ECU) detects a circuit resistance of 0Ω or close to 0Ω for the second-row left seat belt pretensioner. Normally, the squib resistance inside an undeployed pretensioner is 2.0Ω±0.2Ω. A resistance of 0Ω indicates a hard short in the circuit. Potential causes include an internal short in the pretensioner coil, a wiring harness short to body ground, or a short between connector terminals. This is a safety system hard fault. The SRS ECU illuminates the airbag malfunction indicator lamp (MIL) and disables the second-row left seat belt pretensioner and potentially associated airbag functions. During a collision, the pretensioner fails to generate the designed pulling force to tighten the seat belt, reducing occupant restraint protection.
Causes
— Pretensioner wiring harness shorted to ground due to wear: Long-term fore-and-aft seat adjustment and vibration friction damage the harness insulation under the left middle-row seat or near the B-pillar, allowing the wire to contact the vehicle body metal and create a short circuit.— Pretensioner connector internal short circuit: Bent or backed-out connector pins, or water ingress and corrosion (common after vehicle wading or interior cleaning) causing continuity between terminals.— Pretensioner assembly internal short circuit: Squib internal bridge wire blown or chemically deteriorated, causing a sharp drop in resistance, or pretensioner deployed and not reset.+2 more →
Actions
— Safe power-off and discharge: Turn off the ignition switch, disconnect the battery negative terminal, and wait at least 90 seconds for the SRS capacitor to fully discharge, preventing accidental deployment.— Visual inspection and connector check: Remove the left middle-row seat side trim panel. Inspect the pretensioner connector (usually yellow) for looseness, water ingress, or deformed pins. Inspect the wiring harness at the seat slide rail fixing points for wear or cuts.+5 more →
B1778›
DTC B1778 indicates the left middle-row (second-row left) seat belt pretensioner resistance falls below the normal threshold set by the SRS ECU. Standard resistance is typically 2.0–5.0 Ω; the ECU sets the fault upon detecting <1.5 Ω or near 0 Ω. The pretensioner is a pyrotechnic safety device containing an internal heating wire and pyrotechnic charge. During a collision, the ECU triggers deployment to rapidly tighten the seat belt. Low resistance typically indicates a circuit short to ground, an internal short in the pretensioner heating wire, or a grounded connector terminal. Consequently, the SRS system flags a risk of unintended deployment or functional failure, illuminates the airbag warning light, and may disable related crash protection functions. On BYD e-Platform and DM models, this fault may also affect the vehicle high-voltage interlock logic (some models link seat belt status to high-voltage readiness).
Causes
— Short circuit between pretensioner heating wire layers: Prolonged exposure to damp environments or manufacturing defects causes the internal pyrotechnic charge to absorb moisture, damaging the heating wire insulation and abnormally lowering the resistance.— Wiring harness damaged and shorted to ground: Repeated bending, crushing, or rodent bites damage the insulation of the yellow SRS wiring harness (inside the B-pillar trim or under the seat, typically within the left center door sill harness), causing a short to body ground.— Connector water ingress and corrosion: Poor sealing of the left middle-row seat belt pretensioner connector (usually located below the B-pillar or on the seat frame) allows water ingress after car washing or wading, causing a micro-short circuit between terminals.+2 more →
Actions
— Safety preparation: Disconnect the low-voltage battery negative terminal, wait at least 90 seconds (allow the SRS capacitor to fully discharge), and remove the service disconnect plug (execute the high-voltage power-down procedure for new energy vehicles).— Fault Confirmation: Use VDS2000 or a dedicated BYD diagnostic tool to read fault codes. Confirm B1778 is a current fault (Active). Record freeze frame data. Check for accompanying fault codes (e.g., B17771A).+6 more →
B1779›
DTC B1779 indicates the SRS (Supplemental Restraint System) control module detected the second-row left seat belt pretensioner circuit resistance exceeds the calibrated threshold (typically >3.5-4.0Ω; normal range is 1.6-3.0Ω). This passive safety system circuit integrity fault indicates a high-resistance state in the pretensioner deployment circuit. Potential causes include poor connections, an open circuit in the wiring harness, or an aging gas generator coil inside the pretensioner. During a collision, the SRS module might not supply sufficient current to deploy the pretensioner, preventing the seat belt from tightening promptly and increasing the risk of occupant injury. The system also illuminates the airbag warning lamp and may disable the associated airbag protection functions for that seat.
Causes
— Pretensioner wiring harness connector loose or oxidized: Water ingress, cleaning fluid penetration, or prolonged vibration oxidizes the terminals of the pretensioner connector under the left middle-row seat or at the B-pillar, creating contact resistance (usually >2Ω).— Seat adjustment mechanism wearing the wiring harness: Frequent forward and backward sliding or folding of the middle-row seat breaks the internal copper strands of the pretensioner wiring harness at the hinge (broken core with intact insulation), creating a high-resistance path.— Pretensioner unit aging: Material fatigue or long-term micro-current electrolysis from current monitoring increases resistance in the gas generator squib bridge wire, approaching the open-circuit threshold.+2 more →
Actions
— Safety Preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds for the SRS capacitor to discharge fully to prevent accidental airbag deployment. Set up high-voltage safety warnings (for new energy vehicles, confirm the high-voltage system is powered off).— Visual inspection: Remove the left middle-row seat side trim panel or lower B-pillar trim panel. Check that the yellow pretensioner connector (usually marked 'SRS' or 'Pretensioner') is fully seated. Inspect the terminals for green corrosion, burn marks, or backed-out pins.+5 more →
B1789-00›
This DTC indicates a short-to-ground fault in the Stage 2 firing circuit of the dual-stage driver airbag. In modern airbag systems, the second stage usually deploys simultaneously with or after the first stage during a severe collision, providing greater inflation volume for enhanced protection. A short to ground indicates damaged wire insulation or an internal connector fault in the circuit between the Airbag Control Unit (ACU) and the airbag squib. This creates a low-resistance path (typically <1Ω) between the circuit and the vehicle body ground. When the ACU detects an abnormal drop in circuit resistance, it immediately disables the Stage 2 airbag circuit and illuminates the airbag warning lamp to prevent accidental deployment or insufficient trigger energy. If a severe collision occurs in this state, the driver receives only first-stage airbag protection. The second-stage enhanced deployment function fails, but the first-stage airbag typically continues to operate normally.
Causes
— Damaged or broken insulation on the internal flat ribbon cable in the clock spring (spiral cable) causes the conductor to short to the steering wheel metal frame. This is the most common root cause of this fault.— Bent or backed-out pins at the driver's airbag connector (usually located under the steering wheel or on the back of the airbag), or poor connector sealing causing water ingress and corrosion, resulting in a short to ground.— Repeated steering wheel rotation wears the wiring harness between the steering wheel and the steering column over time, causing the damaged insulation to contact the metal vehicle frame.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (120 seconds for some models) to fully discharge the SRS capacitor. Never use a standard multimeter to measure directly across the airbag terminals.— Fault Confirmation: Use the BYD VDS2000 or Launch X431 diagnostic tool to read the fault code. Verify B1789-00 is a current fault (Active), not a historical fault. Record the resistance value in the freeze frame data (usually displaying <1Ω).+6 more →
B177A›
DTC B177A indicates the SRS (Supplemental Restraint System) control unit fails to detect the left middle-row (typically left second-row) seat belt pretensioner during self-diagnosis. This is an open-circuit fault; the ECU detects infinite pretensioner circuit resistance or resistance outside the normal threshold (standard value: 1.5-2.5Ω). The pretensioner is a key actuator in the passive safety system. During a frontal collision, a pyrotechnic igniter instantly tightens the seat belt to eliminate slack between the occupant and the belt. This fault indicates an open pretensioner circuit, preventing pretensioner deployment for this seat during a collision. This condition may also disrupt the coordinated deployment logic of the same-side or related airbags. "Not present" in this fault code does not indicate a missing physical component; it designates an electrical "communication loss" or "open circuit".
Causes
— Loose pretensioner connector or poor contact: Frequent forward and backward sliding or folding of the left middle-row seat can loosen the pretensioner wiring harness connector located under the seat or below the B-pillar. On MPV models like the Song MAX, the large range of movement of the middle-row seats exposes the connector to mechanical stress.— Wiring harness broken or worn: Repeated bending of the pretensioner wiring harness near the seat rails causes fatigue fractures in the internal copper conductors, or the metal seat frame edge wears through the harness insulation, causing an open circuit. This commonly occurs on 7-seat versions of SUV models such as the Tang and Song.— Pretensioner assembly internal fault: The igniter or bridge wire inside the pretensioner has an open circuit. Causes include manufacturing defects, prolonged vibration, or failure to replace the unit after deployment in a previous accident.+2 more →
Actions
— Safety Preparation and Initial Diagnosis: Disconnect the negative battery terminal and wait at least 3 minutes to fully discharge the SRS capacitor. Use a BYD dedicated diagnostic tool (VDS2000 or Launch X431) to read all fault codes. Confirm whether B177A is an Active or History fault, and record the freeze frame data to review the vehicle status at the time of the fault.— Visual inspection and connector check: Inspect the left middle-row seat belt assembly for signs of impact damage or disassembly. Locate the pretensioner connector (usually on the lower inner side of the seat or inside the B-pillar trim). Verify the connector is fully locked and inspect the terminals for oxidation, backed-out pins, or corrosion. If necessary, clean with electrical contact cleaner and reconnect.+3 more →
B177A1B›
DTC B177A1B indicates the SRS (Supplemental Restraint System/airbag system) control module detects an open circuit or resistance exceeding the normal threshold (typically >6Ω or infinite) in the left middle-row seat belt pretensioner circuit. The '1B' sub-code in the BYD diagnostic system typically indicates excessive circuit resistance or an open circuit, causing the ECU to determine the pretensioner is 'not present' or has lost communication. This fault prevents the system from triggering the left middle-row seat belt pretensioner pyrotechnic device during a collision, increasing occupant forward travel and reducing crash protection. The system illuminates the instrument cluster airbag fault warning light (SRS light) and may disable the deployment logic for the corresponding side airbag or curtain airbag.
Causes
— Left middle row seat belt pretensioner connector loose, terminal backed out, or poor contact (often results from seat removal for repair, failure to reconnect after carpet cleaning, or passenger kicking)— Pretensioner gas generator internal open circuit (internal igniter open circuit due to component aging, moisture ingress, or impact)— Wiring harness beneath the seat slide rail or B-pillar worn or broken (long-term fore/aft seat adjustment causes harness fatigue, or metal edges cut the insulation).+2 more →
Actions
— Use the genuine BYD diagnostic tool (VDS2000/3000) to read the complete fault codes and freeze frame data. Confirm the environmental conditions when the fault occurred (temperature, vehicle speed, etc.) and distinguish between current and history faults.— Perform safety procedure: Disconnect the negative battery terminal and wait at least 3 minutes (5 minutes on some models) to fully discharge the SRS system energy storage capacitor to prevent accidental airbag deployment.+7 more →
B177B›
DTC B177B indicates the control circuit for the second-row left seatbelt pretensioner has shorted to the vehicle power supply positive (B+). In the BYD SRS system, the pretensioner operates as a pyrotechnic actuator. Under normal conditions, the SRS ECU controls the pretensioner via a low-side drive and, during a collision, supplies an instant high current (approximately 2-3A) to ignite the gas generator. A short to power means the circuit continuously carries an abnormally high potential (12V). This may result in the following: 1) The SRS ECU falsely detects a permanent trigger state or wiring fault, activating the system protection mechanism. 2) The SRS ECU disables the entire airbag system, preventing protection during a collision. 3) The pretensioner accidentally deploys or the ECU internal driver circuit burns out in extreme cases. This is a hard fault and requires immediate repair.
Causes
— Mechanical wear of under-seat wiring harness: During fore/aft adjustment of the left middle-row seat (common on 7-seat models such as Song MAX and Tang), the pretensioner wiring harness rubs against the seat slide rail or metal bracket. Prolonged friction damages the insulation and shorts the harness to the seat power wire (constant live).— Connector water ingress and corrosion: Water enters the pretensioner connector (usually a yellow waterproof plug) located under the seat or on the B-pillar during vehicle wading, sunroof leaks, or deep interior cleaning, creating an electrolytic conductive path between the power and signal terminals.— Pretensioner internal short circuit: The insulation layer between the gas generator igniter bridge wire and the metal housing breaks down, or the igniter charge base absorbs moisture, causing ionic conduction (common in high-temperature, high-humidity environments or older vehicles).+2 more →
Actions
— Safety preparation: Switch off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS system energy storage capacitor and prevent accidental deployment.— Fault Confirmation: Use the BYD VDS or Launch X-431 diagnostic tool to read fault codes. Confirm B177B is a current fault (Current DTC) rather than a history fault (History DTC). Record freeze frame data to observe vehicle status when the fault occurred.+8 more →
B177B12›
DTC B177B12 indicates a short circuit to vehicle power (+12V B+) in the firing circuit of the left second-row seat belt pretensioner within the Supplemental Restraint System (SRS). The Airbag Control Unit (ACU) controls the pretensioner, a pyrotechnic device with a normal resistance of approximately 2.0-3.0Ω. The ACU determines a short to power when it detects abnormally low circuit resistance (typically <1.0Ω) or abnormal supply voltage. This severe safety fault prevents the pretensioner from firing correctly during a collision, or causes the system to lock it out due to inadvertent deployment risks. Root causes include damaged wiring harness insulation contacting a power wire, misaligned connector terminals, or a short circuit between the pretensioner internal bridge wire and the housing.
Causes
— Worn insulation on the pretensioner wiring harness under the left middle-row seat or inside the B-pillar contacts a body power wire (e.g., constant 12V), causing a short circuit.— Wiring harness crushed during seat adjustment or removal, causing the internal copper wire to short to power.— Water ingress, oxidation, or deformed pins at the pretensioner connector (usually located under the seat or inside the B-pillar trim), causing a short circuit between terminals.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental deployment.— Locate the component: Remove the left middle-row seat or B-pillar lower trim panel, and find the seat belt pretensioner and its yellow dedicated connector (usually includes a shorting bar).+5 more →
B177C›
DTC B177C indicates a short to ground in the left middle-row seat belt pretensioner ignition circuit. In the BYD SRS (Supplemental Restraint System) architecture, the pretensioner operates as a pyrotechnic device. Its ignition circuit normally maintains a high-impedance state (normal resistance approx. 2-3 Ω). The ECU determines a short to ground when it detects circuit voltage continuously below the threshold (<0.5 V) or an abnormal resistance drop (<1 Ω). This fault causes: 1) left middle-row pretensioner failure, preventing normal deployment to tighten the seat belt during a collision; 2) the SRS to enter degraded mode, potentially affecting normal airbag deployment logic; 3) the ECU to cut circuit power to prevent accidental deployment from short-circuit currents. This constitutes a severe active safety system fault. Triggering this fault illuminates the airbag warning light and activates a continuous buzzer alarm.
Causes
— Mechanical wear of the under-seat wiring harness: Frequent forward and backward sliding or folding of the left middle-row seat wears through the pretensioner wiring harness insulation (usually located near the seat rail), causing the harness to contact the metal frame and create a short to ground.— Connector water ingress and corrosion: During vehicle wading or interior cleaning, a poorly sealed pretensioner connector (located below the B-pillar or under the seat) allows moisture to enter, reducing insulation resistance between the terminals or to ground.— Internal short circuit in the pretensioner unit: Manufacturing defects, aging, or previous external impact cause the internal squib coil to short to the housing.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (to allow the SRS capacitor to discharge fully). Wear an anti-static wrist strap. Never use a multimeter to measure resistance directly at the pretensioner connector (use a dedicated SRS resistance measuring tool or the diagnostic tool active test function).— Visual inspection: Inspect the wiring harness sleeves in the left middle-row seat rail area, inside the lower B-pillar trim panel, and under the seat for damage, pinching, water stains, or burn marks. Focus on the wiring harness routing at the seat mounting bolts.+7 more →
B177C11›
DTC B177C11 indicates a short circuit to body ground (GND) in the ignition trigger circuit of the left middle-row (second-row left) seat belt pretensioner. The pretensioner is a critical component of the SRS (Supplemental Restraint System). It contains a pyrotechnic ignition device (squib). During a collision, the airbag control unit (ACU) triggers the squib with a specific current to instantly tighten the seat belt and protect the occupant. This DTC indicates the ACU detected abnormally low resistance in the pretensioner circuit (close to 0Ω), falling outside the normal threshold (typically 1.5–3.0Ω). Potential causes include damaged wiring insulation contacting the vehicle frame, water ingress at the connector shorting the terminal to ground, or an internal short between the pretensioner resistance wire and the metal housing. This critical safety fault disables the pretensioner for the affected seat and may trigger the SRS fail-safe mode, preventing proper airbag deployment. Extreme cases pose a risk of unintended heat generation or ignition.
Causes
— Frequent fore-and-aft seat adjustment or pinching chafes the wiring harness under the seat or inside the B-pillar trim panel, causing the exposed wire to contact the metal body frame and create a short to ground.— After vehicle wading, heavy rain, or deep interior cleaning, water enters the pretensioner connector (usually the yellow plug under the seat), causing terminal-to-terminal or terminal-to-ground short circuits or corrosion.— Manufacturing defect or aging of the pyrotechnic squib inside the seat belt pretensioner assembly causes the resistance wire to short to the metal housing.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the negative battery terminal, and wait at least 90 seconds for the SRS capacitor to discharge completely. This prevents accidental pretensioner activation and personal injury during inspection and repair.— Visual inspection: Remove the left middle-row seat (or move the seat to the foremost/rearmost position), locate the seat belt pretensioner connector (usually a yellow waterproof plug), and inspect for damage, water stains, burn marks, or terminal back-out.+3 more →
B177D›
DTC B177D indicates the airbag system (SRS) detects a 0 Ω circuit resistance in the right middle-row (typically second-row right) seat belt pretensioner. As a pyrotechnic actuator, the seat belt pretensioner squib normally has a resistance of 1.5-3.0 Ω (typically 2.0 Ω). A 0 Ω resistance indicates a short circuit. Potential causes include an internal pretensioner squib short, a wiring harness short to ground, or a short between connector terminals. This fault causes the SRS ECU to determine the pretensioner is in an unsafe state. During a collision, the pretensioner may fail to deploy and tension the seat belt, or the short circuit may force the airbag system into a degraded mode, compromising overall passive safety performance.
Causes
— Worn wiring harness under seat: As the right middle-row seat slides forward and backward, the seat belt pretensioner wiring harness rubs against the seat track or vehicle body metal edges, damaging the insulation and causing a short to ground.— Water ingress or corrosion in the connector: Poor sealing of the pretensioner connector under the seat base or lower B-pillar causes internal pins to short circuit after driving through water, washing the vehicle, or A/C condensate leakage.— Pretensioner internal squib short circuit: Manufacturing defects, aging, or severe impacts cause the pretensioner's internal bridge wire to short-circuit, dropping resistance to zero.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (to fully discharge the SRS capacitor). Do not work on the airbag system with the ignition switch in the ON position.— Visual inspection: Check the pretensioner wiring harness under the right middle-row seat, on the inner side of the seat rail, and below the B-pillar for wear, cuts, or crush marks. Check the connector for looseness, water ingress, or signs of corrosion.+4 more →
B1784-00›
This fault code indicates a low resistance or short circuit in the driver-side front airbag Stage 2 inflator circuit. The SRS control unit detects a circuit resistance of 0 ohms (normal range: 2.0-3.0 ohms). Dual-stage airbag systems deploy based on collision severity: Stage 1 provides partial inflation, and Stage 2 provides full deployment for maximum protection. A 0-ohm resistance typically indicates a short circuit in the inflator itself, the internal wiring of the clock spring (spiral cable), or a wiring harness short to ground. This fault causes the SRS system to identify a risk of unintended Stage 2 deployment. Consequently, the system illuminates the airbag warning light and may disable the entire driver-side front airbag, severely compromising occupant protection during a collision.
Causes
— An internal winding short circuit or a broken and grounded winding in the steering wheel clock spring (spiral cable) is a common steering system fault in the BYD Qin series.— Short circuit in driver airbag assembly internal second-stage igniter (airbag module fault, possibly due to aging or manufacturing defects)— Long-term steering wear damages the airbag wiring harness insulation near the steering column, causing a short circuit to the steering wheel metal frame.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds to fully discharge the SRS backup power supply and prevent accidental airbag deployment.— Initial inspection: Remove the service covers on both sides of the steering wheel, disconnect the airbag module connector, and inspect the connector terminals for green oxidation, water stains, or deformation.+5 more →
B177D1A›
DTC B177D1A indicates the SRS (Supplemental Restraint System) control unit detects the right middle-row seat belt pretensioner circuit resistance is abnormally low, approaching 0 ohms (standard value is typically 2.0–5.0 Ω). This indicates a short to ground, a short between wires, or an internal short circuit in the pretensioner squib circuit. This fault causes the SRS to enter a degraded protection mode. During a collision, the right middle-row seat belt pretensioner may fail to deploy and retract. The fault also illuminates the Airbag Warning Light continuously, compromising occupant passive safety protection.
Causes
— Damaged pretensioner wiring harness insulation under the right middle-row seat or near the B-pillar causes the wire to contact metal body components, creating a short to ground.— Water ingress, moisture, or corrosion at the seat belt pretensioner connector (usually located under the seat rail or inside the B-pillar trim), causing a short circuit between terminals or a short to ground.— A manufacturing defect or aging causes an internal short circuit in the pretensioner squib, dropping the resistance to 0 Ω.+2 more →
Actions
— Perform high-voltage safety procedures: Disconnect the low-voltage battery negative terminal and wait at least 3 minutes to fully discharge the SRS backup power supply and prevent accidental airbag deployment.— Locate the right middle row seat belt pretensioner: Remove the right middle row seat (or check below the B-pillar) and find the pretensioner assembly and its 2-pin connector (usually a yellow waterproof connector).+5 more →
B177E›
DTC B177E indicates the SRS (Supplemental Restraint System) detects the resistance of the right middle-row seat belt pretensioner (typically the second-row right seat belt retractor pretensioner) falls below the system threshold (generally below 1.0-1.5Ω, depending on vehicle calibration). As a pyrotechnic actuator in the airbag system, the pretensioner contains an internal resistance heating wire. Standard resistance typically falls within 2.0±0.5Ω. Low resistance indicates a short circuit risk in the loop. Potential causes include an inter-turn short in the internal pretensioner coil, a wiring harness short to ground, or a short between connector terminals. This fault causes the SRS ECU to register abnormal pretensioner operation. During a collision, the ECU may inhibit pretensioner deployment, preventing the seat belt from retracting. The fault also continuously illuminates the airbag warning lamp and triggers a buzzer alarm on certain models.
Causes
— Pretensioner internal short circuit: Damaged or damp insulation on the pretensioner internal heating coil causes an abnormal drop in resistance (measured value may be <1.0Ω).— Harness short to ground: Long-term chafing or pinching damages the insulation on the floor harness or the harness under the right middle-row seat, grounding it to the vehicle body metal.— Connector water ingress and corrosion: Vehicle wading, floor water ingress, or water entering the pretensioner connector (typically located under the seat or below the B-pillar) during a car wash causes a short circuit between terminals or a short to ground.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal. Wait at least 90 seconds (3 minutes for some models) to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Physical inspection: Visually inspect the right middle-row seat belt assembly, the wiring harness routing under the seat, and the pretensioner connector (usually located under the seat or inside the side trim panel) for water stains, corrosion, damage, or backed-out terminals.+5 more →
B1785-00›
This fault code indicates the circuit resistance of the driver-side dual-stage front airbag second-stage igniter (squib) falls below the threshold set by the SRS control unit (standard value: 2.0 ± 0.3 Ω; fault triggers at <1.0 Ω or near 0 Ω). The second-stage airbag deploys with a delay during severe collisions, providing staged protection alongside the first stage. Low resistance indicates a short circuit risk, which may cause: 1) the second-stage airbag to fail to deploy normally during a collision, reducing protection effectiveness; 2) unintended airbag deployment in extreme cases due to wiring abnormalities. This is a hard fault. The SRS system illuminates the warning light and may disable related airbag functions.
Causes
— Short circuit or damage to the internal second-stage igniter of the driver airbag module (airbag assembly fault)— Short circuit in clock spring (spiral cable/clockspring reel) internal wiring or damaged interlayer insulation— Water ingress, oxidation, or bent pins in the airbag wiring harness connector causing abnormal continuity.+2 more →
Actions
— Use a dedicated diagnostic tool (such as BYD ED400 or Launch X431) to read the fault code. Confirm B1785-00 is a current fault, not a history fault, and record the freeze frame data.— Visually inspect the steering wheel and airbag cover for damage, signs of water ingress or unauthorized modification. Check the status of the SRS fault indicator.+7 more →
B177F›
DTC B177F indicates the SRS (Supplemental Restraint System) control module detects the Second Row Right Seatbelt Pretensioner circuit resistance exceeds the normal upper threshold (typically 2.0-3.0 Ω, depending on the vehicle model). As a key passive safety system actuator, the pretensioner contains a gas generator and an ignition coil. Excessive resistance indicates high circuit resistance or a partial open circuit, which can cause the following: 1) The SRS cannot monitor the pretensioner readiness status. 2) The pretensioner may fail to deploy at the designed timing during a collision, compromising occupant restraint protection. 3) The airbag warning light remains illuminated, forcing the entire SRS into fail-safe mode and potentially preventing front and side airbag deployment. This constitutes a hard or intermittent fault requiring immediate repair.
Causes
— Poor pretensioner connector contact: Moisture, oxidation, or vibration increases terminal contact resistance in the connectors located at the B-pillar or under the seat. This commonly occurs after vehicle wading or operating in high-humidity environments.— Seat belt pretensioner unit fault: Internal ignition coil open circuit or aging of the gas generator internal resistance wire causes resistance to increase from the standard 2.0 Ω to over 3.5 Ω.— Hidden open circuit in wiring harness: Frequent folding and movement breaks internal copper strands in the right middle-row seat wiring harness while the insulation remains intact, creating an intermittent connection.+2 more →
Actions
— Safety Preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (SRS capacitor discharge time). Use the diagnostic tool to confirm the fault code status is Current.— Visual inspection: Remove the right middle-row seat side trim panel or the lower B-pillar trim panel. Check the pretensioner connector (usually a yellow plug) for proper seating, water ingress, corrosion, or terminal back-out.+5 more →
B1780›
This fault code indicates the SRS (Supplemental Restraint System) control module failed to detect the normal load resistance (typically 2.0-3.0Ω) in the Second Row Right Seatbelt Pretensioner circuit during the self-check, registering an open circuit. The pretensioner is a key actuator in the passive safety system. It contains an igniter and a gas generator. During a frontal or side collision, it detonates to produce high-pressure gas, instantly retracting the seatbelt to firmly secure the occupant in the seat and prevent secondary impact injuries. This fault completely disables the second-row right seatbelt pretensioner. The SRS enters degraded mode and continuously illuminates the instrument cluster airbag warning light (SRS light). Some models may also disable the coordinated deployment of the corresponding side airbag, significantly reducing the occupant protection level in a crash.
Causes
— Loose connection, backed-out pins, or poor contact at the pretensioner wiring harness connector (usually the yellow plug) under the right middle-row seat. This commonly occurs after seat removal and installation for maintenance, frequent operation of the third-row access function, or failure to seat the connector properly after carpet cleaning.— Open circuit or abnormal resistance (>5Ω or <1Ω) in the seat belt pretensioner internal igniter. Excessive pretensioner service life, internal moisture ingress, or previous external impact may cause this fault.— Long-term mechanical chafing of the floor wiring harness within the seat slide rail adjustment range damages the insulation and breaks the wires, or seat mounting bolts crush the wiring harness during installation, causing a hidden open circuit.+2 more →
Actions
— Safe power-off and discharge: Turn the ignition switch to OFF, disconnect the negative battery cable, and wait at least 3 minutes (5 minutes for some models) to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Physical connection check: Move the right middle-row seat to the fully forward and fully rearward positions. Verify the yellow SRS-specific connector under the seat (usually equipped with a double-locking mechanism) is fully seated. Inspect the terminals for green copper corrosion, backed-out pins, or cracks in the connector housing.+4 more →
B17801B›
DTC B17801B indicates the SRS (Supplemental Restraint System) control unit detects an open circuit in the right middle-row seat belt pretensioner circuit (resistance exceeds the normal range, typically >10Ω or infinite). This fault essentially constitutes a 'passenger restraint system communication loss'. During a collision, the pretensioner for this seat cannot receive the ignition signal and fails to retract the seat belt at the moment of impact to eliminate slack between the occupant and the belt. This fault triggers the SRS downgrade protection strategy, potentially altering the airbag deployment logic for this seat and surrounding areas (such as delayed deployment or non-deployment), severely compromising passive safety performance. For BYD E2/E3/Qin EV models, the right middle row typically refers to the second-row right seat. The pretensioner integrates into the seat belt retractor and communicates with the SRS ECU via a dedicated yellow connector under the seat.
Causes
— Loose pretensioner wiring harness connector or oxidized contacts: Vehicle vibration, water ingress, or previous repairs loosen the yellow plug under the seat (usually marked 'SRS' or 'AIRBAG'), or terminal oxidation causes excessive resistance.— Wiring harness fatigue fracture at seat slide rail: On models with a sliding right middle-row seat, fore-aft seat adjustment repeatedly bends the pretensioner wiring harness, breaking the internal copper strands while leaving the outer insulation visually intact (hidden open circuit).— Pretensioner internal igniter circuit open: The internal pyrotechnic igniter or motor-driven pretensioner coil has an open circuit measuring infinite resistance. Pretensioner aging, moisture ingress, or failure to replace the pretensioner after deployment typically causes this fault.+2 more →
Actions
— Safety preparation: Turn off the ignition switch, disconnect the low-voltage battery (12V) negative terminal, and wait at least 90 seconds to ensure the SRS capacitor fully discharges. For new energy vehicles, first disconnect the high-voltage service disconnect and confirm the high-voltage system powers down.— Locate the component: Find the right middle-row seat belt pretensioner, usually at the outer base of the seat or below the B-pillar (varies slightly by model). Identify the dedicated yellow connector (with shorting bar protection).+5 more →
B1781›
DTC B1781 indicates the airbag system (SRS) detected an abnormal short to vehicle power (B+, typically 12V battery voltage) in the right middle-row seat belt pretensioner ignition circuit. The pretensioner is an electrically triggered ignition device containing an igniter and a gas generator. Under normal conditions, the circuit remains in a high-resistance open state (showing a low resistance of 2-3Ω only when measured with a dedicated tool). When the Airbag Control Unit (ACU) detects the circuit voltage continuously exceeding the threshold (typically above 5V) or an abnormal resistance drop, it identifies a short to power. This fault forces the SRS into fail-safe mode, disabling the right middle-row and potentially related airbag functions. The airbag warning light illuminates continuously. In severe cases, the pretensioner may fail to deploy during a collision or may trigger unintentionally.
Causes
— Wiring harness physical damage: Long-term friction during seat track adjustment damages the insulation under the right middle-row seat, inside the B-pillar trim panel, or on the floor harness, shorting the pretensioner power wire to the body power wire or a constant power circuit.— Connector fault: Water ingress, oxidation, bent pins, or backed-out pins in the pretensioner connector under the seat (usually located on the seat frame or bottom of the B-pillar) cause a short circuit between adjacent terminals (power and signal/ground).— Pretensioner internal short circuit: Electrical breakdown of internal components in the seat belt retractor assembly pretensioner igniter (e.g., squib short circuit) causes resistance to drop abnormally close to 0Ω.+2 more →
Actions
— Safety preparation and diagnostic confirmation: Use the BYD dedicated diagnostic tool (VDS or ED400) to read the fault code. Confirm B1781 is a current fault (Active Code), not a historical fault. Record the freeze frame data. Disconnect the battery negative terminal and wait at least 3 minutes for the SRS capacitor to fully discharge.— Visual inspection and connector check: Remove the right middle-row seat (or lower B-pillar trim panel). Inspect the pretensioner connector (usually a yellow plug) for looseness, signs of water ingress, corrosion, or physical damage. Check for bent, backed-out, or bridged pins. Clean the connector using compressed air and apply dedicated conductive grease.+3 more →
B178112›
This fault code indicates the SRS (Supplemental Restraint System) ECU detected an abnormally low-resistance connection between the right second-row seat belt pretensioner igniter circuit and the vehicle power supply (12V constant power or ignition switch power). Under normal conditions, the pretensioner igniter circuit maintains a high-resistance state, consisting only of the 2-3Ω igniter resistance and the wiring harness resistance, and must not have continuity with the power supply line. A short to power causes the ECU to detect an abnormally high voltage (near battery voltage), triggering the fault code and illuminating the airbag warning lamp. This fault presents a serious safety risk. The pretensioner may deploy unintentionally while driving, suddenly tightening the seat belt and injuring the occupant. Additionally, during an actual collision, circuit protection mechanisms or energy loss through the short circuit may prevent the pretensioner from deploying, failing to protect the occupant.
Causes
— Right B-pillar or floor wiring harness insulation wear: Long-term vibration, friction, or seat adjustment damages the insulation on the second-row seat belt pretensioner wiring harness (usually located inside the B-pillar trim panel or under the seat), causing a short circuit to vehicle 12V power lines (such as constant power, ignition power, or lighting circuits).— Connector water ingress and corrosion: Vehicle wading, a blocked sunroof drain tube, or improper car washing allows water into the right middle-row seat belt pretensioner connector (usually located under the seat or at the base of the B-pillar). This causes electrolytic corrosion between the terminals, forming a conductive path that shorts the igniter terminal to the power terminal.— Pretensioner body internal short circuit: Manufacturing defects, aging, or moisture ingress cause the internal bridge wire of the seat belt retractor pretensioner igniter to short to the housing, or leaking igniter compound causes internal conductivity.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor. Wear an anti-static wrist strap. Never use a standard multimeter resistance setting to measure directly near the airbag system (use a dedicated airbag resistor or diagnostic tool guided function) to prevent accidentally triggering the pretensioner.— Fault confirmation and data recording: Use the BYD dedicated diagnostic tool (VDS or ED400) to read the complete DTC snapshot data. Record the voltage, resistance values, and environmental data at the time the fault occurred. Confirm whether B178112 is a current fault (Active) or a history fault (History).+6 more →
B1782›
DTC B1782 indicates the SRS (Supplemental Restraint System) control unit detects a short-to-ground fault in the right middle-row seat belt pretensioner circuit. Specifically, the resistance between the pretensioner squib positive or negative circuit and body ground falls below the system threshold (typically < 1Ω), causing the ECU to flag a circuit fault. This fault forces the SRS into a degraded protection mode, disables the right middle-row and associated airbag and pretensioner functions, and continuously illuminates the airbag warning light on the instrument cluster. During a collision, the pretensioner may fail to deploy and tighten the seat belt. This significantly reduces occupant protection and constitutes a severe driving safety fault.
Causes
— Under-seat wiring harness wear: Frequent fore-aft movement of the right middle-row seat (especially sliding-rail types) chafes the pretensioner harness insulation against the seat frame or guide rail edge. The exposed wire contacts metal body parts, creating a short to ground.— Connector water ingress and corrosion: Vehicle wading or interior cleaning allows liquid to enter the yellow SRS connector under the middle-row seat (usually at the base of the B-pillar or seat crossmember), causing a short circuit between terminals or from a terminal to ground.— Pretensioner assembly internal fault: The pretensioner igniter inside the seat belt retractor develops internal coil insulation failure due to manufacturing defects, aging, or moisture ingress, causing a short to the housing (ground).+2 more →
Actions
— Safety preparation: Switch the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation: Use BYD VDS or Launch X-431 to read fault codes, confirm B1782 is a current fault (Active), record freeze frame data (ambient temperature and voltage), and check for accompanying fault codes (e.g., B1781).+5 more →
B178211›
This DTC indicates the SRS (Supplemental Restraint System) ECU detected a short to ground in the right second-row seat belt pretensioner ignition circuit. As a pyrotechnic safety device, the pretensioner typically has a resistance of 1.5-3.0Ω. The ECU determines component status by monitoring circuit current and resistance. The ECU registers a short to ground if circuit resistance falls below the threshold (typically <0.8Ω) or insulation resistance to ground drops abnormally. This fault immediately forces the SRS into fail-safe mode, disables deployment of the affected seat pretensioner and potentially associated airbags, and illuminates the instrument panel airbag warning light. Because the pretensioner uses a squib as the actuating element, a short to ground can cause unintended ignition energy leakage or system misjudgment, creating a potential safety hazard.
Causes
— A worn or split wiring harness sleeve under the right middle-row seat or at the B-pillar causes the ignition circuit wire to directly contact the vehicle body metal frame, creating a short circuit.— Pretensioner connector (usually located under the seat or inside the B-pillar trim, with yellow marking): Seal failure allows water ingress after wading or vehicle washing, causing terminal corrosion and short circuit.— During accident repairs, improper routing of the pretensioner wiring harness allows the seat slide rail to pinch the harness, or a detached retaining clip causes long-term friction that damages the insulation.+2 more →
Actions
— Use a BYD dedicated diagnostic tool (VDS or ED400) to read all DTCs. Confirm if B178211 is an active or history fault. Check the right second-row pretensioner resistance in the SRS data stream (normal range: 1.5-3.0Ω).— Disconnect the low-voltage battery negative terminal and wait at least 90 seconds for the SRS capacitor to discharge fully to prevent accidental airbag deployment.+5 more →
B1784›
DTC B1784 indicates the driver-side front airbag Stage 2 firing circuit resistance is 0 ohms, signifying a short to ground or an internal short circuit in the gas generator secondary firing circuit. Modern airbag systems use a staged deployment strategy: Stage 1 deploys during moderate collisions, while Stage 2 deploys during severe collisions based on parameters such as seat position and seat belt usage to enhance protection. A resistance of 0 ohms means the SRS ECU detects circuit impedance below the threshold (typically less than 1.0Ω). This triggers the safety lockout mechanism and disables the airbag. This fault severely compromises driver protection during a collision and requires immediate repair.
Causes
— Broken internal wire shorting to ground or interlayer short circuit in the airbag clock spring (spiral cable/clockspring), causing the stage 2 ignition circuit to short to ground.— Internal short circuit in the driver airbag module second-stage squib, or inflator body failure (manufacturing defect or internal short circuit due to prolonged moisture).— Airbag wiring harness connector (usually located beneath the steering wheel or near the main crossmember) has water ingress, backed-out terminals, or damaged insulation causing a short to body ground.+2 more →
Actions
— Safe power-off: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault Confirmation: Connect the VDS or a dedicated diagnostic tool to read the DTC. Verify B1784 is a current fault code (Active) and cannot be cleared. Record the freeze frame data.+6 more →
B17841A›
This fault code indicates the SRS control module detects the driver-side front airbag Stage 2 igniter (inflator) circuit resistance at or near 0 ohms, indicating a short circuit (short to ground or short between wires). In dual-stage airbag systems, Stage 2 typically provides additional inflation capacity during severe collisions or delays inflation to optimize protection. A resistance of 0 ohms causes the SRS ECU to determine the igniter circuit is abnormal. The ECU disables the deployment function of this airbag stage and illuminates the airbag warning light. In extreme cases, an unstable short circuit creates a risk of unintended airbag deployment, or the airbag stage may fail to inflate normally during an actual collision, reducing protection and severely compromising occupant safety.
Causes
— The internal conductor in the clock spring (spiral cable/Clock Spring) breaks and shorts to ground, or shorts between windings. Fatigue damage from frequent steering wheel rotation or long-term wear commonly causes this.— Short circuit in the driver airbag module (DAB) second-stage igniter generator. Possible causes: manufacturing defect, long-term vibration causing the internal bridge wire to contact the housing, or internal corrosion after water ingress.— Airbag wiring harness chafes at the steering column, dashboard frame, or wiring channel edges. Damaged insulation causes a short to ground, especially on vehicles with previous accident repairs or modifications.+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS backup power supply and prevent accidental airbag deployment and personal injury during repair.— Fault confirmation and freeze frame analysis: Connect the BYD VDS or dedicated diagnostic tool to read the freeze frame data for DTC B17841A. Confirm whether the fault is currently present (Active) or historical (History). Record key information such as vehicle speed and collision signal status at the time of the fault.+6 more →
B1785›
This fault code indicates the driver-side dual-stage airbag Stage 2 squib circuit resistance falls below the standard threshold (typically <1.0Ω; standard value 2.0-3.0Ω). Electrically, this indicates a short circuit in the airbag ignition circuit (short to ground or wire-to-wire short). The second stage deploys based on collision severity. Low resistance causes the SRS ECU to detect a circuit fault and disable airbag deployment, or in extreme cases, abnormal current triggers unintended deployment. This hard fault in the active safety system triggers an airbag self-test failure, disables the entire front-row frontal airbag protection function, and poses a severe safety hazard.
Causes
— Airbag module internal squib short circuit: Stage 2 gas generator squib inside the driver airbag assembly internally short-circuited due to moisture ingress, aging, or manufacturing defects.— Internal short circuit in the clock spring (spiral cable): Long-term rotation wears or breaks the clock spring coil below the steering wheel, causing the wire end to short to ground, or the internal slip ring short-circuits.— Harness worn and shorted to ground: The harness from the SRS ECU to the steering wheel rubs against the steering column, instrument panel frame, or similar components, damaging the insulation and contacting vehicle body metal.+2 more →
Actions
— Safe power-down and wait: Disconnect the low-voltage battery negative terminal, wait at least 90 seconds (to fully discharge the SRS capacitor), and record the original fault code.— Visual inspection: Check the airbag wiring harness connector under the steering wheel and the clock spring connector for looseness, water ingress, corrosion, or burn marks. Check the wiring harness around the steering column for wear.+5 more →
B1786-00›
This fault code indicates the resistance of the driver's front airbag stage 2 (high-power deployment stage) squib circuit exceeds the normal threshold set by the SRS ECU (standard value is typically 1.0–2.0 Ω; threshold is generally 2.5 Ω). The dual-stage airbag system triggers in stages based on collision severity, with stage 2 providing greater inflation power during a severe collision. Excessive resistance indicates high resistance in the squib circuit, which may cause the ECU to detect an open-circuit risk. This prevents or delays stage 2 deployment during a severe accident, significantly reducing driver protection. This is a hard fault that does not clear automatically and illuminates the airbag warning light on the instrument cluster.
Causes
— Wear, breakage, or poor contact of the internal conductive slip ring in the clock spring (spiral cable) increases circuit series resistance (most common).— Aging, moisture ingress, or a manufacturing defect in the internal second-stage igniter of the driver airbag module, causing an abnormal increase in intrinsic resistance.— Oxidized, loose, or backed-out pins, or green corrosion in the airbag wiring harness connector (yellow plug beneath the steering wheel), creating additional contact resistance.+2 more →
Actions
— Safe power-down: Turn off the ignition, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation: Use the VDS2000/ED400 diagnostic tool to read the fault codes and verify B1786-00 is current (Active). Clear the code and read again to confirm the fault returns.+5 more →
B1786›
DTC B1786 indicates the airbag control module (SRS ECU) detects the ignition circuit resistance of the driver-side dual-stage front airbag Stage 2 inflator exceeds the standard threshold (normal range: 2.0-3.0 ohms; fault threshold: >6 ohms or open circuit). The Stage 2 airbag operates with the Stage 1 airbag during severe collisions, optimizing protection through delayed ignition or increased inflation. High resistance indicates a high-resistance condition or an open circuit. This prevents the Stage 2 airbag from deploying normally during a severe collision, reducing driver protection. It typically does not affect Stage 1 airbag operation.
Causes
— Broken internal wire or excessive contact resistance in the clock spring (spiral cable) second-stage circuit. Frequent steering wheel rotation commonly causes fatigue failure, or driving through water oxidizes the contacts.— Internal open circuit or aging failure of the driver airbag module second-stage squib, causing abnormally high resistance.— Airbag wiring harness connector (yellow waterproof plug) loose, terminals backed out, oxidized, corroded, or water ingress, causing poor contact.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes for the SRS capacitor to fully discharge to prevent accidental airbag deployment during repair.— Fault Confirmation: Use the BYD dedicated diagnostic tool (VDS2100/EDS) to read the fault code. Confirm B1786 is a Current DTC rather than a History DTC, and record freeze frame data.+7 more →
B1787-00›
DTC B1787-00 indicates the SRS (Supplemental Restraint System) control module detects an open circuit fault (abnormal resistance or open circuit) in the second-stage firing circuit of the driver-side dual-stage front airbag. Modern BYD models use a dual-stage airbag design; the first and second stages correspond to different deployment strategies based on collision severity. A "not connected" system report indicates the ECU cannot establish a complete circuit path to the second-stage inflator. This prevents the airbag from executing its staged deployment strategy during a moderate to severe collision, potentially triggering only the first stage or failing completely. The SRS also illuminates the instrument cluster airbag warning light and may disable the entire driver-side front airbag function, severely compromising crash protection performance.
Causes
— Internal open circuit or poor contact in the clock spring (spiral cable), especially a broken internal flat ribbon cable caused by prolonged steering.— Driver airbag module second-stage igniter internal open circuit or resistance out of specification (typical standard value: 1.5-3.0 Ω)— Loose, oxidized, or water-damaged yellow airbag wiring harness connector below the steering wheel (usually a 2-pin yellow plug), or backed-out terminals.+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the 12V low-voltage battery negative terminal, and wait at least 90 seconds (to fully discharge the SRS backup power capacitor). Never use a multimeter resistance setting to measure the airbag module directly.— Initial visual inspection: Verify the yellow airbag connector below the steering wheel is fully locked, inspect the wiring harness for signs of abrasion, crushing, or rodent damage, and check the clock spring housing for damage.+4 more →
B1787›
DTC B1787 indicates an open circuit fault in the second-stage deployment circuit of the driver-side dual-stage front airbag. A dual-stage airbag contains two independent inflation stages: the first stage (low-output deployment) and the second stage (high-output deployment). The second stage typically deploys with a delay or provides greater inflation volume during severe collisions. This fault code indicates the SRS control unit (ACU) detects second-stage deployment circuit resistance exceeding the threshold (typically >10Ω or open circuit), preventing proper second-stage airbag deployment during a collision. This fault does not disable the first-stage airbag, but it eliminates the staged protection function, increasing the risk of occupant injury during a severe collision. An electrical continuity interruption in the circuit causes this fault. The interruption may occur in the clock spring (spiral cable), airbag assembly, wiring harness connector, or inside the SRS ECU.
Causes
— Clock spring (spiral cable) internal break: Frequent steering wheel rotation causes fatigue fracture of the internal flat wiring harness, resulting in an open circuit, particularly in the Stage 2 circuit wire.— Airbag assembly connector loose or oxidized: Yellow connector behind the steering wheel not fully latched, or terminal oxidation or water ingress corrosion causes excessive contact resistance.— Airbag inflator second-stage circuit internal open circuit: Igniter (squib) inside the airbag unit burned out or internal connection disconnected.+2 more →
Actions
— Read the DTC freeze frame data using the BYD dedicated diagnostic tool (VDS2000/VDS2100). Record the vehicle speed, crash signal status, and voltage values at the time of the fault. Clear the DTC and road test the vehicle to verify if the fault recurs.— Disconnect the battery negative terminal and wait at least 3 minutes. Remove the covers on both sides of the steering wheel. Check the connection of the driver airbag yellow connector. Verify the locking tab is fully engaged and free of oxidation or terminal back-out. If necessary, clean the connector and apply conductive grease.+5 more →
B17871B›
This DTC indicates an open circuit or high resistance fault in the second-stage firing circuit of the driver-side dual-stage airbag. In modern passive safety systems, a dual-stage airbag inflates in stages according to collision severity: the first stage provides basic cushioning, and the second stage adds inflation during a severe collision to optimize protection. The "1B" sub-code typically indicates the SRS control module detects second-stage trigger circuit resistance outside the calibrated range (normal: 1.5-3.0 Ω). Possible causes include a disconnected connector, a wiring harness open circuit, an internal open circuit in the clock spring (spiral cable), or a faulty airbag module. During a high-speed frontal collision, this fault causes the airbag to deploy in single-stage mode only. This reduces head and chest protection but typically does not affect normal first-stage airbag operation.
Causes
— Driver airbag module connector loose or making poor contact (common after failing to fully lock the yellow plug following steering wheel removal or airbag replacement)— Open circuit in the clock spring (spiral cable) internal second-stage circuit, especially after frequent steering wheel rotation breaks the internal flat cable.— Prolonged steering movement wears the airbag wiring harness insulation near the steering column, causing wire breakage or intermittent poor contact.+2 more →
Actions
— Read all SRS fault codes using a genuine BYD diagnostic tool (VDS or ED400). Check for accompanying B1787-00 (first-level fault) or B1700 series faults. Record the resistance value from the freeze frame data.— Perform the safe power-down procedure: disconnect the 12V battery negative terminal, wait at least 90 seconds for the SRS backup capacitor to fully discharge, then remove the driver-side airbag module (do not measure the airbag pins directly with a multimeter).+5 more →
B1788-00›
Professional verification confirms BYD and standard OBD-II systems define DTC B1788-00 as "Mirror Passenger Down Circuit Short To Battery," rather than the airbag fault stated in the original information. This fault code falls under the Body System. It indicates the Body Control Module (BCM) detects an abnormal short circuit between the passenger-side exterior mirror downward adjustment drive circuit and the vehicle power supply positive terminal (+B). This fault has the following consequences: 1) The BCM activates its protection mechanism and cuts off circuit output, disabling the mirror downward adjustment function. 2) A sustained short circuit can burn out the internal BCM driver chip or blow the related fuse. 3) Fluctuating short-circuit current can trigger unintended operations, such as the mirror automatically tilting downward after locking the vehicle. Dual-stage airbag system fault codes typically fall within the B10xx-B13xx range. Always refer to the actual scan tool reading.
Causes
— Aged and damaged front passenger-side door wiring harness sleeve causes the door mirror power wire and downward adjustment signal wire to chafe and short together (common location: inside the wiring harness sleeve at the door hinge).— Burned internal coil insulation in the door mirror adjustment motor causes a short circuit between the positive and negative terminals, resulting in abnormally low resistance (normal: 15-25Ω; close to 0Ω when short-circuited).— Installing an aftermarket door mirror assembly with an internal circuit pinout or resistance value that does not match the genuine part causes the BCM to incorrectly detect a short to power.+2 more →
Actions
— Disconnect the battery negative terminal and wait 3 minutes to discharge the residual charge in the BCM capacitor and reset the diagnostic system.— Remove the front passenger door trim panel. Carefully inspect the wiring harness sleeve at the door-to-body connection. Pull back the corrugated conduit and inspect the wire insulation for wear. Repair any damaged wiring and rewrap the harness.+3 more →
B1788›
DTC B1788 indicates a short to power (B+) in the Stage 2 inflator circuit of the driver-side dual-stage front airbag. The SRS control unit continuously monitors the airbag deployment circuit resistance (normally 2.0–3.0 Ω) using internal safety sensors and diagnostic circuits. The control unit identifies a short to power when the Stage 2 airbag circuit voltage continuously exceeds the threshold (typically over 80% of supply voltage) or the resistance drops abnormally low (near 0 Ω). This fault causes: 1) Stage 2 airbag deployment failure during a collision, reducing occupant protection; 2) Accidental deployment risk, where the airbag triggers without a collision; 3) The SRS system to enter fail-safe mode, inhibiting all airbag functions. This fault involves a high-voltage deployment circuit and represents a highest-level safety fault.
Causes
— A broken internal conductor or damaged insulation in the clock spring (spiral cable) shorts the Stage 2 airbag wiring harness to the power supply line. This commonly occurs in vehicles over 5 years old or under operating conditions with frequent steering wheel rotation.— Insulation failure in the driver airbag module (DAB) internal second-stage igniter (squib). Long-term vibration, temperature cycling, or manufacturing defects cause an internal short circuit.— The SRS wiring harness chafes against sharp edges on the steering column or instrument panel frame, causing the damaged insulation to contact vehicle power wires (such as ignition switch power or instrument backlight power).+2 more →
Actions
— Safety Preparation: Disconnect the battery negative terminal and wait at least 90 seconds to discharge the residual charge in the SRS capacitor. Attach an 'Airbag Under Repair' warning label to the steering wheel to prevent accidental operation.— Fault confirmation: Connect the diagnostic tool. Read and record all SRS fault codes. If B1788 is present, check the Freeze Frame data to confirm parameters such as vehicle speed and ambient temperature when the fault occurred. Attempt to clear the fault code. If the fault code is Current and fails to clear, confirm a hardware fault.+6 more →
B178812›
This DTC indicates a short to vehicle power positive (B+) in the driver-side front airbag Stage 2 inflator circuit. In modern dual-stage airbag systems, separate circuits control the Stage 1 and Stage 2 inflators, triggering them in stages based on collision severity (Stage 1 low power, Stage 2 high power). A short to power means the airbag control unit (ACU) detects the Stage 2 inflator circuit voltage remaining abnormally high (12V). This prevents this airbag stage from deploying correctly during a collision (because the power supply bypasses the trigger circuit) and creates a major safety hazard of unintended airbag deployment, as the short-circuit current can accidentally trigger the inflator. The fault may originate in the clock spring, main wiring harness connector, airbag module, or the ACU.
Causes
— Damaged or broken insulation on the internal flat ribbon cable in the steering wheel clock spring (spiral cable) shorts the stage 2 ignition wire to the power wire. This is the most common cause and often occurs with abnormal noise when turning the steering wheel or multifunction button failure.— Long-term steering friction damages the airbag wiring harness insulation near the steering column, causing it to contact the body power wiring harness (such as the ignition switch power wire) and create a short circuit.— During front-end collision repairs or interior trim removal and installation, incorrect installation of the airbag wiring harness connector, bent pins, or screws or cable ties crushing the harness insulation causes a short to power.+2 more →
Actions
— Safety preparation: Switch the vehicle to OFF. Disconnect the 12V low-voltage battery negative terminal and wait at least 3-5 minutes (to ensure the SRS backup capacitor fully discharges). Wear an anti-static wrist strap. Do not use radio equipment near the airbag assembly.— Freeze frame analysis: Connect the VDS or X431 diagnostic tool to read the DTC freeze frame data. Record the vehicle speed, timestamp, and associated DTCs at the time of the fault. Check for accompanying B1788 (Level 1) or other SRS faults.+5 more →
B1789›
On BYD vehicles, DTC B1789 indicates a circuit fault in the driver seat belt pretensioner or the seat belt buckle position sensor, specifically a short to ground, open circuit, or signal range/performance fault. Although early documentation may describe this as a 'second-stage front airbag', the fault code points to the seat belt restraint system components beneath the seat. The SRS control module triggers B1789 when it detects abnormal resistance in the driver-side seat belt pretensioner circuit (below 1.0Ω or above 4.0Ω; normal range is 2.0-3.0Ω) or when the buckle position sensor signal voltage remains below the threshold. This fault forces the airbag system into fail-safe mode. In a collision, the system may fail to accurately determine if the driver is wearing the seat belt, preventing intended airbag deployment, disabling the pretensioner, or triggering start inhibition logic on certain models. The fault also illuminates the instrument cluster SRS warning light continuously, indicating a substantial risk to the occupant protection system.
Causes
— Wiring harness under the driver's seat worn or crushed: Frequent forward and backward seat adjustment causes the seat belt pretensioner wiring harness to interfere with the seat rail, resulting in damaged insulation, broken copper wires, or a short circuit.— Seat belt pretensioner connector (yellow plug) poor contact: Plug not fully locked, internal pins oxidized, backed out, or corroded by water ingress, causing abnormal resistance.— Seat belt pretensioner unit fault: Pretensioner deployed following a vehicle accident (micro gas generator detonated) but remained unreplaced during repair, causing an internal open circuit; or pretensioner internal coil short circuit.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes for the SRS system capacitors to fully discharge to prevent accidental airbag deployment.— Fault confirmation: Use VDS or the BYD dedicated diagnostic tool to read the fault code. Confirm whether B1789 is a current fault (Active) or history fault (History), and record the freeze frame data.+6 more →
B178911›
This DTC indicates an abnormally low-resistance connection (short to ground) between the driver-side dual-stage airbag Stage 2 ignition circuit and body ground. In modern SRS systems, the driver airbag typically features a dual-stage inflator: Stage 1 deploys during minor collisions, and Stage 2 delays deployment during severe collisions to enhance protection. A short to ground indicates the ECU detects an abnormally low voltage on the Stage 2 ignition circuit (typically <1Ω resistance). Damaged wiring harness insulation, an internal clock spring short circuit, or an internal airbag module fault can cause this condition. This fault causes the following: 1) The airbag system enters fail-safe mode; the Stage 2 airbag may fail to deploy or deploy unintentionally during a collision. 2) The SRS warning lamp remains illuminated, degrading the overall vehicle safety rating. 3) In extreme cases, short-circuit current can trigger accidental airbag deployment, posing a severe safety hazard.
Causes
— Clock spring (spiral cable) internal open or short circuit: Frequent steering wheel rotation wears and breaks the internal flat cable. The exposed conductor contacts the metal steering column, creating a short to ground. This is a common SRS fault location for the BYD E2/E3/Qin EV series.— Airbag wiring harness insulation damaged: Friction, crushing, or animal chewing damages the insulation where the driver airbag wiring harness routes near the steering column, causing the wire to contact metal body components.— Airbag assembly (gas generator) internal short circuit: An internal bridge wire short circuit in the second-stage igniter, or a damp and conductive pyrotechnic charge, abnormally drops resistance between the module terminals to near 0Ω.+2 more →
Actions
— Safety preparation: Turn off the ignition switch, disconnect the low-voltage battery negative terminal, wait at least 90 seconds (to fully discharge the SRS backup capacitor), and wear an anti-static wrist strap.— Fault confirmation: Connect the diagnostic tool and read the DTCs. Confirm B178911 is a current (Active) code, not a history code. Record the freeze frame data (crash sensor status, voltage values, etc.).+7 more →
B178A-00›
DTC B178A-00 indicates the SRS (airbag) electronic control unit detects an abnormally low resistance (close to 0 ohms) in the front passenger Stage 2 frontal airbag ignition circuit, indicating a short circuit (short to ground or short between wires). In a dual-stage ignition system, the Stage 2 airbag provides additional protection during severe collisions, typically deploying simultaneously with Stage 1 or triggering with a delay. A resistance of 0 ohms causes the SRS ECU to determine the ignition circuit is unreliable, illuminate the airbag warning light, and disable the front passenger airbag Stage 2 deployment function. In extreme cases, the airbag may deploy inadvertently without a collision or fail completely. This is a hard fault. The ECU stores it continuously until repaired.
Causes
— Front passenger airbag module internal second-stage igniter short circuit (damaged internal coil insulation causing a short circuit between positive and negative terminals)— Airbag wiring harness short to body ground (harness wear, crushing, or aging damages insulation, causing contact with the metal vehicle frame)— Water ingress or corrosion in the front passenger airbag connector (A/C condensate leak or wading causing a short circuit between connector pins)+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (some models require 3 minutes) to fully discharge the SRS capacitor and prevent accidental deployment.— Fault Confirmation: Use the dedicated BYD diagnostic tool (VDS or ED400) to read and record the fault code. Confirm B178A-00 is a current fault (Active) and check the environmental conditions recorded in the freeze frame data.+5 more →
B178A›
DTC B178A indicates the Stage 2 Passenger Front Airbag inflator circuit resistance measures 0 ohms (or near 0 ohms; normal range is 2.0–3.0 ohms). "Stage 2" refers to the secondary trigger circuit of a dual-stage airbag, providing greater deployment energy during a severe collision. A resistance of 0 ohms indicates a hard short (short to ground or short to power), not an open circuit. This fault triggers the SRS fail-safe mechanism: the control unit disables the passenger airbag Stage 2 deployment function, or disables the airbag entirely, and illuminates the instrument cluster SRS warning light. During a collision, this causes insufficient passenger protection, posing a serious safety hazard.
Causes
— Airbag inflator internal short circuit: Manufacturing defects, long-term aging, moisture ingress, or previous accident damage causes the internal squib resistance to drop to 0 ohms, creating a hard short circuit.— Harness short to ground/power supply: Metal edges cut the instrument panel internal harness insulation, retaining screws compress and chafe the insulation, or water ingress corrodes the harness, causing a short to vehicle body ground or +12V power supply.— Connector terminal fault: Dedicated yellow front passenger airbag connector (usually located behind the glovebox or inside the dashboard) has bent terminals, backed-out pins, loose connections, or electrolyte corrosion from water ingress causing a short circuit between pins.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds (120 seconds for some models) to fully discharge the SRS backup capacitor and prevent accidental airbag deployment and personal injury during repair.— Fault status confirmation: Connect the diagnostic tool and read the B178A freeze frame data. Confirm whether the fault is current (Active) or history (History). Record the ambient temperature and vehicle status at the time of the fault. Check for other accompanying SRS fault codes (such as B1780, B1781, etc.).+6 more →
C008208›
C008208 is a sub-fault code for the BYD ABS/ESP system. C0082 indicates an abnormal brake system status, and sub-code 08 identifies the specific signal anomaly type. The ABS (or ESP) control unit sends this abnormal brake system status warning to the instrument cluster. It typically indicates abnormal communication signals between the control unit and the instrument cluster, key brake system sensor signals falling outside the valid range, or a protective warning triggered by prolonged continuous ESP intervention. This DTC indicates the ABS/ESP system may fail to operate normally. The vehicle will lose active safety functions including anti-lock braking, electronic stability control, and automatic emergency braking. Conventional hydraulic braking typically remains unaffected.
Causes
— Loose connection, oxidation, or poor contact in the ABS/ESP control unit power supply or ground circuit, causing intermittent abnormal operation of the control unit.— CAN bus communication fault (including short circuit, open circuit, or signal interference on the powertrain CAN or chassis CAN), causing communication interruption or abnormal data between the ABS control unit, instrument cluster, and VCU.— Abnormal wheel speed sensor signal (damaged sensor, worn or shorted wiring, contaminated tone ring), causing the ABS control unit to receive an implausible wheel speed difference signal.+2 more →
Actions
— Connect the VDS diagnostic tool to read all fault codes. Check for accompanying C0031-C0048 (wheel speed sensor faults), C0051 (steering wheel angle fault), or U-class communication fault codes, and record the freeze frame data.— Check the warning light status displayed on the instrument panel (ABS, ESP, EBD, and brake system fault lights), confirm the fault symptom matches the DTC, and verify the brake fluid level is normal.+6 more →
B178A1A›
DTC B178A1A indicates the SRS control module detects the Passenger Second Stage Front Airbag igniter circuit resistance at or near 0 ohms. The second-stage airbag uses dual-stage ignition technology to control the deployment time interval based on collision severity. A resistance of 0 ohms indicates a short circuit fault in the airbag igniter circuit (short between wires or short to ground), not an open circuit. This fault causes the SRS system to enter degraded mode: the system disables this specific airbag circuit to prevent accidental deployment and illuminates the airbag warning light. In a frontal collision, the passenger side may lose second-stage cushioning protection, deploying only the first-stage airbag or failing to deploy entirely, which significantly reduces occupant protection.
Causes
— Front passenger-side airbag module internal igniter short circuit: A fused internal igniter bridge wire or moisture in the pyrotechnic charge causes a sudden drop in resistance.— Internal dashboard wiring harness chafed and shorted: Vibration and friction damage the Stage 2 airbag wiring harness insulation (usually located on the dashboard crossmember or behind the glove box), shorting it to body metal.— Connector water ingress and corrosion: A/C condensate leakage or vehicle wading causes a short circuit between pins on the front passenger-side floor wiring harness connector (such as CJ103 or near ground point G301).+2 more →
Actions
— Safety preparation: Switch the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS backup power supply.— Fault confirmation: Use VDS or a Launch diagnostic tool to read all DTCs. Verify B178A1A is an active fault rather than a history fault. Check for accompanying fault codes (e.g., B178B - front passenger second-stage resistance too low).+5 more →
B178B-00›
This fault code indicates that the resistance of the second stage (Level 2, typically the full-power deployment mode for severe collisions) inflator squib in the front passenger airbag dual-stage deployment circuit falls below the safety threshold set by the SRS ECU (generally below 1.5 Ω). In BYD dual-stage airbag systems, the first and second stages correspond to different collision severities. The system achieves staged deployment by controlling different firing circuits. Low resistance indicates the ECU detects an abnormal drop in circuit impedance and identifies a short circuit fault. The system enters a safety protection state and disables the airbag to prevent accidental deployment, rendering the airbag inoperative during a collision. This fault directly affects collision safety protection and requires immediate repair.
Causes
— Poor contact or terminal oxidation at the airbag wiring harness connector: The front passenger airbag mounts inside the instrument panel. Moisture, oxidation, or looseness easily causes abnormally low contact resistance or an intermittent short circuit in the yellow wiring harness connector (usually marked F201 or similar).— Airbag module internal short circuit: Damaged gas generator squib insulation or an internal circuit short to the housing drops measured resistance below the standard value (normally 2.0-3.0Ω). This commonly occurs after a collision if an internally damaged airbag remains unreplaced.— Wiring harness damaged and shorted to ground: Dashboard removal/installation, aftermarket equipment installation (e.g., dashcam routing), or small animals chewing the harness damages the insulation layer, creating a short circuit loop with the vehicle body metal.+2 more →
Actions
— Safe power-down and discharge: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds (to fully discharge the SRS backup power capacitor). Never connect or disconnect any airbag-related connectors while the system is powered on.— Visual inspection and cleaning: Remove the passenger-side lower dashboard trim panel and glove box. Locate the yellow airbag wiring harness connector (F201). Check for looseness, water ingress, terminal oxidation, or trapped foreign objects. Clean with electrical contact cleaner, then unplug and reconnect the connector. Ensure the locking tab fully engages.+4 more →
B178B›
This DTC indicates the SRS (Supplemental Restraint System) ECU detects the circuit resistance of the front passenger dual-stage frontal airbag Stage 2 inflator is below the calibrated threshold (typically below 1.0Ω; normal range: 1.5-3.0Ω). In a dual-stage airbag system, the Stage 2 inflator provides additional gas output during a severe collision. Low resistance usually indicates a short circuit (short to ground, wire-to-wire short, or internal inflator short). This condition may prevent proper airbag deployment during a collision (insufficient deployment force) or, in extreme cases, cause unintended deployment due to abnormal current. The ECU continuously monitors the inflator circuit resistance via its internal diagnostic circuit. If the resistance remains below the lower limit for a specified duration (typically several hundred milliseconds), the ECU sets this DTC, illuminates the SRS warning lamp, and may disable the front passenger airbag function.
Causes
— Front passenger airbag module internal second-stage igniter short circuit: Moisture ingress or aging of the bridge wire or igniter charge inside the gas generator causes an internal short circuit, resulting in abnormally low measured resistance.— Wiring harness short to ground or power supply: Wear, crushing, or rodent damage to the internal instrument panel wiring harness causes the stage 2 igniter circuit (usually the positive or negative wire) to short to body ground or the 12V power supply line.— Connector water ingress or corrosion: The front passenger airbag connector is located on the right side of the instrument panel. Vehicle wading, A/C condensate leakage, or improper cleaning causes connector pin oxidation or electrolysis, creating a low-resistance path.+2 more →
Actions
— Safety preparation: Switch the vehicle OFF, disconnect the 12V battery negative terminal, wait at least 3 minutes (to fully discharge the SRS capacitor), and wear an anti-static wrist strap.— Fault confirmation: Connect the VDS2000/3000 diagnostic tool, read the DTC to confirm whether B178B is an active code or a history code, and check the resistance value in the freeze frame data (usually displays <0.8Ω).+6 more →
B178C-00›
B178C-00 indicates the resistance of the front passenger-side Stage 2 frontal airbag ignition circuit falls outside the normal range set by the SRS ECU (typically 1.5–3.0 Ω). In the BYD dual-stage airbag system, the Stage 2 gas generator provides higher deployment power during a severe collision. High resistance indicates excessive impedance or a potential open circuit in the ignition circuit. Potential causes include an internal open circuit in the airbag squib, poor contact at the wiring harness connector, or a clock spring fault. This safety system hard fault forces the SRS ECU into fail-safe mode, disabling deployment of this airbag stage and severely reducing front passenger protection during a collision. Repair immediately.
Causes
— Aging, moisture ingress, or internal open circuit in the front passenger airbag module (PAB) second-stage igniter, causing resistance to exceed 3.0Ω.— Airbag wiring harness connector (usually located under the center console, behind the glove box, or at the airbag module interface) is loose, oxidized, has water ingress, or has backed-out pins, causing increased contact resistance.— Broken or poor contact in the internal second-stage circuit wire of the clock spring (spiral cable), common after turning the steering wheel to its end stop. (Note: On some models, the front passenger airbag also routes through the clock spring or a similar transfer connector.)+2 more →
Actions
— Safety Preparation: Set the vehicle to OFF, disconnect the 12V battery negative terminal, and wait at least 3 minutes to fully discharge the SRS backup power supply. Wear an anti-static wrist strap. Do not use radio equipment near the airbag assembly.— Fault confirmation and freeze frame analysis: Use the BYD VDS2000/ED400 diagnostic tool to read the DTC, confirm B178C-00 is a current fault (Active), record the resistance reading and ambient temperature from the freeze frame data, and check for accompanying fault codes (e.g., B178B, B178D).+4 more →
B178C›
This DTC indicates the SRS (Supplemental Restraint System) ECU detected the circuit resistance of the front passenger-side second-stage frontal airbag (a dual-stage inflator using staged ignition technology) exceeds the calibrated upper limit (normal value approximately 2.0-3.0Ω, fault threshold typically >3.5Ω or open circuit). The second-stage airbag deploys in stages based on the collision severity sensor signal (delayed ignition) to reduce occupant impact during a low-speed collision. Excessive resistance indicates a high-resistance connection or potential open circuit. Oxidized or corroded connectors, loose wiring harness connections, fatigue fracture of the spiral resistance wire inside the airbag inflator, or an abnormal ECU sampling circuit can cause this condition. This fault causes the airbag to deploy only in single-stage mode during a collision (delayed ignition failure) or fail completely, severely degrading crash protection performance. This is a safety-critical fault.
Causes
— Front passenger airbag module wiring harness connector loose, oxidized, or making poor contact (common in flooded vehicles or after long-term use in high-humidity environments)— Airbag wiring harness pinches and chafes where it passes through the center console frame or near the steering column, breaking the copper conductor without completely damaging the insulation (hidden high resistance).— Second-stage gas generator internal igniter resistance wire broken due to aging, or poor solder joint (internal airbag assembly fault; unrepairable, replace the complete assembly).+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor and enter safe repair mode.— Initial inspection: Remove the passenger-side glove box or lower airbag trim panel. Visually inspect the yellow SRS connector for backed-out pins or pin oxidation (green corrosion). Measure the resistance between the connector terminals (standard: 2.0-3.0 Ω).+3 more →
B178D-00›
DTC B178D-00 indicates the SRS (Supplemental Restraint System) control module detects an open circuit or disconnection in the front passenger-side dual-stage frontal airbag second-stage inflator circuit. The dual-stage airbag system contains two independent inflator trigger circuits (stage 1 and stage 2) that deploy in stages based on collision severity. This fault code specifically indicates the second-stage inflator circuit resistance falls outside the normal range (typically > 3Ω or < 1Ω), causing the system to register a 'not connected' state. This fault may prevent the front passenger airbag second-stage inflator from deploying correctly during a collision, reducing protection effectiveness, and illuminates the airbag warning light continuously.
Causes
— Front passenger airbag module connector loose, terminals backed out, or corroded. Located behind the instrument panel, this often results from incorrect refitting after previous instrument panel repairs.— Open circuit or abnormal resistance in the airbag module internal second-stage inflator squib. Common causes include airbag aging, moisture ingress, or failure to replace the module after a previous collision.— Poor contact at the intermediate connector between the floor wiring harness and the instrument panel airbag wiring harness, especially pin oxidation after driving through water.+2 more →
Actions
— Use the VDS2000/BYD dedicated diagnostic tool to read fault codes, confirm B178D-00 is a current code, record freeze frame data, and check for accompanying communication fault codes.— Disconnect the battery negative terminal and wait at least 90 seconds. Remove the front passenger side lower instrument panel trim. Verify the airbag module white 2-pin connector (usually marked PAB Stage 2) is fully locked. Inspect the pins for oxidation, backing out, or enlarged sockets.+5 more →
B178D›
DTC B178D indicates the front passenger second-stage frontal airbag (Passenger Frontal Airbag Stage 2) ignition circuit is disconnected or has abnormal resistance. In BYD e-Platform 3.0 models featuring a distributed electronic architecture (e.g., Dolphin, Seal, Yuan PLUS), this DTC may also indicate a communication interruption between the Right Body Domain Controller (R-DCU) and the SRS module, or a sub-node fault. The airbag utilizes a dual-stage ignition design to deploy in stages based on collision severity (stage 1 low-pressure deployment; stage 2 high-pressure supplementary deployment). This fault prevents the front passenger airbag from executing the second-stage deployment during a collision or causes complete airbag failure, severely compromising occupant protection. Inspect the airbag module wiring harness, connectors, clock spring (if applicable), and domain controller communication status.
Causes
— Front passenger airbag stage 2 ignition circuit open or resistance exceeds threshold (>4.5Ω), preventing the SRS control unit from detecting a valid load.— Loose airbag wiring harness connector, oxidation from water ingress, or backed-out terminal pins (focus inspection on the instrument panel airbag connector and domain controller interface).— Internal open circuit or poor contact in the clock spring (for models with a conventional clock spring design)+2 more →
Actions
— Use the VDS diagnostic tool to read the DTC freeze frame data, confirm the fault status as current (Active) or history (History), and check for other related fault codes (e.g., B178C, U0187).— Disconnect the negative battery terminal and wait at least 3 minutes to ensure complete system discharge. Inspect the front passenger airbag module connector (located inside the right side of the instrument panel or at the right domain controller interface) for looseness or oxidation. Measure the Stage 2 ignition circuit resistance (standard value: 2.0-3.0Ω).+4 more →
B178D1B›
This fault code indicates an open circuit or abnormal resistance in the Stage 2 squib circuit of the front passenger dual-stage frontal airbag (sub-code 1B typically indicates an open circuit or excessive resistance). In the BYD SRS system, dual-stage airbags feature two independent squibs (Stage 1 for moderate collisions, Stage 2 for severe collisions; the stages can deploy simultaneously or sequentially). B178D1B indicates the ECU detects the Stage 2 deployment circuit resistance falls outside the calibrated range (typically 2.0–3.0 Ω), showing infinite resistance (open circuit) or intermittent high resistance. During a severe frontal collision, this fault prevents the passenger airbag from deploying the second inflation stage as designed, reducing occupant protection. The SRS system enters fail-safe mode and continuously illuminates the instrument panel airbag warning light.
Causes
— Front passenger airbag module second-stage plug (yellow connector) not fully seated or locking tab loose. Commonly caused by failing to reconnect the plug after dashboard removal and installation, or missing it during new vehicle PDI.— Airbag wiring harness open circuit or excessive contact resistance. This typically occurs when the harness behind the instrument panel fractures at a frame bend after prolonged vibration, or when connector terminals oxidize or back out.— Failure or open circuit in the airbag module second-stage igniter (Squib). This internal module fault is unrepairable. Replace the complete assembly.+2 more →
Actions
— Perform the high-voltage power-down and airbag power-down procedure: disconnect the battery negative terminal and wait at least 3 minutes (to fully discharge the SRS capacitor). Do not operate any electrical switches during this time.— Visual inspection: Remove the glovebox or lower dashboard trim panel. Check if the yellow passenger airbag module connector (usually located behind the right side of the dashboard) is fully seated. Verify the dual locking mechanism (CPA lock) is fully engaged. Check the connector for water ingress or burn marks.+4 more →
B178E-00›
This DTC indicates the airbag control unit (SRS ECU) detects a short to vehicle power (12V/B+) in the front passenger airbag Stage 2 inflator circuit. Dual-stage airbags feature two independent inflators for different crash severities: Stage 1 provides cushioning in minor collisions, and Stage 2 provides additional protection in severe collisions. A short to power indicates an abnormal electrical connection between the inflator wiring and the battery positive terminal. This fault causes the SRS system to enter fail-safe mode, illuminates the airbag warning light, and disables the front passenger airbag Stage 2 deployment function. In extreme cases, it causes unintended airbag deployment or prevents normal deployment during a collision, creating a severe safety risk.
Causes
— Damaged internal wire insulation in the airbag clock spring (spiral cable/clock spring) shorts the Stage 2 squib circuit to the power wire.— Damaged insulation on the wiring harness between the front passenger airbag module and the SRS ECU, contacting the vehicle body metal frame or power supply wiring.— A retaining screw pinched or chafed the instrument panel internal wiring harness during removal and installation, causing a power supply short circuit.+2 more →
Actions
— Safety preparation: Turn off the vehicle. Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS backup power supply and prevent accidental airbag deployment.— Fault confirmation: Connect the VDS or dedicated diagnostic tool, read the complete fault codes and freeze frame data, confirm B178E-00 is a current fault (not a history fault), and record the environmental data at the time of the fault.+8 more →
B178E›
DTC B178E indicates a short to the vehicle power supply (B+, 12V) in the front passenger frontal airbag Stage 2 squib circuit. Modern BYD models use a dual-stage airbag design: Stage 1 provides low-power inflation for moderate collisions; Stage 2 provides high-power inflation for severe collisions. The SRS ECU internal diagnostic circuit continuously monitors the airbag squib circuit resistance (normally 2-3 Ω) and its insulation to ground and power. The ECU sets B178E when it detects a short to power in the Stage 2 squib circuit (resistance below the specified threshold, typically <200 Ω to power). This fault forces the airbag circuit into a fail-safe state. In extreme cases, the short circuit could accidentally deploy the airbag during driving (despite shorting bar protection) or prevent the designed staged inflation during a collision, risking occupant injury.
Causes
— Front passenger airbag wiring harness worn or pinched: Retaining clips or metal edges cut the internal dashboard wiring harness during removal and installation, causing the ignition wire to short-circuit to the constant power wire.— SRS ECU internal drive circuit fault: Airbag control module internal ignition drive transistor (IGBT/MOSFET) breakdown causes the second-stage control terminal to short to power.— Front passenger airbag connector terminal issue: The connector is behind the glovebox or at the instrument panel frame. Backed-out, bent, or water-corroded terminals short-circuit to an adjacent power supply terminal.+2 more →
Actions
— Safe power-down and wait: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS ECU internal energy storage capacitor and prevent accidental airbag deployment during repair.— Fault code freeze frame analysis: Use the BYD dedicated diagnostic tool (VDS2000/VDS3000) to read the Freeze Frame Data for DTC B178E. Record the vehicle speed, timestamp, and ambient temperature at the time of the fault to determine if it is an intermittent fault.+5 more →
B178E12›
DTC B178E12 indicates a short to power (B+) in the front passenger-side second-stage frontal airbag (PAB Stage 2) ignition circuit. The BYD SRS system uses a dual-stage airbag ignition design: the first stage provides a low-energy trigger, and the second stage provides a high-energy trigger for varying collision severities. This DTC indicates an abnormal electrical connection to the vehicle power circuit within the wiring harness between the SRS control module and the front passenger airbag second-stage inflator (resistance below threshold, typically <2Ω). This short circuit may cause: 1) unintended airbag deployment (extremely dangerous); 2) airbag deployment failure during a collision (due to bypassed current); 3) the SRS system to enter protection mode, disabling all airbag functions. The BYD diagnostic protocol identifies the fault suffix '12' as 'Short to Battery+'.
Causes
— Front passenger airbag wiring harness insulation worn: Inside the dashboard, A-pillar trim, or floor wiring channel, chafing from vibration or improper assembly damages the harness outer sheath, causing a short circuit to a power wire (such as constant 12V+).— Airbag connector water ingress or corrosion: The front passenger airbag connector (usually located behind the dashboard or glovebox) is poorly sealed; after water wading, exposure to high humidity, or an A/C condensate leak, electrolytic corrosion between the terminals forms a conductive path.— Clock spring internal short circuit: On vehicles equipped with an integrated clock spring, damaged interlayer insulation on the internal flat cable causes a short circuit between the airbag ignition circuit and the horn/multifunction switch power supply wire.+2 more →
Actions
— Safety Preparation and Diagnostic Confirmation: Use a BYD VDS or Launch X431 diagnostic tool to read all fault codes. Verify B178E12 is a current fault (not a history code). Record freeze frame data (including vehicle speed, crash signal status, etc.). Disconnect the battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor.— Wiring harness visual inspection: Remove the front passenger lower dashboard trim panel, glove box, and lower A-pillar trim panel. Inspect the airbag wiring harness (usually wrapped in yellow corrugated conduit) for wear, crushing, or burn marks. Focus on the contact points between the wiring harness and the dashboard metal bracket, air conditioning duct, and sharp body edges.+4 more →
B178F-00›
DTC B178F-00 indicates an abnormally low resistance connection (typically <1Ω) between the front passenger dual-stage frontal airbag Stage 2 squib circuit and body ground (GND). The dual-stage airbag system achieves staged inflation via two independent igniters: the first stage triggers a small amount of gas, and the second stage triggers delayed supplemental inflation based on collision severity. A short to ground causes: 1) The SRS control module to detect a circuit anomaly, illuminate the airbag warning lamp, and disable the system. 2) Unintended airbag deployment in extreme cases. 3) The second stage to fail to deploy normally during an actual collision, reducing protection effectiveness. This fault involves a high-voltage ignition circuit and is a safety-critical fault.
Causes
— Airbag wiring harness insulation worn: Long-term vibration or seat adjustment friction damages the wiring harness under the front passenger seat or inside the dashboard, wearing through the outer sheath and shorting it to the vehicle body metal.— Connector water ingress and corrosion: After vehicle wading or interior cleaning, the internal pins of the airbag connector (usually located under the center console or seat) become damp and oxidize, causing a Pin-to-Case short circuit.— SRS control module internal fault: A damaged internal driver chip or monitoring circuit in the airbag ECU falsely reports a short to ground (rule out by measuring resistance on the wiring harness side).+2 more →
Actions
— Safety preparation: Turn off the ignition, disconnect the 12V battery negative terminal, and wait at least 3 minutes for the SRS capacitor to fully discharge to prevent accidental airbag deployment.— Initial diagnosis: Connect the diagnostic tool to read all fault codes and freeze frame data. Confirm B178F-00 is a current fault (Active), not a historical fault. Record the vehicle mileage and ambient temperature.+6 more →
B178F›
DTC B178F indicates a short to ground in the stage 2 deployment circuit of the front passenger dual-stage frontal airbag. In a dual-stage airbag system, the stage 1 and stage 2 inflators trigger in stages based on collision severity: stage 1 provides basic protection, and stage 2 supplements inflation during a severe collision. This fault means the SRS control module detects an abnormally low resistance (typically below 1.0 Ω) between the stage 2 inflator circuit and body ground. Possible causes include an internal short circuit in the clock spring (spiral cable), damaged airbag wiring harness insulation contacting the metal frame, corroded connector terminals causing a ground fault, or an internal short circuit in the airbag module inflator. This fault prevents the stage 2 airbag from deploying normally, reduces protection performance during a severe collision, forces the SRS system into fail-safe mode, and illuminates the airbag warning lamp.
Causes
— A broken internal wire or worn insulation in the clock spring (spiral cable) shorts the second-stage ignition circuit to the grounded housing. Frequent steering wheel rotation commonly causes this fatigue damage.— Vibration and chafing inside the dashboard or near the A-pillar damages the insulation on the wiring harness between the front passenger airbag module and the SRS ECU. The harness contacts the metal body frame, causing a short to ground.— Water ingress in the airbag connector (usually located under the dashboard or at the airbag module interface) due to wading, vehicle washing, or poor sealing, causing electrolytic corrosion between the terminals and a short to ground.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the 12V low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Fault confirmation: Use a dedicated BYD diagnostic tool (ED400 or X431) to read the DTC. Confirm B178F is a current fault (not a history fault). Record the freeze frame data and check for accompanying fault codes (such as B178E, B178D).+6 more →
B178F11›
DTC B178F11 indicates a short to body ground in the front passenger dual-stage airbag (Stage 2) ignition circuit. In the BYD SRS system, the airbag utilizes a dual-stage ignition design: low speeds trigger the first stage, and high speeds trigger the second stage. The '11' suffix indicates the control unit detects circuit resistance below the threshold (typically <0.8Ω), determining a short to ground. This safety-critical fault prevents the SRS system from deploying the second-stage airbag during a collision or creates a risk of unintended deployment. The fault can originate in the clock spring, instrument panel harness, floor harness, or inside the airbag module.
Causes
— Worn front passenger airbag wiring harness insulation contacting body metal, commonly due to improper harness securing after instrument panel removal and installation.— Internal short circuit in the airbag clock spring (spiral cable). Long-term steering wheel rotation breaks the internal wiring, causing a short to ground.— Water ingress and oxidation at the SRS system connector. Poor sealing, especially below the A-pillar or at the floor wiring harness firewall pass-through, causes corrosion and short circuits.+2 more →
Actions
— Perform high-voltage system power-down: disconnect the 12V battery negative terminal, wait at least 3 minutes to ensure the SRS capacitor fully discharges, and press the horn button during this time to release residual charge.— Read freeze frame data: Use the VDS2000/Launch X431 diagnostic tool to record the ambient temperature, vehicle speed, and crash sensor status when the fault occurred to confirm if the fault is intermittent.+6 more →
B1791-00›
DTC B1791-00 indicates the driver-side Stage 2 Seatbelt Pretensioner resistance measures 0 ohms. Normal pretensioner igniter resistance is 2.0-4.0 ohms. A 0-ohm reading indicates a circuit Short to Ground or an internal short in the pretensioner squib. This fault prevents the SRS control unit from triggering the Stage 2 Seatbelt Pretensioner during a collision (typically used for secondary tightening in severe impacts), compromising occupant restraint system effectiveness. Additionally, the SRS warning lamp remains illuminated, the system enters fail-safe mode, and the airbags may fail to deploy.
Causes
— Pretensioner internal squib short circuit: Moisture, aging, or manufacturing defects cause an internal short circuit in the pretensioner ignition device, dropping resistance to 0 ohms.— Wiring harness worn and shorted to ground: Long-term friction and compression from seat movement damage the yellow SRS wiring harness under the driver’s seat, causing the wire to short to the vehicle body metal.— Connector water ingress and corrosion: Poor sealing of the seat pretensioner connector (usually located at the B-pillar or under the seat) allows water to enter after car washing or wading, causing a short circuit between pins.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (allowing the SRS capacitor to fully discharge) to prevent accidental airbag deployment.— Fault confirmation: Use a dedicated diagnostic tool (such as BYD ED400 or Launch X431) to read the fault code and confirm B1791-00 is a current fault (Active), not a history fault.+6 more →
B1791›
DTC B1791 indicates the SRS (Supplemental Restraint System) control module detects a circuit resistance of 0 Ω or near 0 Ω for the driver side seat belt second-stage pretensioner (Dual-stage Pretensioner). BYD SRS seat belt pretensioners typically feature a dual-stage ignition design. During a severe collision, the second-stage pretensioner triggers sequentially or simultaneously with the first stage. Normal pretensioner squib resistance measures 2.0-3.0 Ω. A 0 Ω resistance indicates a short circuit (short to ground or internal squib short). This causes the SRS to detect a pretensioner circuit fault, enter fail-safe mode, and continuously illuminate the instrument panel airbag warning light. In extreme cases, the pretensioner fails to deploy or deploys unintentionally during a collision, severely compromising occupant restraint system effectiveness.
Causes
— Driver seat belt pretensioner squib internal short circuit: Moisture or aging causes the internal igniter charge or bridgewire to short to ground, resulting in zero resistance.— Under-seat harness wear and short circuit: Frequent driver seat fore/aft adjustment wears the pretensioner harness insulation (typically routed along the seat track), causing contact with vehicle body metal and a short to ground.— Water ingress or corrosion at the SRS ECU connector: Poor sealing of the SRS control module connector located under the center console or floor allows water entry after washing the vehicle or wading, causing a short circuit between terminals.+2 more →
Actions
— Safety preparation: Switch the vehicle to OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS backup power supply and prevent accidental airbag deployment.— Fault confirmation: Use a dedicated BYD diagnostic tool (VDS or ED400) to read the fault code. Confirm B1791 is a current fault (Active Code), not a history fault, and record the freeze frame data.+6 more →
B1792-00›
This fault code indicates the driver-side second stage seat belt pretensioner ignition circuit resistance falls below the normal threshold set by the SRS control unit (ACU) (typically 2.0-4.0Ω; actual detected value below 1.5Ω or close to 0Ω). The second stage pretensioner is part of the dual-stage gas generator system, providing progressive restraint force during a severe collision. Low resistance typically indicates an internal squib short circuit, a wiring harness short to ground, or internal connector bridging. This fault causes the ACU to disable the pretensioner function. In extreme cases, the pretensioner may fail to deploy during a collision, or false fault detection during driving may continuously illuminate the SRS warning light, compromising the overall occupant restraint system protection strategy.
Causes
— Pretensioner squib internal short circuit: Long-term exposure to heat and humidity, manufacturing defects, or chemical corrosion dampens the igniter charge, reducing insulation resistance between the terminals.— Wiring harness connector fault: Water ingress at connectors under the driver's seat or near the B-pillar, bent/backed-out pins, terminal bridging, or corrosion, causing the signal wire to short to ground or power.— Mechanical damage: Repeated chafing from the seat rail adjustment mechanism, improper seat removal or installation, or crushing by a foreign object damages the pretensioner wiring harness insulation, causing a short to ground.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes for the SRS backup power supply to fully discharge to prevent accidental airbag deployment.— Initial diagnosis: Use BYD VDS or Launch X431 to read all DTCs and freeze frame data. Confirm if B1792-00 is a current code or history code, and check for other SRS-related fault codes.+6 more →
B1792›
DTC B1792 indicates the driver-side second-stage seat belt pretensioner circuit resistance falls below the normal range calibrated by the SRS ECU (typically 2.0-3.0Ω). The second-stage pretensioner features a seat belt retractor with a dual-stage igniter that deploys in stages based on collision severity. A low resistance value (<1.5Ω or close to 0Ω) indicates abnormal conduction resulting from an internal short circuit in the pretensioner igniter, a wiring harness short to ground, or connector water ingress and oxidation. This fault forces the SRS system into fail-safe mode, disabling the pretensioner and associated airbag functions. In extreme cases, the pretensioner may deploy without a collision or fail to operate during a collision, severely compromising the occupant restraint system's protection performance.
Causes
— Seat belt pretensioner internal igniter short circuit: Moisture ingress, aging, or manufacturing defects in the pretensioner cause the internal bridge wire to short to the housing, resulting in an abnormally low resistance value.— Wiring harness connector fault: Water ingress, oxidation, or deformed/loose pins at the K71 connector under the seat (pins 17/18) causing a signal wire short to ground or abnormal contact resistance.— Seat movement interference: Frequent seat adjustment chafes the pretensioner wiring harness at the slide rail, wearing through the insulation and shorting the core wire to body ground.+2 more →
Actions
— Safe power-down: Turn the power switch to OFF, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental deployment.— Fault confirmation: Connect VDS or dedicated diagnostic tool, read SRS system fault codes, confirm B1792 is a current fault rather than a history fault, and record freeze frame data.+5 more →
B1793-00›
DTC B1793-00 indicates the Driver 2nd Stage Seat Belt Pretensioner circuit resistance exceeds the normal threshold set by the SRS ECU (typically >3.6Ω, standard value approx. 2.0Ω ± 0.4Ω). In the BYD dual-stage airbag system, the seat belt pretensioner uses a staged ignition design: minor collisions trigger the first stage, and severe collisions activate the second stage to provide additional tightening force. This fault indicates the ECU detected a high-resistance condition in the second-stage squib circuit, likely resulting from poor contact, wiring harness oxidation, or an internal pretensioner open circuit. This fault disables the second-stage pretensioning function, preventing optimal seat belt restraint during severe collisions and increasing the risk of occupant forward movement. Additionally, the fault continuously illuminates the SRS warning light and forces the system into a degraded protection mode.
Causes
— Pretensioner connector (yellow plug) under the driver's seat is loose, oxidized, or has insufficient terminal contact pressure, causing increased contact resistance.— Frequent forward and backward seat adjustment wears or pinches the wiring harness beneath the seat frame, causing partial breakage of the internal copper wires or a poor connection.— Seat belt pretensioner internal squib resistance drift caused by aging, moisture, or manufacturing defects.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Verify the yellow pretensioner connector under the driver's seat is fully locked, and inspect the terminals for green oxidation, burn marks, or backed-out pins.+5 more →
B1793›
This DTC indicates the Airbag Control Module (ACM) detects the driver-side second-stage seatbelt pretensioner circuit resistance exceeds the calibrated range (typically 2-5 ohms). This Passive Safety System (SRS) circuit fault indicates high resistance or an open circuit in the pretensioner circuit. The pretensioner is a critical protective device that uses a pyrotechnic charge to instantly tighten the seatbelt during a collision. This fault indicates the driver-side seatbelt may fail to pretension correctly during a frontal collision, increasing occupant forward travel, reducing restraint system effectiveness, and posing a severe safety hazard.
Causes
— Open circuit, aging, or increased resistance in the driver seat belt pretensioner internal coil.— Loose connection, backed-out pins, oxidation, or water ingress at the pretensioner wiring harness connector (yellow plug) under the seat, causing increased contact resistance.— Prolonged bending and wear of the pretensioner wiring harness at the seat slide rail causes internal wire breakage or a partial open circuit.+2 more →
Actions
— Use the dedicated diagnostic tool to read the fault code, confirm if B1793 is an Active or History fault, and record the resistance value from the freeze frame data.— Disconnect the battery negative terminal and wait at least 90 seconds for the airbag system capacitor to fully discharge (observe safety operating procedures).+6 more →
B1794-00›
DTC B1794-00 indicates the SRS (Supplemental Restraint System) control unit detects an open circuit or abnormal resistance (typically greater than 10Ω or less than 1Ω) in the driver-side seat belt pretensioner second-stage deployment circuit. The BYD Qin series dual-stage airbag system features a seat belt pretensioner with a dual-stage igniter. This igniter tightens the seat belt in stages based on collision severity (first stage at approximately 30% force, second stage at 100% force). This fault signifies the second-stage deployment circuit cannot form an effective closed circuit. As a result, the second-stage pretensioning function fails during a severe collision, leaving only first-stage protection active. The SRS control unit determines connection status by continuously monitoring circuit resistance (normally 2.0-3.0Ω). When the unit detects an open circuit or high resistance, it stores this code and illuminates the airbag warning light.
Causes
— Loose or disconnected yellow SRS connector under the seat: Frequent driver seat adjustments loosen the pretensioner harness plug (usually located inside the seat rail). On 2017-2018 Qin series models, the seat slide rail design provides insufficient harness length. Repeated forward and backward movement often partially disconnects the plug.— Wiring harness worn or broken: Burrs on the seat frame edge cut through the pretensioner wiring harness insulation, or frequent seat height adjustment causes metal fatigue and breakage of the wiring harness at bend points, resulting in an intermittent open circuit.— Terminal oxidation causing poor contact: Driving through water or operating in humid environments oxidizes the internal terminals of the pretensioner connector (usually a yellow waterproof plug), increasing contact resistance (exceeding 5Ω may trigger the fault).+2 more →
Actions
— Safety Preparation and Diagnostic Confirmation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor. Use a BYD VDS2000 or Launch X431 diagnostic tool to read the complete fault codes. Confirm B1794-00 is a current fault (Active) rather than a historical fault. Record the freeze frame data to check the circuit resistance value (a reading above 10.8Ω typically indicates an open circuit).— Visually inspect the connector: Remove the driver's seat (4 retaining bolts, torque 25 N·m). Check if the yellow 2-pin SRS connector under the seat frame (marked DAB-Pretensioner-Stage2) is fully locked. Confirm the connector locating pin is intact and the locking tab engages fully (listen for a 'click'). Inspect the wiring harness corrugated conduit for damage.+4 more →
B1795›
DTC B1795 indicates a short to B+ in the driver-side seat belt pretensioner Stage 2 squib circuit. In the BYD SRS system, the seat belt pretensioner uses a dual-stage ignition design: Stage 1 triggers early in a collision to provide basic tightening force, and Stage 2 triggers during a severe collision to generate greater tightening force to better restrain the occupant. This DTC indicates the airbag control unit (ACU) detects an abnormal voltage increase in the Stage 2 pretensioner circuit to near battery voltage (12V) and an abnormal resistance value. This fault prevents the pretensioner from deploying correctly during a collision because the short to power prevents the firing current from forming a complete circuit. It may also damage the ignition driver chip inside the ACU. Because this is an active safety system fault, the vehicle illuminates the airbag warning lamp and may fail to protect the driver properly during a collision.
Causes
— Damaged wiring harness sheath under the driver's seat or B-pillar pretensioner exposes copper wire that contacts body power supply wires (such as seat heating or power adjustment wires), causing a short circuit.— Water ingress, oxidation, or deformed terminals in the pretensioner connector (usually located under the seat or inside the B-pillar trim), causing a short to power between terminals.— Insulation breakdown in the seat belt pretensioner squib causes a short circuit between the internal coil and the housing, which indirectly connects to the vehicle power supply via the bracket.+2 more →
Actions
— Safety preparation: Turn off the vehicle, disconnect the negative battery terminal, and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment during repair.— Visual inspection: Remove the driver's seat (keep the wiring harness connected) and the left B-pillar lower trim panel. Inspect the pretensioner wiring harness (typically in a yellow sleeve) for wear, cuts, or burn marks. Focus on the seat slide rail friction points and the wiring harness retaining clips.+6 more →
B1794›
DTC B1794 indicates the SRS (Supplemental Restraint System) ECU detects an open circuit (infinite resistance) in the driver-side seat belt pretensioner stage 2 firing circuit. "Stage 2" means the pretensioner uses dual-stage firing technology, triggering in stages based on collision severity. "Disconnected" means the ECU cannot detect the firing circuit's normal resistance (standard value: 2.0–3.0 Ω). During a moderate or severe collision, the pretensioner may fail to execute the stage 2 tensioning, reducing occupant restraint protection. Typical causes for this critical passive safety system fault include an open wiring harness, a disconnected connector, a damaged clock spring, or an internal open circuit in the pretensioner.
Causes
— Internal open circuit or poor contact in the clock spring (spiral cable) under the steering wheel, interrupting the signal to the seat belt retractor pretensioner.— Loose connection, backed-out pins, or corrosion at the pretensioner connector under the driver's seat or at the B-pillar, causing an open circuit.— Open circuit in the internal igniter of the seat belt pretensioner assembly (possibly due to reaching the deployment threshold or a manufacturing defect)+2 more →
Actions
— Use the VDS2000/VDS3100 diagnostic tool to read all SRS fault codes, confirm whether B1794 is an Active or History fault, and record the freeze frame data.— Disconnect the battery negative terminal and wait 90 seconds to fully discharge the SRS capacitor. Inspect the pretensioner connectors under the driver's seat and inside the B-pillar trim panel for looseness, oxidation, or water ingress. Clean and retighten if necessary.+4 more →
B1795-00›
DTC B1795-00 indicates the airbag control module (SRS ECU) detects an abnormal short to vehicle power (B+) in the driver-side seat belt pretensioner drive circuit (second-stage firing circuit). In a dual-stage pretensioner system, the second stage further tightens the seat belt during a severe collision. Normally, this circuit remains open or low. When the ECU detects the pretensioner circuit voltage continuously exceeding the threshold (near the 12V battery voltage), it registers a short to power. This fault causes the ECU to immediately disable the pretensioner circuit and illuminate the airbag warning light. In extreme cases, the pretensioner may fail to deploy or deploy abnormally during a collision. This severe fault compromises occupant safety.
Causes
— Long-term chafing of the wiring harness under the driver's seat or inside the B-pillar trim damages the insulation, shorting the pretensioner harness to the constant power wire (B+).— Water ingress, oxidation, or deformed terminals in the seat belt pretensioner connector (under the seat or on the B-pillar), causing a short circuit between the ignition circuit terminal and the power supply terminal.— SRS ECU internal drive transistor breakdown or control circuit fault causes continuous high-level voltage at the output terminal.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes (or the time specified in the repair manual) to fully discharge the SRS capacitor and ensure the system is in a safe state.— Fault Confirmation: Connect the diagnostic tool to read fault codes. Confirm B1795-00 is active. Record freeze frame data and check for other associated SRS fault codes.+6 more →
B1796-00›
DTC B1796-00 indicates a short to ground in the control circuit of the driver-side second-stage seat belt pretensioner. The second-stage pretensioner is a dual-stage ignition component of the Supplemental Restraint System (SRS). During a severe collision, a pyrotechnic device rapidly tightens the seat belt to eliminate slack between the occupant and the belt. "Short to ground" indicates an insulation failure between the pretensioner drive harness (typically the positive control wire) and the vehicle body ground (GND), causing resistance to drop abnormally (<1Ω). This fault causes the SRS control unit (ACM) to detect abnormal circuit current, trigger fail-safe mode, and disable the pretensioner. In extreme cases, this prevents the seat belt from tightening properly during a collision or creates a risk of unintended deployment under specific conditions.
Causes
— Wiring harness abrasion inside the B-pillar trim panel: As the driver seat belt pretensioner wiring harness routes through the lower B-pillar, repeated seat adjustment or door operation vibration causes a metal edge to cut the insulation, resulting in a short to ground.— Under-seat connector corrosion: Vehicle wading, improper interior cleaning, or a blocked sunroof drain allows water to flow under the seat. This oxidizes and electrolytically corrodes the pretensioner connector (yellow) terminals, creating a short-to-ground path.— Internal short circuit in the pretensioner body: Moisture in the second-stage igniter pyrotechnic charge or a manufacturing defect causes insulation failure between the ignition wire and the metal housing.+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 3 minutes to fully discharge the SRS system capacitors and prevent accidental pretensioner deployment.— Visual inspection: Remove the driver-side B-pillar lower trim panel and the under-seat cover panel. Inspect the pretensioner wiring harness (yellow corrugated conduit) for wear, cuts, or burn marks. Focus on the contact points between the wiring harness and the body sheet metal.+5 more →
B1796›
This DTC indicates a short to body ground in the driver-side second-stage seat belt pretensioner deployment circuit. The second-stage pretensioner is a pyrotechnic device in the SRS (Supplemental Restraint System). It operates in series or parallel with the first-stage pretensioner to provide greater seat belt tightening force during a severe collision (high-speed frontal impact). A short to ground occurs when damaged insulation on the positive wire from the SRS ECU to the pretensioner squib contacts the vehicle body metal, causing circuit resistance to drop abnormally (typically <1Ω). The SRS ECU detects this abnormal current path, illuminates the airbag warning lamp, and disables the second-stage pretensioner function. In a severe collision, the driver may lose second-stage protection, increasing the risk of injury. In extreme cases, the short-circuit current can accidentally trigger the pretensioner, locking the seat belt and requiring costly replacement.
Causes
— Wiring harness wear under the seat: Long-term forward and backward movement of the driver seat adjustment mechanism wears through the floor wiring harness insulation (especially the SRS harness routed under the seat slide rail), causing the copper wire to contact body ground.— Pretensioner connector water ingress and corrosion: During vehicle wading or interior cleaning, poor sealing of the pretensioner connector under the B-pillar or seat causes internal pins to oxidize and short to ground.— Pretensioner internal short circuit: A manufacturing defect or long-term vibration causes internal coil insulation failure, shorting the secondary pretensioner squib directly to the metal housing.+2 more →
Actions
— Safety preparation and power-down: Confirm the vehicle is in the OFF position, wear insulated gloves, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor. For hybrid/pure electric models, perform the high-voltage system power-down procedure first (disconnect the service plug).— Locate the faulty component: Remove the driver-side lower B-pillar trim panel and seat side trim panel to expose the second-stage seat belt pretensioner (usually integrated into the retractor assembly or at the base of the B-pillar). Identify the two-wire connector with the yellow protective sleeve.+4 more →
B1797-00›
This DTC indicates the front passenger seat belt pretensioner (second-stage deployment circuit) resistance is 0 Ω, indicating a short circuit. In the BYD SRS (Supplemental Restraint System) architecture, the dual-stage pretensioner deploys in stages based on collision severity: the first stage provides light tightening, and the second stage provides strong tightening to secure the occupant. A 0 Ω resistance usually indicates an internal short circuit in the pretensioner generator winding, a wiring harness short to ground, or a short between connector terminals. Upon detecting this fault, the SRS ECU enters fail-safe mode and disables the pretensioner circuit. This may cause the second-stage protection to fail during a collision or create a risk of unintended deployment; therefore, the system illuminates the airbag warning lamp.
Causes
— Pretensioner generator internal short circuit: The internal bridge wire of the pyrotechnic generator breaks or the charge absorbs moisture, causing the resistance between the two terminals to drop to 0.— Seat wiring harness wear and short circuit: Prolonged friction between the pretensioner wiring harness and the seat rail or frame during front passenger seat fore/aft adjustment damages the insulation and causes a short to ground.— Connector water ingress and corrosion: Water entering the pretensioner connector (usually located under the seat) during vehicle wading or interior cleaning causes a short circuit between terminals.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Visual inspection: Remove the front passenger seat (leave the wiring harness connected). Inspect the pretensioner connector under the seat (usually yellow) for looseness, water ingress, or obvious burn marks.+5 more →
B1797›
DTC B1797 indicates the SRS (airbag) control module detects a 0-ohm circuit resistance in the front passenger second-stage seat belt pretensioner (typically the igniter/squib). Normal seat belt pretensioner resistance is 1.5-3.0 ohms. A 0-ohm resistance indicates a short circuit (short to ground or internal short) within the pretensioner or its wiring. This fault forces the SRS into degraded protection mode. The front passenger airbag may fail to deploy, severely compromising crash safety. The second-stage pretensioner works with the airbag to rapidly retract the seat belt during a collision, limiting forward occupant movement.
Causes
— Pretensioner igniter internal short circuit: Moisture ingress or aging of the pyrotechnic charge inside the seat belt pretensioner causes a short circuit between the two terminals, reducing resistance to 0 ohms.— Harness damaged and shorted to ground: Frequent door opening and closing wears through the seat belt pretensioner harness insulation near the B-pillar, causing a short to the vehicle body metal.— Connector water ingress and corrosion: Water enters the pretensioner connector during car washing or front passenger-side floor flooding, causing a short circuit between pins.+2 more →
Actions
— Safe power-down: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental deployment.— Location and inspection: Remove the front passenger-side B-pillar trim and locate the second-stage seat belt pretensioner connector (usually a yellow connector below the seat belt retractor or in the middle of the B-pillar).+5 more →
B1798-00›
DTC B1798-00 indicates the front passenger seat belt second-stage pretensioner firing circuit resistance falls below the SRS control module threshold (typically under 1.0Ω or the manufacturer-calibrated value). The second-stage pretensioner operates within a staged restraint system, deploying sequentially with the first stage during a severe collision to provide greater retraction force. Low resistance indicates a circuit short to ground, an internal short in the pretensioner squib, a short between connector pins, or an abnormal ground path caused by damaged wire insulation. Consequently, the SRS module detects a risk of unintended deployment (potential misfire or failure to reach design deployment energy). The module then illuminates the airbag warning light and disables the front passenger airbag functions, severely compromising occupant restraint protection during a collision.
Causes
— Front passenger seat belt pretensioner unit internal short circuit (igniter moisture, aging, or manufacturing defects causing internal resistance to drop abnormally to a near-short-circuit state)— Short to ground in the wiring harness under the seat or inside the B-pillar trim panel (frequent front passenger seat movement damages the harness insulation, or a metal bracket edge cuts the harness, causing copper wire to contact body ground).— Pretensioner connector short circuit due to water ingress and corrosion (spilled drinks, car wash water, or sunroof leaks create a low-resistance path between the yellow SRS connector pins or a short to the housing).+2 more →
Actions
— Safety Preparation: Disconnect the battery negative terminal and wait at least 90 seconds for the SRS capacitor to fully discharge. Wear an anti-static wrist strap. Do not measure the pretensioner directly with a multimeter set to resistance, as excessive trigger current can cause accidental deployment. Use a dedicated SRS diagnostic tool or ensure the multimeter current is below 1 mA.— Fault status confirmation: Use VDS2000 or a dedicated BYD diagnostic tool to read the freeze frame data. Confirm B1798-00 is a current fault (Active Code) and not a historical fault. Record the displayed resistance value (e.g., 0.3Ω, 0.8Ω) to compare with the standard value (usually 2.0-3.0Ω).+5 more →
B1798›
This fault code indicates the SRS (Supplemental Restraint System) ECU detected the front passenger side second stage seat belt pretensioner circuit resistance fell below the system-calibrated threshold (typically below 1.0Ω; normal range is 1.5–3.0Ω). During a severe collision (high-speed or high-intensity impact), the second stage pretensioner provides a stronger restraining force than the first stage. It typically integrates into the seat belt retractor or seat anchorage point. Low resistance indicates a circuit short. Possible causes include an internal inter-turn short in the pretensioner igniter, a wiring harness short to ground, or abnormal connector continuity. This fault triggers the SRS airbag warning lamp and may disable the front passenger side airbag and pretensioner functions. This severely degrades collision safety performance and requires immediate repair.
Causes
— Seat belt pretensioner internal squib short circuit: Internal coil insulation damage causes an inter-turn short circuit, resulting in abnormally low resistance.— Wiring harness chafing or insulation damage under the seat or inside the B-pillar: Frequent adjustment of the front passenger seat rubs the harness against the seat frame or body metal edges, damaging the insulation and causing a short to ground.— Connector water ingress or corrosion: Vehicle wading, improper interior cleaning, or poor sealing causes oxidation or short circuits at the pretensioner connector pins (usually located under the seat or inside the B-pillar trim).+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment during repair.— Fault Confirmation: Use VDS2000 or a dedicated BYD diagnostic tool to read fault codes. Confirm B1798 is a current fault (Active) rather than a history fault (History), and record freeze frame data.+5 more →
B1799-00›
DTC B1799-00 indicates the SRS (Supplemental Restraint System) ECU detects the front passenger-side second-stage seat belt pretensioner circuit resistance exceeds the normal upper limit (typically >3.0-3.5Ω, normal range is 2.0-3.0Ω). The second-stage pretensioner is a critical component of the airbag system. During a severe collision, a pyrotechnic charge generates a rapid tightening force, working with the first-stage pretensioner to provide enhanced occupant restraint. Excessive resistance typically indicates a high-resistance circuit contact, a partial open circuit, or an aging internal resistance wire within the pretensioner. This causes the ECU to identify a pretensioner failure risk, illuminate the airbag warning light, and potentially disable the front passenger-side airbag and pretensioner functions. During a collision, the second-stage pretensioner may fail to deploy properly, allowing excessive forward occupant movement and increasing injury risk.
Causes
— Aging internal resistance element in the seat belt pretensioner or near open circuit: Long-term use or moisture ingress causes the pretensioner squib resistance wire value to drift and exceed the ECU monitoring threshold.— Mechanical damage to under-seat wiring harness: During front passenger seat fore/aft adjustment, the seat bottom rubs against and pinches the frame-mounted pretensioner wiring harness, causing partial breakage of the internal copper wires or poor contact.— Poor connection: The pretensioner connector under the B-pillar or seat has oxidized pins, looseness, corrosion from water ingress, or a failed locking tab, causing increased contact resistance.+2 more →
Actions
— Connect the VDS2000 or VDS6000 diagnostic tool to the vehicle and read the DTC B1799-00 status. Confirm whether it is a current or history fault, and record the resistance value in the freeze frame data (typically 3.5-5.0 Ω).— Disconnect the battery negative terminal and wait at least 90 seconds for the SRS backup power supply to fully discharge. This ensures safe operation and prevents accidental airbag deployment.+7 more →
B1799›
DTC B1799 indicates the squib circuit resistance of the front passenger-side second-stage seat belt pretensioner (usually located under the front passenger seat or lower B-pillar) exceeds the SRS ECU threshold (standard value: 2.0 Ω ± 0.4 Ω; typically triggers at >2.4 Ω). This passive safety fault in the Supplemental Restraint System (SRS) means the ECU detects a high-resistance condition in the pretensioner circuit. Poor contact, a partial open circuit in the wiring, or an aging internal pretensioner squib can cause this condition. This fault may prevent the second-stage pretensioner from deploying correctly during a collision, reducing occupant restraint protection. The SRS warning light remains illuminated to alert the driver.
Causes
— Loose pretensioner connector or oxidized terminal: The pretensioner plug under the front passenger seat or in the B-pillar area loosens due to vibration, or terminal surface oxidation or water ingress increases contact resistance (contact resistance exceeding 0.5 Ω causes total resistance to exceed the specification).— Partial open circuit or poor contact in the wiring harness: Prolonged bending or compression of the pretensioner wiring harness inside the B-pillar trim panel or near the seat slide rail partially breaks the internal copper strands, reducing the effective conductive cross-section and creating a high-resistance point.— Pretensioner internal squib aging: Age or environmental factors oxidize the internal resistance wire of the pretensioner squib, causing the resistance value to drift beyond the upper limit.+2 more →
Actions
— Safety preparation: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental deployment.— Fault Confirmation: Connect the BYD VDS diagnostic tool, enter the SRS system to read fault codes, confirm B1799-00 and freeze frame data (record the specific resistance value), and check for associated fault codes.+7 more →
B179A-00›
This DTC indicates the Airbag Control Unit (ACU) detects an open or disconnected circuit in the front passenger side second stage seat belt pretensioner. The second stage pretensioner is a critical component of the restraint system. During severe collisions, it works with the first stage, using an igniter to detonate the gas generator and rapidly tighten the seat belt. The ACU continuously monitors this circuit's resistance (normal range: approx. 1.8-3.2Ω). When the ACU detects infinite resistance or a value exceeding the threshold, it determines a disconnected fault and logs B179A-00. This fault prevents the pretensioner from deploying during a collision, reducing chest and head restraint protection for the front passenger. It also illuminates the SRS warning light continuously. Some models may enter a safety protection mode, restricting the normal deployment logic of other airbags.
Causes
— Front passenger seat belt pretensioner electrical connector loose or making poor contact (commonly caused by failing to fully seat the connector after B-pillar trim removal/installation, window tinting, or modifications)— Open circuit in the pretensioner body internal igniter or gas generator failure (internal open circuit, possibly due to aging or damage from a minor collision without deployment)— Open circuit, wear, or short to body ground in the wiring harness between the ACU and the pretensioner (especially fatigue breakage in the B-pillar hinge area from repeated door opening and closing).+2 more →
Actions
— Use a dedicated diagnostic tool (BYD ED400 or Launch X431) to read the fault code. Confirm B179A-00 is a current fault (Active). Record the ambient temperature and vehicle status from the freeze frame data.— Perform the safe power-down procedure: Turn off the ignition switch, disconnect the negative battery terminal, and wrap it with insulating tape. Wait at least 3 minutes to ensure the SRS energy storage capacitor fully discharges to prevent accidental airbag deployment.+6 more →
B179A›
DTC B179A indicates the SRS (Supplemental Restraint System) ECU detects an open circuit or disconnected front passenger-side second-stage seat belt pretensioner. The "second stage" typically refers to the retractor pretensioner (distinct from the first-stage buckle pretensioner), which uses a pyrotechnic igniter to rapidly tighten the seat belt during a collision. The SRS ECU monitors the pretensioner circuit resistance (normally 2.0-4.0 Ω) to determine connection status. The ECU sets this DTC when resistance exceeds the threshold (typically >10 kΩ or a complete open circuit). This fault prevents pretensioner activation during a collision, reducing chest and head restraint protection for the front passenger, and illuminates the instrument panel airbag warning light. Because occupants of various body sizes frequently adjust the front passenger seat, this fault occurs significantly more often in shared vehicles than on the driver side.
Causes
— Loose or disconnected wiring harness connector under the front passenger seat (frequent fore-and-aft seat adjustment wears the connector locking tab or strains the wiring harness)— Pretensioner gas generator internal open circuit (igniter aging, moisture ingress, or broken internal bridge wire causing infinite resistance)— Wiring harness inside B-pillar trim chafed and broken (prolonged friction from the mechanical movement of seat belt extension and retraction causes copper wire fatigue and breakage)+2 more →
Actions
— Safety preparation: For new energy vehicles, first disconnect the high-voltage service disconnect switch. For all models, disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.— Inspection procedure: Remove the front passenger-side B-pillar lower trim panel (remove the seat on some models). Locate the yellow second-stage pretensioner wiring harness connector. Verify it inserts fully with an audible locking click, and confirm the waterproof sealing ring is intact.+5 more →
B179B-00›
This DTC indicates the front passenger seat belt pretensioner Stage 2 squib circuit is shorted to vehicle power positive (B+). Modern vehicle seat belt pretensioners typically use a dual-stage ignition design: the first stage deploys during the initial collision phase to provide basic restraint, and the second stage deploys upon detecting a more severe collision to increase protective force. A short to power indicates an abnormal high-potential path in the squib circuit, which may cause: 1) The pretensioner to deploy unintentionally in non-collision situations, causing personal injury and property damage; 2) The Airbag Control Unit (ACU) to detect abnormal circuit voltage and enter fail-safe mode, disabling the front passenger airbag and pretensioner functions; 3) Continuous short-circuit current to damage the internal ACU driver circuit or trigger fuse protection. This constitutes a severe electrical fault in the passive safety system and requires immediate repair.
Causes
— Worn SRS wiring harness sleeve under the front passenger seat or inside the B-pillar causes the pretensioner drive wire to short to the power supply wire (constant power or ignition power).— Power MOSFET breakdown or drive chip failure in the Airbag Control Unit (ACU) internal ignition drive circuit, causing the ignition terminal to continuously output a high level.— Frequent seat track adjustment pinches and bends the pretensioner wiring harness secured under the seat, damaging the insulation and causing a short circuit to the vehicle frame or a power wire.+2 more →
Actions
— Safety Preparation: Disconnect the 12V battery negative terminal. Wait at least 3-5 minutes for the SRS system energy storage capacitor to fully discharge. Wear an anti-static wrist strap. Do not use a standard multimeter to directly measure the ignition circuit (use a dedicated airbag resistor or diagnostic tool).— Visual inspection: Remove the front passenger B-pillar lower trim panel and seat (if necessary). Inspect the seat belt pretensioner wiring harness (wrapped in yellow corrugated conduit) for obvious wear, damaged insulation, or burn marks. Focus on the harness mounting points and bends near the seat slide rail.+5 more →
B179B›
DTC B179B indicates a short-to-power fault in the front passenger seat belt pretensioner second-stage deployment circuit. In the BYD SRS (Supplemental Restraint System) architecture, the pretensioner utilizes a dual-stage ignition design: the first stage lightly retracts the seat belt during the initial collision phase, and the second stage forcefully retracts it to secure the occupant as the collision intensifies. This DTC sets when the SRS control module detects an abnormally low-resistance path (typically <1Ω) between the front passenger pretensioner second-stage ignition circuit (usually marked as terminals P+ and P-) and vehicle power (B+) or ground (GND), causing the control module to identify a short circuit. This fault results in the following: 1) the front passenger airbag system enters fail-safe mode, and the instrument cluster airbag warning lamp remains illuminated; 2) the second-stage pretensioner may fail to deploy or deploy unintentionally during an actual collision; 3) because the pretensioner is a pyrotechnic device (containing explosive propellant), continuous short-circuit current creates an accidental ignition and deflagration risk. Therefore, the system classifies the fault as severe (Level 3) and prohibits vehicle operation.
Causes
— Worn under-seat wiring harness: Frequent fore-and-aft adjustment of the front passenger seat wears the insulation of the pretensioner wiring harness (usually routed from the B-pillar through the seat slide rail). The internal copper wire contacts the vehicle body metal frame, creating a short to ground.— Pretensioner actuator internal short circuit: The ignition bridge wire inside the second-stage pretensioner shorts to the housing, or moisture in the propellant increases conductivity, usually causing abnormal resistance (<0.5Ω).— Connector water ingress and corrosion: Vehicle wading or interior cleaning allows water to enter the yellow SRS connector under the front passenger seat (usually at the front of the seat rail), causing a short circuit between terminals or a short to ground.+2 more →
Actions
— Safety preparation: Disconnect the 12V battery negative terminal, wait at least 90 seconds to allow the SRS capacitor to discharge fully, wear an anti-static wrist strap, and place high-voltage warning signs around the front passenger seat.— Freeze frame analysis: Use the BYD VDS2000 or Launch X431 diagnostic tool to read the fault freeze frame. Record vehicle speed, seat position, and ambient temperature when the fault occurred. Determine if the fault is continuous or intermittent.+6 more →
B179C-00›
DTC B179C-00 indicates the Airbag Control Unit (ACU) detects an abnormally low-resistance connection (typically <2Ω) between the front passenger side second-stage seatbelt pretensioner firing circuit and body ground. The second-stage pretensioner is a component of the dual-stage adaptive seatbelt system. During a severe collision, it triggers sequentially with the first stage to provide progressive restraint protection. A short to ground causes the ACU to flag this firing circuit as failed, which illuminates the SRS warning lamp, disables the front passenger side airbag and pretensioner functions, and prevents second-stage pretensioner activation during a collision. This hard fault remains active, and cycling the ignition does not clear it. Repair the wiring insulation or replace the faulty component.
Causes
— Worn under-seat wiring harness: During front passenger seat fore/aft adjustment, prolonged friction between the pretensioner wiring harness and the seat track metal edge damages the insulation, causing a short to body ground.— Connector water ingress and corrosion: Water enters the front passenger seat pretensioner connector under the seat (usually on the inner side of the seat rail) during vehicle wading or carpet cleaning, causing electrolyte conduction between the pins and creating a short to ground.— Harness pinched during modifications: When retrofitting seat ventilation/heating, installing full-coverage floor mats, or fitting seat covers, retaining clips or screws pierce the pretensioner wiring harness and cause a short to ground.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor. Remove the front passenger seat headrest and adjust the seat to the rearmost position to access the wiring harness.— Visual inspection: Check the pretensioner wiring harness under the seat (usually a two-wire harness wrapped in yellow corrugated conduit) for wear, cuts, or burn marks. Focus on the seat slide rail mounting bolt area and the floor opening where the harness passes through.+6 more →
B179C›
DTC B179C indicates an abnormally low-resistance connection between the ignition circuit of the front passenger-side seat belt second stage pretensioner and body ground. In the BYD SRS (Supplemental Restraint System) architecture, a twisted pair typically connects the second stage pretensioner to the Airbag Control Unit (ACU), with a normal resistance of approximately 2.0–3.0 Ω. The ACU sets this DTC when it detects the circuit-to-ground resistance falls below the threshold (typically <1.0 Ω). This fault causes: 1) unintentional pretensioner deployment in non-collision situations, causing personal injury; 2) failure of the pretensioner to deploy correctly during a collision; 3) the ACU to enter fault protection mode, which may subsequently disable the front passenger airbag and side curtain airbags, greatly reducing crash safety. This is a hard fault; once confirmed, it continuously illuminates the SRS warning lamp.
Causes
— Under-seat wiring harness wear: Long-term friction from the front passenger seat fore-and-aft adjustment mechanism damages the pretensioner wiring harness insulation. The exposed copper core contacts the seat rail or body metal, creating a short to ground.— Pinched wiring harness inside B-pillar trim panel: Failing to properly secure the wiring harness during B-pillar interior trim panel removal and installation or body sheet metal repair allows trim panel clips or metal edges to damage the harness, causing a short to ground.— Connector terminal corrosion due to water ingress: Vehicle wading or a blocked sunroof drain tube causes water to accumulate on the front passenger floor. The seal on the pretensioner connector (usually located under the seat or at the base of the B-pillar) fails, forming an electrolytic corrosion path between the terminals.+2 more →
Actions
— Safety preparation: Turn off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds (to fully discharge the SRS capacitor). Wear an anti-static wrist strap. Do not use radio equipment near airbags/pretensioners.— Fault Confirmation and Freeze Frame Analysis: Use the BYD dedicated diagnostic tool (VDS or ED400) to read the B179C freeze frame data. Record the vehicle speed, temperature, and voltage when the fault occurred, and confirm whether the fault is intermittent or continuous.+6 more →
B179E00›
This fault code indicates the Airbag Control Unit (ACU) detects an abnormal electrical series connection between an airbag ignition circuit (e.g., driver/front passenger frontal airbag, side airbag, or curtain airbag) and another vehicle electrical circuit (e.g., another airbag circuit, seat belt pretensioner circuit, or sensor circuit). Normally, each ignition circuit remains independent with a specific resistance (typically 2.0 ± 0.2 Ω). When a series connection occurs, total circuit resistance increases abnormally (combining to exceed 4 Ω) or the control unit detects cross-circuit signal interference. This prompts the ACU to flag compromised circuit integrity. This fault can prevent airbag deployment during a collision (due to insufficient ignition energy) or cause unintended deployment, severely compromising occupant protection.
Causes
— Short circuit or crossed wires between wiring harness connector terminals, particularly where moisture, oxidation, or physical damage bridges the terminals in connectors under the seat, in the steering wheel clock spring, or inside the B-pillar trim.— Airbag Control Unit (ACU) internal MOSFET drive circuit or detection circuit fault causes signal crosstalk between circuits, resulting in false detection of an external series connection.— Incorrect wiring during airbag or seat belt pretensioner replacement after accident repairs cross-connects pins from different ignition circuits, creating an electrical series circuit.+2 more →
Actions
— Use the VDS2000 or VDCI diagnostic tool to read the complete DTC and freeze frame data. Identify the specific airbag circuit (e.g., driver side stage 1/stage 2 airbag, side airbag) and the associated series circuit. Record the environmental conditions (temperature, voltage) when the fault occurred.— Perform the airbag system power-down procedure: disconnect the battery negative terminal and wait at least 3 minutes (5 minutes recommended) to fully discharge the system. Inspect the Airbag Control Unit (ACU) connector and related airbag component connectors (focusing on areas under the seats, under the steering wheel, and the B-pillar and C-pillar areas) for water ingress, green corrosion, or deformed terminals.+3 more →
B179F00›
DTC B179F00 indicates a fault in the sensor series circuit of the SRS (Supplemental Restraint System/airbag system). In the BYD Qin PRO, a series or parallel circuit typically connects multiple safety sensors (including the front impact sensor, side impact sensor, and seat occupancy sensor) to the SRS ECU. The ECU determines sensor status by monitoring the circuit resistance and voltage signals. The ECU triggers this DTC when it detects abnormal circuit resistance (open circuit, short circuit, or resistance outside the calibrated range of 2.0-4.5kΩ), an incorrect signal sequence, or a communication interruption. This fault forces the airbag system into a degraded mode. In extreme cases, it prevents normal airbag deployment during a collision or creates a risk of unintended deployment. This is a safety-critical fault.
Causes
— Wear, open circuit, or poor connection in the front bumper or B-pillar crash sensor wiring harness caused by chassis scraping or improper accident repairs.— Improper cleaning or liquid spills cause water ingress or pin oxidation in the under-seat occupancy sensor connector, resulting in abnormal circuit resistance.— Failure to torque the sensor or wiring harness to specification after accident repairs causes poor grounding or shielding layer damage, resulting in signal interference.+2 more →
Actions
— Use the BYD VDS2000/VDS2100 diagnostic tool to read the complete fault codes and freeze frame data. Record the vehicle status at the time of the fault and check for accompanying fault codes (such as B179E00, B17A000, etc.).— Disconnect the negative battery terminal and wait at least 90 seconds for the SRS capacitor to discharge fully. Check the airbag warning light status on the instrument cluster.+6 more →
B17A000›
DTC B17A000 indicates the airbag control unit (SRS ECU) detected a logic error or hardware fault during its internal self-check. Specifically, this fault indicates a failure in the ECU internal processor, memory (EEPROM/Flash), safety sensor, or power management module. During the power-on self-test, the SRS ECU performs CRC checks and logic diagnostics on the internal accelerometer, crash algorithm logic area, backup power circuit, and CAN communication interface. The ECU sets this code if it detects a data verification failure, RAM test failure, watchdog reset, or internal communication bus fault. This is a functional safety fault that may cause the airbag system to enter fail-safe mode (disabling airbag deployment), fail to provide protection during a collision, or create a risk of unintended deployment.
Causes
— Power supply system fault: Battery voltage is too low (<9V) or too high (>16V), or poor contact in the SRS ECU constant power (B+) or ignition power (IGN) circuits causes the ECU internal power management chip to reset or operate erratically.— Internal memory data corruption: Data checksum error in the EEPROM/Flash of the crash data storage area (EDR) or configuration data area. Abnormal power loss, electromagnetic interference, or chip aging may cause this.— Software/firmware defect: ECU internal program enters an infinite loop, watchdog timeout triggers a reset, or a software bug causes the internal logic self-check to fail. Common in early production batches or vehicles lacking recent updates.+2 more →
Actions
— Step 1 - Initial Diagnosis and Data Recording: Use the VDS2000/BYD dedicated diagnostic tool to read all DTCs. Record freeze frame data, including vehicle speed, voltage, and temperature at the time of the fault. Check for other related fault codes (such as B17A1xx series communication faults). Photograph the SRS warning light status.— Step 2 - Power supply and ground circuit check: Disconnect the battery negative terminal, wait 3 minutes, then unplug the SRS ECU connector (usually located under the center console or behind the armrest). Measure the resistance and voltage between ECU connector terminal 30 (constant B+), terminal 15 (IGN power), and ground. Standard values: Voltage 9-16V; ground resistance <1Ω. Check if fuses SB03 (10A) and SB10 (10A) are blown.+3 more →
B17A100›
B17A100 is an internal diagnostic fault code for the BYD SRS (Supplemental Restraint System) control unit. "Invalid Fault" indicates the airbag control module detects data frames from internal logic circuits, external crash sensors, or CAN bus communication containing format errors, CRC check failures, or values outside physically reasonable ranges during self-checks or real-time monitoring. These conditions do not meet other specific fault definitions (such as open circuit, short circuit, or abnormal signal). This fault typically indicates the ECU received "logically implausible" status information. This forces the system into a safety fallback mode (e.g., airbag deactivation, pretensioner standby, or a continuously illuminated fault indicator), severely compromising crash protection functions. In Qin PRO models, this fault commonly stems from ECU internal ADC reference voltage drift, momentary CAN bus interference, or marginal sensor signal values.
Causes
— Electromagnetic interference or momentary short circuit on the CAN bus (powertrain or comfort network) causing the SRS ECU to receive corrupted data frames or incorrect node information.— Transient voltage drop in the vehicle power supply system (e.g., aging battery at start-up or alternator regulator fault) causing abnormal internal ECU logic levels or EEPROM data checksum errors.— Front or side impact sensor internal resistance is marginal. Signal voltage fluctuates between 2.4V and 2.6V, exceeding the ECU adaptive learning range.+2 more →
Actions
— Use the VDS2000/VDS3000 diagnostic tool to read the complete fault tree. Confirm if B17A100 is a Current DTC. Record key parameters from the freeze frame data, such as vehicle speed, voltage, and temperature. Check for accompanying U-class communication fault codes.— After disconnecting the battery negative terminal for 5 minutes, check the SRS ECU power supply and ground: measure the voltage drop between connector pin 16 (constant B+) and pin 8 (GND). Verify the static voltage is 12.4V-12.8V. Check fuses SB07 (10A) and FB10 (15A) for poor connections.+4 more →
B17A200›
This DTC indicates that the airbag control unit (SRS ECU) has detected a collision event meeting the deployment threshold, permanently written the crash data to the ECU internal non-volatile memory (NVRAM), and activated the crash lock protection mechanism. In this state, the SRS system enters safe mode, disables further airbag deployment to prevent secondary injury, and illuminates the warning lamp continuously. A genuine collision event (deployed or recorded without deployment) can trigger this lock. Crash sensor faults, wiring harness short/open circuits, ECU algorithm miscalculations, or power supply system anomalies can also generate a false record. Once locked, standard DTC clearing cannot erase the code. Reset the data using dedicated diagnostic equipment, or replace the ECU.
Causes
— The vehicle experienced an actual collision (regardless of airbag deployment). The SRS ECU recorded longitudinal/lateral acceleration sensor data and locked the system.— Internal short circuit, open circuit, or signal drift in the front impact sensor, side impact sensor, or central sensor causes the ECU to receive an abnormal acceleration signal.— SRS ECU internal memory chip damage, software bugs, or power supply fluctuations (such as voltage spikes when jump-starting a discharged battery) cause incorrect writes to the data area.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000/3000 or ED400) to access the SRS system. Read the complete fault codes, freeze frame data, and crash records. Verify the trigger time, triggered sensor location, and collision severity value (Delta-V).— Check the vehicle repair history against the freeze frame time. Visually inspect the front and rear longitudinal rails, crash beams, B-pillars, and sills for signs of sheet metal repair to confirm a genuine collision or a false alarm.+4 more →
B17A300›
In the BYD SRS system, DTC B17A300 carries two technical indications: 1) The surface description, "seat belt pretensioner collision", indicates the system detects a trigger signal or ignition circuit fault in the driver or passenger seat belt pretensioner (Pyrotechnic Pretensioner); 2) The underlying technical definition, "SRS CAN Signal Abnormal", means the airbag control unit (ACU) loses communication with the vehicle CAN network (typically the powertrain or comfort network) or detects a data checksum error. This fault forces the airbag system into a degraded mode, potentially preventing airbag and pretensioner deployment during a collision. It also triggers a continuous airbag warning light on the instrument cluster. In models such as the Qin PRO, this fault frequently accompanies B17A200 (collision record locked) or B17A400 (hardwired signal abnormal), indicating the vehicle experienced a collision or the CAN bus physical layer has an intermittent fault.
Causes
— CAN bus physical layer fault: Short circuit between CAN-H and CAN-L, short to power or ground, or terminal resistor (120Ω±2%) drift causing signal reflection. Typically occurs at dashboard wiring harness junctions or results from floor wiring harness oxidation after water ingress.— Airbag Control Unit (SRS ECU) power supply fault: blown constant power (B+) circuit fuse, missing ignition switch signal (IGN), or loose ground points G301/G302, causing the ACU to lose power during the communication cycle.— Seat belt pretensioner ignition circuit fault: Water ingress and oxidation at the pretensioner connector (usually below the B-pillar) causes abnormal resistance (normal: 2.0-2.4Ω), or a deployed but unreplaced pretensioner after a collision creates an open circuit (>10Ω).+2 more →
Actions
— Safety Preparation and Initial Inspection: Disconnect the 12V battery negative terminal and wait 3 minutes for the SRS capacitor to discharge. Use VDS or Launch X431 to read the complete DTC snapshot and check for accompanying codes B17A200 (crash lock) or B17A400 (hardwire fault). Check the vehicle for collision repair history. Visually inspect the airbag module and pretensioner connectors for signs of deployment.— Power supply and ground check: Reconnect the battery and turn the ignition ON. Measure the voltage at ACU connector pin 1 (constant B+) and pin 9 (IGN); the voltage should be 11-14V. Measure the resistance between the ground pin (usually pin 10/11) and the vehicle body; the resistance should be <1Ω. If the voltage is abnormal, check instrument panel power distribution box fuses F1/9 and F2/3, and ground point G301.+3 more →
B17A400›
DTC B17A400 indicates the Supplemental Restraint System (SRS) detects an abnormal signal in the driver-side side airbag circuit or related hardwiring. This DTC typically indicates an open circuit, short circuit, or out-of-range resistance (normal circuit resistance is typically 2.0-5.0Ω) in the hardwired communication between the Airbag Control Unit (ACU) and the driver-side side airbag module (SAB-D), left side impact sensor (SIS), or seat belt pretensioner. This fault can prevent the driver-side side airbag from deploying during an actual collision or trigger the fault warning lamp without a collision, severely compromising passive safety system functionality. The literal fault description reads 'driver side collision'; however, this indicates a side airbag system circuit anomaly, not an actual collision event.
Causes
— Driver-side side airbag module circuit fault: Includes loose, oxidized, or backed-out pins in the airbag connector under the seat, or repeated bending of the wiring harness during seat rail adjustment breaking internal wires.— Left B-pillar side impact sensor (SIS) fault: damaged internal piezoelectric element, loose mounting bolt causing poor grounding, or water ingress and corrosion in the connector causing signal distortion.— Seat belt pretensioner circuit fault: poor contact at the driver-side seat belt pretensioner connector, wiring short circuit, or pretensioner internal resistance deviation.+2 more →
Actions
— Use the BYD VDS2000 or ED400 diagnostic tool to read all DTCs. Confirm B17A400 is a Current fault, not a History fault. Record the resistance or voltage value from the freeze frame data.— Perform safety procedure: disconnect the battery negative terminal and wait at least 90 seconds to ensure full system discharge. Inspect the white/yellow 2-pin connector (usually marked SAB-D) on the side airbag module under the driver's seat for looseness, backed-out pins, or oxidation. If necessary, clean with electrical contact cleaner, apply conductive grease, and reconnect.+6 more →
B17A500›
This fault code typically indicates a circuit fault in the left electronic parking brake (EPB) actuator (passenger side). Associated issues include motor damage, abnormal control wiring, or module drive circuit faults. Some documentation labels this code as an SRS 'passenger-side side collision' record. However, field cases on BYD Qin, Han, Song, and Tang models confirm B17A500 indicates an open circuit, short circuit, or current overload in the left EPB motor drive circuit. This fault disables the electronic parking brake (unable to apply or release) and triggers a 'Please check the electronic parking system' instrument cluster warning. Extreme cases cause rear brake drag, increased driving resistance, or parking failure, posing a severe safety hazard.
Causes
— Excessive wear or open circuit in the left EPB actuator internal DC motor carbon brushes causes abnormal resistance (normal: 1.0-2.5 Ω; fault: infinite).— Harness connector terminal spread, poor connection, or oxidation/corrosion. This commonly occurs at the body-to-floor harness inline connector or as poor contact at ground point G106 below the left A-pillar.— Vehicle wading or seal failure causes water ingress into the actuator or connector, resulting in a short to ground or motor rust and seizure.+2 more →
Actions
— Use the VDS diagnostic tool to read the complete fault codes and freeze frame data. Confirm whether B17A500 is a current or stored fault. Check the data stream for the left actuator operating current (normal peak <15A) and the position sensor signal.— Raise the vehicle and visually inspect the left EPB actuator and electrical connector. Check for obvious signs of water ingress, burn marks, or impact damage. Confirm the mechanical connection is not binding.+5 more →
B17A600›
DTC B17A600 indicates the Airbag Control Unit (ACU) detects a triggered front impact sensor circuit or an abnormal signal. This event-type DTC typically indicates the SRS system recorded a front collision event (regardless of severity), or the Front Impact Sensor (FIS) and its wiring harness have an electrical fault (such as a short circuit, open circuit, or abnormal impedance). On BYD Qin PRO models, the front impact sensors typically mount on both sides of the front longitudinal rails or radiator support frame to detect front-end acceleration changes. The ACU sets this code when it detects a sensor signal exceeding the threshold (>2.5g for a specific duration) or abnormal sensor circuit resistance (normally approx. 2.0-3.0kΩ). This fault may prevent airbag deployment or cause accidental deployment. Repair the vehicle immediately.
Causes
— The vehicle sustained an actual frontal collision (minor scrape or severe accident), the SRS module recorded the collision event, and the collision data clearing (CDR) reset procedure was not performed.— Front crash sensor internal fault (piezoelectric element aging, internal short or open circuit), causing it to send an incorrect acceleration signal to the ACU.— Poor contact, oxidation from water ingress, or terminal corrosion at the front collision sensor wiring harness connector, causing abnormal circuit resistance (>10kΩ or <500Ω)+2 more →
Actions
— Connect the VDS2000/BYD dedicated diagnostic tool, read all DTCs and freeze frame data, record the acceleration value (Delta-V) and trigger time at the moment of collision, and verify if the collision record is genuine.— Perform a full vehicle DTC scan and check for related codes such as B17A100 (ACU internal fault), B17B100 (front left sensor fault), or B17B200 (front right sensor fault) to locate the specific faulty side.+4 more →
B17A700›
This DTC indicates the Airbag Control Unit (ACU) recorded a rear collision event. The system sets this code when the Rear Impact Sensor detects a deceleration threshold trigger in a specific direction, or the accelerometer integrated within the SRS control unit identifies a G-value change consistent with a rear collision. This event-recording DTC may accompany seat belt pretensioner activation or an airbag deployment command. Upon storing this code, the system illuminates the airbag fault warning lamp, may disable specific airbag functions to prevent unintended secondary deployment, and records key collision data in the freeze frame (such as vehicle speed, seat occupancy status, and seat belt buckle switch status) for accident analysis. If no actual collision occurred, the sensor or control unit has an electrical fault or signal interference.
Causes
— An actual rear collision caused the rear impact sensor (located on the rear panel or C-pillar) to reach its trigger threshold.— Rear collision sensor mounting bracket deformed or loose, or internal piezoelectric element damaged, causing a false signal.— The sensor wiring harness shorts to ground or power, or electromagnetic interference affects the signal circuit, generating a false collision signal.+2 more →
Actions
— Use VDS2000 or the latest diagnostic tool to read the complete SRS fault codes and freeze frame data. Confirm the specific collision detection sensor location, trigger time, and vehicle status parameters.— Visually inspect the rear of the vehicle (rear bumper, rear body panel, tail lamp housing) for signs of collision, repair, or water ingress.+5 more →
B17FF-00›
DTC B17FF-00 indicates the airbag control unit (SRS ECU) continuously detects an abnormal vehicle speed pulse signal input or completely loses the vehicle speed signal. In BYD Qin series vehicles, the SRS system receives the vehicle speed pulse signal from the wheel speed sensors (ABS sensors) or the vehicle control unit (VCU) via hardwire or the CAN bus. The crash judgment algorithm uses this signal—the system determines the airbag deployment trigger threshold, ignition timing, and multi-stage airbag deployment intensity based on real-time vehicle speed. The SRS ECU stores this DTC when it detects, within a set time window (typically exceeding 2-5 seconds), that the pulse signal frequency falls outside the valid range (such as the frequency corresponding to 0-255 km/h), the signal completely drops out, or the signal deviates significantly from the vehicle speed data transmitted on the CAN bus. This fault forces the airbag system into Degradation Mode. During a collision, the airbags may deploy late, fail to deploy, or deploy inadvertently at low speeds, severely compromising passive safety performance.
Causes
— Wheel speed sensor (ABS sensor) component fault or contaminated sensor tip: internal coil open circuit, resistance drift (normal 1.0-1.5 kΩ), or metal filings, mud, or sand covering the sensor attenuates the magneto-electric signal and prevents the generation of sufficient pulse voltage (usually requires >0.5V AC).— Physical damage to the vehicle speed signal transmission circuit: Wiring harness from the wheel speed sensor to the SRS ECU chafed through the insulation at suspension movement interference points, or connector pins backed out, oxidized, or subjected to water ingress, causing an intermittent signal open circuit or short to ground.— CAN bus communication fault: Short circuit between the H and L lines of the Powertrain CAN or Body CAN, short to power or ground, or abnormal terminating resistor (standard 60Ω), preventing the SRS ECU from validating vehicle speed data via the bus.+2 more →
Actions
— Use the genuine BYD diagnostic tool VDS2000/VDS3100 to perform a full scan and confirm whether B17FF-00 is a current (Active) or historical (History) fault. Read the freeze frame data to record the vehicle speed when the fault occurred. Simultaneously check for accompanying wheel speed sensor fault codes (e.g., C0035-C0052 series) or CAN communication fault codes.— Raise the vehicle until the wheels are off the ground. Visually inspect the installation gap of the four wheel speed sensors (standard 0.3-1.2 mm) and the cleanliness of the sensor heads. Remove any metal filings and oil contamination. Measure the sensor resistance with a multimeter (1.0-1.5 kΩ at 20°C). Rotate the wheel by hand and observe the AC voltage output (must be >0.5 V and increase with wheel speed).+3 more →
B17A800›
The BYD SRS (airbag system) control unit logs diagnostic trouble code (DTC) B17A800 to indicate interrupted communication or a physical layer connection fault between the airbag control module and the vehicle CAN bus network. In models such as the BYD Qin PRO, the SRS ECU exchanges real-time data with the vehicle control unit (VCU), body control module (BCM), instrument cluster, and gateway via the CAN bus (typically the powertrain CAN or chassis CAN, depending on the configuration). The ECU transmits critical safety data, including crash signals, airbag status, fault information, and system readiness status. The SRS ECU sets this fault code when it continuously detects abnormal voltage on the CAN_H and CAN_L lines (recessive level outside the normal 2.0-3.0 V range, or abnormal dominant level), bus termination resistance deviating from the standard 60 Ω value (after parallel connection), or no valid data frame received within the specified time limit (usually 250 ms-500 ms). This functional safety fault may prevent proper airbag deployment and seat belt pretensioner operation during a collision. It also disables the collision-triggered automatic unlocking and high-voltage cut-off functions. As a result, the instrument panel airbag warning lamp remains illuminated and the vehicle enters safety protection mode.
Causes
— Physical damage to the CAN bus wiring harness: After an accident, water ingress, or prolonged vibration, the CAN_H (orange/black) or CAN_L (orange/brown) wires in the front compartment or chassis harness develop an open circuit, short to ground, or short to power. Connectors oxidize or loosen. Specifically, the SRS ECU connector (usually located at the center tunnel or bulkhead) has backed-out or corroded pins.— Abnormal terminal resistance: Internal damage to the 120Ω terminating resistors at both ends of the CAN bus (located in the gateway or instrument cluster) causes a bus impedance mismatch, or an internal transceiver fault in the SRS ECU causes an abnormal bus load, resulting in signal reflection and communication interruption.— Power supply fault: Poor contact at the SRS ECU constant power (B+), ignition switch power (IG1), or ground wire (GND), or voltage below 9V or above 16V, causing control unit reset or unstable CAN transceiver power supply.+2 more →
Actions
— Initial inspection and fault confirmation: Use the BYD dedicated diagnostic tool (ED400/VDS) to read all fault codes. Verify B17A800 is a Current code, not a History code. Check the instrument cluster airbag warning light status. Determine if the vehicle experienced a collision or water ingress. Inspect the front compartment and center tunnel wiring harnesses for damage, modifications, or signs of water ingress.— CAN bus physical layer check: Disconnect the battery negative terminal, wait 3 minutes, and measure the resistance between pins 6 (CAN_H) and 14 (CAN_L) of the diagnostic connector (OBD). Normal resistance is approximately 60 Ω (two 120 Ω terminating resistors in parallel). A reading of 120 Ω indicates an open circuit in one terminating resistor or the wiring. A reading of 0 Ω indicates a short circuit in the wiring. Measure the resistance from CAN_H to ground and power, and from CAN_L to ground and power. All readings must exceed 1 MΩ.+3 more →
B17FF›
DTC B17FF indicates an abnormal vehicle speed pulse signal at the airbag control unit (SRS ECU). In BYD electronic architecture, wheel speed sensors typically generate the vehicle speed signal. The ABS/ESP control unit processes this signal and transmits it via the CAN bus to the instrument cluster and SRS module. The SRS system relies on accurate vehicle speed data for crash algorithm decisions: low-speed collisions (<25km/h) normally do not trigger the front airbags, while medium- and high-speed collisions require precise vehicle speed data to calculate airbag deployment timing and ignition level. When the SRS module detects the vehicle speed pulse signal is missing, out of range, erratic, or inconsistent with CAN bus vehicle speed data, it logs DTC B17FF and illuminates the airbag warning light. The system enters a degraded mode, potentially causing unintended or delayed airbag deployment during a collision.
Causes
— Wheel speed sensor fault or dirty/damaged signal tone ring causing an abnormal pulse signal.— CAN bus communication fault from the ABS/ESP control unit to the SRS module (open circuit, short circuit, or signal interference)— SRS control unit internal vehicle speed signal processing circuit fault (ADC converter or signal conditioning circuit damaged)+2 more →
Actions
— Use the BYD VDS diagnostic tool to read all fault codes, check for accompanying U-class communication faults or C-class chassis faults, and view the 'Vehicle Speed Validity' status in the live data stream.— Check the four wheel speed sensors and signal tone rings: clean metal filings from the sensor heads, check the tone rings for missing teeth or deformation, and measure the sensor resistance (normal: 1.3–1.8 kΩ) and AC output voltage (0.1–3 V when rotating the wheel).+4 more →
B185014›
This fault code indicates a short to ground or open circuit in the rear HVAC blower motor speed control signal circuit. Modern BYD vehicles typically use a PWM (pulse-width modulation) signal or an analog voltage signal (0-5V/0-12V) for stepless rear blower speed control. The HVAC ECU triggers this fault code when it detects an abnormal control signal voltage (a constant 0V short to ground or a high-impedance open circuit) to the rear blower speed control module (power transistor) or blower motor. This fault results in no airflow from the rear HVAC vents, prevents fan speed adjustment, or restricts operation to a fixed fan speed. In extreme cases, it triggers the HVAC thermal management protection and limits battery or motor cooling capacity, classifying this as a severe fault.
Causes
— Internal breakdown of the rear blower speed control module (Power Transistor) causes the control signal line to short to ground.— Internal short circuit in rear blower assembly motor pulls down control signal voltage.— Harness wear or crushing: Damaged wiring harness insulation at the front seat rails, under the carpet, or in the center tunnel causes the signal wire to short to body ground.+2 more →
Actions
— Read freeze frame data: Use the BYD VDS diagnostic tool to record vehicle speed, ambient temperature, and blower duty cycle data when the fault occurred. Confirm whether the fault is continuous or intermittent.— Visual inspection: Remove the rear center console or roof air conditioning control panel (depending on vehicle configuration). Check the rear blower assembly for abnormal noise, binding, or burn marks. Check for detached wiring harness retaining clips.+4 more →
B2A0716›
The internal voltage monitoring circuit in the Air Conditioning Control Unit (ACU) or Integrated Thermal Management System (ITMS) controller triggers DTC B2A0716. This indicates the supply voltage in power circuit 161 (typically the constant B+ or IG ignition supply for the air conditioning module) falls below the 9V operating threshold. This fault signifies a low-voltage supply abnormality in the thermal management system. Upon detecting insufficient operating voltage, the controller logs the fault and may enter a degraded protection mode. This mode limits the electric compressor speed, shuts off the PTC heater, or halts electronic expansion valve operation, reducing or disabling air conditioning cooling and heating functions. In extreme cases, this condition affects the traction battery cooling circuit and triggers overheat protection.
Causes
— 12V low-voltage battery aging, discharge, or excessive voltage drop during cold start causes the air conditioning controller power supply to momentarily drop below 9V.— A/C controller power supply fuse (IF08/IF09) in the front compartment distribution box or instrument panel distribution box blown, poor contact, or burnt fuse holder base.— Loose connection, backed-out terminals, oxidation, or water ingress corrosion at the air conditioning controller wiring harness connector (e.g., plug G06/JA01), causing increased contact resistance.+2 more →
Actions
— Scan the entire vehicle system using the VDS2000/VDS1000 diagnostic tool, confirm B2A0716 is a current fault code, and record the freeze frame data (voltage at the time of occurrence, ambient temperature, etc.).— Measure the 12V battery static voltage (≥12.4V) and minimum voltage at startup (≥9.6V). Check the battery state of health (SOH ≥80%). Replace the battery if necessary.+5 more →
B2A0717›
This DTC indicates the A/C controller or thermal management system control module detects a power supply voltage exceeding the 16V safety threshold. In BYD new energy vehicles, the DC-DC converter typically converts high-voltage traction battery energy to power the low-voltage system (12V/14V system). Normal output voltage should range between 13.5V and 14.5V. When the monitoring point voltage continuously exceeds 16V, the controller identifies an overvoltage condition and triggers a protection mechanism to prevent electronic component damage. This fault may restrict A/C system functions, reduce thermal management efficiency, or force the system into a power derating mode. Extreme cases may damage sensitive electronic components on the control board. The '161' in the DTC typically refers to a specific voltage monitoring circuit or sensor number.
Causes
— DC-DC converter output voltage regulation failure causes the low-voltage side output voltage to rise abnormally above 16V.— A/C controller internal power management chip or voltage sampling circuit fault causing a false overvoltage report.— 12V low-voltage battery aging, sulfation, or poor connection causing voltage fluctuations and transient overvoltage spikes.+2 more →
Actions
— Use the VDS2000/VDS1000 diagnostic tool to read the complete fault codes and freeze frame data. Record the specific voltage value and environmental conditions when the overvoltage occurred. Confirm whether B2A0717 is a current fault or a history fault.— Measure the low-voltage battery static voltage (vehicle off) and dynamic voltage (OK/Ready state). Verify if the actual DC-DC output voltage exceeds 16V to determine whether the overvoltage is genuine or a false sensor reading.+4 more →
B2A0811›
On BYD new energy vehicles, DTC B2A0811 indicates a short to ground or abnormal signal transmission in the Electric A/C Compressor control circuit. Although the original description mentions a 'PT temperature sensor', repair practice links this code primarily to unintended continuity between the Compressor Controller low-voltage control circuit (12V supply, PWM signal, or CAN communication line) and body ground, or a breakdown short circuit of the internal power transistor (IGBT). This fault forces the compressor controller into protection mode and stops high-voltage output, causing complete air conditioning failure or intermittent system shutdown. Because new energy vehicles rely on the air conditioning system for battery thermal management, this fault can cause insufficient traction battery cooling, trigger overheat protection, and limit vehicle power. This serious fault compromises driving safety.
Causes
— A broken or missing front compartment wiring harness retaining clip causes the harness to rub against metal body brackets or high-temperature components (such as the turbocharger pipe or exhaust pipe). The resulting insulation damage shorts the control wire to ground.— An aged or improperly assembled electric compressor controller low-voltage connector seal allows rainwater or car wash water to enter, causing terminal oxidation, corrosion, or a short circuit between terminals.— Compressor controller internal power drive circuit board burnout, power transistor (IGBT/MOSFET) breakdown, or capacitor leakage causing a short circuit between the high-voltage side and low-voltage control side.+2 more →
Actions
— Safety Preparation: Wear insulated gloves. Disconnect the manual service disconnect (MSD). Wait 5-10 minutes to ensure the high-voltage system discharges completely (voltage <60V). Use a multimeter to verify zero voltage on the high-voltage bus.— Fault confirmation: Use a BYD VDS2000 or Launch X431 diagnostic tool to read all fault codes and freeze frame data. Confirm whether B2A0811 is an Active or Historic code. Record the ambient temperature, compressor speed, and battery temperature at the time of the fault.+8 more →
B2A0813›
DTC B2A0813 indicates an open circuit in the air conditioning system evaporator outlet refrigerant temperature sensor (PT sensor) circuit. This sensor uses an NTC thermistor to monitor the evaporator outlet refrigerant temperature in real time (typical range -40°C to +85°C). It provides critical temperature feedback to the HVAC ECU to precisely control the electronic expansion valve opening, compressor speed, and blower airflow, preventing evaporator surface icing and optimizing cooling efficiency. The ECU logs an open circuit fault when it detects the sensor signal voltage continuously exceeding the threshold (typically above 4.95V, indicating an open circuit) for longer than a set time (e.g., 2 seconds). This fault triggers the air conditioning system fail-safe mode, forcibly limiting compressor operation or completely stopping cooling, and may illuminate the relevant thermal management warning lamp. Continuing to drive the vehicle may cause abnormal battery pack or motor heat dissipation, making this a severe fault.
Causes
— Aging or physical damage to the thermistor element inside the sensor body causes an open circuit. Common in high-mileage vehicles (>80,000 km) or vehicles exposed to prolonged extreme temperatures.— Loose wiring harness connectors, backed-out terminals, or poor contact, especially in high-vibration areas near the evaporator housing, and connectors not fully seated after previous repairs.— Physical damage to the wiring harness, including insulation wear breaking internal copper wires, vehicle underbody scraping severing the harness, or rodents gnawing the wiring and interrupting the circuit.+2 more →
Actions
— Read fault codes using the BYD VDS2000/VDS6000 diagnostic tool. Confirm B2A0813 is a current (Active) fault, not a history fault. Record freeze frame data (ambient temperature, evaporator temperature values, etc.).— Visually inspect the appearance of the temperature sensor on the evaporator outlet pipe and the wiring harness routing. Check for obvious damage, crushing, or loose connectors. Focus on the harness protective sleeve at the firewall pass-through.+5 more →
B2A0D13›
DTC B2A0D13 indicates an open circuit in the Battery Pack Inlet Coolant Temperature Sensor. This sensor is located at the inlet of the battery thermal management system cooling circuit. Typically an NTC thermistor, the sensor provides a 0-5V analog voltage signal to the Battery Management System (BMS) or Thermal Management Controller (TMS) to monitor the temperature of the coolant entering the battery pack in real time. An open circuit fault means the control unit detects that the signal voltage remains continuously in an open-circuit state (typically the 5V reference voltage or 0V, depending on circuit design), preventing it from obtaining actual temperature data. This fault causes the thermal management system to enter fail-safe mode. The system cannot accurately regulate the battery pack temperature, which may result in the following: (1) The system disables high-power charging and discharging, limiting vehicle power output. (2) The battery coolant pump and PTC heater fail to regulate to the target temperature, creating a risk of battery overheating or low-temperature damage. (3) In extreme cases, the system triggers the high-voltage interlock, preventing the vehicle from starting.
Causes
— Broken sensor wiring harness or loose connector: Long-term vibration, thermal cycling, or improper assembly breaks internal copper wires in the harness near the battery pack, or a failed connector latch causes poor contact.— Internal open circuit in the coolant temperature sensor: Aging or cracking of the internal thermistor element, or detached solder joints, causes infinite resistance.— Connector terminal corrosion or backed-out pins: Coolant leaks or vehicle wading causes water ingress at the sensor connector, leading to terminal oxidation, corrosion, or backed-out pins.+2 more →
Actions
— Connect the VDS2000/VDS1000 diagnostic tool, read the freeze frame data for DTC B2A0D13, and record the ambient temperature, battery temperature, and vehicle status when the fault occurred.— Visually inspect the coolant temperature sensor connector located near the battery pack coolant inlet pipe for obvious looseness, signs of water ingress, corrosion, or wiring harness damage.+6 more →
B2A0E12›
This DTC indicates a short to battery in the signal circuit of the Battery Thermal Management System (BTMS) inlet coolant temperature sensor (typically located on the line before the battery cooling circuit enters the battery pack). The sensor utilizes an NTC (Negative Temperature Coefficient) thermistor and outputs a 0-5V analog voltage signal to the BMS or thermal management controller during normal operation. During a short to battery (12V), the ECU detects a continuous signal voltage above the normal range (e.g., >4.8V or equal to battery voltage) and registers a short circuit fault. This fault prevents the BMS from accurately reading the battery pack inlet coolant temperature, affecting the battery thermal management strategy and potentially triggering: 1) Disabled battery fast charging or limited discharge power; 2) False battery over-temperature protection triggers, forcing the battery cooling system (electric compressor, water pump) to operate; 3) Thermal runaway risk in extreme cases due to the inability to monitor actual battery temperature. This is a severe DTC. Inspect and repair immediately due to the high-voltage battery system thermal runaway risk.
Causes
— Internal short circuit in the battery pack inlet coolant temperature sensor body (thermistor breakdown or internal package failure), shorting the signal terminal to the power supply terminal.— Worn or damaged sensor wiring harness insulation causes the signal wire to short to a vehicle 12V power wire (such as the reversing light power supply or a constant power circuit). This commonly results from chassis impacts or loose wiring harness retaining clips rubbing against sharp edges.— Water ingress or severe corrosion in the sensor connector (e.g., from wading or improper car washing) creates electrolytic conduction between the signal and power terminals inside the connector, causing a short circuit.+2 more →
Actions
— Safety Preparation: Wear insulated gloves, disconnect the high-voltage manual service disconnect (MSD), wait 5 minutes for the high-voltage system to discharge, and locate the battery pack inlet coolant temperature sensor (typically at the cooling pipe connection at the front of the battery pack).— Visual inspection: Check the sensor connector for looseness, backed-out pins, water ingress, or obvious burn marks. Check the wiring harness for damage at wear-prone areas such as the battery pack housing, crossmember, and underbody shield mounting points.+5 more →
B2A0F13›
This fault code indicates an open circuit in the refrigerant temperature sensor signal circuit at the inlet or outlet of the plate heat exchanger (chiller, battery cooler). The sensor is an NTC thermistor that monitors the temperature of the refrigerant exchanging heat with the battery coolant, serving as a key feedback component in the BYD thermal management system. The ECU monitors this temperature to adjust the electronic expansion valve opening and electric compressor speed, precisely controlling the battery pack temperature. When the ECU detects the sensor signal voltage continuously exceeding the upper threshold (typically the 5V reference voltage, indicating an open circuit), it sets an open circuit fault. The thermal management system consequently loses precise control over battery cooling and heating. This failure may trigger the battery thermal management protection strategy, forcing the vehicle into power limitation mode (limp mode), disabling fast charging, or triggering a high coolant temperature warning. Extreme cases pose a risk of battery thermal runaway.
Causes
— Internal open circuit in the sensor body: Long-term exposure to high-temperature, high-pressure refrigerant degrades the plate heat exchanger refrigerant temperature sensor (NTC thermistor), breaking the internal resistor element and causing infinite resistance.— Loose wiring harness connector or backed-out terminal pins: The sensor connector (usually a 2-pin plug) located in the high-temperature and vibration area of the front compartment comes loose due to a failed retaining clip or improper assembly, or the female terminal pins back out or terminal holes enlarge due to repeated connection and disconnection.— Physical damage to the wiring harness: Vibration and friction cause insulation damage and internal copper wire fatigue fractures in the engine compartment-to-chassis harness section where it routes through the firewall and frame mounting holes, or along the battery pack edge; or maintenance work crushed or cut the harness.+2 more →
Actions
— Fault confirmation and freeze frame analysis: Use VDS or a dedicated BYD diagnostic tool to read the DTC freeze frame. Record the vehicle speed, battery temperature, ambient temperature, and air conditioning status at the time of the fault. Determine if the fault is current or historical. Check for accompanying thermal management system DTCs (e.g., electronic expansion valve fault, compressor fault).— Visual and wiring inspection: Raise the vehicle. Inspect the sensor at the plate heat exchanger (located in the front compartment, near the battery coolant pipes) for deformation or oil leaks. Trace the wiring harness routing and inspect for wear, damaged insulation, or burn marks, focusing on the firewall pass-through and harness retaining clips.+5 more →
B2A1012›
This DTC indicates a short to ground in the refrigerant temperature sensor signal circuit at the inlet or outlet of the battery cooling system plate heat exchanger (Chiller/battery cooler), or an internal short circuit within the sensor. This NTC thermistor outputs a 0.5-4.5 V analog voltage signal to the Thermal Management System (TMS) controller or A/C controller to monitor the temperature of the refrigerant flowing through the plate heat exchanger in real time. This parameter is critical for precisely controlling battery cooling intensity and preventing battery overcooling or overheating. The controller logs a short circuit fault when the signal voltage remains below 0.1 V (near 0 V) for a specified duration (typically 2-5 seconds). The thermal management system then enters fail-safe mode, immediately cutting off refrigerant flow to the battery cooling circuit and limiting battery charge and discharge power. In severe cases, the system triggers a vehicle-level 'Thermal Management System Fault' warning and prohibits high-voltage power-on. This prevents continued operation with unknown refrigerant temperatures, which could cause battery thermal runaway or compressor liquid slugging damage.
Causes
— Damaged sensor wiring harness insulation causing a short to body ground (commonly due to underbody impacts, stone strikes, or prolonged chafing against sharp metal edges after a harness retaining clip loosens)— Internal NTC thermistor breakdown in the plate heat exchanger refrigerant temperature sensor, or circuit board short circuit (aging, overheating, or manufacturing defects).— Water ingress and corrosion in the connector causing a short circuit between the signal pin and ground pin (wading, improper high-pressure washing, aging seal)+2 more →
Actions
— Use BYD VDS2000 or Launch X431 to read all fault codes. Check for accompanying B2A0F (open circuit) or other thermal management-related fault codes. Record abnormal temperature values in the freeze frame data.— Visually inspect the wiring harness at the plate heat exchanger (located in the front compartment or at the front of the chassis battery pack, connecting the electric compressor outlet pipe and the battery cooling pipe) for damage, crushing, or signs of water ingress. Focus on the contact points between the wiring harness and the body metal brackets.+6 more →
B2A1113›
This DTC indicates an open circuit in the refrigerant pressure sensor signal circuit at the plate heat exchanger (Chiller/battery cooler) of the thermal management system. The sensor monitors the refrigerant pressure flowing through the plate heat exchanger and serves as a key feedback component for the battery thermal management and cabin air conditioning systems. An open circuit causes the ECU to receive an open-circuit voltage (typically the saturated 5V reference voltage or 0V), preventing it from acquiring actual pressure data. This forces the thermal management control unit to enter fail-safe mode, which limits battery fast-charging power, disables the battery cooling function, and reduces drive motor power. In extreme cases, this fault triggers a battery high-temperature warning or shuts down the high-voltage system, severely impacting vehicle safety and driving range.
Causes
— Loose sensor wiring harness connector or poor contact: High temperatures and humidity in the front compartment, combined with long-term vibration, cause terminal back-out or locking tab failure.— Internal open circuit in the pressure sensor body: Refrigerant pressure shock, liquid slugging, or aging damaged the sensor diaphragm or internal circuit.— Physical damage to the wiring harness: Front compartment wiring harness rubbing against sharp body edges, rodent gnawing, or excessive bending during accident repairs causing copper wire breakage.+2 more →
Actions
— Fault confirmation and freeze frame analysis: Use VDS2000/VDS3000 to read DTC B2A1113 and freeze frame data. Confirm the ambient temperature and pressure sensor voltage at the time of the fault (typically 4.9-5.0V or 0V). Check for accompanying DTCs (e.g., a concurrent B2A1212 short circuit DTC indicates an intermittent wiring harness fault).— Visual inspection: Inspect the pressure sensor connector near the plate heat exchanger (usually located on the battery cooler outlet pipe) for looseness, water ingress, corrosion, or recessed pins. Inspect the wiring harness corrugated conduit for damage or signs of chafing against nearby sharp edges.+5 more →
B2A1212›
This DTC indicates the Thermal Management Control Unit (TMS) or air conditioning control module detects a short circuit in the signal circuit of the high-pressure side pressure sensor for the plate heat exchanger (Chiller/battery cooler) refrigerant circuit. The sensor outputs an abnormal voltage (near 0 V when shorted to ground, or near 5 V or 12 V when shorted to power), exceeding the normal 0.5–4.5 V signal range. This piezoresistive sensor monitors real-time refrigerant circuit pressure (typically 0–3.5 MPa) to control the Electronic Expansion Valve (EXV) opening and regulate compressor speed. The short circuit eliminates system pressure feedback and prevents accurate refrigerant flow control. This fault can trigger thermal management derating: limiting battery fast-charging power, prohibiting high-power discharge, and reducing motor power output. In extreme cases, the loss of overpressure protection can cause pipe rupture or compressor damage.
Causes
— Wiring harness insulation abrasion causes the signal wire to short to ground (commonly at front compartment firewall pass-throughs, harness clip wear points around the battery pack, or inside the underbody shield).— Short circuit on the internal circuit board of the pressure sensor body due to moisture (sensor seal failure allowing refrigerant or moisture ingress).— Short circuit between connector terminals (water ingress into the connector after wading causes terminal electrolytic corrosion, shorting the signal wire to the ground or power wire)+2 more →
Actions
— Connect VDS or a dedicated diagnostic tool, read DTC status and freeze frame data, confirm the pressure sensor voltage (a short circuit typically reads 0V or 5V reference voltage), and record the ambient temperature and system status at the time of the fault.— Disconnect the refrigerant pressure sensor connector near the plate heat exchanger (usually on the right side of the front compartment or at the front of the chassis battery pack). Measure the resistance on the sensor side. Normal resistance is 2kΩ-10kΩ (depending on the model). If the resistance is <100Ω, replace the sensor assembly.+5 more →
B2A2013›
BYD technical documentation defines DTC B2A2013 as "Evaporator Temperature Sensor Circuit Open," rather than a generic "cabin temperature sensor" fault. Located inside the HVAC evaporator case, this sensor monitors the evaporator core surface temperature in real time. It sends critical feedback to the air conditioning controller (AC ECU) to prevent evaporator icing, regulate compressor displacement, and control the electronic expansion valve opening. The AC ECU logs an open circuit fault when it detects the sensor signal voltage remaining above 4.95V or below 0.05V (outside the valid range). This fault triggers the A/C system protection logic, which forcibly disengages the compressor electromagnetic clutch or stops the electric compressor, completely disabling A/C cooling. Because BYD New Energy Vehicles (NEVs) deeply integrate the A/C and battery thermal management systems (typically incorporating the battery chiller into the A/C refrigerant circuit), this fault can cascade into a battery cooling system failure. This causes abnormal vehicle thermal management and may restrict power output.
Causes
— Internal open circuit in the evaporator temperature sensor or thermistor characteristic drift, failing to generate a valid temperature-resistance signal.— Sensor wiring harness wear, breakage, or crush damage at stress concentration points such as the firewall wiring grommet and instrument panel frame mounting points.— Oxidation, corrosion, or poor contact of the sensor connector pins caused by evaporator condensate leakage, floor water ingress, or leakage during car washing.+2 more →
Actions
— Use a dedicated diagnostic tool (such as VDS2000 or Launch X-431) to read air conditioning system fault codes. Confirm B2A2013 is present and record freeze frame data (abnormal ambient and evaporator temperature values are typically -40°C or a fixed high value).— Enter data stream mode and monitor the 'evaporator temperature sensor' value in real time. Turn on the air conditioning. If the value does not change or remains at an extreme value (-40°C/120°C), confirm the signal is abnormal.+7 more →
B2A2111›
In-Car Temperature Sensor signal circuit short to ground. This sensor typically mounts near the center instrument panel air vent or inside the HVAC duct and uses a Negative Temperature Coefficient (NTC) thermistor. Normal operating voltage ranges from 0.5-4.5V (varying with temperature). When the HVAC ECU detects the sensor signal line voltage remaining below 0.5V for longer than the set time threshold (typically 2-5 seconds), it determines a short to ground. This fault causes the air conditioning system to lose the cabin ambient temperature feedback signal, resulting in automatic temperature control failure, disrupted compressor start-stop logic, and abnormal outlet air temperature (continuous maximum cooling or heating). The fault may also affect the battery thermal management system comfort control strategy and, in severe cases, trigger Level 3 fault protection to limit air conditioning power.
Causes
— Long-term vibration wears through the sensor wiring harness insulation where it passes through the dashboard metal frame or firewall, shorting the signal wire to body ground.— The thermistor package inside the cabin temperature sensor failed or suffered moisture ingress, causing an internal short circuit between the terminals.— Poor drainage from the air conditioning evaporator housing causes water accumulation in the air duct. Water ingress corrodes the sensor connector, shorting the pins to ground.+2 more →
Actions
— Connect the BYD VDS diagnostic tool, read the fault codes to confirm B2A2111 is a current active fault, record the voltage value in the freeze frame data (usually displaying 0.0V or close to 0V), and check for accompanying historical faults such as B2A2013 (open circuit).— Remove the center control panel or passenger-side glove box, locate the in-cabin temperature sensor (on Song/Qin series, this is usually behind the A/C control module or inside the center air vent duct), and visually inspect the connector for oxidation, water stains, or backed-out terminals.+5 more →
B2A2311›
DTC B2A2311 indicates a short to ground or short to power in the Ambient Temperature Sensor (ATS) signal circuit. This causes the air conditioning controller (ACECU) or thermal management controller (TMCU) to detect a voltage signal outside the normal range (typically 0.1-4.9V). The sensor is an NTC thermistor with a normal resistance of approximately 2.3-2.5 kΩ at 25°C. A short circuit causes the ECU to continuously receive an abnormally high or low temperature signal (depending on the short type). This triggers automatic air conditioning system protection, prevents compressor startup, limits PTC heater power, and affects the battery thermal management system cooling or heating strategy. Extreme cases may trigger high-voltage interlock protection and limit overall vehicle power output.
Causes
— Internal short circuit in the sensor body: Sensor seal failure allows rainwater or car wash fluid to enter, causing the internal thermistor to short to the housing, or sensor aging causes abnormal resistance characteristics.— Wiring harness insulation damaged: Front bumper collisions, underbody impacts, or loose harness retaining clips cause the harness to rub against metal body edges, shorting the signal wire to ground.— Connector water ingress and corrosion: The sensor mounts under the front grille or bumper. When driving through water, an aged or failed connector seal causes a short circuit between terminals or a short to ground.+2 more →
Actions
— Diagnostic tool check: Use VDS or ED400 to read fault codes. Confirm B2A2311 is a current fault (Active). Record the ambient temperature value from the freeze frame data. Check for related fault codes (e.g., B2A2213, U0146).— Visual inspection: Open the bonnet and check the ambient temperature sensor installation position (usually in the centre or left side of the front bumper air intake grille). Inspect the sensor housing for damage or cracks. Check the wiring harness for obvious wear or crush marks.+4 more →
B2A2213›
DTC B2A2213 indicates an open circuit fault in the Ambient Temperature Sensor circuit. Typically an NTC (Negative Temperature Coefficient) thermistor installed near the front bumper or side mirror, this sensor monitors ambient temperature in real time and sends a feedback signal to the HVAC ECU. The controller logs an open circuit if it detects the sensor signal voltage remaining continuously high (typically the undivided 5V reference voltage, representing an open circuit) beyond the set threshold (generally 2–5 seconds). This fault prevents the automatic air conditioning system from accurately calculating the target outlet air temperature. It affects compressor start-stop control, PTC heater power regulation, fresh/recirculated air switching logic, and battery thermal management strategies (such as low-temperature charging preheating and high-temperature cooling activation). In extreme cases, the system triggers thermal management derating protection and limits motor power output to protect the high-voltage powertrain. Therefore, the system classifies this as a severe fault.
Causes
— Internal open circuit or resistance drift in the ambient temperature sensor (impact cracking or seal failure causing water ingress results in an open thermistor)— Sensor harness connector terminal backed out, oxidized, or making poor contact (common after front compartment water ingress, high-pressure washing, or long-term salt spray exposure)— Physical open circuit in the signal wiring harness between the sensor and the air conditioning controller (high engine compartment temperatures causing the insulation to become brittle and break, or a poor connection at the firewall pass-through connector)+2 more →
Actions
— Visual inspection: Confirm the ambient temperature sensor has no visible damage or cracks, sits in the correct unobstructed position, and the wiring harness sleeve shows no mechanical damage or signs of heat melting.— Sensor measurement: Disconnect the sensor connector. Use a multimeter to measure the resistance between the two sensor terminals (standard value at 25°C: approx. 2.0-2.5 kΩ; resistance decreases non-linearly as temperature increases). Replace the sensor if the resistance is infinite.+3 more →
B2A2413›
DTC B2A2413 indicates the air conditioning control unit (AC ECU) detects an open circuit in the evaporator temperature sensor circuit. This sensor, typically a negative temperature coefficient (NTC) thermistor, mounts to the evaporator fin surface inside the HVAC assembly. It monitors real-time evaporator core temperature (normal operating range: 2–8°C). If the sensor fails open, the wiring harness disconnects, or the connector has poor contact, the ECU detects a continuous 5V signal (or open-circuit voltage) and cannot obtain accurate evaporator temperature data. The system then triggers a protection strategy. To prevent evaporator icing, expansion, and core damage, the ECU forcibly disengages the compressor electromagnetic clutch or disables the electric compressor. It may also default to a substitute value (such as 0°C or ambient temperature) to maintain limited cooling. This causes air conditioning performance to degrade severely or fail completely. Prolonged operation with this fault can cause frequent compressor cycling, abnormal battery pack thermal management (on models where the air conditioning system couples with battery cooling), and even high-voltage system insulation faults.
Causes
— Evaporator temperature sensor internal open circuit: Prolonged exposure to a low-temperature, high-humidity environment causes the internal thermistor element to age and crack, or package seal failure allows moisture ingress, resulting in corrosion and an open circuit.— Loose harness connector or backed-out terminal: Prolonged driving on rough roads causes the sensor plug (usually a 2-pin white connector) on the HVAC assembly inside the front passenger-side dashboard to loosen, the locking tab to break, or a terminal to back out, resulting in poor contact.— Physical wiring harness damage: Metal edges cut the wiring harness inside the dashboard during assembly or repair, or rodents chew through the signal wire (quiet EV motor compartments attract rodents to chew wiring harnesses).+2 more →
Actions
— Connect the VDS2000/Launch X431 diagnostic tool. Access the air conditioning system to read fault codes. Confirm B2A2413 is a Current DTC. Record the Freeze Frame data to observe the ambient temperature and system status when the fault occurred.— Remove the front passenger-side glovebox or lower trim panel, locate the evaporator temperature sensor (positioned between the fins on the right side of the evaporator core, usually a black plastic housing with a 2-wire connector), and visually inspect the connector for looseness and the wiring harness for damage.+5 more →
B2A2511›
DTC B2A2511 indicates a circuit fault in the left front seat belt pretensioner (Driver Seat Belt Pretensioner), specifically a short to ground or an open circuit. The Airbag Control Module (ACM) sets this fault code when it detects abnormal resistance in the left front pretensioner circuit (standard value: 2-3 Ω; fault condition: short circuit at <1.0 Ω, or open circuit at >4.0 Ω/infinite resistance). This fault forces the airbag system into fail-safe mode and continuously illuminates the instrument cluster airbag warning light. In a collision, the pretensioner may fail to deploy. This severe fault compromises driving safety. Note: Some online sources incorrectly identify this code as the evaporator temperature sensor; it strictly applies to the seat belt pretensioner system.
Causes
— Improper routing allows the seat slide rail to pinch and chafe the under-seat wiring harness, causing a short to ground or open circuit.— G09 or GJK mating connector pins backed out, oxidized, corroded, or excessive contact resistance— Internal short circuit or open circuit in the seat belt pretensioner assembly (e.g., pretensioner deployed after a vehicle collision but not replaced)+2 more →
Actions
— Use the VDS2000/VDS3100 diagnostic tool to read the fault code, confirm whether B2A2511 is an active or history code, and record the freeze frame data.— Disconnect the battery negative terminal and wait 3 minutes for the capacitor to discharge. Inspect the pretensioner wiring harness under the left front seat for pinch marks from the seat slide rail, wear, damaged insulation, or water ingress.+4 more →
B2A2712›
This DTC indicates the signal circuit of the automatic air conditioning system’s sun sensor (solar intensity sensor) has shorted to the vehicle power supply (B+, usually a constant 12V supply). The sun sensor generally uses a photodiode or photoresistor. During normal operation, the sensor outputs an analog voltage signal of 0.1-4.9V to the air conditioning controller (integrated into the thermal management module). The signal voltage increases as sunlight intensity increases. When the signal wire shorts to power, the controller detects the voltage remains continuously above 4.9V (close to battery voltage, 12-14V) and logs a short-to-power fault. This fault disables the automatic air conditioning system's solar compensation function. The air conditioning controller cannot automatically adjust outlet air temperature and blower speed based on sunlight intensity. In extreme cases, the short-circuit current may burn out the air conditioning controller's internal sampling circuit. Consequently, the system reports a severe fault and may enter protection mode.
Causes
— The sunlight sensor wiring harness chafes against a sharp metal edge inside the dashboard, wearing through the insulation and shorting the signal wire to the constant power wire. This commonly occurs after driving on rough roads or after dashboard removal and installation.— During front windshield replacement or dash cam installation, the technician accidentally damaged the sun sensor wiring harness, crushing the signal wire and power wire together and causing a short circuit.— Internal photoelectric element breakdown or seal failure in the sun sensor causes an internal short circuit between the signal and power terminals. This typically occurs in high-temperature, high-humidity environments or after driving through water.+2 more →
Actions
— Use the VDS2100 diagnostic tool to read the DTC freeze frame, confirm the sun sensor voltage when the fault occurred (usually reading above 5.0V or 12V), and observe if the current data stream remains abnormal.— Remove the upper dashboard trim panel and locate the sunlight sensor below the windscreen (usually integrated into the same module as the automatic headlight sensor). Disconnect the sensor connector.+4 more →
B2A2912›
This fault code indicates abnormal continuity between the air conditioning system defrost flap actuator (Mode Actuator/Defrost Motor) drive circuit and the vehicle positive power supply (12V/B+). In BYD new energy vehicles, the defrost motor is a stepper motor or DC servo motor that drives the mode flap inside the HVAC housing to switch between face, foot, defrost, and other air distribution modes. When the air conditioning control module (ACU) or body control module (BCM) detects a short to power in this motor control circuit, it triggers DTC B2A2912 and enters protection mode. The module stops drive output to the motor to prevent control chip burnout or wiring harness fires. This fault disables the front windshield defrost function, severely compromising driving visibility and safety in low-temperature or high-humidity environments. Secondary risks include blown air conditioning system fuses or control module overheating.
Causes
— Internal coil insulation damage in the defrost flap actuator causes a short circuit between the positive and negative terminals, or a seized motor bearing causes an abnormal current rise that the system misdiagnoses as a short circuit.— The under-dash wiring harness chafes against a sharp metal body edge, damaging the insulation and causing the motor drive wire to contact a constant power wire (such as the dashboard fuse box power supply wire).— Condensation leakage or water ingress from wading causes a short circuit between pins in the connector near the air conditioning evaporator housing (usually a 4-pin or 6-pin white plug), especially between PIN1 (power supply) and PIN3 (motor drive).+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000 or Launch X431) to read the complete DTCs and freeze frame data. Verify parameters such as ambient temperature and motor duty cycle at the time of the fault. Attempt to clear the fault code and observe if it recurs immediately.— Check the air conditioning system fuses in the engine compartment and under-dash fuse boxes (usually F1/10, F2/13, or 15A/20A fuses marked HVAC). If blown, replace with a fuse of the same rating. Do not install a higher-rated fuse.+5 more →
B2A2914›
DTC B2A2914 indicates a short to ground or open circuit in the HVAC Defrost Door Actuator drive circuit. The air conditioning control module (ACECU) controls this actuator via a PWM signal or LIN bus to switch the door to the front windshield defrost mode. The "14" in the fault code indicates the ECU detects abnormal circuit current: excessive current (short to ground) or zero/extremely low current (open circuit). This fault disables the front windshield defrost function, causing glass fogging in low-temperature, high-humidity environments and severely impairing driving visibility and safety. Additionally, due to the integrated logic between the thermal management and air conditioning systems, this fault may trigger a thermal management safety protection strategy, limit air conditioning compressor power, or illuminate the relevant high-temperature warning light.
Causes
— Defrost flap actuator internal motor coil burnt out or shorted to ground, causing abnormal resistance (normal: 20-80 Ω; short circuit: near 0 Ω; open circuit: infinite).— A worn or pinched wiring harness under the dashboard shorts the power or signal wire to body ground, or vibration breaks the wire, creating an open circuit.— Oxidation, pin back-out, or corrosion from water ingress at the actuator connector (usually located on the right side of the HVAC assembly, near the blower), causing excessive contact resistance or a complete open circuit.+2 more →
Actions
— Use a VDS2000 or Launch X431 diagnostic tool to read the complete fault codes. Check for accompanying faults such as B2A2912 (short to power) or B2A2992 (failed to reach position). Record the ambient temperature and air flap position from the freeze frame data.— Remove the trim panel below the passenger-side dashboard. Locate the defrost actuator (usually a white or black plastic box-shaped component with a 4-pin or 5-pin connector). Check the connector for looseness, water ingress, or obvious burn marks. Clean the terminals with electrical contact cleaner.+5 more →
B2A2992›
This DTC indicates the HVAC Defrost Mode Actuator fails to reach the control module's commanded target position within the specified time. The defrost motor, typically a stepper motor or DC gear motor with position feedback (potentiometer or Hall sensor), drives the mode door to engage the front windshield defrost mode. After sending a position command, the HVAC control module continuously monitors the position sensor feedback voltage (typically a 0-5V analog signal or PWM signal). The module triggers DTC B2A2992 if the deviation between the actual and target positions exceeds the threshold (e.g., 5%-10%) within the specified time (typically 10 seconds), or if it detects abnormal motor current (stall current). This fault disables the defrost function or causes abnormal airflow distribution. In low-temperature and high-humidity environments, the system fails to defog the front windshield, severely compromising driving safety.
Causes
— Internal gear binding, broken plastic gear teeth, or worn motor carbon brushes in the defrost flap actuator causing insufficient drive force.— Deformed air flap shaft inside the HVAC housing, broken or detached plastic linkage, or foreign objects (such as leaves, foam particles, or labels) jamming the air flap.— Poor contact or wear in the position sensor (potentiometer) causing an erratic signal, or an open or short circuit in the sensor power supply or signal circuit.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (ED400/VDS) to read the data stream. Compare the 'Defrost Damper Target Position' and 'Actual Position' values to confirm the deviation. Simultaneously check the data of other dampers (mode motor, fresh/recirculated air motor) to rule out a bus fault.— Operate the A/C panel to cycle through defrost/face/foot modes. Listen for an abnormal clicking or continuous buzzing noise inside the dashboard to determine if the motor is attempting to operate but is jammed.+3 more →
B2A2A12›
DTC B2A2A12 indicates a short to vehicle power positive (B+) in the HVAC mode door actuator motor or its control circuit. This stepper or DC geared motor drives the mode door to switch between face, foot, and defrost modes. The A/C ECU logs a short to power when it detects the motor drive circuit current abnormally exceeding the threshold (typically >2A) or the feedback voltage remaining continuously high. This fault causes: 1) the air outlet mode to lock in the default position (typically defrost or face mode) and prevents adjustment; 2) the controller’s internal driver chip to trigger overheat protection, potentially blowing a fuse; 3) a risk of circuit overheating in extreme cases. Because this fault impairs the front windshield defrost function, it carries a severe classification and requires immediate repair.
Causes
— Damaged or burnt internal winding insulation in the mode motor causes the coil to short directly to the motor housing or power terminal. This commonly occurs in older vehicles or motors with a history of air flap jamming.— Wiring harness chafing or pinching under the dashboard damages the insulation, shorting the motor control wire (typically a PWM signal or power wire) to the vehicle 12V power wire. This commonly results from improperly securing the harness after dashboard removal and installation.— Internal drive MOSFET breakdown in the air conditioning controller (AC ECU) causes continuous high voltage at the output terminal, triggering a false motor short circuit detection; or connector pin back-out, water ingress, and corrosion cause a short circuit between terminals.+2 more →
Actions
— Safety preparation: Turn off the vehicle, disconnect the low-voltage battery negative terminal, and wait 5 minutes for the system to completely power down. Wear insulated gloves and prepare a multimeter, megohmmeter, and VDS2000 diagnostic tool.— DTC confirmation: Connect the diagnostic tool, access the air conditioning system, and read the fault codes. Confirm B2A2A12 is present as a current fault (not a history fault). Record the voltage and temperature information from the freeze frame data, and check for accompanying B2A2A14 (short to ground) or communication fault codes.+7 more →
B2A2A14›
DTC B2A2A14 indicates a short to ground or open circuit in the A/C system mode door actuator (Mode Motor) control circuit. The mode motor is the core actuator in the HVAC door system, switching the door between FACE, FOOT, DEF, and other positions. This fault indicates the integrated Body Control Module (BCM) detects abnormal circuit current (high current indicates a short circuit; low current indicates an open circuit) or a lost position feedback signal when driving the mode motor. Consequently, the BCM cannot accurately control the door position. This fault locks the A/C outlet mode in a fixed position or causes complete failure, severely impacting driving comfort and safety (especially if the front windshield defogging function fails). This fault usually appears alongside DTC B2A2A92 (mode motor fails to reach position). As a hard-wired circuit fault, it requires immediate repair to prevent further damage to the BCM drive circuit.
Causes
— Mode motor internal damage: Worn motor brushes or burnt coils cause an internal short or open circuit, resulting in abnormal resistance (normal: 30-50 Ω).— Wiring harness connector fault: The mode motor 6-pin connector (especially pin 6 ground and pins 1-2 drive) exhibits backed-out terminals, corrosion, looseness, or poor contact; or vibration wear causes an open or short circuit in the wiring harness near the evaporator case.— Poor fuse holder contact: Drawing power for aftermarket devices (dash cam, GPS) deforms or creates excessive clearance at the instrument panel power distribution box IF03 (A/C fuse) or IF23 fuse holder terminals, causing intermittent power supply interruption.+2 more →
Actions
— Diagnostic scan: Connect the VDS diagnostic tool, read the integrated body controller fault codes, confirm B2A2A14 is present, and check for related fault codes such as B2A2A92 and B2A2C14. Read the data stream to verify the mode motor position feedback value changes with operation.— Power supply and fuse check: Check dashboard distribution box IF03 (air conditioning system fuse) and IF23. Verify correct fuse ratings (typically 10A or 15A). Inspect the fuse holder terminals for deformation or excessive clearance caused by tapping power for external equipment. Repair the terminal clearance if necessary.+5 more →
B2A2A92›
DTC B2A2A92 indicates the Mode Door actuator in the HVAC assembly cannot reach the target position commanded by the control module, or the actual position reported by the position sensor deviates from the target position by more than the allowed threshold (typically ±5°). This fault involves the A/C airflow direction control mechanism. The mode motor drives the mode door flap to switch airflow direction between face, foot, and defrost modes. The integrated Body Control Module (BCM) sets this fault code if it does not receive the correct position signal from the position sensor within the specified time after sending an adjustment command, or if it detects a motor stall or abnormal current. This fault causes the airflow mode to become fixed or unresponsive, reducing occupant comfort. It may also indirectly affect thermal management system efficiency (e.g., defrost function failure compromising safety).
Causes
— Mechanical binding or interference: worn or aging air flap shaft bushings, foreign objects (leaves, plastic debris) jamming the air duct, or a deformed or detached linkage mechanism, causing excessive motor load and preventing the motor from driving the flap into position.— Mode motor assembly fault: worn internal reduction gear set, motor rotor demagnetization causing insufficient driving force, or position sensor (potentiometer) signal drift or failure causing abnormal position feedback.— Wiring and power supply faults: loose, oxidized, or backed-out pins at the motor connector; excessive terminal spread at A/C fuse (IF03) (often due to aftermarket equipment); poor ground connection; or open circuit, resulting in excessive voltage drop.+2 more →
Actions
— Use the VDS diagnostic tool to read the fault code and freeze frame. Check the difference between the 'target air flap position' and 'actual air flap position' in the data stream to confirm if the deviation angle exceeds the 5° threshold.— Check the IF03 air conditioning fuse (10A/15A) in the engine compartment fuse box. Inspect the terminals for melting or excessive gaps (specifically check if aftermarket GPS or dash cam installations expanded the terminals). Measure the fuse downstream voltage; it must remain stable at ≥12V.+6 more →
B2A2B12›
DTC B2A2B12 indicates a short to vehicle power positive (B+) in the driver-side HVAC blend door actuator control circuit. The motor receives commands from the HVAC controller via LIN bus or PWM signal, drives the gear mechanism to adjust the hot/cold air mix ratio, and provides position feedback through a potentiometer or Hall sensor. A short to power typically results from insulation failure between the motor power supply line (usually constant 12V) and the signal or ground line, or an inter-turn breakdown in the motor internal winding causing abnormally low impedance. This fault causes the HVAC controller to detect abnormally high voltage (near battery voltage), trigger circuit protection, and cut off the circuit output. This prevents driver-side vent temperature adjustment (stuck in hot or cold position). Severe cases can burn out the HVAC controller internal driver chip or blow a fuse, affecting normal vehicle thermal management system operation.
Causes
— A burnt internal motor coil or inter-turn short circuit in the temperature flap actuator creates continuity between the power terminal and the signal/ground terminal, typically causing abnormal motor noise or binding.— Long-term chafing damages the internal instrument panel wiring harness insulation where it passes through the firewall or near the steering column, causing a short circuit between the power wire and the motor control wire.— Internal power drive MOSFET breakdown in the air conditioning controller (HVAC ECU) causes the output terminal to continuously output a high level, triggering a false short-to-power detection.+2 more →
Actions
— Use VDS or a dedicated diagnostic tool to read the complete fault code stream. Confirm if B2A2B12 is a current fault (Active). Check for accompanying B2A2B14 (short to ground) or communication fault codes, and record the freeze frame data.— Check the air conditioning system fuse in the engine compartment and under-dash fuse boxes (usually 10A-15A). If blown, replace it with a fuse of the same rating. Do not repeatedly test-run the system to prevent further damage.+7 more →
B2A2B14›
DTC B2A2B14 indicates an electrical fault in the driver-side A/C blend door actuator. This stepper or DC motor actuator drives the hot/cold blend door inside the HVAC unit to adjust the driver-side outlet temperature. A "short to ground" occurs when the motor power supply circuit (B+) or control circuit abnormally connects to the vehicle body ground (GND), typically due to damaged insulation or burnt motor windings. This condition can blow the fuse or trigger a protective shutdown of the A/C controller. An "open circuit" indicates interrupted electrical continuity in the motor circuit, likely caused by a burnt coil, broken wiring harness, or loose connector. This fault disables driver-side temperature adjustment, locking the door in the hottest or coldest position. Driving with an active short circuit risks wiring overheating or fire, classifying this as a severe fault.
Causes
— Driver's side temperature blend door actuator internal motor short or open circuit: motor carbon brush wear, burned commutator, or coil insulation aging causing an inter-turn short or short to ground.— Harness mechanical wear: Vibration and friction damage the insulation where the instrument panel harness passes through the firewall, near the steering column, or at instrument panel frame mounting points, exposing the wire to body metal and creating a short to ground.— Connector water ingress and corrosion: Poor sealing allows water to enter the connector between the A/C controller and actuator (usually located near the evaporator housing), causing a short circuit between terminals or an open circuit due to corrosion.+2 more →
Actions
— Connect the VDS or BYD dedicated diagnostic tool, read and confirm B2A2B14 is a current fault (Active), record the freeze frame data, and check for accompanying B2A2B12 (short to power) or communication fault codes.— Check the air conditioning system fuse in the instrument panel fuse box (IPM) (usually 10A-15A). If blown, locate and repair the short circuit before installing a replacement fuse of the same rating.+6 more →
B2A2B92›
This fault code indicates the driver-side HVAC (Heating, Ventilation, and Air Conditioning) temperature blend door actuator (hot/cold blend door motor) cannot reach the target position or the position feedback signal is abnormal. The actuator uses a stepper motor or DC motor to drive a gear mechanism, adjusting the hot/cold blend door opening (0-100%). This accurately controls the airflow mixing ratio through the heater core and evaporator, providing stepless adjustment of the outlet air temperature. The air conditioning controller (AC ECU) logs this fault code if the deviation between the actual and target positions continuously exceeds the calibrated threshold (typically 5-10%) or if the motor stall current times out. Triggering conditions include a faulty motor drive circuit, position sensor (potentiometer) signal drift, a binding gear drive mechanism, or excessive mechanical resistance at the blend door shaft. This fault causes driver-side temperature adjustment failure, abnormal outlet air temperature (stuck excessively cold or hot), unstable temperature control in automatic air conditioning mode, or a clicking gear noise during temperature adjustment.
Causes
— Worn, broken, or missing teeth in the internal plastic gear set of the air mix door actuator cause drive slippage or binding, preventing the door from reaching the target position.— Poor contact, carbon track wear, or resistance drift in the actuator position sensor (potentiometer) causes an inaccurate or erratic position feedback signal.— Mechanical binding of the air flap linkage or shaft (e.g., foreign objects in the HVAC housing, worn or deformed air flap shaft bushing, or lack of lubrication), causing excessive motor load and preventing the motor from reaching the target position.+2 more →
Actions
— Read fault codes using BYD VDS or a dedicated diagnostic tool. Confirm B2A2B92 is active and cannot be cleared. Check for accompanying fault codes (e.g., B2A2B14 circuit fault, B2A2C12 front passenger side fault). Record the ambient temperature and air flap position data stream at the time the fault occurred.— Perform the air flap actuator self-learning/initialization procedure: Access the air conditioning system special functions using the diagnostic tool, select 'Air Flap Initialization' or 'Actuator Reset', or disconnect the battery negative terminal for 10 minutes and reconnect power. Observe if the fault code changes to a history code or disappears.+5 more →
B2A2C12›
DTC B2A2C12 indicates a short to battery positive (B+) in the drive circuit of the passenger-side temperature control flap actuator (air mix motor/blend door actuator). In the BYD thermal management system, the air mix motor controls the hot and cold air mixing ratio via a PWM signal to adjust the passenger air outlet temperature. A short to power means the resistance between the motor power supply or control line and the battery positive terminal drops abnormally (typically <1Ω). This causes the HVAC ECU to detect an abnormal voltage (near 12V battery voltage instead of the normal 0-5V PWM signal or feedback voltage), triggering the overvoltage protection mechanism and stopping the motor drive. This fault prevents passenger-side temperature adjustment, typically leaving the flap stuck in a fixed position or defaulting to maximum hot or cold. Extreme cases risk wiring overheating, blown fuses, control module damage, or localized overheating.
Causes
— Damaged internal winding insulation in the heating/cooling motor causes an inter-turn short circuit or short to power (common with motor aging or overheating after prolonged binding).— Harness abrasion or pinching shorts the power wire to the motor drive wire or signal wire (commonly occurs at the instrument panel frame edge, HVAC housing seam, or harness retaining clips).— Breakdown of the internal power driver chip (MOSFET or H-bridge) in the air conditioning controller (HVAC ECU) causes the output terminal to short to power.+2 more →
Actions
— Fault confirmation and data stream reading: Use the VDS2000/3000 diagnostic tool to read the fault code and confirm B2A2C12 is present. Access the air conditioning system data stream. Verify the Actual Position and Target Position of the Passenger Side Temperature Control Motor match. Check if the motor position feedback voltage is abnormally high (close to battery voltage).— Power-off and circuit insulation test: Disconnect the 12V battery negative terminal. Unplug the air conditioning controller (HVAC ECU) and front passenger blend door actuator connectors. Use a multimeter to measure the resistance between the motor harness side drive pin and power (B+). A resistance of <1Ω confirms a short circuit. Simultaneously measure the resistance to ground to rule out a short to ground.+4 more →
B2A2C14›
DTC B2A2C14 indicates a drive circuit fault in the front passenger side temperature blend door actuator (hot/cold motor), specifically a short to ground (abnormal connection to vehicle ground causing overcurrent) or an open circuit (circuit interruption, infinite resistance). The integrated Body Control Module (BCM) controls this motor via a PWM signal or stepper drive to adjust the front passenger side hot/cold air mixing ratio, enabling dual-zone climate control. The BCM sets this DTC upon detecting abnormal motor drive current (excessive or zero), an abnormal position feedback signal, or a LIN communication fault. This fault prevents front passenger side temperature adjustment (sticking in the cold or hot position). In severe cases, the BCM may enter protection mode, limiting overall air conditioning system functionality and potentially affecting the thermal management system's control of battery or motor temperatures.
Causes
— Wiring harness wear causing a short to ground: A detached wiring harness retaining clip near the evaporator housing allows the harness to rub against the steering column or instrument panel frame. This wear damages the power or signal wire insulation, resulting in a short to ground.— Internal motor fault: Blend door motor internal coil shorted or burnt out, worn carbon brushes causing an open circuit, or gear mechanism binding or slipping, resulting in abnormal drive current.— Abnormal power supply: Poor contact at dashboard fuse IF03 (especially when aftermarket dash cam/GPS power taps deform fuse holder terminals and create excessive gaps), causing intermittent power connections or voltage drops.+2 more →
Actions
— Connect the VDS or dedicated diagnostic tool, read the complete fault code, and record the freeze frame data. Attempt to clear the fault code, then adjust the air conditioning temperature and observe if the fault reoccurs immediately.— Check fuse IF03 (air conditioning system fuse) in the instrument panel distribution box and confirm the correct rating (usually 10A or 15A). Check if aftermarket equipment spread or deformed the fuse holder terminals. Restore terminal clamping force if necessary.+7 more →
B2A2C92›
This DTC indicates the front passenger side temperature flap actuator (air mix flap motor) cannot reach the target position or the position feedback signal is abnormal. The integrated Body Control Module (BCM) drives this stepper/DC motor via the LIN bus or PWM signal to adjust the air mix flap opening and control the front passenger outlet temperature. "Cannot reach position" means the motor fails to reach the target angle within the set time (typically 3-5 seconds), or the position sensor feedback voltage deviates from the expected value by more than the threshold (generally >5%). This fault disables front passenger temperature adjustment (no hot or cold air). Severe cases may cause abnormal flap noise or trigger air conditioning system protection mode, but typically do not affect vehicle driving safety.
Causes
— Internal damage to the temperature blend door actuator motor (worn gear set, seized motor rotor, or excessively worn carbon brushes), causing insufficient drive force to overcome blend door resistance.— Poor wiring contact or open circuit, especially excessive pin clearance or deformation at the instrument panel distribution box A/C fuse socket (e.g., IF03), causing excessive power supply voltage drop (common after tapping power for aftermarket accessories like GPS units and dash cams).— Air flap mechanism jammed (broken flap shaft, deformed plastic flap, detached foam seal causing binding, or foreign object blocking the air duct), causing motor stall and triggering protection.+2 more →
Actions
— Connect the VDS diagnostic tool, read all fault codes, and record the freeze frame data. Verify if related fault codes such as B2A2C14 (short to ground/open circuit) accompany B2A2C92. Check if the BCM software version requires an upgrade.— Check the air conditioning system fuse (IF03, etc.) in the instrument panel power distribution box. Inspect the fuse holder terminals for excessive clearance, looseness, or burn damage caused by aftermarket devices (GPS, dash cam) drawing power. Measure the voltage drop across the fuse; it must be <0.1V.+4 more →
B2A2F09›
DTC B2A2F09 indicates the air conditioning thermal management system detected abnormal refrigerant line pressure. Specifically, the high-pressure side pressure sensor reading falls outside the normal range (too high or too low). This fault involves the electric compressor high-pressure line monitoring circuit. The system triggers the fault when the pressure sensor detects a high-pressure side pressure > 3.2 MPa (overpressure protection) or < 0.2 MPa (underpressure protection). This fault activates the air conditioning system safety protection mechanism and forces an electric compressor shutdown to prevent pipe rupture or compressor dry running, resulting in a loss of cooling. In BYD new energy vehicles with highly integrated thermal management systems, this fault may also impair the battery cooling function, triggering vehicle thermal management power derating protection.
Causes
— High-pressure line pressure sensor body damage or installation damage (stripped threads or aging seal ring causing poor internal circuit contact)— Pressure sensor wiring harness circuit fault (B13-2 pin signal wire open circuit, short to ground, or abnormal 5V reference voltage/ground circuit)— Abnormal refrigerant charge amount (system leak causing insufficient refrigerant and excessively low pressure, or overcharging causing excessively high pressure on the high-pressure side)+2 more →
Actions
— Use the VDS2000 diagnostic tool to read the fault code and freeze frame data. Record the specific pressure value, ambient temperature, and compressor speed when the fault occurred to determine whether the high pressure is too high or the low pressure is too low.— Perform a static pressure test: Allow the vehicle to sit for 2 hours, then measure the high and low-side pressures. The standard value is 0.6-0.8MPa (at 25℃). A significant deviation indicates an abnormal refrigerant charge.+7 more →
B2A3214›
This DTC indicates the air conditioning control unit (ACU) or thermal management controller detects an abnormal electrical condition in the front HVAC blower motor power supply circuit, specifically a short to body ground (impedance <1Ω) or an open circuit/high resistance (impedance >10kΩ). In the BYD e-platform architecture, a PWM (pulse-width modulation) or LIN bus communication speed control module typically controls the blower motor. The ACU determines the circuit status by monitoring the blower motor current or feedback signal. The ACU triggers this DTC when it detects sustained high current (short circuit) or zero current (open circuit) exceeding the calibrated threshold (typically 200ms-1s). This fault prevents the front HVAC module from supplying air and affects cabin temperature regulation. In extreme cases, a short circuit can overheat the wiring harness and trigger the high-voltage interlock protection.
Causes
— Burnt blower motor internal windings or worn commutator causing a short to the housing. Common in vehicles over 3 years old or vehicles operating under prolonged high air conditioning loads.— Assembly issues or vibration typically cause the instrument panel wiring harness insulation to chafe at the firewall pass-through hole and contact body metal, resulting in a short to ground.— Internal power transistor breakdown and short circuit in the blower speed control module (Power Transistor) causes the ACU to detect an abnormally high current.+2 more →
Actions
— Safety preparation: Wear insulated gloves, disconnect the high-voltage service disconnect (MSD), wait 5 minutes to ensure the high-voltage capacitors fully discharge, and disconnect the 12V battery negative terminal.— Fault confirmation: Use the VDS2000 or DiLink diagnostic tool to read all DTCs. Check for accompanying fault codes (such as B2A3314 speed control signal fault). Record the current value in the freeze frame data.+6 more →
B2A3314›
DTC B2A3314 indicates a short to ground or open circuit in the Front Left Corner Sensor signal circuit. This fault code belongs to the Park Assist System (APA) / Around View Monitor (AVM) system, not the thermal management system. The APA control module sets this fault when it detects the Front Left Corner Sensor signal voltage remains below 0.5V (short to ground) or above 4.5V (open circuit) for more than 500ms. This fault causes front left obstacle detection failure, potentially triggering false park assist warnings or complete loss of function. The system classifies this as a severe fault because it may affect Automatic Emergency Braking (AEB) operation in extreme cases.
Causes
— Radar sensor internal coil open or short circuit, typically resulting from physical impact, aging, or internal water ingress due to seal failure.— Wiring harness chafing or pinching causes the signal wire to short to ground or open circuit. Common locations include where the front bumper harness passes through the wheel arch, side member, or front compartment firewall.— Loose sensor connector, corroded pins, or failed sealing ring, especially common after water wading, car washing, or in high-humidity environments.+2 more →
Actions
— Use the BYD VDS2000 dedicated diagnostic tool to read fault codes, confirm if B2A3314 is a current fault, and check for related history fault codes (such as U024587 communication fault).— Visually inspect the left front radar sensor and verify the sensor surface has no scratches or deformation, the installation gap meets the standard (0.5-1.0mm), and the bumper shows no signs of modification.+6 more →
B2A4B12›
DTC B2A4B12 indicates a short to power in the HVAC circulation air door actuator drive circuit. When driving the circulation motor (typically a 12V DC permanent magnet or stepper motor), the AC ECU detects an abnormally low-resistance path between the motor drive circuit (M+ or M- terminal) and the vehicle power supply (B+), causing an abnormal current increase. This hard short circuit triggers the controller's overcurrent protection. Severe cases may cause: 1) the air door to stick in the recirculation or fresh-air position, failing to switch based on operating conditions; 2) the motor to stall and overheat, reducing thermal management efficiency; 3) reverse short-circuit current to damage the AC ECU power drive module; 4) a fire risk due to continuous circuit heating in extreme conditions. This fault and B2A4B14 (short to ground/open circuit) form a mutually exclusive diagnostic pair that jointly monitors the circulation motor circuit integrity.
Causes
— Insulation breakdown on the recirculation motor internal coil causes the enameled wire to short to the motor housing or power terminal. This commonly occurs in vehicles over 5 years old or actuators operating in prolonged high-temperature environments.— Harness wear or crushing exposes the power wire, causing physical contact with the circulation motor drive signal wire. This frequently occurs in vibration and friction areas near the firewall wiring grommet, instrument panel frame edge, or blower assembly.— Internal breakdown and short circuit of the H-bridge driver chip or MOSFET power transistor in the air conditioning controller (AC ECU), keeping the motor terminals continuously energized. This often occurs simultaneously with other motor-related fault codes (such as mode motor and temperature motor faults).+2 more →
Actions
— Connect the VDS or BYD dedicated diagnostic tool and read the complete air conditioning system DTCs. Confirm only B2A4B12 or related fault codes exist. Record the freeze frame data (motor duty cycle and voltage values at the time of occurrence).— Operate the A/C control panel to test the fresh air/recirculation switching function. Check for air flap binding, abnormal motor noise, or an inoperative motor. Verify if the fault code is a current fault (Active).+5 more →
B2A4B14›
This DTC indicates a fault in the drive circuit of the HVAC Recirculation Air Door Actuator motor. Specifically, a "short to ground" indicates insulation failure between the motor supply line (typically the PWM control line or power line) and the vehicle body ground (GND), causing abnormal current leakage. An "open circuit" indicates a broken internal motor coil, a loose connector, or a severed wiring harness. This motor switches the HVAC air door between fresh air and recirculation modes. A fault prevents mode switching or causes the door to stick in a fixed position, reducing cabin temperature control efficiency. In extreme cases, this reduces battery thermal management performance (e.g., preventing effective heat dissipation via fresh air mode). Therefore, the system classifies this as a severe fault.
Causes
— Recirculation air flap actuator motor internal coil burned out or short-circuited: Prolonged motor jamming or overload damages the coil insulation, causing a short to ground or internal open circuit.— Wiring harness and connector fault: Water ingress or poor sealing corrodes or oxidizes pins in the wiring harness connector near the HVAC unit (usually located behind the glove box or at the firewall), or vehicle vibration loosens the male and female terminals.— Motor damage caused by mechanical binding: Foreign matter (such as leaves or accumulated dust) jams the air flap mechanism, or the linkage mechanism deforms. Excessive motor stall current eventually burns out the drive circuit or motor winding.+2 more →
Actions
— Diagnostic confirmation: Use the BYD VDS diagnostic tool to read all DTCs. Confirm if B2A4B14 is present alone or with related fault codes. Record the freeze frame data (such as motor duty cycle and position feedback values when the fault occurred). Clear the fault codes, operate the fresh air/recirculation switch, and confirm if the fault returns.— Visual and connector inspection: Remove the glove box or passenger lower trim panel and locate the recirculation flap actuator (usually marked 'REC' or 'Intake'). Inspect the connector for looseness, backed-out pins, or green/white corrosion. Measure the connector terminal resistance to ground to check for a short circuit.+5 more →
B2A4B92›
This fault code indicates abnormal damper actuator position control within the air conditioning thermal management system. Specifically, the recirculation door or blend door servo motor fails to reach the target position within the set time (typically 3-5 seconds), or the actual position feedback from the position sensor (generally a Hall effect sensor) deviates from the controller command by more than the threshold (typically >5%). According to the control logic, the AC controller outputs a PWM signal to drive the motor while monitoring the sensor feedback voltage (0.5-4.5V range). The controller triggers this code upon detecting a motor stall, step loss, sensor signal interruption, or abnormal voltage. This fault disables fresh air/recirculation switching, delays cabin temperature adjustment, and causes abnormal demist mode operation. In extreme cases, it affects battery pack cooling efficiency on vehicles utilizing an A/C refrigerant battery cooling architecture.
Causes
— Recirculation flap actuator internal gear set worn or broken: The actuator uses plastic reduction gears. After long-term use, thermal expansion and contraction or dried grease causes the gears to slip or strip, resulting in the motor spinning freely while the flap fails to actuate.— Abnormal position sensor signal: A loose Hall sensor solder joint, a displaced magnetic ring, or metal debris on the sensor surface causes the feedback signal to fluctuate or distort, leading the controller to falsely determine the actuator failed to reach its target position.— Mechanical binding: air flap shaft bushing wear generating debris, improperly installed cabin air filter deforming and obstructing the air flap, or evaporator icing or foreign objects (such as leaves or small animals) jamming the air flap linkage mechanism.+2 more →
Actions
— Use the VDS2000 or VDS3100 diagnostic tool to read the freeze frame data. Record the ambient temperature, set temperature, and the difference between the motor target position and actual position at the time of the fault to confirm if it is an intermittent fault. Clear the DTC, operate the fresh air/recirculation switch for 10 cycles, and observe if the fault reoccurs.— Remove the glove box or center console. Visually inspect the recirculation flap actuator (typically a white or black plastic box-shaped component located above the blower) for proper installation. Inspect the wiring harness connector (BYD standard part number: KPB-4P-XXX) for green corrosion or looseness. Measure the power supply voltage at connector pins 1-2 (should be 12V±0.5V with key ON). Measure the signal wire resistance to ground at pins 3-4 (should be >1MΩ).+4 more →
B2A4E13›
DTC B2A4E13 indicates an open control circuit fault in the left front (driver side) seat belt pretensioner. It belongs to the body safety system (SRS), not the thermal management system. DTC structure breakdown: 'B' represents the Body system, '2A4E' designates the left front seat belt pretensioner control circuit, and '13' indicates an open circuit. The Airbag Control Unit (ACU) triggers this fault upon detecting abnormal resistance (open circuit or excessive resistance) in the pretensioner circuit, which prevents the formation of an effective monitoring circuit. This fault continuously illuminates the instrument cluster SRS warning light and forces the airbag system into a degraded mode. In extreme cases, it prevents the pretensioner from deploying during a collision, posing a severe safety risk. Note: Unofficial sources sometimes incorrectly label this code as a high-voltage line pressure sensor fault; it strictly indicates a seat belt pretensioner circuit fault.
Causes
— Seat belt pretensioner connector under the left front seat is loose, not fully locked, or has oxidized/corroded terminals, causing excessive contact resistance or an open circuit.— Repeated bending during fore/aft seat movement breaks internal wires in the wiring harness transition area between the vehicle floor and the seat (especially near the seat slide rail).— Vehicle wading or damp environments cause water ingress and oxidation at the pretensioner connector, or a damaged wiring harness sheath causes terminal corrosion.+2 more →
Actions
— Safety preparation: Set the vehicle to OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the airbag system and prevent accidental deployment.— Visual inspection: Remove the left front seat (leave the wiring harness connected). Verify the yellow plug (pretensioner connector) under the seat is fully locked. Inspect for water ingress, oxidation, or burn marks.+5 more →
B2A4F11›
DTC B2A4F11 indicates a short to battery in the signal circuit of the air conditioning system high-pressure line pressure sensor. In BYD new energy vehicle thermal management systems, a 5V reference voltage typically powers this sensor. The sensor outputs a 0.5–4.5V analog voltage signal reflecting the refrigerant high-side pressure (normal range approximately 0.8–2.8V, corresponding to 0.3–3.0MPa). The ECU logs a short to battery when it detects the sensor signal voltage remaining above 4.8V or near the reference supply voltage (5V) for longer than the calibrated time (typically over 200ms). This fault prevents the air conditioning ECU from accurately reading high-side pressure data and triggers system protection strategies: disabling the electric compressor and suspending cooling/heating functions. In severe cases, the system may limit vehicle power output to prevent loss of thermal management control. The short circuit can occur within the sensor, the wiring harness connector, or the internal ECU sampling circuit.
Causes
— Damaged high-pressure sensor wiring harness insulation contacts a nearby 12V power wire (such as the compressor controller power supply or PTC heater power wire), causing a short circuit. This commonly occurs at harness bend points, such as the engine compartment firewall or fender liner.— Pressure sensor internal integrated circuit failure causing internal breakdown between the signal output terminal and power input terminal. This typically results from prolonged vehicle operation in high-temperature environments or abnormal refrigerant pressure shocks.— Air conditioning controller (ECU) internal signal sampling circuit fault, abnormal pull-up resistor, or damaged chip input stage, resulting in a false sensor short circuit detection.+2 more →
Actions
— Safety preparation: Turn the vehicle OFF, disconnect the 12V battery negative terminal, wait 5 minutes to ensure the high-voltage system de-energizes, wear insulated gloves and safety goggles, and verify the high-voltage interlock circuit is disconnected.— Fault confirmation: Connect the VDS2000/VDS3100 diagnostic tool. Read the air conditioning system fault codes. Confirm B2A4F11 is a current fault (Active). Record freeze frame data (ambient temperature, battery temperature, compressor speed, etc.). Analyze the operating conditions at the time of the fault.+5 more →
B2A5112›
DTC B2A5112 indicates a short circuit in the thermal management system Pressure Transducer (PT). Specifically, the signal circuit shorts to power or ground (BYD DTC subtype definition '12' typically indicates a short to power). This sensor mounts in the air conditioning high-pressure line or battery coolant circuit. It monitors refrigerant or cooling system pressure in real time, providing key parameters to the thermal management controller (TMS) or air conditioning controller to regulate electric compressor speed, electronic expansion valve opening, and cooling fan speed. During a short circuit, the controller loses accurate pressure readings and enters fail-safe mode. This can disable the air conditioning, reduce battery cooling, and trigger motor over-temperature protection. In severe cases, the system limits drive power or disables driving to prevent critical component damage from thermal management failure.
Causes
— PT pressure sensor internal short circuit: The sensor's pressure-sensitive element or signal processing circuit shorts internally due to overvoltage, aging, or manufacturing defects, connecting the signal wire directly to power or ground.— Wiring harness worn or crushed: Vibration chafing, sharp edges, or bottoming out damages the sensor wiring harness insulation in the engine compartment or under the chassis, shorting the signal wire (usually the 5V reference voltage wire) to the 12V power wire or body ground.— Connector water ingress and corrosion: Aged sensor plug seals, improperly seated connectors, or water ingress from washing or wading cause electrolytic corrosion between pins, creating a short circuit. This fault occurs frequently in damp environments.+2 more →
Actions
— Fault Confirmation and Freeze Frame Analysis: Use the BYD dedicated diagnostic tool (VDS2000/VDS2100) to read the fault code. Confirm B2A5112 is a current fault (Present), not a history fault. Record the freeze frame data, including ambient temperature, compressor speed, and pressure sensor voltage at the time of the fault, to determine if this is an intermittent fault or a continuous short circuit.— Visual and connector inspection: Disconnect the low-voltage service switch for high-voltage safety. Inspect the PT pressure sensor connector (located at the A/C high-pressure line or battery cooling line interface) for backed-out pins, water ingress, ablation, or corrosion. Measure the resistance between the connector pins to verify no abnormal continuity.+3 more →
B2A5811›
This DTC indicates a short to ground in the driver-side face vent (FACE mode) temperature sensor signal circuit. The sensor is an NTC (negative temperature coefficient) thermistor. During normal operation, it sends a 0.5-4.5V analog voltage signal to the air conditioning control unit (ACU) to indicate the vent outlet temperature. When the ACU detects the signal voltage remains below 0.1V (logic low threshold) for longer than the set time (typically 200-500ms), it determines a short to ground. This fault causes the ACU to enter Limp Home Mode, disables independent dual-zone temperature control, and may lock the driver-side temperature flap in the full cold or full hot position, severely affecting air conditioning comfort. In extreme cases, continuous full-load compressor operation affects overall vehicle energy consumption.
Causes
— Thermistor breakdown or encapsulation failure inside the temperature sensor body causes the signal terminal to short to the housing/shielding layer.— During removal and installation, retaining clips or sharp metal bracket edges chafed the internal dashboard wiring harness and damaged its insulation, causing the signal wire (usually the cathode wire) to contact body ground.— Seal failure at the connector between the air conditioning controller and the sensor (usually located on the evaporator housing or dashboard crossmember) allows water ingress, causing a short circuit between terminals or a short to the housing.+2 more →
Actions
— Use VDS2000 or the BYD dedicated diagnostic tool to read complete DTC and freeze frame data. Record the ambient temperature, air outlet temperature set value, and actual feedback value when the fault occurred. Confirm whether B2A5811 is a current fault (Present).— Remove the trim panel below the driver's side dashboard and locate the face outlet air temperature sensor (usually located on the evaporator housing outlet air duct, with a white or grey 2PIN connector). Visually inspect the connector for looseness, water ingress, or burn marks.+5 more →
B2A5C14›
DTC B2A5C14 indicates a short to ground or open circuit in the Heater Core Three-Way Water Valve drive motor circuit. The three-way water valve acts as a key thermal management system actuator. It controls the flow path of engine coolant or PTC heating fluid to the heater core to distribute flow for cabin heating and battery thermal management. Damaged wiring insulation contacting the vehicle body typically causes a short to ground; the resulting excessive current can burn out the drive circuit. Broken wiring, a loose connector, or a burnt-out internal motor winding can cause an open circuit. This fault completely disables the heating function and forces the thermal management system into Limp Home mode. In extreme cases, it compromises battery temperature regulation. Consequently, the system classifies this as a Level 3 (severe) fault and triggers a protection mechanism. This restricts continued vehicle use to prevent circuit overheating or further damage.
Causes
— Worn or pinched three-way coolant valve motor power or control harness, causing a short to body or an open circuit from a broken wire (commonly due to interference between the front compartment harness and engine bracket).— Burned out water valve motor internal coil, damaged insulation causing a short to ground, worn motor carbon brushes, or corroded connector causing an open circuit.— Water ingress, oxidation, corrosion, or backed-out pins at the motor connector (plug/socket) causing poor contact (presenting as an intermittent open circuit) or a short circuit between terminals.+2 more →
Actions
— Fault Confirmation: Use VDS or a dedicated diagnostic tool to read the fault codes. Confirm B2A5C14 is a current fault, not a history fault, and record the freeze frame data. Check if the heating function is inoperative. Listen for the water valve operating sound (clicking).— Visual inspection: Locate the heater core three-way water valve (usually near the front compartment firewall or at the heater core inlet pipe; on the Qin PRO series, mostly on the left side of the compartment). Inspect the motor wiring harness for obvious damage, crushing, or burn marks. Inspect the connector for looseness, water ingress, or corrosion.+5 more →
B2A5911›
This DTC indicates a short to chassis ground (GND) in the signal circuit of the driver-side Foot Outlet Temperature Sensor. In the BYD thermal management system, this NTC thermistor sensor monitors the actual temperature at the foot air duct outlet. The signal voltage is typically a 0-5V analog signal. A short to ground causes the ECU to continuously read an abnormally low voltage near 0V, registering a corresponding temperature of -40℃ or an extreme low. This forces the air conditioning control unit into fault protection mode. The system may force the compressor off, switch to demist mode, or restrict battery coolant flow. These conditions severely impact occupant comfort and battery/motor thermal management efficiency. In extreme cases, this triggers high-voltage system overheat protection.
Causes
— A breakdown and short circuit of the thermistor inside the sensor body causes continuity between the signal and ground terminals.— Vibration wears through the wiring harness insulation where it passes through the dashboard or floor, causing the signal wire (usually yellow/green or blue/white) to contact the metal body frame.— Condensation leakage inside the A/C duct causes a short circuit or corrosion between sensor connector pins (typically located on the duct housing).+2 more →
Actions
— Use the VDS2000/3000 diagnostic tool to read the complete fault code stream, confirm B2A5911 is a current fault (Present) rather than a history fault, and check if 'Driver footwell temperature' in the data stream displays -40°C, 0°C, or a fixed extremely low value.— Remove the driver-side footwell air outlet trim panel and locate the temperature sensor (usually on the lower surface of the air duct, 2-pin connector). Inspect the connector for looseness, water ingress, or obvious corrosion. Measure the sensor resistance (normal is approx. 1.8-2.2 kΩ at 25°C; close to 0 Ω when shorted to ground).+5 more →
B2A5913›
This DTC indicates an open circuit in the signal circuit of the driver-side footwell air outlet temperature sensor (NTC negative temperature coefficient thermistor). In BYD dual-zone/multi-zone automatic air conditioning systems, this sensor provides real-time footwell air outlet temperature feedback to the air conditioning controller (integrated into the right domain controller) for closed-loop temperature control. An internal open circuit in the sensor, an open circuit in the wiring harness, or poor connector contact causes the controller to detect a signal voltage outside the valid range (typically reading -40°C or a fixed high voltage) and trigger this DTC. This fault disables driver-side temperature control and may force the compressor into protection mode. In extreme cases, it disrupts the coordinated operation of the battery thermal management system (on models with coupled air conditioning and battery cooling circuits).
Causes
— Open circuit in the sensor body internal NTC element: Long-term thermal cycling causes the thermistor to age and fracture, or internal solder joints are cold or detached.— Abnormal pins in right domain controller G86(G) connector: Pin 27 (signal) or pin 28 (ground) bent, backed out, or spread, causing excessive contact resistance or a complete open circuit (this connector sits below the right front A-pillar; previous repair work easily damages it).— Wiring harness physical damage: Dashboard removal and installation, carpet water ingress, or loose harness retaining clips cause signal wire chafing or breakage, especially at the connection between the HVAC assembly and the body harness.+2 more →
Actions
— Diagnostic tool data stream verification: Connect the VDS or Launch diagnostic tool, enter the air conditioning system, and read the 'driver footwell temperature' data stream. Verify if it displays -40°C, 255°C, or a fixed abnormal value.— Connector physical inspection: Disconnect the battery negative terminal, remove the right front lower guard panel, and check the condition of pins 27 (signal) and 28 (ground) on the right domain controller G86(G) connector. Use the dedicated terminal removal tool to straighten bent pins, and check for pin push-back and terminal oxidation.+5 more →
B2A5A11›
This DTC indicates a short to ground in the signal circuit of the front passenger side FACE mode outlet air temperature sensor. In the BYD dual-zone automatic air conditioning system, this sensor uses an NTC (negative temperature coefficient) thermistor. Under normal conditions, sensor resistance decreases as temperature increases (approximately 2 kΩ at 20°C). The air conditioning controller calculates the actual outlet air temperature by detecting the voltage signal (typically in the 0-5 V range) through a voltage divider circuit. When the signal wire shorts to the vehicle body ground, the controller detects a continuous voltage below 0.1 V (or close to 0 V) and sets DTC B2A5A11. This disables the front passenger side temperature control. The air conditioning system may enter limp mode and default to a fixed output temperature, reducing passenger comfort. In extreme cases, false readings may trigger thermal management system protection.
Causes
— A breakdown and short circuit of the thermistor inside the temperature sensor body directly grounds the signal terminal.— Damaged wiring harness insulation inside the right dashboard A/C duct causes the signal wire to contact the metal duct or sharp body edges and short to ground.— Poor sensor connector sealing allows A/C condensate ingress, causing a short circuit between pins or a short to ground.+2 more →
Actions
— Connect the VDS2000 or BYD dedicated diagnostic tool, read the fault codes to confirm B2A5A11 is a current fault, and record the ambient temperature value from the freeze frame data.— Remove the passenger-side lower dashboard trim panel and locate the face outlet temperature sensor (usually located inside the right HVAC assembly outlet duct). Disconnect the connector and measure the sensor resistance: at 20°C, it should be 1.8-2.2 kΩ. If it reads 0-10 Ω, the sensor is internally shorted. Replace the sensor.+5 more →
B2A5A13›
This DTC indicates an open circuit fault in the front passenger side face vent (face mode) temperature sensor circuit. The BYD dual-zone automatic air conditioning system uses an NTC (negative temperature coefficient) thermistor as the temperature sensor. Its resistance decreases as temperature rises. If an open circuit occurs in the sensor body, wiring harness, or connector, the air conditioning controller (AC ECU) detects a continuous high signal voltage (typically near the 5V reference voltage). This exceeds the normal operating voltage range (0.5V-4.5V), prompting the AC ECU to log an open circuit fault. This fault forces the front passenger side temperature control into fail-safe mode. The air conditioning system cannot accurately regulate the front passenger side outlet air temperature. Symptoms may include one side blowing cold while the other blows hot, the compressor running continuously at high frequency or failing to start, and dual-zone synchronization failure. A prolonged fault may reduce air conditioning system efficiency and increase high-voltage battery power consumption.
Causes
— Internal open circuit in the sensor body: Aged and fractured NTC thermistor or pin dry solder joint, resulting in infinite resistance.— Wiring harness break or wear: The copper core of the passenger-side dashboard internal wiring harness fractures under frequent temperature changes or vibration stress, leaving the insulation visually intact (hidden break).— Poor connector contact: G86 connector (usually located near the front passenger-side air duct) has backed-out pins, oxidation, corrosion, or a loose locking tab, causing an intermittent connection.+2 more →
Actions
— Diagnostic tool verification: Use the VDS2000/BYD dedicated diagnostic tool to read the live data stream. Confirm the front passenger face vent temperature sensor displays -40°C or 255°C (depending on calibration logic) and differs significantly from other air outlet temperature sensors.— Physical location check: Remove the passenger-side lower dashboard trim panel and locate the temperature sensor mounting position (usually at the face-level air duct outlet). Visually inspect sensor connector G86 for looseness, backed-out pins, or signs of water ingress.+4 more →
B2A5B11›
This DTC indicates the Passenger Side Floor Vent Temperature Sensor signal circuit shorts to body ground (GND). In the BYD thermal management system, this sensor uses a negative temperature coefficient (NTC) thermistor. During normal operation, it changes resistance between 2-10kΩ as the vent temperature changes, outputting a 0.5-4.5V analog voltage signal to the HVAC ECU. A short to ground pulls the signal voltage near 0V. The controller detects this abnormal signal, typically interpreting it as an excessively high temperature or a circuit fault. This condition causes the following: 1) The passenger side floor vent closed-loop temperature control fails, potentially resulting in continuous maximum cooling or heating and affecting occupant comfort. 2) The air conditioning system enters fault protection mode and limits compressor speed. In extreme cases, this affects the heat exchange efficiency of the battery pack thermal management circuit. 3) In extreme ambient temperatures, the incorrect temperature signal causes the thermal management system to miscalculate and trigger vehicle power limitation.
Causes
— Thermistor breakdown or packaging failure inside the temperature sensor causes internal continuity between the signal and ground terminals.— Worn wiring harness insulation near the front passenger footwell air outlet (commonly below the A-pillar, at the evaporator housing edge, or at the floor harness retaining clip) allows the signal wire (usually yellow/black or white/black) to directly contact the vehicle body metal frame.— Bent or backed-out pins in the air conditioning controller connector (such as G64, G65, or G22, depending on vehicle model), or metallic debris between the pins, causing a short circuit between the signal and ground pins.+2 more →
Actions
— Use the VDS2000 or VDS2100 diagnostic tool to read the air conditioning system data stream and check the 'Passenger Foot Outlet Temp' value. Verify if the value remains fixed at -40°C (below lower limit) or 150°C (above upper limit) and does not change when adjusting the air conditioning temperature.— Disconnect the temperature sensor connector located on the lower passenger-side evaporator housing or footwell air duct (typically a 2-pin black waterproof connector). Use a multimeter to measure the resistance between the two pins on the sensor body. At 25°C, the normal resistance is 2-10 kΩ (refer to the specific vehicle workshop manual; e.g., Qin Pro is approx. 4.5 kΩ). If the resistance is near 0 Ω or infinity, replace the sensor.+5 more →
B2A5B13›
DTC B2A5B13 indicates an open signal circuit in the Passenger Side Floor Vent Temperature Sensor. This sensor typically uses a Negative Temperature Coefficient (NTC) thermistor and mounts at the passenger-side air-conditioning duct outlet. It monitors the footwell outlet air temperature in real time and provides closed-loop control feedback for the dual-zone or multi-zone automatic air-conditioning system. When the ECU detects the sensor signal voltage continuously exceeding the calibrated threshold (typically corresponding to infinite resistance or >100kΩ), it sets an open circuit fault. This fault prevents the air-conditioning controller from reading the actual passenger-side outlet air temperature and may trigger a fail-safe mode. The system may disable the independent passenger-side temperature control, force a default temperature (e.g., 24℃), or operate solely based on the driver-side setting. This severely impacts occupant comfort but does not directly affect the vehicle powertrain or safety systems.
Causes
— Internal open circuit in the sensor body: NTC thermistor element aging, internal cold solder joints, or lead breakage from vibration. This results in an infinite resistance reading at room temperature.— Wiring harness connector fault: The mating connector between the front passenger side floor wiring harness and the body wiring harness (usually located under the front passenger seat or near the A-pillar) has a loose connection, backed-out terminals, water ingress/oxidation, or poor contact.— Wiring harness physical damage: Long-term chafing causes copper wire breakage in the internal instrument panel harness where it interferes with air flap actuator movement, or in the floor harness at the seat tracks.+2 more →
Actions
— Fault Confirmation and Freeze Frame Analysis: Use VDS or X431 to read the DTC freeze frame. Record the ambient temperature, air outlet mode, and sensor voltage values at the time of the fault. Determine whether the fault is continuous (current code) or intermittent (history code).— Visual and physical inspection: Check the front passenger footwell air duct temperature sensor connector (usually located on the right side or underneath the air duct) for looseness. Inspect the pins for green oxidation, backed-out pins, or deformation. Check the floor wiring harness for seat crush damage or signs of water ingress.+4 more →
B2A5C12›
This DTC indicates a short to battery positive in the power supply or drive circuit of the heater core three-way coolant valve control motor. A stepper or DC motor drives the three-way coolant valve (typically installed at the heater core inlet) to regulate the coolant flow ratio to the heater core, enabling precise cabin heating temperature control. A short to power occurs when the motor coil, control wiring harness, or connector terminals abnormally connect to the vehicle 12V power supply (or the converted high-voltage power supply). This triggers motor driver chip overcurrent protection or burns out the chip. In severe cases, it blows the fuse and causes complete heating system failure. In Qin PRO DM/EV models, the air conditioning controller (or integrated thermal management controller) controls this valve via PWM or the LIN bus. A short circuit triggers fail-safe mode and disables the heating function to prevent wiring overheating.
Causes
— Wiring harness wear or crushing: In the high-temperature engine compartment, the three-way coolant valve motor wiring harness interferes with and rubs against sharp metal body edges, the exhaust pipe, or the high-voltage wiring harness. This friction damages the insulation, allowing the copper wire to contact a power wire (such as 12V constant power or ignition power) and cause a short circuit.— Internal motor short circuit: Aged or damp insulation on the three-way water valve motor coil shorts the winding to the motor housing (ground) or internal power terminal. Signs of motor overheating and burnout usually accompany this fault.— Connector water ingress and corrosion: When driving the vehicle through water or washing the motor compartment, a poorly sealed water valve connector allows water ingress, causing an electrolytic short circuit between the terminals. This frequently occurs during the rainy season or after driving through water.+2 more →
Actions
— Fault confirmation and freeze frame reading: Use the VDS2000 or Launch diagnostic tool to read the DTC B2A5C12 status (current/history). Record the freeze frame data (voltage and temperature when the fault occurred) and verify the fault is present. Disconnect the battery negative terminal for 5 minutes, restore power, and observe if the fault code reappears immediately.— Visual inspection and insulation test: Inspect the three-way coolant valve body (located on the heater hose in the front compartment) for deformation or burning, and check the connector for looseness or water ingress. Use a multimeter to measure the resistance between the motor power supply pins (usually a 2-pin or 3-pin connector) and vehicle ground. The resistance must be greater than 10 MΩ. A lower value indicates a short circuit.+3 more →
B2A6600›
This DTC indicates the vehicle control system disabled high-voltage components of the thermal management or air conditioning systems (e.g., electric compressor, PTC heater, battery chiller). Trigger logic: When the air conditioning controller (ACU) or thermal management controller detects a high-voltage module status of "OK" or false "OK" (pseudo OK) via CAN bus message 244, it identifies a potential safety risk (such as a high-voltage interlock fault, over-temperature protection, or self-check failure with an incorrect status bit) and triggers the protection mechanism to cut off the high-voltage power supply. Typical causes include loss of high-voltage interlock loop (HVIL) integrity, thermal management over-temperature protection, unsynchronized CAN communication data, or internal high-voltage component faults.
Causes
— Open circuit, backed-out pins, or poor contact in the high-voltage interlock loop (HVIL) wiring, causing the system to falsely detect an abnormal high-voltage module connection status.— Thermal management system temperature sensor fault (battery pack water inlet temperature, motor coolant temperature, or air conditioning system temperature out of range), triggering over-temperature protection logic.— CAN bus communication fault, specifically loss, data error, interference, or transmission delay of message 244 (A/C/thermal management status message).+2 more →
Actions
— Connect the VDS diagnostic tool, read the complete fault codes and data stream, and check for accompanying B2A6700 (compressor start failure), U-series communication fault, or temperature sensor fault codes.— Check high-voltage interlock loop integrity: Measure continuity at the HVIL pins on the low-voltage connectors of high-voltage components such as the electric compressor and PTC heater. Inspect the pins for backing out, oxidation, or water ingress.+5 more →
B2A6700›
This DTC indicates the Electric A/C Compressor (EAC) fails to establish normal speed or pressure after multiple consecutive start attempts following a start command. The system logs a start failure fault. The root cause is the compressor controller failing to provide a valid speed signal within the specified time (typically 2-3 seconds) or failing to build torque. On plug-in hybrid (DM) models, an electric compressor failure prompts the system to start the engine to drive the mechanical compressor (Belt-driven Compressor) as a backup cooling solution, triggering DTC B2A6700. This fault causes a complete loss of A/C cooling capacity, which is particularly severe in pure electric mode. Additionally, because the BYD thermal management system couples the battery chiller (Chiller) with the A/C system, a prolonged fault can cause power battery thermal management failure, triggering power limits or even high-voltage interlock disconnection.
Causes
— Electric compressor high-voltage power supply fault: Causes include a blown compressor fuse in the high-voltage distribution box, poor contact in the high-voltage interlock loop (HVIL), burnt main negative/main positive contactors, or a damaged IPM module on the compressor's internal motor drive board, preventing the compressor from receiving sufficient high-voltage DC power (typically 320V-750V).— Compressor mechanical seizure or motor fault: Internal scroll plate wear and seizure, motor permanent magnet demagnetization, bearing seizure, or degraded refrigerant oil causes excessive start-up torque, which triggers controller overcurrent protection and causes start-up failure.— Low-voltage control communication fault: LIN bus or CAN bus communication interruption (between the BMS, VCU, and compressor controller), abnormal wake-up signal, or enable signal circuit open or short to ground, preventing the compressor controller from receiving the correct speed command.+2 more →
Actions
— Diagnostic tool reading and freeze frame analysis: Use VDS2000 or Launch X431 to read all fault codes. Check for accompanying high-voltage interlock (P0A0D, P0A0E) or insulation (P1A00 series) faults. Record the ambient temperature, battery SOC, compressor target speed, and actual speed data streams at the time of the fault.— High-voltage safety check and insulation test: Disconnect the manual service disconnect (MSD) and wait 5 minutes for high-voltage discharge. Use a megohmmeter to measure the electric compressor high-voltage harness insulation resistance to ground (standard >20MΩ). Inspect the high-voltage connectors for burning or backed-out pins. Measure the high-voltage interlock circuit continuity.+4 more →
B2A7914›
This DTC indicates a short to ground or open circuit fault in the drive motor circuit of the 4-Way Heater Core Valve. The 4-way valve is a core actuator in the BYD thermal management system. It switches the coolant flow path to distribute heat among the heater core (PTC heating circuit), motor cooling circuit, and battery pack thermal management circuit. Damaged insulation in the motor winding or power supply wiring causes a short to ground, leaking abnormal current to the vehicle body ground. An internal motor break, a broken wiring harness, or a loose connector causes an open circuit, resulting in a loss of continuity. This fault causes the valve to stick in its current position, preventing coolant path switching based on thermal management demands. This failure leads to a loss of cabin heating, an inability to heat the battery, or insufficient motor cooling. Severe cases trigger thermal management system protective power limiting (limp mode), and extreme cases cause overheating damage to the motor or battery.
Causes
— Water valve motor wiring harness insulation chafed or pinched, causing a short circuit to vehicle body metal parts, commonly found in high-temperature, high-vibration areas of the front compartment.— Four-way water valve internal stepper motor/DC motor coil burnt out or internally short-circuited, usually due to prolonged water valve seizing causing motor stall and overheating.— Water ingress in the connector causes oxidation and corrosion, resulting in excessive contact resistance that presents as an open circuit, or a short circuit between pins causing a short to ground.+2 more →
Actions
— Use VDS2000/VDS3.0 to read complete fault codes and freeze frame data. Confirm the ambient temperature, water valve target position, and actual position when the fault occurred. Check for related fault codes (such as B2A7A12 short circuit to power supply, B2A7B00 implausible position, etc.).— Visually inspect the front compartment heater core four-way water valve assembly (typically located near the firewall or on the left side of the front compartment) for coolant leaks, damaged wiring harness sheaths, loose connectors, or burn marks.+5 more →
B2A7A12›
This DTC indicates the heater core 4-way water valve drive motor control circuit has shorted to the vehicle power supply (B+, typically 12V or a 5V reference voltage, depending on the specific drive circuit design). When the HVAC ECU or thermal management controller sends a PWM drive signal to the stepper or DC motor, it detects the motor feedback or drive circuit voltage remains continuously high (close to battery voltage). This exceeds the normal range; normal operation requires a pulsed voltage or ground return path. This prevents the controller from driving the 4-way water valve to switch the coolant flow direction, affecting the switch between the cabin PTC heating loop and the battery/motor cooling loop. In severe cases, this fault causes the drive chip to overheat and fail or the related fuse to blow, which triggers the thermal management system protection mechanism and limits power output.
Causes
— Physical damage to the wiring harness: Vibration chafing, sharp edges, or animal bites damaged the motor wiring harness insulation in the engine compartment or under the chassis, shorting it to the vehicle positive wiring harness (such as constant B+ or IGN power).— Internal motor short circuit: Aged, burnt, or damp internal winding insulation in the four-way water valve motor causes abnormal continuity between the coil and the motor housing (if grounded) or the power terminal.— Connector fault: Motor connector seal failure allows water ingress, causing electrolytic corrosion between terminals and forming a conductive path, specifically a short circuit between the power pin and motor drive pin; or backed-out or bent terminals contact adjacent power terminals.+2 more →
Actions
— Safety preparation and initial inspection: Disconnect the high-voltage service disconnect (MSD) and wait 5 minutes for the high-voltage system to fully discharge; use a multimeter to check the DTC status and confirm it is a current fault (Current), not a history fault (History); visually inspect the engine compartment and front compartment wiring harnesses for obvious damage or burn marks.— Harness continuity and short circuit test: Disconnect the HVAC controller and four-way water valve motor connectors. Use a multimeter in resistance mode to measure the insulation resistance between the motor-side harness and the power supply (B+). Normal resistance must exceed 10MΩ. Measure the controller-side harness for short circuits to ground and power to check for power supply cross-wiring.+4 more →
B2A7B92›
DTC B2A7B92 indicates the actuator motor for the heater core (PTC heater assembly) 4-way valve cannot reach the target position. A stepper or DC motor drives the valve, changing the valve core position to switch coolant flow direction (e.g., directing heat to the heater core, battery heater, or bypass circuit). The ECU monitors the actual valve opening via a position sensor (potentiometer or Hall effect sensor). The ECU sets this fault when the deviation between the commanded position and the actual feedback position exceeds the calibrated threshold (typically 5%-10%), or when the motor drive current continuously exceeds the stall protection value (approximately 600-800mA) for 2-5 seconds. This fault prevents the thermal management system from distributing heat as required, resulting in poor cabin heating, limited charging power at low battery temperatures, or abnormal coolant circulation. It does not directly affect high-voltage safety.
Causes
— Four-way water valve internal mechanical binding: Coolant impurities, scale, or aged sealant obstruct the valve core guide rail, resulting in insufficient motor drive torque and preventing the valve from reaching its target position.— Water valve drive motor fault: Worn internal carbon brushes, burned commutator, worn reduction gear teeth, or insufficient lubrication, causing reduced output torque or freewheeling.— Position sensor signal distortion: Oxidized sensor sliding contacts, a worn resistive track, or magnetic interference on the Hall element cause non-linear deviation between the feedback voltage and actual position.+2 more →
Actions
— Use the VDS diagnostic tool to read the DTC freeze frame data. Record the ambient temperature, Target Position, and Actual Position values at the time of the fault, and confirm the deviation amount.— Perform an Active Test: Use the diagnostic tool to command the water valve to cycle from 0% to 100%. Observe the valve for smooth operation and listen to the motor for abnormal clicking or humming stall noises to determine if the fault is electrical or mechanical.+5 more →
B2AB1-49›
This DTC specifically indicates a phase-loss fault in the built-in three-phase permanent magnet synchronous motor of the electric A/C compressor (E-Compressor). The compressor controller (Inverter) detects a severe three-phase current imbalance via Hall sensors or current sampling circuits (one phase current is zero or the difference is >30%), or detects an abnormal back-EMF waveform, determining a phase-loss condition. This fault typically indicates poor contact at the compressor high-voltage harness, an open motor winding, a damaged controller power module (IPM), or an abnormal low-voltage control signal. Because BYD uses an integrated thermal management system for the battery, motor, and cabin, the A/C compressor handles both cabin cooling and battery/motor coolant heat dissipation. This fault causes A/C failure and, under high-load operating conditions, triggers battery or motor overheat protection, limiting power output (entering limp mode).
Causes
— Loose compressor three-phase high-voltage harness connector (U/V/W phases), or backed-out, oxidized, or burned pins, causing excessive contact resistance or an intermittent open circuit, especially on early Qin series models where the front compartment layout subjects the harness to vibration.— A damaged internal IGBT power module or drive circuit in the electric compressor controller (inverter) prevents complete three-phase waveform output. This failure typically occurs after poor heat dissipation or a high-voltage surge.— Compressor motor winding open circuit (broken enameled wire) or phase-to-phase short circuit causing three-phase impedance imbalance, typically resulting from compressor overheating or mechanical seizure due to insufficient refrigerant.+2 more →
Actions
— Use BYD VDS or X-431 to read complete fault codes and freeze frame data. Record vehicle speed, SOC, compressor speed, and three-phase current values (Iu/Iv/Iw) at the time of the fault. Confirm if the fault is current or historical, and check for related faults such as B2AB049 (current sampling circuit fault).— Perform the high-voltage power-down procedure (disconnect the service disconnect and wait 5 minutes). Remove the front compartment lower undertray. Visually inspect the electric compressor three-phase high-voltage wiring harness connector (usually marked U, V, W) for looseness, burn marks, backed-out terminals, water ingress, or verdigris oxidation. Specifically check 2018-2019 Qin PRO models for detached wiring harness retaining clips.+5 more →
B2AB149›
This DTC indicates a phase loss in the internal three-phase permanent magnet synchronous motor of the electric A/C compressor (E-Compressor). When the compressor controller (inverter) supplies power to the motor U/V/W three-phase windings, it detects a loss of at least one phase current or a voltage drop exceeding the threshold. Open windings, open high-voltage harnesses, or damaged IGBT power modules typically cause this condition. This fault prevents the compressor from generating effective torque and forces it to stop, which disables the A/C cooling and heating functions and triggers the thermal management system derating protection. In vehicles like the BYD Qin EV, battery cooling relies on the A/C refrigerant circuit; therefore, this fault may indirectly raise the battery pack temperature and limit charge and discharge power.
Causes
— Compressor high-voltage wiring harness connector burnt or loose: Long-term vibration or excessive contact resistance generates high temperatures at the three-phase high-voltage plug (usually located on top of the compressor). This causes burnt or recessed pins, resulting in an open circuit in one phase.— Electric compressor controller (IPM module) fault: Breakdown of the upper and lower bridge arms in one or more phases of the built-in IGBT power module, or drive circuit damage, preventing the output of a complete three-phase sine wave voltage.— Compressor motor winding burnt out: Insulation breakdown, overheating, or overload caused an open circuit (infinite resistance) or inter-turn short circuit in one phase of the internal three-phase winding.+2 more →
Actions
— Diagnostic scan: Use VDS2000/3000 to read all fault codes. Check for accompanying B2AB2-49 (IPM fault), B2AB3-11 (compressor overcurrent), or high-voltage interlock faults. Record the freeze frame data at the time of the fault (bus voltage, three-phase current values).— High-voltage safety check: Disconnect the low-voltage battery negative terminal, wait 5 minutes, put on insulated gloves, remove the compressor high-voltage service disconnect, and verify the high-voltage system has no residual voltage (<60V DC).+4 more →
B2AB2-49›
This fault code indicates the IPM (Intelligent Power Module) inside the air conditioning compressor controller detects an IGBT (Insulated Gate Bipolar Transistor) malfunction. In the BYD thermal management system, the electric compressor operates on a high-voltage DC drive. The IPM module inverts the high-voltage DC into three-phase AC to drive the compressor motor. DTC B2AB2-49 indicates the controller detects a hardware-level fault in the power semiconductor device. Possible causes include a triggered IGBT overcurrent protection, module overheating (junction temperature exceeding 150°C), an upper and lower bridge arm shoot-through short circuit, abnormal gate drive voltage, or activation of the IPM internal self-protection circuit (FO fault output). This fault shuts down the compressor, affecting cabin cooling and battery pack thermal management (liquid cooling). In extreme cases, it can trigger a protective disconnection of the high-voltage system.
Causes
— IPM/IGBT power module thermal or electrical breakdown: prolonged high-load operation, insufficient refrigerant causing poor heat dissipation, or excessive internal junction temperature damaging the IGBT chip.— Compressor motor winding fault: Stator winding inter-turn short circuit or insulation failure to ground (insulation resistance below 2MΩ), causing power module output overcurrent.— Compressor controller drive circuit fault: Burnt gate drive resistor, damaged drive optocoupler/isolation chip, or failed bootstrap capacitor causing an abnormal IGBT drive waveform.+2 more →
Actions
— Diagnostic scan: Use VDS or BYD Diagnosis to read all fault codes. Check for related faults such as B2AB149 (motor phase loss) and B2AC349 (compressor overcurrent). Record freeze frame data (high voltage, compressor speed, IGBT temperature).— Visual and wiring harness inspection: Inspect the compressor controller low-voltage connector (8PIN/12PIN) for water ingress, oxidation, or backed-out terminals; inspect the high-voltage wiring harness (HV+, HV-) insulation for damage, and verify the tightening torque meets the 9N·m standard.+6 more →
B2AB249›
DTC B2AB249 indicates a fault in the IGBT (Insulated Gate Bipolar Transistor) power device or drive circuit inside the electric air conditioning compressor drive module (IPM, Intelligent Power Module). In models such as the BYD Qin EV, high-voltage DC drives the electric compressor. The IPM converts this high-voltage DC power into three-phase AC power to drive the compressor motor. IGBT overcurrent, overtemperature, overvoltage, or an internal module short circuit typically triggers this fault, initiating compressor shutdown protection. This affects air conditioning cooling/heating functions and battery thermal management capabilities. This is a hardware-level fault; in most cases, a power reset cannot permanently clear it.
Causes
— Poor heat dissipation in the electric compressor drive module (IPM) or cooling circuit blockage causes the IGBT junction temperature to exceed the protection threshold (usually >150°C).— IGBT power device breakdown or aging due to compressor motor winding short circuit, insulation failure, or high-voltage surge.— Internal fault in the compressor controller current detection circuit triggers a false overcurrent fault.+2 more →
Actions
— Use the VDS2000/VDS2100 diagnostic tool to read complete fault codes and freeze frame data. Record key parameters at the time of the fault, including compressor speed, high voltage, and IGBT temperature.— Check the electric compressor high-voltage wiring harness connector (usually located on the top or side of the compressor) for burning or looseness, and measure the continuity of the high-voltage interlock circuit.+5 more →
B2AB3-49›
This DTC indicates a fault in the internal temperature monitoring circuit of the electric air conditioning compressor (E-Compressor). Specifically, the compressor control module (IPM) detects the internal NTC thermistor signal falls outside the valid range (open circuit, short circuit, or signal drift). As a result, the module cannot accurately read the real-time temperature of the compressor motor windings or power module. This failure disables the thermal management strategy. To prevent overheating damage, the system forces the compressor off, directly degrading air conditioning cooling performance and disrupting the battery pack thermal management loop. In severe cases, the system fails to cool the traction battery effectively.
Causes
— Compressor internal temperature sensor (NTC thermistor) aging, open circuit, or short circuit— Backed-out terminals, poor contact, or corrosion at the compressor low-voltage wiring harness connector (commonly connector G09)— Compressor cooling circuit fault (insufficient coolant, electronic water pump failure, or radiator blockage) causes actual overheating, triggering protection.+2 more →
Actions
— Use the dedicated diagnostic tool to read the DTC freeze frame and record the temperature, high voltage, and compressor speed at the time of the fault.— Check the compressor low-voltage wiring harness connectors (G09, etc.) for backed-out pins, looseness, water ingress, or corrosion, and measure the terminal resistance value.+5 more →
B2AB349›
This DTC indicates an abnormal signal or functional failure of the temperature sensor integrated inside the Electric A/C Compressor. This sensor is embedded near the compressor motor winding or power module (IPM). It monitors the operating temperature of the compressor core components in real time to prevent motor demagnetization or controller damage from overheating. When the sensor experiences an open circuit, short circuit, signal drift, or detects a value outside the normal threshold (-40°C to 150°C), the compressor controller triggers DTC B2AB349 and enters protection mode, forcibly cutting operating power to the compressor. This fault directly causes the air conditioning system to lose cooling capacity. In extreme cases, the lack of cooling may indirectly affect the traction battery thermal management circuit, but it typically does not limit vehicle power.
Causes
— Compressor internal temperature sensor damaged, or thermistor resistance drift (due to long-term high-temperature aging or refrigerant chemical corrosion).— Temperature signal acquisition circuit fault on the compressor controller PCB (e.g., burnt sampling resistor, failed filter capacitor, or cold solder joint)— Open circuit in the compressor internal temperature sensor wiring harness, or poor connector contact (due to continuous compressor vibration)+2 more →
Actions
— Scan the entire vehicle system using VDS2000 or the latest diagnostic tool. Verify B2AB349 is a current fault that does not clear, and record the freeze frame data.— Read the air conditioning system data stream and check if the displayed 'compressor internal temperature' value is abnormal (e.g., displays -40°C, 150°C, or significantly deviates from ambient temperature).+7 more →
B2AB4-1D›
This DTC indicates the electric air conditioning compressor (E-Compressor) internal high-voltage drive circuit detected an abnormal overcurrent condition. Specifically, the compressor's built-in permanent magnet synchronous motor (PMSM) drive current exceeded the IGBT power module safety threshold (typically 30-50A, depending on the vehicle model). This fault involves the compressor internal high-voltage inverter module, motor winding insulation condition, or an abnormal mechanical load. The compressor control unit (ECU) triggers this fault when it detects, via the Hall current sensor, that the instantaneous phase current continuously exceeds the calibrated threshold (e.g., 60A/100ms or 80A/10ms). This fault initiates an automatic compressor protective shutdown, affecting air conditioning cooling and battery thermal management functions. In extreme cases, it may damage the high-voltage fuse or high-voltage wiring harness.
Causes
— Inter-turn short circuit in the compressor internal motor winding or decreased phase-to-phase insulation resistance (below 20MΩ) causes abnormally high operating current, usually resulting from prolonged high-temperature operation or refrigerant oil deterioration.— Compressor controller IGBT power module breakdown (e.g., Infineon or ST brand modules) causes upper and lower bridge arm shoot-through or phase-loss operation, triggering overcurrent protection.— Mechanical seizure or wear of the scroll plate (commonly due to refrigerant contamination or poor lubrication) causes a sudden increase in motor load torque and a corresponding rise in drive current.+2 more →
Actions
— High-voltage safety procedure: Perform the standard power-down procedure (OFF position → disconnect the low-voltage battery negative terminal → remove the service disconnect/MSD → wait 5 minutes → verify voltage) to ensure the high-voltage system voltage is below 60V.— In-depth fault diagnosis: Use VDS2000 or Launch X431 to read complete DTCs. Check for accompanying fault codes (such as B2AB349 temperature sensor fault, B2AB149 motor phase loss). View the Fault Freeze Frame data for the compressor speed, current value, and bus voltage recorded when the fault occurred.+5 more →
B2AB41D›
This fault code indicates the internal drive current of the thermal management system electric scroll compressor (E-Compressor) exceeds the safety threshold set by the MCU (microcontroller unit) (typically peak current >45A or sustained RMS current >15A). This hardware-level protection fault indicates the compressor permanent magnet synchronous motor (PMSM) or its integrated controller (including the IPM intelligent power module) detects abnormal current consumption. During compressor start-up or operation, the controller triggers this fault if Hall sensors detect a three-phase current imbalance exceeding 10%, or if the instantaneous DC bus current exceeds the calibrated limit (approximately 22-25A) for over 100ms. The compressor stops immediately to protect the IGBT power devices, affecting cabin air conditioning cooling/heating and battery pack liquid cooling functions. A prolonged fault may burn out the compressor controller or blow the high-voltage fuse (typically 30A-40A).
Causes
— Inter-turn short circuit in the electric compressor internal motor winding, or reduced phase-to-phase insulation (insulation resistance <20MΩ), causing an abnormal increase in electromagnetic load and a surge in operating current.— Compressor integrated controller fault, including IGBT breakdown in the IPM (Intelligent Power Module), current sampling resistor (shunt resistor) drift, or abnormal gate drive circuit causing three-phase drive waveform distortion.— Excessive mechanical load in the air conditioning system, such as refrigerant overcharge (exceeding the standard value of 550g±25g), receiver-drier/expansion valve blockage causing excessive high-side pressure (>2.5MPa), internal compressor mechanical seizure, or lack of refrigerant oil (POE oil) causing poor lubrication.+2 more →
Actions
— Use the VDS2000/3000 diagnostic tool to read the complete fault codes and freeze frame data. Specifically record the following data at the time of the fault: compressor speed (rpm), high-voltage bus voltage (V), three-phase current values (A), refrigerant high- and low-side pressures (kPa), IGBT temperature (°C), and fault occurrence count (Trip Counter).— Perform the standard high-voltage power-down procedure (turn off the ignition, disconnect the low-voltage battery negative terminal, and wait 5 minutes). Wear CAT III 1000V insulated gloves. Use an insulation resistance tester to measure the insulation resistance between the compressor high-voltage input terminal and the vehicle body (standard: >500MΩ).+5 more →
B2AB5-73›
DTC B2AB5-73 indicates the electric air conditioning compressor (E-Compressor) failed its start-up self-check. The compressor controller (Inverter) generates this fault if it receives a start command from the VCU (Vehicle Control Unit) but fails to establish normal speed feedback or a normal high-voltage DC bus within the specified time (usually 3-5 seconds). Technical causes include abnormalities in the high-voltage interlock (HVIL) circuit integrity, DC bus pre-charge logic, compressor motor phase current detection, or the LIN bus communication handshake protocol. In the BYD thermal management system, this compressor handles both cabin air conditioning and battery pack liquid cooling/heating functions. When this fault triggers, the system inhibits compressor operation. This inhibition can cause battery thermal management failure, subsequently triggering power limitation (reduced-power driving) or preventing high-voltage power-up.
Causes
— High-voltage interlock loop (HVIL) pin backed out or corroded: Poor contact at the compressor high-voltage connector interlock pin causes the vehicle control unit to detect an incomplete high-voltage circuit and disable compressor startup.— Compressor controller internal IGBT or drive circuit fault: Power module damage on the controller PCB prevents three-phase AC output to drive the scroll plate, resulting in high-voltage input but no current output.— LIN bus communication fault: Short circuit, open circuit, or signal interference in the LIN wiring harness between the compressor controller and the air conditioning controller (AC ECU) prevents speed command transmission or causes feedback signal loss.+2 more →
Actions
— Read the complete DTC and freeze frame using the diagnostic tool: Use VDS or ED400 to read the data stream at the time of the fault, including ambient temperature, battery SOC, compressor target speed, actual speed, high-voltage bus voltage, and compressor current, to determine if the fault is intermittent.— High-voltage interlock circuit check: Disconnect the compressor high-voltage connector and measure continuity between the HVIL circuit pins (should be less than 1 Ω). Inspect the connector for backed-out pins, burn marks, or signs of water ingress. Clean or replace the wiring harness if necessary.+5 more →
B2AB64B›
DTC B2AB64B indicates the electric A/C compressor internal temperature monitoring point detects an abnormally high temperature or an abnormal temperature signal. On 2019 BYD Qin EV models, this fault typically indicates the electric scroll compressor (BYD in-house or third-party supplied) internal motor winding temperature, power module (IPM) temperature, or compressor housing temperature exceeds the normal operating range (typical threshold: 110–130°C). When this fault occurs, the compressor controller enters protection mode. It limits compressor speed or stops operation to prevent insulation damage or mechanical seizure. Because the Qin EV uses the A/C system for battery thermal management (the battery chiller integrates into the A/C circuit), this fault causes loss of cabin cooling and can reduce traction battery cooling capacity, subsequently triggering battery thermal management power derating protection.
Causes
— Abnormal refrigerant circulation: A system refrigerant leak causes insufficient flow, or air/moisture in the refrigerant causes poor compressor cooling and lubrication, resulting in frictional heating of the compressor pump body.— Compressor temperature sensor fault: NTC thermistor open circuit, short circuit, or resistance drift; water ingress or poor connection at the sensor wiring harness connector, causing a false high-temperature warning.— Compressor mechanical fault: Scroll plate wear, bearing seizure due to lack of lubrication, or degraded motor insulation increases running resistance and copper loss, generating abnormal heat.+2 more →
Actions
— Use VDS2000 or the BYD dedicated diagnostic tool to read freeze frame data. Record compressor speed, high-side pressure, internal temperature, and ambient temperature at the time of the fault to determine whether the condition is actual overheating or a false sensor reading.— Check the A/C system refrigerant quantity and purity. Use a refrigerant recovery machine to extract and weigh the refrigerant to check for a low charge (standard charge: approx. 600-700g, depending on configuration). If necessary, perform a pressure holding leak test (hold pressure at 1.5MPa, 30-minute pressure drop <0.1MPa).+4 more →
B2AB573›
This DTC indicates an abnormal driver seat fore-aft position sensor signal or a Seat Control Unit (SCU) communication fault. The ECU detects a sensor signal voltage outside the normal range (0.5-4.5V), an inconsistent signal, or a complete signal loss. This disables the seat memory system and easy entry/exit functions. Typically a Hall-effect or potentiometer type, the sensor mounts on the seat rail. It monitors the seat fore-aft position in real time, providing position feedback to the memory function and intelligent cockpit system. Although the fault message displays "start-up failure", a seat position signal failure actually prevents the related functions from starting.
Causes
— Oxidation, looseness, or pin corrosion (green corrosion) in the under-seat wiring harness connector, interrupting signal transmission or causing excessive resistance.— Faulty longitudinal position sensor (internal wiper wear, Hall element failure, or open resistor), causing the signal at a specific position to jump or remain fixed.— Jammed seat rail, ingress of foreign objects (such as coins), or insufficient lubrication, causing excessive wear of the sensor mechanical structure, stalling, or motor overload.+2 more →
Actions
— Use VDS2000 or Launch X431 to read the Seat Control Module (SCU) fault codes, confirm if B2AB573 is a current code, and review the freeze frame data for the seat status when the fault occurred.— Access the data stream and monitor the "Driver seat fore-aft position" value. Manually adjust the seat through its full range of travel and observe if the value changes linearly (normal values change continuously between 0-255mm or 0.5-4.5V without jumps or fixed values).+7 more →
B2AB6-4B›
DTC B2AB6-4B indicates the Electric A/C Compressor internal temperature sensor detects a temperature outside the normal operating range (typically >120°C or an abnormal temperature rise rate). This fault indicates the compressor internal thermal protection mechanism triggered. Electrical insulation failure, mechanical friction overheating, abnormal controller drive, or refrigerant circulation faults can cause this condition. This fault disables the air conditioning cooling function. In severe cases, thermal management system anomalies may trigger the 'EV Function Limited' protection mode, restricting the vehicle's pure electric driving capability. It typically does not affect high-voltage system safety.
Causes
— Internal insulation failure in the electric compressor (short to ground or insulation resistance <0.5MΩ), causing leakage current to convert into heat.— Compressor Controller fault causing abnormal drive current or loss of speed control, resulting in overheating.— Scroll plate wear or design defect (early version without sealing ring), causing internal leakage, reduced compression efficiency, and abnormal heat generation.+2 more →
Actions
— Connect the VDS diagnostic tool to read the complete fault codes. Check for accompanying fault codes such as B2AB573 (operation unsuccessful) and B2AB41D (internal current too high), and record the compressor speed, current, and temperature data streams.— Use a megohmmeter to measure the insulation resistance between the electric compressor high-voltage terminal and ground. Normal value: >20MΩ. A reading <0.5MΩ confirms insulation failure.+5 more →
B2AB7-74›
DTC B2AB7-74 (diagnostic tools typically display this as B2AB774) indicates the actual speed of the electric compressor or PTC heater deviates from the target speed beyond the system threshold (typically ±10%-15%), or the speed feedback signal is abnormal or missing. This fault indicates a thermal management system closed-loop control anomaly involving the permanent magnet synchronous motor (PMSM) field-oriented control (FOC) algorithm monitoring. The controller triggers this fault upon detecting the speed feedback from the rotor position sensor (resolver or Hall sensor) mismatches the PWM modulation target, or when an abnormal three-phase current waveform causes a loss of synchronization. This fault may limit air conditioning cooling/heating functions and reduce thermal management efficiency. In extreme cases, it triggers high-voltage interlock protection and cuts off the compressor high-voltage power supply to protect the motor and controller.
Causes
— Internal mechanical binding or wear in the electric compressor or PTC heater, or degraded refrigerant oil, preventing actual speed from matching target speed.— Three-phase high-voltage wiring harness connector is burnt, loose, or has excessive contact resistance, causing drive voltage drop and speed fluctuation.— Oxidized or loose compressor/PTC controller ground point, or internal 12V/5V power supply module fault, causing abnormal speed signal acquisition.+2 more →
Actions
— Use VDS or a dedicated diagnostic tool to read the complete fault codes and data stream. Compare the difference between 'target speed' and 'actual speed', and confirm the operating condition when the fault occurred (start-up/running/shifting).— Perform a high-voltage system insulation test. Measure the insulation resistance to ground of the compressor/PTC high-voltage positive and negative terminals (standard >500MΩ). Check the integrity of the high-voltage interlock circuit.+5 more →
B2AB774›
DTC B2AB774 indicates abnormal speed feedback from the electric A/C compressor. Specifically, the compressor control module (MCU) detects a deviation between the actual compressor motor speed and the target commanded speed exceeding the threshold (typically >15%), a lost speed signal, or excessive speed fluctuation (jitter). This fault affects a core actuator in the thermal management system. It can reduce A/C cooling/heating performance, cause thermal management failure, and subsequently trigger motor or battery over-temperature protection. In pure electric models like the Qin EV, high voltage (typically 320V-750V) directly drives the electric compressor. The system uses sensorless vector control (FOC) or Hall sensor feedback for speed control. This fault essentially indicates instability in the closed-loop speed control.
Causes
— Compressor mechanical fault: Scroll plate wear and binding, motor bearing seizure, or refrigerant oil degradation increases frictional torque, preventing actual speed from tracking the target value.— Compressor controller fault: Damaged IPM power module, MCU chip program runaway, or aging bus capacitor causing drive waveform distortion, resulting in speed fluctuation or loss of synchronization.— Abnormal speed feedback signal: Damaged Hall sensor, poor signal harness shielding allowing EMC interference, oxidized connector pins causing loss of speed pulse signal.+2 more →
Actions
— Diagnostic scan: Use VDS2000 or Launch PAD5 to read all DTCs. Review the freeze frame data (compressor speed command, actual feedback, bus voltage, phase current, and IGBT temperature at the time of the fault) to determine whether the condition is "speed too high", "speed too low", or "abnormal speed signal".— Visual and wiring harness inspection: Inspect the compressor high-voltage wiring harness (orange) insulation for damage and the low-voltage signal connector (usually 4-6 pin) for water ingress or oxidation. Measure the connector pin voltages (constant power, IG signal, PWM control, feedback signal).+4 more →
B2AB8-1C›
DTC B2AB8-1C (abbreviated from B2AB81C) indicates the Electric A/C Compressor controller detected an abnormally high three-phase drive voltage. This fault involves the Intelligent Power Module (IPM) or IGBT drive circuit inside the compressor controller (Inverter). The controller triggers this fault upon detecting any of the following conditions: 1) Inter-turn short circuit, open circuit, or unbalanced resistance in the compressor internal permanent magnet synchronous motor (PMSM) three-phase windings, causing abnormal back electromotive force (BEMF); 2) Overcurrent, overheating, or power transistor breakdown in the controller internal IPM; 3) Transient spike in the high-voltage DC bus voltage (e.g., precharge failure or stuck HV battery relay); 4) Compressor mechanical seizure (e.g., scroll plate wear or lack of refrigerant oil) causing a sudden load increase and abnormal current and voltage rise. This fault triggers a protective compressor shutdown, causes complete air conditioning system failure, and may affect battery thermal management (e.g., liquid cooling plate circulation). This is a level 2 severe fault.
Causes
— Compressor internal motor winding fault: Unbalanced three-phase winding resistance (normal resistance approximately 0.5-1.0Ω, difference between any two phases less than 0.1Ω) or decreased winding-to-housing insulation resistance (below 20MΩ) causes abnormal phase voltage detection.— Compressor controller IPM module damaged: IGBT or MOSFET breakdown in the intelligent power module, or gate drive circuit fault. Typically presents with controller overheating, burn marks, or concurrent DTC B2AB249 (IPM IGBT fault).— High-voltage wiring harness and connector fault: Backed-out pins, loose connections, or water ingress and ablation at compressor high-voltage connector (B28/B29) increase contact resistance and generate voltage spikes, or damaged shielding causes electromagnetic interference.+2 more →
Actions
— Step 1 - Fault code reading and freeze frame analysis: Use a VDS or X431 diagnostic tool to read all DTCs. Confirm B2AB81C (or B2AB8-1C) and any accompanying fault codes (e.g., B2AB249 IPM fault, B2AB997 overload, B2AB349 temperature sensor fault). Record the freeze frame data (HV voltage, compressor speed, inverter temperature, phase current values).— Step 2 - High-voltage safety and visual inspection: Disconnect the high-voltage service disconnect (MSD) and wait 5 minutes to allow the capacitors to discharge. Inspect the front compartment electric compressor high-voltage harness connectors (B28, B29) for looseness, backed-out pins, water ingress, burn marks, or corrosion. Inspect the controller heat sink for blockages and the controller mounting bracket for looseness.+4 more →
B2AB81C›
This DTC indicates abnormal three-phase inverter voltage in the electric A/C compressor (electric scroll compressor) drive system. Specifically, the Intelligent Power Module (IPM) driving the compressor's built-in Permanent Magnet Synchronous Motor (PMSM) detects the equivalent voltage of any U/V/W phase exceeding the safety threshold (typically >650V DC peak voltage after PWM modulation). This fault triggers a protective compressor shutdown, disabling the A/C system. It may also derate the vehicle thermal management system, affecting power battery cooling and heating functions. Fundamentally, this indicates a high-voltage drive circuit or voltage sampling circuit fault. Determine whether the condition is a true overvoltage (high-voltage bus fault) or a false overvoltage (sensor drift).
Causes
— Abnormal bus voltage surge in the high-voltage power distribution system: such as DC fast charger overvoltage output, abnormal regenerative braking energy recovery causing instantaneous traction battery overcharge, or a faulty precharge/voltage divider resistor in the high-voltage power distribution box distorting the sampled voltage.— Compressor controller (IPM module) voltage sampling circuit fault: Voltage divider resistor drift, operational amplifier damage, or A/D converter chip failure causes the controller to falsely detect high phase voltage.— Compressor three-phase high-voltage wiring harness insulation damage: Harness wear causes high voltage to leak into the low-voltage signal circuit, or shielding failure introduces electromagnetic interference, causing voltage sampling values to spike.+2 more →
Actions
— Read freeze frame data: Use the BYD VDS2000/3000 diagnostic tool to read the freeze frame at the moment the fault occurred. Record the high-voltage bus voltage (HV Voltage), phase current (Phase Current), compressor speed (RPM), and IGBT temperature to determine whether the condition is a steady-state overvoltage or a transient spike.— High-voltage system voltage verification: In the Ready state, use a CAT III 1000V multimeter to measure the total power battery voltage. Compare it with the diagnostic tool reading; the deviation must be <5V. Check the fast charging port CC/CP signals and BMS data stream to rule out charging system overvoltage.+5 more →
B2AB9-97›
DTC B2AB9-97 indicates an internal fault or performance abnormality in the passenger seat Occupant Classification System (OCS) sensor, not "air conditioning load too high" as stated in the original information. Integrated into the front passenger seat cushion, the sensor uses pressure-sensitive elements to detect seat occupancy and passenger weight range. It outputs an analogue voltage signal to the airbag control unit (SRS ECU) (normal range 2.5V-3.5V, varying with weight). The ECU sets this code upon detecting a fixed sensor signal voltage, a voltage outside the valid range, or an open or short circuit exceeding the threshold. This fault forcibly disables the front passenger airbag (the instrument cluster displays "PASS AIR BAG OFF") or prevents the system from adjusting the deployment strategy based on passenger weight during a collision. This severely compromises passive safety system operation and requires immediate repair.
Causes
— OCS sensor faulty: Internal pressure-sensitive resistor or circuit board failure keeps the output signal voltage constant (e.g., stuck at 0.2V or 5V) and prevents it from changing with seat load.— Wiring harness connection fault: Loose connection at the dedicated yellow connector under the seat, backed-out terminal pins, broken locking tab, or wiring harness tension during seat track adjustment causing an intermittent open circuit.— Liquid ingress damage: Rainwater, beverages, or wet clothing penetrates the seat cushion, causing sensor circuit board oxidation, short circuits, or reduced insulation performance.+2 more →
Actions
— Diagnostic scan: Use BYD VDS or ED400 to access the SRS system, read the freeze frame data for DTC B2AB9-97, and check if the 'OCS sensor voltage' in the data stream varies with pressure within the 2.5V-3.5V range. If the voltage remains constant at 0V or 5V, it indicates an open or short circuit in the sensor or wiring.— Basic circuit inspection: Inspect the yellow 2-pin or 3-pin connector under the front passenger seat (usually located beneath the front of the seat) for looseness, water ingress, or corrosion. Measure the voltage from the connector power supply terminal to ground; it must be 12V (Ignition ON). Measure the resistance from the ground terminal to ground; it must be less than 1Ω.+5 more →
B2AB997›
DTC B2AB997 indicates the electric air-conditioning compressor (E-Compressor) operating load exceeds the system-calibrated safety threshold. The compressor controller or vehicle control unit (VCU) triggers this fault in the BYD Qin EV thermal management system when it detects a compressor drive current continuously exceeding the rated value (typically >15-20A, depending on operating conditions), an abnormal drop in speed feedback (stall risk), or an abnormal rise in torque demand. The system then registers an 'excessive load'. This protective fault prevents compressor mechanical damage, high-voltage circuit overload, or thermal management system failure. The fault can reduce air-conditioning cooling capacity and automatically shut down the compressor. Extreme cases may trigger high-voltage interlock protection, affecting battery thermal management functions.
Causes
— Electric compressor internal mechanical seizure or lubrication failure: scroll plate wear, bearing seizure, degraded or insufficient refrigerant oil, resulting in increased mechanical resistance torque.— Abnormal air conditioning system pressure: high condenser pressure (dirty or blocked condenser, cooling fan fault, high ambient temperature), low evaporator pressure (expansion valve fault, line blockage), or refrigerant overcharge (excess liquid refrigerant creates risk of liquid slugging).— High-voltage power supply system fault: Unstable traction battery voltage (undervoltage or overvoltage), poor contact in high-voltage wiring harness (burnt or loose connectors causing increased resistance), compressor controller (IPM) power module fault+2 more →
Actions
— Fault confirmation and data reading: Use the VDS2000/VDS3000 diagnostic tool to read all fault codes and confirm B2AB997 is a current fault. Read the data stream, monitoring compressor current (A), speed (rpm), duty cycle (%), high-voltage bus voltage (V), A/C high-side pressure (MPa), and condenser outlet temperature (°C).— High-voltage safety check: Perform the high-voltage power-down procedure, wear insulated gloves, measure the compressor high-voltage wiring harness insulation resistance (standard value ≥20MΩ), check the high-voltage connectors (B23/B24) for burn marks or backed-out pins, and measure the contact resistance (should be <0.1Ω).+5 more →
B2ABA-1C›
DTC B2ABA-1C indicates a fault in the internal low-voltage power conversion module of the Electric Air Conditioning Compressor (EAC) controller. The compressor controller converts the vehicle 12V low-voltage DC power into lower voltages, such as 5V and 3.3V, to power the internal MCU, CAN transceiver, position sensor, and drive circuit. If the internal DC-DC conversion circuit, voltage regulator chip, or related filter capacitors experience a short circuit, open circuit, or abnormal voltage output (overvoltage or undervoltage), the compressor control unit fails its self-check and reports this fault. This fault prevents the compressor from starting or causes a sudden shutdown during operation, affecting air conditioning cooling and battery/motor thermal management functions. This condition typically does not shut down the high-voltage system; the vehicle remains drivable with caution.
Causes
— Overheating damage to the 12V-5V DC-DC conversion chip or power management IC inside the compressor controller, commonly occurring during prolonged high-load operation or poor heat dissipation conditions.— Loose connection in the external low-voltage power supply circuit, poor fuse contact, or excessive voltage fluctuation, causing frequent cycling or overload damage to the internal power supply module.— Capacitor aging and breakdown or inductor open circuit on the compressor internal drive board, causing a load short circuit in the power conversion circuit.+2 more →
Actions
— Use BYD VDS or a dedicated diagnostic tool to read all fault codes and freeze frame data. Check if other related fault codes (such as communication faults, overheating faults, etc.) accompany B2ABA-1C.— Check the air conditioning compressor low-voltage power supply fuse (usually 10A-15A) and relay in the front compartment fuse box. Measure their continuity and contact resistance.+8 more →
B2ABA1C›
DTC B2ABA1C indicates a fault in the internal low-voltage DC power conversion module of the electric air conditioning compressor (E-Compressor) controller. This module converts the vehicle 12V battery voltage to 5V/3.3V to power the main control MCU, temperature sensor, current sensor, and LIN/CAN communication chips on the compressor control board. The controller sets this code when the internal DC-DC conversion circuit output voltage falls outside the permitted range (typically below 4.5V or above 5.5V), triggers short-circuit protection, or sustains a MOSFET breakdown. This fault disables the compressor control logic and prevents it from responding to air conditioning start commands. This directly affects cabin cooling/heating and the battery pack liquid cooling circuit, but does not compromise high-voltage drive system safety.
Causes
— Aging or breakdown of the MOSFET or filter capacitor in the compressor controller internal DC-DC power module, causing abnormal 5V output.— An intermittent open circuit or voltage fluctuation (below 9V or above 16V) in the 12V low-voltage power supply line triggers a protective lock-up of the internal power supply module.— Compressor controller seal failure allows condensation or moisture ingress, causing a short circuit or corrosion on the internal circuit board.+2 more →
Actions
— Connect the BYD dedicated diagnostic tool (ED-400 or Launch X-431), read the complete DTC freeze frame data, and confirm B2ABA1C is a current fault (Present), not a history fault.— Check the compressor low-voltage connector: measure the 12V supply (PIN1/2) voltage; it must be 12.0-14.5V. Measure the LIN line (PIN3) resistance to ground; it must be approximately 60Ω. Verify there are no backed-out pins, oxidation, or signs of water ingress.+4 more →
B2ABB-17›
This fault code indicates the voltage on the high-voltage side of the electric air conditioning compressor exceeds the controller's safety threshold (typically 750V-800V DC, depending on the vehicle's high-voltage platform). The system triggers the high-voltage interlock protection mechanism to prevent overvoltage breakdown of the compressor's internal power semiconductors (IGBT or SiC modules). When the BMS or compressor controller detects the bus voltage momentarily or continuously exceeds the calibrated upper limit, it logs this fault and limits or disables compressor operation. This causes a loss of air conditioning cooling and heating functions and, in extreme cases, triggers reduced-power operation of the vehicle's high-voltage system.
Causes
— During the final stage of DC fast charging or strong regenerative braking, the traction battery pack voltage spikes momentarily, exceeding the compressor controller's maximum tolerance.— Internal voltage sampling circuit fault in the air conditioning compressor high-voltage controller (ACCM), such as voltage divider resistor drift or Hall sensor miscalibration causing a false code.— Main positive or negative contactor in the high-voltage power distribution unit (PDU) welds or sticks, causing uneven voltage distribution and generating voltage spikes.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (ED-400/ED-500) to read the detailed fault data stream. Record the bus voltage, SOC, and ambient temperature at the time of the fault to determine whether the overvoltage is genuine or a sampling error.— Check the consistency between the traction battery pack total voltage and individual cell voltages. Use the diagnostic tool to perform the BMS active balancing test to rule out an artificially high total voltage caused by cell overcharging.+5 more →
B2AF614›
DTC B2AF614 indicates a power supply circuit fault for the Rear HVAC Blower Motor, specifically a short to ground or an open circuit. This fault affects the rear air delivery function of the HVAC system, part of the thermal management subsystem. A short to ground typically indicates damaged blower motor power harness insulation contacting the vehicle body ground, or failed internal motor winding insulation. An open circuit indicates a break in the circuit resulting from a severed wiring harness, a loose connector, or internal motor burnout. This fault completely disables the rear HVAC blower function and impairs cabin temperature regulation. This classifies as a severe fault because short-circuit currents can overheat the wiring harness or blow a fuse in extreme cases.
Causes
— Burnt internal winding or damaged insulation in the rear blower motor causes a short to ground, usually resulting from prolonged overload operation or motor aging.— Friction, crushing, or water ingress damages the wiring harness insulation under the vehicle floor or seats, causing a short to ground against the metal body.— Internal power drive circuit fault in the rear air conditioning control module (Rear HVAC ECU); fails to properly output PWM control signals or supply power.+2 more →
Actions
— Use the BYD VDS diagnostic tool to read the complete fault code stream. Confirm B2AF614 is a current (Active) fault, not a historical fault, and check for associated communication fault codes.— Disconnect the battery negative terminal. Wait 3 minutes, then remove the rear seat and the centre tunnel rear trim panel to expose the rear blower assembly (typically located on the front wall of the boot or under the rear seat).+5 more →
C000100›
DTC C000100 indicates an electrical or mechanical fault in TCS (Traction Control System) Control Valve A inside the IPB (Integrated Power Brake). In BYD e-Platform 3.0 and DM-i architectures, the IPB module integrates the ABS/ESP/TCS hydraulic unit and ECU into a single assembly. Valve A is typically the TCS main control solenoid valve or the left front wheel changeover valve. This fault occurs when the ECU detects an abnormal valve drive circuit (open circuit, short circuit, or overcurrent) or an abnormal valve spool position feedback signal (delayed response or sticking). When triggered, the fault disables the TCS function and forces the vehicle into fail-safe mode. The system may limit ABS function but typically retains basic hydraulic braking (unassisted or partially assisted). Due to the integrated design of the hydraulic oil circuit and solenoid valve inside the IPB assembly, technicians typically replace rather than repair this component.
Causes
— IPB module internal solenoid valve coil fault: open circuit, short circuit, or resistance drift (normal range typically 20-60 Ω, depending on model), causing abnormal drive circuit detection.— Valve spool mechanically stuck: Prolonged failure to replace brake fluid causes impurity deposits and poor valve spool lubrication, or abnormal brake fluid viscosity in low temperatures slows valve spool movement.— Control circuit board fault: The solenoid valve driver chip (MOSFET or dedicated driver IC) on the IPB internal PCB failed due to overheating, or has cold or broken solder joints.+2 more →
Actions
— Initial diagnosis: Use the BYD VDS diagnostic tool (VDS2000/3000) to read all fault codes. Check for accompanying C000104 (Circuit Control Valve 1 fault), U-prefix communication faults, or other wheel speed sensor faults. Record vehicle speed, brake pedal status, and hydraulic pressure values from the freeze frame data.— Visual and wiring inspection: Disconnect the 12V battery negative terminal and inspect the IPB module for brake fluid leakage, especially at the joint between the motor and the valve body. Measure the voltage at the IPB connector power pins (constant power, ignition power) and ground pins, and the CAN line voltages (CAN-H 2.5-3.5V, CAN-L 1.5-2.5V). Inspect the Valve A drive circuit for abnormal resistance.+4 more →
C000104›
DTC C000104 indicates a functional fault in Inlet Valve 1 (circuit control valve) inside the ESP (Electronic Stability Program) hydraulic modulator. This solenoid valve controls brake fluid flow from the main brake line to the corresponding wheel cylinder and serves as a key actuator for ESP wheel cylinder pressure regulation. Root causes include an open or short circuit in the solenoid coil, mechanical sticking of the valve spool, or ECU internal drive circuit failure. This fault prevents the ESP from independently regulating pressure in this circuit during emergency avoidance maneuvers or skidding. As a result, the vehicle loses yaw moment control, although conventional hydraulic braking remains functional. The valve is a non-serviceable component because it integrates with the ECU inside the hydraulic modulator assembly and involves high-pressure brake fluid sealing.
Causes
— ESP hydraulic modulator internal solenoid valve coil burnt out or open circuit: Increased conductivity from overdue brake fluid replacement, or damaged insulation layer from coil aging and overheating.— Valve spool mechanically stuck: Metal debris in the brake fluid, residue from degraded rubber seals, or moisture-induced corrosion prevents the valve spool from returning.— Hydraulic modulator ECU internal driver chip fault: Voltage fluctuations, overheating, or water ingress damage the power MOSFET or drive circuit, preventing drive current delivery to the solenoid valve.+2 more →
Actions
— Diagnostic tool deep scan: Use VDS or Launch X-431 to read all fault codes. Confirm whether C000104 is a Current or History code. Record key parameters in the Freeze Frame data, such as vehicle speed and yaw rate.— Basic circuit check: Disconnect the hydraulic modulator connector, measure the pin supply voltage (should be 10-16V) and ground resistance (should be less than 1Ω), and check the 25A/40A fuse continuity and contact resistance.+5 more →
C000200›
DTC C000200 indicates a functional fault (Fault Type 2) in TCS (Traction Control System) Control Valve A within the IPB (Intelligent Integrated Braking System) electro-hydraulic control module. This solenoid valve belongs to the high-speed switching valve array in the Hydraulic Control Unit (HCU). It precisely regulates hydraulic pressure to the drive wheel brake calipers during TCS activation, preventing drive wheel slip during starting or acceleration. 'Fault Type 2' typically indicates mechanical binding in the valve body, abnormal solenoid coil resistance (open or short circuit), or a spool position feedback signal exceeding the calibrated threshold. This fault causes TCS failure or performance degradation. The vehicle may lose traction control during hard acceleration on slippery surfaces. Extreme conditions trigger the brake system degradation mode (limp mode), limiting vehicle speed and illuminating multiple warning lights.
Causes
— Mechanical sticking of TCS control valve A inside the IPB electro-hydraulic control module: Impurity buildup due to overdue brake fluid replacement, or debris from valve spool wear, binds the valve spool inside the valve body and prevents it from reaching the target opening.— Solenoid valve coil electrical fault: Internal coil open circuit (infinite resistance) or short to power/ground. Wiring harness aging, water ingress corrosion, or manufacturing defects typically cause this fault, preventing the ECU from driving the valve.— IPB control unit drive circuit fault: Damaged internal power driver chip (MOSFET or H-bridge) cannot supply sufficient drive current to the solenoid valve (typically requires 3-5A peak current).+2 more →
Actions
— Safety preparation and initial inspection: Shift the vehicle into Park (P) and apply the parking brake. Use the diagnostic tool to read all fault codes and freeze frame data. Record the vehicle speed, wheel speed, and brake pedal status at the time of the fault. Inspect the IPB electro-hydraulic module exterior for leaks or signs of impact. Check the brake fluid level and colour (replace if dark or contaminated).— Electrical connection check: Disconnect the 12V battery negative terminal, unplug the IPB module main connector, and check the pins for corrosion, pushback, or burn marks. Measure wiring harness continuity from the connector to the solenoid valve (normal resistance < 1 Ω). Measure the solenoid valve coil resistance (standard value is typically 2-8 Ω; compare with C000204 circuit control valve 2 for reference).+4 more →
C000204›
This DTC indicates an electrical fault (typically an open circuit or abnormal resistance) in Circuit Control Valve 2 inside the ESP (Electronic Stability Program) hydraulic modulator. During active ESP braking intervention, this solenoid valve precisely controls the build-up and release of hydraulic pressure in a specific brake circuit (typically the rear wheel brake circuit). When this fault triggers, the ESP system enters degraded mode and disables electronic stability control, traction control (TCS), and automatic emergency braking (AEB). The vehicle typically retains conventional hydraulic braking. This is a hardwired circuit fault, not a software false positive. Focus inspection on the solenoid valve coil integrity and the ECU driver circuit.
Causes
— ESP hydraulic modulator assembly internal solenoid valve coil open circuit or resistance out of specification (normal range is typically 12-25Ω; refer to the vehicle repair manual for the specific model).— Oxidized, loose, or water-corroded pins in the hydraulic modulator wiring harness connector (usually located on the top or side of the modulator), causing an open circuit.— Damaged ABS/ESP ECU internal valve body drive circuit (e.g., shorted or open power MOSFET), unable to supply operating current to the valve.+2 more →
Actions
— Use the BYD VDS2000/VDS3000 diagnostic tool to read the complete fault code data stream and freeze frame data. Confirm vehicle speed, voltage, and other operating conditions at the time of the fault to rule out intermittent faults.— Disconnect the battery negative terminal, remove the ESP hydraulic modulator assembly (located at the front left or front right of the engine compartment, with brake lines), and inspect the exterior for impact damage, leaks, or burn marks.+5 more →
C000300›
DTC C000300 indicates an electrical fault in Traction Control System (TCS) control valve B inside the Intelligent Integrated Braking System (IPB) (fault type 1 typically indicates an open circuit, short circuit, or out-of-range performance). In the BYD One-Box braking system, the TCS solenoid valve regulates brake fluid pressure when the drive wheels slip, restoring traction by applying intermittent braking to the slipping wheels. This fault means the IPB module detects an abnormal drive circuit for valve B or a valve body response exceeding the calibrated threshold, disabling the TCS function. Normal braking remains unaffected. However, when starting or accelerating on low-traction surfaces such as ice, snow, or mud, the drive wheels may spin uncontrollably, compromising driving safety. This is an internal actuator fault within the IPB hydraulic control unit. Use professional diagnostic equipment to determine whether the fault lies in the solenoid valve itself or the control circuit.
Causes
— Open circuit, short circuit, or short to ground in the TCS solenoid valve B coil inside the IPB electro-hydraulic module, causing abnormal drive current.— Old or contaminated brake fluid causes the solenoid valve spool to stick in the open/closed position, resulting in a response timeout.— Water ingress, oxidation, or terminal back-out at the IPB module wiring harness connector (especially the 32-pin main connector), causing abnormal power supply or signal transmission.+2 more →
Actions
— Use VDS or the BYD dedicated diagnostic tool to read the complete fault codes and freeze frame data. Confirm whether C000300 is a current or history fault. Record the vehicle speed, wheel speed, and other data at the time the fault occurred.— Visually inspect the exterior of the IPB electro-hydraulic module for brake fluid leaks, housing damage, or loose wiring harness connectors. Focus on the sealing condition of the TCS valve body area.+5 more →
C000304›
DTC C000304 indicates an electrical or functional fault in High Pressure Switch Valve 1 inside the ESP (Electronic Stability Program) hydraulic modulator. This solenoid valve is a core actuator in the ESP Hydraulic Control Unit (HCU). It controls the brake fluid pressure build-up path from the master cylinder to the wheel cylinders during ABS/ESP intervention. The ECU sets this fault upon detecting an open circuit or short circuit (to ground or power) in the valve drive circuit, or an abnormal valve spool response. When this fault occurs, the ESP system enters fail-safe mode, disables active intervention functions, retains only conventional hydraulic braking, and illuminates the ABS/ESP warning light on the instrument cluster.
Causes
— Open circuit, short circuit, or resistance drift (outside the standard 5-20Ω range) in the High-Pressure Switching Valve 1 solenoid coil inside the ESP hydraulic modulator assembly— Poor contact between the hydraulic modulator and wiring harness connector, backed-out terminals, oxidation, corrosion, or waterproofing failure interrupting signal transmission.— ESP ECU internal solenoid valve drive circuit fault, such as a burnt H-bridge driver chip, MOSFET, or associated sampling resistor.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS/VDS2000/VDCI) to read the fault codes and freeze frame data. Record operating parameters such as vehicle speed and voltage at the time of the fault. Clear the fault codes and perform a road test to reproduce the fault.— Check that the brake fluid level is between the MAX and MIN marks. Inspect the brake fluid for discoloration, cloudiness, or metal debris. Replace the brake fluid if necessary.+5 more →
C000400›
DTC C000400 indicates an electrical fault in TCS (Traction Control System) Control Valve B within the IPB (Intelligent Integrated Braking System) (Fault Type 2 typically designates an open circuit, short circuit, or abnormal current). In the BYD One-Box brake-by-wire system, the IPB integrates the ESP function. TCS Valve B typically identifies the solenoid valve controlling rear wheel brake hydraulic pressure (or a specific channel valve). This fault means the IPB ECU detects the Valve B drive circuit current falls outside the specified threshold (too high or too low). Causes include an open or shorted coil, or mechanical binding of the valve spool resulting in abnormal drive current. This fault disables the TCS function, preventing the system from actively applying braking force to control the slip ratio during drive wheel slip. Under extreme conditions, the system downgrades the ESP function, retaining only basic ABS capabilities.
Causes
— Open circuit or inter-turn short circuit in TCS solenoid valve B coil inside the IPB assembly (internal electrical fault)— Poor contact or broken solder joint in the internal wiring harness between the IPB and the solenoid valve.— Severe brake fluid contamination or crystallization causes the valve spool to stick, triggering abnormal drive current.+2 more →
Actions
— Use VDS or Launch X431 to read all fault codes. Confirm whether the C000400 status is current or history, and check for related faults such as C0003XX/C0005XX.— Check the IPB wiring harness connectors (especially the 24-pin main connector) for backed-out pins, corrosion, or signs of water ingress. Measure the terminal contact resistance.+5 more →
C000404›
DTC C000404 indicates an electrical fault in High Pressure Switch Valve 2 inside the ESP (Electronic Stability Program) hydraulic modulator. This solenoid valve, a key actuator in the ESP hydraulic unit, switches the brake fluid pressure path from the master cylinder to the wheel cylinder during ESP intervention. The ESP ECU detects an anomaly in the valve drive circuit, such as an open solenoid coil, a short to power or ground, drive current exceeding the threshold (normal resistance is 2-8 Ω), or a damaged H-bridge drive circuit inside the ECU. This fault disables the ESP, ABS, and TCS functions, but basic hydraulic braking remains functional. This is a moderate safety-related fault.
Causes
— Internal solenoid valve coil in the ESP hydraulic modulator assembly burnt out or mechanically stuck: Prolonged use or brake fluid contamination causes the valve spool to seize, resulting in abnormal drive current that triggers the fault code.— Wiring harness and connector fault: Oxidation, loose connection, or water ingress at hydraulic modulator pin 25 (solenoid valve power supply) or pin 38 (ground), causing excessive contact resistance or intermittent open circuit.— Power supply system fault: low battery charge, unstable DC-DC converter output (outside the 9-16V range), or ground wire corrosion, causing solenoid drive undervoltage or overvoltage.+2 more →
Actions
— Use the BYD VDS/ED400 diagnostic tool to read the complete fault codes. Confirm C000404 is a Current fault, not a History fault, and check for accompanying related faults such as C080001 (low voltage) or C007204 (overtemperature).— Basic power supply check: Measure battery static voltage (>12V) and cranking voltage. Check DC-DC output stability. Inspect the ABS 25A fuse and ESP ground wires (G101/G102) to verify connections are secure and free of oxidation.+5 more →
C000A08›
DTC C000A08 indicates the IPB (Integrated Power Brake) received a data packet from the ACC (Adaptive Cruise Control) controller containing a checksum error, missing data frame, or out-of-range signal. The ACC controller (typically integrated into the MRR [Mid-Range Radar]) calculates the distance, relative speed, and angle of the target vehicle ahead. It transmits this information in real time via the CAN bus to the IPB to execute Automatic Emergency Braking (AEB) and Adaptive Cruise Control. The IPB logs "ACC data corruption" when it detects a CRC failure, abnormal data length, physically unreasonable values (e.g., sudden distance jumps), or a communication timeout. This fault deactivates the AEB and ACC functions and triggers the "Automatic Emergency Braking Limited" message on the instrument cluster. Basic hydraulic braking typically remains unaffected.
Causes
— Internal software error or hardware fault in the MRR (Mid-Range Radar) controller, causing transmission of incorrect data frames.— Interference, poor connection, or abnormal terminating resistance (standard: 60Ω) on the CAN communication line between the IPB and MRR.— MRR radar mounting position shifted due to collision or vibration, causing calibration data to mismatch the actual detection environment.+2 more →
Actions
— Use the VDS2000/VDS3100 diagnostic tool to read complete fault codes, record freeze frame data, and check for accompanying U-class communication faults or MRR-related fault codes.— Visually inspect the MRR radar inside the front bumper. Verify the mounting bracket is not deformed or loose, and the radar surface is free of obstructions, damage, or heavy dirt.+5 more →
C000B04›
The BYD new energy vehicle fault code system defines C000B04 as Left Rear Wheel Speed Sensor Circuit Low Input. The IPB (Intelligent Integrated Braking System) or ESC module triggers this code when the left rear wheel speed sensor signal voltage remains continuously below the threshold (typically <0.5V), or when the sensor circuit experiences a short to ground or an open circuit. This fault limits or disables the ABS, ESC, TCS, and Automatic Emergency Braking (AEB) functions, and illuminates the ABS/ESC warning light on the instrument cluster. Some sources incorrectly label this code as "ACC communication timeout" (the C000Axx series typically covers actual ACC communication faults). However, based on BYD’s standard fault code structure ('B' represents Left Rear and '04' represents circuit low input), this code fundamentally identifies a chassis wheel speed signal fault that severely compromises vehicle dynamic stability and braking safety.
Causes
— Internal short or open circuit in the left rear wheel speed sensor body (damaged sensor coil insulation causing abnormal resistance)— Sensor wiring harness short to ground, open circuit, or connector oxidation/water ingress (frequently occurs due to poor sealing after water exposure in the left rear wheel area).— Wheel hub bearing magnetic encoder ring (magnetic tone ring) damaged, cracked, contaminated with metal filings, or demagnetized+2 more →
Actions
— Use the VDS2000/VDS1000 diagnostic tool to read the DTC freeze frame data, verify the vehicle speed, wheel speed values, and system status at the time of the fault, and check for accompanying wheel speed sensor fault codes.— Raise the vehicle and visually inspect the left rear wheel speed sensor. Check the connector for looseness, water ingress, or oxidation (focusing on damaged sections of the corrugated wiring harness conduit), and inspect the wiring harness for wear or damage.+5 more →
C001000›
This DTC indicates the IPB (Intelligent Integrated Braking System / One-Box Integrated Braking System) ECU detected an electrical fault in the left front inlet valve (normally open valve) drive circuit. The inlet valve is a key solenoid valve in the ABS/ESC hydraulic modulator. It controls the brake fluid path from the brake master cylinder to the left front wheel brake cylinder. A "drive fault" occurs when the ECU detects an abnormal circuit condition while supplying power to the solenoid valve coil (typical resistance 3-6Ω) through the driver chip (usually an H-bridge driver or high-side drive MOSFET). These abnormal conditions include an open coil circuit, short to power, short to ground, driver chip over-temperature protection, or an abnormal drive circuit power supply. This fault prevents the left front wheel from establishing normal ABS/ESC pressure regulation and triggers system degradation (ABS/ESC function limited or disabled). The system retains only basic hydraulic braking, severely compromising vehicle active safety performance.
Causes
— Open circuit or inter-turn short circuit in the left front inlet valve solenoid coil inside the IPB electro-hydraulic module (valve body assembly fault, possibly with brake fluid contamination or overheating)— Damaged IPB ECU internal drive circuit, such as MOSFET power transistor breakdown or corresponding channel failure in dedicated driver chips (e.g., L9369/L99MC6).— Poor contact, terminal back-out, or pin corrosion/oxidation in the internal wiring harness or external connector between the IPB electro-hydraulic module and the ECU (common in vehicles after wading or chassis submersion).+2 more →
Actions
— Deep diagnostic check: Use VDS or a dedicated BYD diagnostic tool to read the complete fault code stream. Confirm if C001000 is a current (active) or historical fault. Check for accompanying fault codes (e.g., C001001-C00100F series wheel cylinder valve faults or C003000 series pressure sensor faults) to determine if a systemic fault exists.— Basic inspection: Inspect the IPB electro-hydraulic module for leaks or impact damage; verify the IPB wiring harness connector (usually located near the firewall) is secure and free of water ingress or corrosion; measure the battery voltage and verify the IPB main power supply and ground are normal (standard 12V system, operating voltage 9-16V).+3 more →
C001004›
DTC C001004 indicates the ABS electronic control unit (ECU) detected an electrical or functional fault in the left front wheel inlet valve. The ECU controls this key solenoid valve within the ABS hydraulic modulator assembly via an H-bridge driver circuit to regulate brake fluid flow from the master cylinder to the left front wheel cylinder during ABS/ESC intervention. Fault trigger mechanisms include a solenoid valve coil open or short circuit (abnormal resistance), a driver circuit short to power or ground, mechanical valve sticking causing abnormal feedback current, or internal ECU MOSFET driver stage damage. This fault disables the left front wheel ABS anti-lock function and limits the ESC stability control system, but the vehicle usually retains normal hydraulic braking. Because the E5 uses an integrated ABS/ESC hydraulic unit (HEU) combining the valve body and ECU into a single assembly, the fault may involve either the hydraulic mechanical section or the electronic control section.
Causes
— Open circuit or inter-turn short circuit in the internal left front inlet valve solenoid coil of the ABS hydraulic modulator assembly (insulation aging from prolonged high-temperature operation)— Oxidation, terminal back-out, or water ingress corrosion in the internal wiring harness or external connector pins between the ABS hydraulic modulator and the ECU, interrupting signal transmission.— ABS ECU internal H-bridge drive circuit fault (power MOSFET breakdown or pre-driver chip damage), unable to supply the valve body with the required approximately 5A peak holding current.+2 more →
Actions
— Connect the VDS or ED-400 diagnostic tool. Read the complete fault codes and record the Freeze Frame data. Check for accompanying codes C001000 (drive fault) or C001100 (oil outlet valve fault). Clear the fault codes and perform a road test to reproduce the fault.— Disconnect the electrical connector from the ABS hydraulic modulator assembly (24-pin or 28-pin, depending on E5 model year). Inspect the pins for green corrosion, backed-out pins, or burn marks. Clean with electrical contact cleaner and apply conductive grease.+5 more →
C001100›
DTC C001100 indicates a malfunction in the drive circuit of the internal left front wheel outlet solenoid valve within the Integrated Power Brake (IPB) system. This solenoid valve returns high-pressure brake fluid from the left front wheel brake cylinder to the reservoir during ABS/ESP activation to release wheel cylinder pressure. A "drive fault" indicates the IPB ECU detects an open circuit, short circuit, or short to ground or power in the H-bridge circuit driving this solenoid valve, or it detects a drive current exceeding the calibrated threshold (typically 2-3A). This fault prevents independent pressure release at the left front wheel, affecting ABS, ESC, AUTOHOLD, and Automatic Emergency Braking (AEB) functions. The IPB enters a degraded mode, retaining conventional hydraulic braking while potentially limiting electronic brake assist.
Causes
— Open circuit or inter-turn short circuit in the left front outlet valve solenoid coil inside the IPB assembly: solenoid resistance deviates from the standard range (normally approx. 2-5Ω), causing abnormal drive circuit detection.— Loose or corroded connector on the integrated wiring harness from the IPB to the left front wheel speed sensor/valve body: Although C001100 indicates an internal valve drive fault, some models use a split connection between the IPB valve body and ECU. Backed-out or oxidized connector pins can interrupt the drive signal.— Damaged solenoid valve driver chip (H-bridge driver) inside the IPB ECU: Overvoltage, static electricity, or brake fluid ingress causes power MOSFET breakdown, preventing PWM drive signal output.+2 more →
Actions
— Fault Confirmation and Freeze Frame Analysis: Use VDS or DMS1000 to read all fault codes and confirm if C001100 is a current fault. Check freeze frame parameters including vehicle speed, hydraulic pressure, and battery voltage to rule out a false code.— Visually inspect the wiring harness and connectors: Inspect the IPB assembly connector (usually located near the firewall) for looseness or water ingress, measure continuity from the connector to the valve body wiring harness (resistance must be less than 1Ω), and inspect the pins for corrosion or push-out.+3 more →
C001104›
DTC C001104 indicates a circuit or functional fault in the left front wheel outlet valve (LF Outlet Valve) inside the ABS (Anti-lock Braking System) Hydraulic Electronic Control Unit (HECU) assembly. This solenoid valve integrates into the ABS pump body. During the ABS pressure reduction phase, it returns high-pressure brake fluid from the left front brake caliper to the reservoir or master cylinder, rapidly reducing wheel cylinder pressure and preventing wheel lock-up. Fault trigger conditions include an open or short circuit in the solenoid coil, a mechanically stuck valve core, a damaged internal ABS ECU driver circuit (MOSFET), or an open or short circuit in the control wiring. This fault disables the left front wheel ABS pressure reduction function. During emergency braking, this wheel may lock up prematurely, causing the vehicle to pull or lose directional control and severely compromising driving safety.
Causes
— Open circuit or short circuit in the solenoid coil, or stuck valve spool in the internal left front outlet valve of the ABS hydraulic modulator assembly (internal mechanical fault)— Oxidized, loose, or backed-out ABS pump connector pins, or a poor wiring harness connection, interrupting the solenoid valve power supply (pin 25) or control signal.— Damaged ABS ECU internal solenoid valve drive circuit (e.g., burnt driver chip), unable to output approximately 12V drive current to the solenoid valve.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000/VDS2100) to read the fault code and confirm C001104 is present. Check the freeze frame data to verify the vehicle speed and system status when the fault occurred.— Run the ABS system 'Actuator Test', select the left front outlet valve (LF Outlet Valve), and listen for a clear 'click' sound to determine if the solenoid valve actuates normally.+6 more →
C001400›
C001400 is an ISO 14229 standard fault code. 'C' represents the chassis system, '0014' specifies the right front wheel brake line inlet valve, and '00' indicates a General Electrical Failure. In BYD vehicles equipped with Bosch ESP 9.x or the in-house IPB (Intelligent Integrated Braking System), this fault indicates a circuit malfunction inside the Hydraulic Control Unit (HCU) driving the right front inlet solenoid valve. Possible causes include an open or short circuit in the solenoid valve coil, a damaged driver stage (MOSFET) on the control circuit board, or abnormal current caused by a sticking valve core. This fault disables the ABS, ESP, and Automatic Emergency Braking (AEB) functions, but does not affect conventional hydraulic braking. This safety-related fault requires immediate repair.
Causes
— Right front inlet solenoid valve coil inside the ABS Hydraulic Control Unit (HCU) burnt out or open circuit (internal hardware damage).— IPB/ESC module internal circuit board driver chip fault (such as solenoid valve driver MOSFET breakdown or cold solder joint)— Poor contact in the ABS pump assembly power supply or ground circuit (oxidation or loose connection at the front compartment wiring harness connector causing unstable voltage)+2 more →
Actions
— Use the BYD VDS2000 or Bosch KT770 diagnostic tool to read fault codes. Confirm C001400 and accompanying codes (e.g., C001100 left front fault) and record freeze frame data (vehicle speed, temperature, etc.).— Visually inspect the ABS pump assembly (located on the left side of the engine compartment or near the firewall) for leaks, check the connector for water ingress or oxidation, and measure the connector power supply (constant 12V, IGN power) and ground resistance (<1Ω).+5 more →
C001404›
DTC C001404 indicates an electrical fault or functional abnormality in the inlet solenoid valve (normally open valve, NO Valve) controlling the right front brake wheel cylinder within the ABS (Anti-lock Braking System) Hydraulic Control Unit (HCU). During normal braking, this solenoid valve remains open to allow brake fluid into the wheel cylinder. When ABS activates, the ECU rapidly closes the valve to regulate pressure. Root causes include an open or short circuit in the solenoid valve coil, a failed ABS ECU internal drive circuit (MOSFET or intelligent power chip), a stuck valve spool causing a response timeout, or abnormal wiring connections. This fault disables the ABS/ESP functions, though normal hydraulic braking remains available. Emergency braking carries a risk of right front wheel lockup, and the system may limit the Automatic Emergency Braking (AEB) function.
Causes
— Open circuit or inter-turn short circuit in the right front inlet valve solenoid coil inside the ABS hydraulic modulator assembly (resistance deviates from the standard value of 2-6Ω)— Damaged solenoid valve drive circuit inside the ABS ECU (e.g., high-side/low-side driver chip breakdown or dry solder joint).— Backed-out pins, oxidation, or poor contact at harness connectors (such as X1 and X2 plugs) interrupts the drive signal.+2 more →
Actions
— Use a VDS2000 or X431 diagnostic tool to read the complete fault codes and freeze-frame data. Record parameters such as vehicle speed, wheel speed, and battery voltage. Clear the fault codes and road test the vehicle (including braking at speeds above 30 km/h) to determine if the fault is intermittent.— Visually inspect the ABS hydraulic modulator assembly for leaks. Check the wiring harness connectors (especially the front right) for looseness or water ingress. Check the brake fluid level and color. Replace the fluid if it is black or crystallized.+5 more →
C001500›
DTC C001500 indicates the IPB (Integrated Power Brake) ECU detects a circuit fault while actuating the right front wheel outlet valve (RF Outlet Valve, a Normally Closed Valve). This solenoid valve returns brake fluid from the right front wheel cylinder to the reservoir or master cylinder during the ABS/ESC pressure release phase, enabling precise brake force control. Root causes include an open or short circuit in the solenoid coil, a damaged ECU on-board driver chip (MOSFET/ASIC), abnormal current feedback (e.g., mechanical valve sticking causing a current over-limit), or a wiring harness fault. This fault prevents the right front wheel from achieving accurate pressure build-up, hold, and release cycles, and disables ABS/ESC functions. In extreme cases, it causes right front wheel brake drag and uneven brake force distribution, severely compromising driving safety.
Causes
— Open circuit, inter-turn short circuit, or short to housing in the right front outlet valve solenoid coil inside the IPB assembly— Damaged onboard solenoid valve drive circuit in the IPB control unit (ECU) (e.g., L9305 chip or high-side/low-side driver transistor breakdown)— IPB wiring harness connector (usually a 32-pin or 48-pin plug): Oxidation, backed-out terminals, corrosion from water ingress, or poor contact at the corresponding pins.+2 more →
Actions
— Diagnostic Tool Reading: Use a BYD VDS or Launch X-431 diagnostic tool to read the complete DTC, freeze frame data, and Fault Occurrence Counter (FDC). Record key data at the time of the fault, such as vehicle speed, wheel speed, and brake pedal travel.— Visual inspection: Check the IPB assembly (located on the left side of the front bulkhead in the engine compartment) for impact deformation and brake fluid leaks. Inspect wiring harness connectors X1 and X2 specifically for looseness, failed locking tabs, damaged sealing rings, or water stains/corrosion.+7 more →
C001504›
DTC C001504 indicates a circuit or functional fault in the Right Front Outlet Valve inside the Anti-lock Braking System (ABS) Hydraulic Control Unit (HCU) assembly. This solenoid valve is a core component of the ABS actuator. It opens during the pressure reduction phase of the anti-lock control cycle to release hydraulic pressure from the right front wheel brake cylinder. The ABS ECU sets this fault code when it detects an open or short circuit in the valve drive circuit, or an abnormal valve spool response (such as sticking or a response timeout). This fault disables the ABS pressure regulation function for the right front wheel. During emergency braking, the wheel may lose anti-lock protection and lock up prematurely, severely compromising braking performance and driving safety. This condition may also trigger a degraded operating mode in related systems, including Electronic Stability Control (ESC) and Automatic Emergency Braking.
Causes
— Open circuit, short circuit, or resistance drift in the internal right front outlet solenoid valve coil of the ABS hydraulic control unit (HCU) assembly (normal range: typically 2-5 Ω)— Mechanical sticking of the solenoid valve spool, often resulting from prolonged failure to replace brake fluid, causing fluid degradation, crystallization, or contaminant buildup.— Poor contact, pin corrosion, oxidation, or moisture ingress due to poor sealing at the wiring harness connector between the ABS ECU and the hydraulic modulator assembly.+2 more →
Actions
— Use the BYD VDS2000 or VDS6000 diagnostic tool to read and confirm DTC C001504 and freeze frame data. Check for accompanying C0010xx series valve body fault codes to determine if a system fault exists.— Perform the hydraulic modulator Actuator Test and listen for a clear 'click' from the right front outlet valve solenoid. If the valve makes no sound, disconnect the HCU wiring harness connector and measure the solenoid coil resistance between the two terminals of the right front outlet valve. Compare the reading with the workshop manual standard value (usually 2-5Ω) to check for an open circuit (infinite resistance) or a short circuit (close to 0Ω).+4 more →
C001800›
DTC C001800 indicates the IPB (Intelligent Power Brake) electro-hydraulic control module detects an abnormal drive circuit for the left rear wheel inlet valve. This is a hardware-level fault. During self-check or operation, the ECU detects an open circuit, a short circuit (to ground or power), or a driver chip fault in the left rear inlet valve solenoid coil drive circuit. The inlet valve is a key component of the ABS/ESC Hydraulic Control Unit (HCU) and controls the hydraulic passage between the brake master cylinder and the left rear wheel brake cylinder. This fault prevents the left rear wheel from participating in ABS, ESC, and regenerative braking coordination. In extreme cases, it may cause left rear wheel brake failure or brake drag, severely compromising driving safety.
Causes
— Open or short circuit in the left rear inlet valve solenoid coil inside the IPB electro-hydraulic module (abnormal resistance; normal: 2-5Ω)— Water ingress, oxidation, or loose pins at the IPB module wiring harness connector (32-pin or 48-pin), causing poor contact in the drive signal circuit.— Solenoid valve driver chip (MOSFET or dedicated driver IC) on the IPB internal ECU circuit board is burnt out or has a cold solder joint.+2 more →
Actions
— Use VDS or the BYD dedicated diagnostic tool to read the complete fault code and freeze frame data. Confirm parameters such as vehicle speed, hydraulic pressure, and system voltage at the time of the fault to rule out a false code.— Switch off the ignition and disconnect the IPB electro-hydraulic module wiring harness connector. Inspect the connector pins for corrosion, deformation, or signs of water ingress. If necessary, clean the pins with electrical contact cleaner and apply conductive grease.+3 more →
C001804›
On the BYD E5 and similar new energy vehicles, DTC C001804 indicates a left rear wheel speed sensor (WSS) circuit performance fault, rather than a hydraulic modulator inlet valve fault (early reference materials may contain code definition errors). The sensor is typically a variable reluctance or Hall-effect type mounted on the left rear knuckle. It generates a sine wave or square wave signal by detecting magnetic field changes in the wheel hub bearing magnetic encoder ring, supplying precise wheel speed data to the ABS/ESP control unit. The ECU sets this DTC when it detects a continuously missing left rear wheel speed signal, out-of-range voltage amplitude, intermittent signal interruption, or an abnormal logical relationship between this wheel speed and the other three (e.g., reading 0 while the vehicle moves). This fault restricts or completely disables the Anti-lock Braking System (ABS), Electronic Stability Program (ESP), Traction Control System (TCS), Electronic Parking Brake (EPB), and Automatic Emergency Braking (AEB). On certain 4WD models (such as the Tang DM), it triggers the 4WD protection mechanism, forcing the vehicle into 2WD mode and severely compromising driving safety.
Causes
— Open or short circuit in the wheel speed sensor internal coil (normal magnetic inductive sensor resistance is approximately 1.2-1.8kΩ; values outside this range indicate a faulty sensor).— Water ingress and oxidation at the sensor wiring harness connector, loose terminals, or poor contact (common after driving through water during the rainy season, washing the vehicle, or due to an aging seal)— Incorrect sensor installation gap (standard air gap: 0.3-1.0 mm) or loose retaining bolts, resulting in low signal amplitude.+2 more →
Actions
— Connect the VDS2000 or Launch X431 diagnostic tool. Enter the ABS/ESP system to read fault codes. Confirm C001804 is the current fault code. Check the vehicle speed and wheel speed information in the freeze frame data.— Access the live data stream. Slowly push or drive the vehicle and check if the left rear wheel speed signal remains at 0 km/h, fluctuates erratically, or differs from the other three wheel speeds by more than 5 km/h.+6 more →
C001900›
DTC C001900 indicates a malfunction in the drive circuit or mechanical components of the Rear Left Outlet Valve inside the IPB (Integrated Power Brake) hydraulic control unit. During ABS/ESC operation, this solenoid valve controls brake fluid return from the left rear wheel cylinder to the low-pressure accumulator or reservoir to precisely regulate wheel cylinder pressure. The ECU detects an abnormal valve drive current (open circuit, short circuit, or short to ground/power) or mechanical sticking of the valve spool, preventing the IPB from releasing pressure at the left rear wheel. This fault triggers ESP system degraded mode and may limit ABS, ESC, energy recovery, and automatic emergency braking functions. The system usually retains conventional hydraulic braking (depending on the IPB failsafe strategy).
Causes
— Open circuit, short circuit, or short to ground in the left rear outlet valve solenoid coil inside the IPB hydraulic unit causes drive current to exceed the calibrated threshold (typical abnormal range: 0.3-1.5A).— Brake fluid contamination (excessive water content, metal debris, or gel-like deposits) causes the outlet valve spool to stick in the open or closed position, causing the ECU to detect abnormal position feedback.— IPB ECU internal valve body drive circuit fault, such as a damaged power MOSFET, a burnt sampling resistor, or a poor solder joint on the driver chip.+2 more →
Actions
— Use the BYD VDS2000 or a diagnostic tool to access the IPB system, read and confirm C001900 is a current fault (Active), and record the vehicle speed, hydraulic pressure, and valve body drive current values from the freeze frame data (Freeze Data).— Clear the fault codes and perform the IPB dynamic function test: in a safe area, drive at 20-40 km/h and brake sharply to trigger ABS operation. Observe whether the fault recurs. If the fault recurs, confirm a hardware fault.+4 more →
C001904›
This DTC indicates an electrical fault in the drive circuit or actuator body of the left rear wheel outlet solenoid valve (Dump Valve/Outlet Valve) inside the ABS/ESP hydraulic control unit (HCU). The outlet valve is a switching solenoid in the ABS pressure modulation unit that controls brake fluid return from the left rear wheel to the reservoir. The ABS ECU drives it via a PWM signal. The '04' sub-code in DTC C001904 typically indicates an open drive circuit, an open solenoid coil, or a short to ground. This fault prevents the ABS/ESP system from reducing pressure at the left rear wheel. During emergency braking or stability control, the left rear wheel may lock up or experience abnormal brake force distribution, severely compromising vehicle handling safety.
Causes
— Open circuit, short circuit, or abnormal resistance in the left rear outlet valve solenoid coil inside the ABS hydraulic modulator assembly (normal range typically 20-60 Ω, depending on specific model).— ABS pump wiring harness connector (usually located near the engine compartment firewall) pins backed out, oxidized, corroded, or making poor contact, interrupting the drive signal.— Damaged ABS ECU internal solenoid valve drive circuit (e.g., MOSFET power transistor breakdown or driver chip failure), unable to provide approximately 5-6A drive current.+2 more →
Actions
— Step 1: Visual inspection and basic measurement. Disconnect the ABS hydraulic modulator assembly wiring harness connector and check the pins for corrosion or backing out. Measure the left rear outlet valve solenoid resistance using a multimeter (refer to the specific vehicle repair manual for pin positions, usually MR or ML+ corresponding to the Out terminal). The standard resistance is 20-60 Ω. Infinite resistance or a value significantly outside the standard range indicates a faulty internal solenoid valve in the hydraulic modulator.— Step 2: Wiring harness continuity and insulation check. In the disconnected state, measure the continuity resistance of the drive circuit from the ECU to the solenoid valve (should be <1Ω), and measure the insulation resistance of this circuit to body ground and to the power supply (should be >10MΩ). Repair the wiring harness if a short or open circuit exists.+3 more →
C001C00›
DTC C001C00 indicates the IPB (Intelligent Integrated Braking System) ECU detects a fault in the right rear wheel inlet valve (normally open valve) drive circuit. This typically occurs when the internal ECU valve drive circuit (MOSFET or dedicated driver chip) detects an open circuit, short to power, short to ground, or abnormal current feedback while attempting to drive the right rear inlet valve. The inlet valve acts as a key actuator in the ABS/ESP hydraulic control unit, controlling brake fluid flow from the master cylinder to the right rear wheel cylinder. This fault prevents the right rear wheel from participating in ABS pressure regulation and ESP active braking intervention. Extreme cases may affect braking balance; however, the system retains basic hydraulic braking functions (direct pedal pressure build-up). The warning lamp illuminates, and the system disables functions including ABS, ESP, and Automatic Emergency Braking (AEB).
Causes
— Open or short circuit in right rear inlet valve solenoid coil inside IPB electro-hydraulic module (resistance value outside standard 3-7Ω range)— Hardware fault in the IPB ECU internal valve drive circuit, such as a damaged driver chip (e.g., L9369 or other dedicated IC) or MOSFET breakdown.— Loose IPB wiring harness connector (usually located on the top or side of the module), corrosion from water ingress, or oxidized pins causing excessive contact resistance.+2 more →
Actions
— Use a dedicated diagnostic tool (VDS or equivalent) to read the complete fault codes and freeze frame data. Check for accompanying sub-codes such as C001C01 (right rear inlet valve short to power) or C001C02 (short to ground), and verify the hydraulic unit version number.— Visually inspect the IPB electro-hydraulic module exterior for leaks. Disconnect the battery negative terminal, then check for corroded, bent, or backed-out connector pins. Measure the wiring harness continuity from the connector to the ECU.+5 more →
C001C04›
DTC C001C04 indicates an electrical or mechanical fault in the right rear wheel inlet valve within the ABS/ESC Hydraulic Control Unit (HCU). The right rear inlet valve is a normally open high-speed solenoid valve controlling the hydraulic passage from the brake master cylinder to the right rear wheel brake cylinder. This fault indicates the ABS ECU detects an open circuit or short circuit (to power or ground) in the right rear inlet valve drive circuit, a stuck valve spool, or an abnormal response. This prevents the ECU from accurately regulating brake pressure at the right rear wheel. This directly affects the execution of Anti-lock Braking System (ABS), Electronic Brakeforce Distribution (EBD), Electronic Stability Control (ESC), and Automatic Emergency Braking (AEB) functions at the right rear wheel. In extreme cases, this causes right rear wheel braking failure or lock-up, triggers multiple system warnings, and initiates fail-safe mode (conventional hydraulic braking remains operational, but electronic assist functions are limited).
Causes
— Open circuit or abnormal resistance in the right rear inlet valve solenoid coil within the hydraulic modulator assembly (normal resistance is typically 2-5Ω; out of tolerance).— Poor contact at the wiring harness connector between the ABS ECU and hydraulic modulator, corroded pins, or damaged wiring harness, interrupting drive signal transmission.— ABS ECU internal valve drive circuit fault (e.g., damaged power MOSFET, driver chip, or sampling resistor) resulting in insufficient drive current (typically requires 1-2A peak current)+2 more →
Actions
— Use a dedicated diagnostic tool (such as BYD VDS or Launch X431) to read all fault codes and freeze frame data. Confirm if C001C04 is a current fault. Check for accompanying faults such as C001C00 (right rear inlet valve drive fault) or other wheel speed sensor faults. Clear the fault codes and perform a road test to observe if the fault returns.— Inspect the appearance of the ABS hydraulic modulator and wiring harness connector: check the hydraulic modulator assembly plug near the right rear wheel for looseness, water ingress, oxidation, or burn damage. Measure the wiring harness continuity (must be less than 1Ω) and insulation resistance (must be greater than 10MΩ to prevent a short to ground or power) between the ABS ECU and the corresponding hydraulic modulator pins.+3 more →
C001D00›
This DTC indicates a drive circuit fault for the Right Rear Outlet Valve inside the Intelligent Integrated Braking System (IPB) electro-hydraulic module. The outlet valve is a key actuator in the ABS/ESP hydraulic modulator. During the pressure reduction phase, it routes brake fluid from the right rear wheel cylinder back to the reservoir to reduce wheel cylinder pressure. A drive fault typically indicates the ECU detected an open or short circuit in the solenoid valve coil, abnormal drive current, or a damaged power stage circuit (MOSFET/driver chip). This fault disables the right rear wheel ABS/ESP pressure reduction function and forces the system into a degraded protection mode (ABS/ESC functions limited or disabled). Symptoms include a hard brake pedal, increased braking distance, and, in extreme cases, compromised vehicle stability control.
Causes
— Open circuit or inter-turn short circuit in the right rear outlet valve solenoid coil inside the IPB electro-hydraulic module causes the drive current to exceed the threshold range.— IPB control board power drive circuit fault, such as damaged intelligent high-side/low-side switch chip, drive MOSFET breakdown, or faulty sampling resistor.— Mechanical binding in the hydraulic valve body (due to contamination, corrosion, or seal debris) causes excessive resistance to solenoid valve movement, resulting in a continuous high drive current that triggers protection.+2 more →
Actions
— Use BYD VDS or a dedicated diagnostic tool to read complete DTCs, confirm C001D00 is currently active, and record freeze frame data (vehicle speed, brake pressure, voltage, etc.).— Visually inspect the IPB electro-hydraulic module for impact damage, brake fluid leakage, and corrosion or water ingress at the connector. Check the continuity and insulation of the relevant wiring harnesses (power, ground, CAN).+4 more →
C001D04›
This DTC indicates an electrical or mechanical fault in the right rear wheel outlet valve (discharge valve/release valve) inside the ABS (Anti-lock Braking System) hydraulic modulator assembly. This solenoid valve is a key actuator in the ABS hydraulic unit and controls the release of hydraulic pressure from the right rear wheel brake caliper during the ABS activation cycle. The ECU sets this DTC when it detects an open circuit, short circuit, short to ground, or short to power in the solenoid valve circuit, or when the valve spool fails to open or close normally due to mechanical sticking. This fault causes the right rear wheel ABS pressure regulation function to fail. During emergency braking, the right rear wheel may fail to release pressure normally (causing premature lock-up) or retain pressure abnormally, severely affecting braking stability and safety. The system enters fail-safe mode, disables the ABS, EBD, and ESC functions, and illuminates the relevant warning lamps.
Causes
— Open circuit, short circuit, or resistance drift in the right rear wheel outlet valve solenoid coil inside the ABS hydraulic modulator assembly.— Damaged ABS ECU internal solenoid valve drive circuit (e.g., burnt-out driver chip or power MOSFET, or cold solder joint)— Brake fluid contamination, degradation, or impurities causing solenoid valve spool binding, sealing ring swelling, or hydraulic circuit blockage.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS or ED400) to read all fault codes, confirm C001D04 is a current fault that will not clear, and record the freeze frame data.— Check the ABS system power supply: Measure the voltage at the ABS ECU power pins. The voltage must be 9-16V (normally about 12.5V). Check the fuses, relays, and power supply wiring.+6 more →
C002100›
DTC C002100 indicates the IPB (Integrated Power Brake) detects brake master cylinder pressure (booster pressure) below the system-calibrated normal operating threshold. In BYD models equipped with the IPB system, such as the Song PLUS DM-i, a motor-driven hydraulic pump generates brake assist, replacing the conventional vacuum booster. When the internal IPB pressure sensor detects the master cylinder pressure fails to reach the target value within the specified time or remains below the safety threshold, the ECU sets this fault code and illuminates the ABS/ESP warning light. This condition can cause a hard brake pedal (loss of assist), increased braking distance, Automatic Emergency Braking (AEB) deactivation, and limited energy recovery, compromising driving safety in severe cases. This functional braking system fault can result from an internal IPB hydraulic circuit leak, pressure sensor signal drift, reduced motor/pump assembly efficiency, or abnormal ECU control logic.
Causes
— IPB electro-hydraulic module internal master cylinder pressure sensor fault, signal drift, or poor circuit contact (connector oxidation, backed-out pins)— Wear, binding, or drive circuit fault in the IPB motor or hydraulic pump assembly, causing slow or insufficient pressure build-up.— Brake fluid leak prevents the system from maintaining pressure (aging IPB unit seal ring, master cylinder seal failure, or loose line joints)+2 more →
Actions
— Use the BYD VDS2000/3000 diagnostic tool to read the fault code and freeze frame data. Record the vehicle speed, master cylinder pressure, motor status, and ambient temperature at the time of the fault.— Visually check that the brake fluid level is between MAX and MIN, and inspect the IPB unit, brake lines, and calipers for signs of fluid leakage.+4 more →
C002004›
DTC C002004 indicates a functional fault in the return pump motor inside the ABS/ESC Hydraulic Control Unit (HCU). The return pump is a core actuator in the ABS system. During the anti-lock braking cycle, it pumps brake fluid from the low-pressure side of the wheel cylinder back to the high-pressure side or the reservoir. The fault falls into two categories: 1) "Unable to run" — Indicates an open or shorted motor winding, completely worn carbon brushes, a burnt commutator, or a damaged motor drive circuit (H-bridge MOSFET or relay) inside the ABS control module, preventing the pump motor from receiving drive current. 2) "Unable to stop running" — Indicates stuck motor drive relay contacts, failed control chip logic, or an abnormal feedback signal, causing the pump motor to run continuously when not required. This fault directly disables ABS, ESP, and TCS functions. In extreme cases, it affects brake pedal feel (hardening or abnormal pulsation). This is a Level 2 fault affecting driving safety.
Causes
— Recirculation pump motor damaged: Excessive motor carbon brush wear causing poor contact, a burnt commutator, or an open/short circuit in the armature winding prevents the motor from starting or causes weak operation.— ABS control module drive circuit fault: The motor drive chip (H-bridge circuit), power MOSFET, or relay contacts inside the control module are burnt out or stuck, causing a failure to drive the motor or disconnect the motor power supply.— Power supply and wiring issues: Blown ABS hydraulic unit high-current power supply fuse (usually 30A-60A), loose or oxidized power wiring connections, or poor ground wiring contact, causing insufficient motor supply voltage or abnormal control signals.+2 more →
Actions
— Fault confirmation and freeze frame recording: Use a dedicated BYD diagnostic tool (VDS2000/VDS6000 or Launch X431) to read fault code C002004. Record freeze frame data (vehicle speed, voltage, temperature, etc.) and confirm whether the fault frequency is intermittent or continuous.— Basic circuit check: Check if the ABS pump high-current fuse in the engine compartment fuse box (marked ABS MOTOR or similar, usually 40A-60A) is blown. Measure the power supply (BAT+), ignition power (IG+), and ground (GND) voltages at the ABS control module connector. Verify the battery voltage is normal (above 12.6V).+5 more →
C002192›
This fault code indicates the IPB (Integrated Power Brake) system detects pressure inside the brake booster chamber below the normal operating threshold. In models such as the Song PLUS DM-i, the IPB system generates brake assist pressure via an electric vacuum pump or direct motor drive and continuously monitors this pressure using a pressure sensor. The system triggers DTC C002192 when it detects assist pressure remaining below the target value (typically below -0.6bar or the set threshold range) for longer than the specified time (e.g., 500ms) and rules out sensor signal interference. This fault causes a hard brake pedal and increased braking distance. The system restricts the regenerative braking function and illuminates the ABS/ESC warning light. Extreme conditions may trigger Limp Home mode, severely compromising driving safety.
Causes
— Electric vacuum pump assembly fault: Worn vacuum pump motor carbon brushes, aging pump body vanes, or a drive circuit fault prevents the pump from building sufficient vacuum (common in vehicles with over 60,000 km).— IPB integrated module internal pressure sensor fault: Sensor signal drift, internal circuit fault, or seal failure between the sensor and the hydraulic chamber, causing a false low-pressure reading.— Vacuum line system leak: Aged or cracked vacuum lines, failed vacuum reservoir sealing ring, loose line joints, or a sticking check valve causing insufficient vacuum retention.+2 more →
Actions
— Use the VDS2000/VDS3000 diagnostic tool to read the DTC freeze frame data. Record the vehicle speed, brake pedal travel, Brake Booster Pressure, and vacuum pump status at the time of the fault to determine whether the fault is intermittent or persistent.— Visually inspect the IPB module exterior for signs of brake fluid leakage. Check the wiring harness connectors (especially the 24-pin main connector) for oxidation or looseness. Check the vacuum lines (if applicable) for cracks, collapse, or loose connections.+6 more →
C002400›
DTC C002400 indicates the IPB (Integrated Electro-Hydraulic Braking) system detects an electrical fault in the brake pedal pressure feedback signal circuit. The IPB system uses the brake pedal travel sensor (or pressure sensor) to monitor the driver's braking intent in real time. This sensor typically mounts on the brake pedal mechanism or master cylinder input and provides an analog voltage or PWM signal to the IPB ECU. The ECU triggers this DTC when it detects an open circuit, a short to ground or power in the signal circuit, a signal voltage outside the calibrated range (e.g., 0.5-4.5V), or an abnormal signal drift rate. This fault limits or disables the brake assist function, deactivates the ESC/ABS system, and disables the Automatic Emergency Braking (AEB) function. The vehicle may enter mechanical backup braking mode, which significantly increases pedal effort and severely compromises driving safety.
Causes
— Brake pedal travel/pressure sensor internal coil open circuit, Hall element failure, or signal drift.— Sensor wiring harness worn, open, or shorted to ground at the pedal mechanism, firewall pass-through, or high-temperature area of the motor compartment.— Fault in the internal signal acquisition circuit, ADC conversion circuit, or power supply circuit of the IPB electro-hydraulic module+2 more →
Actions
— Use the BYD VDS or Launch X-431 diagnostic tool to read the fault code. Confirm whether C002400 is an active or history fault, and record the pedal signal voltage from the freeze frame data.— Visually inspect the brake pedal mechanism for smooth movement. Inspect the sensor body and wiring harness for damage or crush marks, focusing on the wiring harness sleeve between the pedal arm and the firewall.+5 more →
C003108›
This DTC indicates the ABS control unit detects an abnormal or completely lost signal input while monitoring the left front wheel speed sensor. The wheel speed sensor (typically magnetic or Hall-effect) generates a pulse signal by monitoring the rotation of the tone ring on the half shaft or wheel hub. Systems such as ABS, ESC, and EPB rely on this signal to calculate wheel speed. The control unit sets C003108 when the signal voltage falls outside the threshold (<0.5V or >4.5V), the signal frequency is abnormal, or intermittent interruptions occur. This fault prevents accurate detection of the left front wheel speed. It triggers ABS failure, deactivates the ESC system, disables the automatic emergency braking system, and potentially affects the coordinated control of the energy recovery system. On pure electric models such as the E5, it also affects motor torque distribution and coasting energy recovery smoothness.
Causes
— Left front wheel speed sensor failure: Internal coil open circuit (magnetic type resistance should be 1.2-1.6kΩ) or damaged Hall element, resulting in no signal output or insufficient output amplitude.— Abnormal sensor installation gap: Bearing wear, loose sensor retaining bolts, or mounting bracket deformation causes the gap between the sensor and tone ring to exceed the standard value (0.3-1.2mm), attenuating signal amplitude.— Wiring harness and connector fault: Steering or driving over bumps places tension on the chassis wiring harness, breaking internal wires (commonly near the fender liner); water ingress oxidizes the connector; or damaged shielding allows electromagnetic interference.+2 more →
Actions
— Initial inspection: Raise the vehicle. Visually inspect the left front wheel speed sensor for damage. Check the wiring harness routing for chafing or crush marks. Check the connector for looseness, water ingress, or oxidation.— Reluctor ring inspection: Rotate the left front wheel and inspect the reluctor ring for missing teeth, deformation, cracks, or attached foreign matter. Clean metal filings and oil contamination from the reluctor ring surface. Check the driveshaft bearing clearance (replace if radial play >0.5 mm).+5 more →
C003200›
This DTC indicates the IPB (Intelligent Integrated Brake Control Unit) detects an abnormal supply voltage to the left front wheel speed sensor. Specifically, the ECU detects the sensor supply circuit voltage (typically 12V battery voltage or 5V reference voltage) falls outside the normal threshold range (e.g., below 9V, above 16V, or deviating from the standard value by more than ±0.5V), or detects an open circuit, short to ground, or short to power in the supply circuit. This fault causes a missing or distorted left front wheel speed signal, triggering degradation protection in the ABS, ESC, and EPB systems. It affects regenerative braking efficiency, Automatic Emergency Braking (AEB), and vehicle stability control functions. In extreme cases, it may extend braking distance or cause the vehicle to pull to one side.
Causes
— Open circuit, chafing, or short to ground in the left front wheel speed sensor wiring harness (especially at moving sections near the suspension control arm and fender liner)— A shorted or burnt-out internal coil in the wheel speed sensor causes excessive supply current and pulls down the voltage.— Internal power supply drive circuit fault in the IPB control unit (e.g., damaged MOSFET, damaged LDO voltage regulator chip, or cold solder joint).+2 more →
Actions
— Use the VDS2000/VDS3000 diagnostic tool to read all fault codes and freeze frame data. Check for accompanying C003108 (signal fault) or C003204 (circuit fault) codes. Record the vehicle speed and ambient temperature at the time of the fault.— Raise the vehicle. Visually inspect the exterior of the left front wheel speed sensor connector (located near the shock absorber or brake hose bracket). Check the pins for corrosion, backing out, or water ingress. Test the connector sealing.+5 more →
C003204›
DTC C003204 indicates an electrical fault in the left front wheel speed sensor (WSS) circuit within the BYD ABS system. This variable reluctance or Hall-effect sensor supplies the wheel speed signal to the ABS/ESC control unit. The control unit sets this code upon detecting an open circuit, short to ground, short to power, or abnormal signal interruption in the sensor circuit. In BYD new energy vehicles, this fault impairs normal ABS/ESP operation. It also limits regenerative braking, disables cruise control, disrupts four-wheel-drive torque distribution (if applicable), and may trigger a "Check braking system" warning. Because electric vehicles rely on wheel speed signals to calculate coasting energy recovery and estimate driving range, this fault reduces driving smoothness and causes inaccurate range displays. In severe cases, it triggers false ABS activation or complete ABS failure, compromising driving safety.
Causes
— Left front wheel inner wiring harness wear: Long-term bending at the steering knuckle or suspension moving parts damages the harness insulation, causing an intermittent open circuit or short to ground.— Sensor connector oxidized/loose: Wading or damp environments cause connector pin oxidation and corrosion, or a damaged locking tab causes excessive contact resistance.— Sensor failure: Internal coil open circuit, magnetic core demagnetization, or Hall element aging resulting in abnormal or no signal output.+2 more →
Actions
— Visual inspection: Check the left front wheel speed sensor connector for looseness, oxidation, or water ingress. Check the wiring harness at the steering knuckle and control arm for wear, damaged insulation, or pinch marks.— Diagnostic tool check: Use VDS or a generic diagnostic tool to read the fault code status (current/history). Check the data stream for abnormal left front wheel speed (displaying 0, erratic, 255 km/h, or differing significantly from the other three wheels).+7 more →
C003408›
DTC C003408 indicates the ABS control unit detects an abnormal right front wheel speed sensor (WSS) signal, specifically signal amplitude out of range, signal interruption, or excessive signal noise. On models such as the BYD E5, this sensor typically features a magnetic induction (passive inductive) design, generating a sine wave signal via the alternating magnetic field produced by the rotating tone ring (target wheel). If the signal voltage drops below the threshold (typically <0.1V), experiences interruption, or exhibits waveform distortion, the ABS/ESC system cannot accurately calculate the right front wheel angular speed. This disables anti-lock control, Electronic Brakeforce Distribution (EBD), the Traction Control System (TCS), and the energy recuperation braking coordination strategy. This classifies as a hard fault or an intermittent signal fault. The instrument cluster illuminates the ABS/ESC warning light, and some models limit energy recuperation strength and switch to a conventional hydraulic braking priority mode.
Causes
— Open or short circuit in the right front wheel speed sensor internal coil, or Hall element aging failure (if Hall-type), causing insufficient output signal amplitude.— Sensor wiring harness open circuit, short to ground, or short to power; or connector terminals (usually located behind the right front fender liner or below the A-pillar) oxidized, backed out, or making poor contact.— The sensor tone wheel (reluctor ring) is deformed, cracked, missing teeth, or accumulates heavy ferromagnetic debris (such as brake dust or metal shavings) on its surface, causing abnormal magnetic reluctance changes.+2 more →
Actions
— Initial visual inspection: Raise the vehicle. Inspect the right front wheel speed sensor connector for looseness, water ingress, oxidation, or corrosion. Check the wiring harness at the fender liner and suspension control arm for wear or crush marks.— Sensor static inspection: Disconnect the connector and use a multimeter to measure the sensor resistance (magnetic type standard value: approx. 1.0–1.6 kΩ at 20°C). Measure the insulation resistance between the pins and to ground (should be >10 MΩ). If the resistance is infinite or zero, replace the sensor.+5 more →
C003500›
DTC C003500 indicates the IPB (Intelligent Integrated Braking System) detected an abnormal supply voltage to the right front wheel speed sensor. On BYD e-Platform 3.0 and DM-i models, the wheel speed sensor typically uses a 12V DC supply (some earlier models use a 5V reference voltage). The IPB module identifies faults by monitoring the supply circuit voltage. The IPB sets this code when it detects a supply voltage below 9V (undervoltage), above 16V (overvoltage), or a complete open circuit (0V) lasting longer than the set threshold (typically 200ms). This fault causes a loss of the right front wheel speed signal. The IPB forcibly disables the ABS, ESC, EHB (Electro-Hydraulic Braking), and automatic emergency braking functions. The vehicle enters limp mode and multiple system warning lights illuminate on the instrument cluster, severely compromising driving safety.
Causes
— Right front wheel speed sensor power supply circuit short to ground or open circuit: Frequent steering chafes the wiring harness against the fender liner or suspension control arm, wearing through the insulation and exposing the copper core to short to body ground. Alternatively, long-term bending causes an internal wire break.— IPB control module internal power supply circuit fault: A damaged internal DC-DC converter or MOSFET driver chip in the IPB causes abnormal power supply output to the right front channel, often triggering other wheel speed sensor power supply fault codes.— Wheel speed sensor internal short circuit: Insulation aging and breakdown on the internal sensor coil or a damaged Hall element causes excessive current in the power supply circuit, triggering the IPB overcurrent protection to cut off the power supply.+2 more →
Actions
— Fault confirmation and freeze frame reading: Read all fault codes using the VDS2000/3000 diagnostic tool. Confirm if C003500 is a current fault (Class A) or a history fault (Class B). Record freeze frame data from when the fault occurred, including vehicle speed, voltage, and temperature. Clear the fault codes and perform a road test to verify if the fault returns.— Sensor supply voltage static measurement: Disconnect the right front wheel speed sensor connector (2-pin or 3-pin), turn the ignition switch to ON, and use a multimeter set to DC voltage to measure the voltage to ground at the connector-side supply pin (usually pin 1, yellow/red wire). The normal value is 12V±0.5V (battery voltage). If the voltage is abnormal (0V, below 9V, or above 16V), the fault lies in the wiring harness or the IPB side.+4 more →
C003504›
DTC C003504 indicates a right front wheel speed sensor (RF Wheel Speed Sensor) circuit or signal abnormality, specifically low sensor supply voltage, signal voltage out of range, or compromised circuit integrity. In the BYD ABS/ESP system, this fault prevents the control unit from obtaining an accurate right front wheel speed signal and triggers limp mode. Effects include: ABS function disabled, ESP deactivated, EBD malfunction, automatic emergency braking (AEB) function limited, regenerative braking efficiency reduced or disabled, and cruise control unavailable. This DTC is a hard fault. The control unit triggers this code upon continuously detecting the abnormality with the ignition switch in the ON position or while driving.
Causes
— Wheel speed sensor component fault: Internal coil open/short circuit, abnormal magnetic induction sensor resistance (normal 1.0-1.5kΩ), abnormal Hall sensor power supply, or internal circuit damage causing weak or distorted signal output.— Wiring and connector issues: sensor plug oxidation, water ingress corrosion, loose pins; wiring harness insulation wear causing a short to ground or intermittent open circuit; high engine compartment temperatures causing wiring harness aging and cracking, especially prone to rubbing against the body where the right front longitudinal beam retaining clip is loose.— Abnormal mechanical installation and clearance: Sensor-to-signal tone ring (reluctor ring) clearance is too large (standard: 0.3-1.2 mm) or too small, causing scraping; excessive right front wheel bearing play or damage causes signal tone ring radial runout to exceed tolerance (>0.1 mm), preventing the sensor from detecting a stable signal.+2 more →
Actions
— Pre-inspection and fault confirmation: Connect the VDS or OEM diagnostic tool to read the complete fault codes. Confirm if C003504 is an Active or History fault. Review the freeze frame data and record parameters such as vehicle speed and voltage when the fault occurred. Clear the fault codes and perform a road test to confirm fault reproduction conditions.— Visual and mechanical inspection: Raise the vehicle and check the right front wheel speed sensor installation. Verify the bolt torque (typically 8-12N·m). Inspect the sensor head for metal shavings, oil contamination, or physical damage. Check the signal tone ring integrity and clean its surface. Manually rock the right front wheel to check bearing clearance and verify there is no radial or axial play.+3 more →
C003708›
C003708 is a UDS-compliant fault code; subtype '08' indicates Signal Invalid/Plausibility Failure. In the BYD E5 ABS/ESC system, this fault indicates the ABS ECU detects a persistent abnormality or intermittent interruption in the electrical signal from the left rear wheel speed sensor (RL Wheel Speed Sensor). Specific conditions include: signal amplitude outside the normal range (too high/too low), distorted signal waveform, excessive deviation from the reference model calculation, or logical inconsistency with the other three wheel speed signals (e.g., the left rear wheel speed reads significantly lower than the others during straight-line driving). In new energy vehicles, this fault also causes inaccurate torque calculation in the regenerative braking system (RBS), which may restrict regenerative braking functions. When this fault triggers, the system disables ABS and ESC functions, the ABS/ESC warning lamp illuminates on the instrument cluster, and the vehicle enters conventional hydraulic braking mode.
Causes
— Wheel speed sensor component failure: Aging, open circuits, or short circuits in the internal Hall element or electromagnetic coil cause insufficient output signal amplitude or complete signal loss; metal filings stuck to the sensor tip alter the magnetic gap.— Abnormal sensor installation gap: The air gap between the sensor and the reluctor ring is outside the standard range (typically 0.3-1.2 mm). A deformed, loose, or worn mounting bracket causes an excessive or insufficient gap, resulting in signal loss.— Wiring and connector faults: Repeated bending of the sensor wiring harness in suspension travel areas (such as the E5 rear suspension-to-body connection) causes internal wire breakage and insulation damage; water ingress into the connector causes oxidation, terminal back-out, or excessive contact resistance; shielding layer damage causes electromagnetic interference.+2 more →
Actions
— Diagnostic tool deep scan: Use VDS or a dedicated diagnostic tool to read the complete fault codes and freeze frame data. Record parameters such as vehicle speed, wheel speed values, and longitudinal acceleration when the fault occurred. Enter live data stream mode. Observe changes in the left rear wheel speed signal while the vehicle is stationary and driving. Check for signal spikes, fixed values, or obvious desynchronization with the other three wheels.— Physical inspection and cleaning: Remove the left rear wheel and inspect the wheel speed sensor head for metal debris, oil contamination, or physical damage; inspect the rear axle tone ring for missing teeth, deformation, or corrosion; clean the sensor head and tone ring surface; inspect the sensor mounting bracket for looseness or deformation.+3 more →
C003800›
DTC C003800 indicates the IPB (Intelligent Integrated Braking System) control unit detects the left rear wheel speed sensor supply voltage is outside the normal range (typically 12V or 5V, depending on the sensor model). This fault indicates an open circuit, short to ground, short to power, or excessive contact resistance in the power supply circuit between the IPB module and the left rear wheel speed sensor. This prevents the sensor from receiving a stable operating voltage. Because the wheel speed signal is a core parameter for ABS, ESC, TCS, AEB, and vehicle speed calculations, this fault causes these functions to fail or enter a degraded mode. On some hybrid models (such as DM-i), the abnormal vehicle speed signal may also restrict EV mode switching and permit only HEV mode driving for safety.
Causes
— Short circuit or intermittent short circuit to ground in the left rear wheel speed sensor power supply circuit, pulling the voltage low (commonly caused by worn wiring harness insulation at moving suspension parts).— Sensor connector oxidation, terminal back-out, or looseness increases contact resistance in the power supply circuit, causing an abnormal voltage drop.— Short circuit in the wheel speed sensor internal power supply circuit causes the IPB control unit to cut power for protection or results in abnormal voltage.+2 more →
Actions
— Use VDS or a dedicated diagnostic tool to read the complete fault codes and freeze frame data. Check for an accompanying C003708 (signal fault) or U-class communication fault. Monitor the data stream to verify if the left rear wheel speed value reads 0 km/h or fluctuates abnormally.— Raise the vehicle and visually inspect the left rear wheel speed sensor connector for looseness, oxidation, or water ingress. Check the wiring harness securing points at the suspension control arm and body pass-through holes, and inspect for wear, cuts, or scorch marks.+5 more →
C003804›
This DTC indicates the ABS control unit (ESC module) detected abnormal electrical characteristics in the left rear wheel speed sensor circuit, including a signal line open circuit, short to ground, short to power, or intermittent connection. The ABS ECU fails to receive the square-wave speed signal from the left rear wheel, or the signal voltage falls outside the threshold range (normal static voltage approximately 11V; dynamic switching 0.5-11V). This fault triggers the ABS fail-safe mode, disabling or limiting the anti-lock braking, electronic stability control (ESC), autonomous emergency braking (AEB), and traction control (TCS) functions, and illuminates the ABS/ESC warning lamp on the instrument cluster. Due to the compact chassis layout and long wiring harness on pure electric models like the BYD E5, vehicle vibration rubbing the harness against sharp body edges, connector oxidation after water exposure, or poor internal contact in the power distribution box frequently cause this fault.
Causes
— Worn left rear wheel speed sensor wiring harness insulation causing a short to ground against sharp edges of the body frame, suspension control arm, or seat bracket (common after driving on rough roads).— Loose or backed-out pins, oxidation due to water ingress, or increased contact resistance at sensor connector (K08A), interrupting signal transmission.— Open or short circuit in the left rear wheel speed sensor internal coil (displays as a wiring fault code, but actually indicates an internal sensor circuit fault)+2 more →
Actions
— Use the BYD VDS or a dedicated diagnostic tool to read the ABS system fault codes and confirm C003804 is a current fault (Active). Check the live data stream and confirm the left rear wheel speed displays 0 km/h or a fixed abnormal value (such as 2252 km/h) that differs significantly from the other wheel speeds.— Raise the vehicle and visually inspect the left rear wheel speed sensor installation. Clean metal filings from the sensor tip, measure the gap between the sensor and the tone ring (standard 0.3-1.2mm), and inspect the tone ring for missing teeth or contamination.+6 more →
C003A08›
C003A08 indicates the ABS control unit detects an abnormal right rear wheel speed sensor (RR WSS) signal. Trigger conditions for this fault code include: complete loss of sensor signal (0 signal), signal amplitude below threshold, signal frequency mismatching the vehicle dynamics model (e.g., the other three wheels operate normally but the right rear signal changes abruptly), or electromagnetic interference causing signal noise. In BYD ABS systems, subtype 08 specifically denotes a signal plausibility fault or intermittent signal interruption, distinct from an open circuit (C003B) or power supply fault. This fault causes partial or complete failure of the ABS, EBD, ESC, TCS, and Automatic Emergency Braking (AEB) functions. The vehicle enters limp braking mode, retaining only basic hydraulic braking.
Causes
— Wheel speed sensor failure: Internal coil open/short circuit (magnetic induction type) or Hall element aging (Hall type). On E5 models, prolonged high temperatures near the exhaust pipe thermal management area accelerate aging of the right rear wheel sensor.— Wiring harness and connector fault: The right rear sensor wiring harness passes through the chassis side member mounting point. Vibration easily chafes the insulation, or an aging connector seal allows water ingress, causing an intermittent short circuit.— Abnormal sensor installation gap: Hub bearing wear causes the air gap between the sensor and tone ring to exceed tolerance (standard: 0.3-1.2 mm), or the sensor retaining bolt is loose.+2 more →
Actions
— Diagnostic confirmation: Use VDS3000 to read complete DTCs and freeze frame data. Confirm vehicle speed and wheel speed values at the time of the fault. Check for accompanying C003B00 (power supply fault) or U-class communication faults.— Visual inspection: Raise the vehicle and check the installation status of the right rear wheel speed sensor. Inspect the sensor tip for dirt, the wiring harness for wear, and the connector for looseness or water ingress. Check the inner side of the tyre for foreign metal objects.+5 more →
C003B00›
This DTC indicates the IPB (Intelligent Integrated Brake System) controller detects the right rear wheel speed sensor (WSS) supply voltage falls outside the normal threshold range (typically 4.5V-16V, depending on vehicle configuration). This is a hardwire circuit fault at the power supply level, not a signal transmission issue. The IPB triggers C003B00 upon detecting a short to ground (voltage too low/0V), a short to power (voltage too high/battery voltage), or high circuit resistance (unstable voltage) at the right rear wheel speed sensor power terminal. Because the wheel speed sensor provides a key input signal for the ABS, ESP, Automatic Emergency Braking (AEB), and Auto Hold systems, this fault causes a missing or distorted right rear wheel speed signal and triggers the brake system degraded mode. Some models also limit maximum vehicle speed or disable regenerative braking.
Causes
— Right rear wheel speed sensor power supply circuit short to ground: chassis wiring harness insulation wears through at the cabin pass-through grommet, suspension moving parts, or floor wiring channel, causing the 12V/5V supply wire to short to ground.— Poor connector contact or corrosion: The right rear wheel speed sensor connector (near the rear steering knuckle) or IPB module connector (engine compartment) exhibits terminal back-out, intermittent connection, or excessive resistance due to water ingress, washing, or oxidation.— Internal short circuit in the wheel speed sensor power supply circuit: A breakdown in the sensor's internal voltage regulator circuit creates a short to ground, pulling down the supply voltage.+2 more →
Actions
— Diagnostic tool verification: Use VDS or a dedicated BYD diagnostic tool to read the DTC freeze frame. Verify the vehicle speed, supply voltage, and ambient temperature at the time of the fault to rule out intermittent false codes.— Visual inspection: Check the right rear wheel speed sensor connector (near the rear brake caliper) and the IPB module connector (left side of the front compartment or at the firewall) for water ingress, terminal oxidation, looseness, or wiring harness damage. Closely inspect the chassis wiring harness for wear at the bulkhead rubber grommet.+5 more →
C003B04›
DTC C003B04 indicates the ABS control unit detects an electrical fault in the right rear wheel speed sensor signal circuit, including open circuit, short to ground, short to power, or abnormal signal. The wheel speed sensor (typically utilizing Hall effect or electromagnetic principles) serves as a key input component for the ABS/ESC system. It converts wheel speed into electrical signals and transmits them to the control unit to calculate slip ratio, vehicle speed, and travel direction. Triggering this DTC degrades or disables functions such as Anti-lock Braking System (ABS), Electronic Brakeforce Distribution (EBD), Electronic Stability Program (ESP), and Automatic Emergency Braking (AEB). The instrument cluster illuminates the ABS/ESC warning lamp to alert the driver. In models such as the BYD E5, the sensor typically integrates into the wheel hub assembly and connects to the ABS control unit via the floor wiring harness. The wiring routes through wear-prone areas like the chassis side member, frequently developing hidden faults after long-term use.
Causes
— Wheel speed sensor damage: Internal Hall element failure, coil open circuit, or coil short circuit, preventing signal generation or causing signal distortion.— Harness wear or crushing: Long-term vibration and friction damage the harness insulation under the chassis and at the bottom of the frame rail, causing a short to ground or an intermittent open circuit.— Internal open circuit in the floor wiring harness: The internal copper conductor breaks but the insulation remains intact. Vehicle vibration causes poor contact, resulting in an intermittent fault.+2 more →
Actions
— Use the VDS diagnostic tool to read the fault code and freeze frame data. Check the data stream for an abnormal right rear wheel speed signal (e.g., displaying an unreasonable value such as 2252km/h, or differing excessively from other wheel speeds).— Visual inspection: Check the right rear wheel speed sensor installation. Check the connector for looseness, water ingress, or oxidation. Measure the sensor supply voltage (Ignition ON: should be approximately 12V or 5V, depending on vehicle model).+6 more →
C004008›
DTC C004008 indicates the ABS/ESC control unit detected an abnormal Brake Pedal Switch signal. The Brake Pedal Switch typically contains primary and secondary contact sets (a normally open/normally closed combination) to provide hard-wired driver braking intent signals to the Vehicle Control Unit (VCU) and the ABS module. These signals directly affect brake light control, regenerative braking cancellation, Auto Hold logic, and vehicle power-up (Ready) permission. This DTC sets when the ABS module detects the switch signal voltage, logic combination (whether primary and secondary signals are mutually exclusive), or signal change rate exceeds calibrated thresholds. Potential causes include a single-circuit open, simultaneous dual-circuit short, signal desynchronization, or internal switch failure. A persistent fault causes abnormal regenerative braking, ESP function degradation, and brake lights stuck on or off. Extreme conditions trigger vehicle limp mode or prevent vehicle power-up.
Causes
— Burnt internal contacts, spring fatigue, or Hall element failure inside the brake pedal switch prevents the signal from switching on and off normally.— Aged switch connector seal allows water ingress, causing oxidation (green copper corrosion) or terminal pin back-out, resulting in intermittent poor contact.— Wiring harness chafed or damaged near the firewall, steering column, or pedal mechanism, causing a short to ground or short to power.+2 more →
Actions
— Use the diagnostic tool to read freeze frame data. Verify vehicle speed, pedal status, and main and secondary switch signal logic at the time of the fault to determine if the fault is static or dynamic intermittent.— Visually inspect the physical installation of the brake pedal switch. Verify the retaining clip is intact and the push rod shows no excessive wear. Check the wiring harness for interference during full pedal travel and at steering wheel limit positions.+4 more →
C004601›
DTC C004601 indicates an abnormal brake master cylinder pressure sensor signal in the ESP (Electronic Stability Program) system. This sensor integrates into the ABS hydraulic modulator (pump unit) and monitors brake system hydraulic pressure in real time, providing key input signals for ESP, HDC (Hill Descent Control), and AEB (Automatic Emergency Braking). A pressure signal outside the normal range (such as an open circuit, short circuit, signal drift, or delayed response) triggers this fault code. This limits or disables the ESP function, affecting vehicle stability control, but basic braking usually remains unaffected. Clearing the code will not resolve this hardware-level fault.
Causes
— Aging, damage, or drift of the internal pressure sensor element in the ABS hydraulic modulator (most common; the sensor and pump body are an integrated unit and are not serviceable separately).— Brake fluid severely contaminated, degraded, or containing excessive water, causing distorted sensor readings or blockage.— Poor contact or loose connection in the ABS pump power supply circuit or ground point, causing abnormal sensor supply voltage.+2 more →
Actions
— Use a dedicated diagnostic tool (such as BYD VDS or Launch X431) to read the complete fault codes and data stream. Check the pressure sensor live data for abnormalities (e.g., reading 0 kPa, a fixed value, or out of range) and record the freeze frame data.— Check the brake fluid quality and level. Inspect for darkening, cloudiness, or contaminants. If necessary, completely replace with DOT4 brake fluid and thoroughly bleed the brake system.+3 more →
C004900›
DTC C004900 indicates an abnormal brake fluid level detected by the IPB (Intelligent Integrated Braking System). The fluid level sensor installed in the brake master cylinder reservoir (typically a Hall-effect or float switch) triggers this fault. The IPB control unit records the fault when the brake fluid level remains continuously below the minimum mark (MIN) or the sensor signal voltage falls outside the calibrated range (normally 0.5V-4.5V, varying linearly with fluid level). This is a safety-related fault. When triggered, the system limits ESC, ABS, Automatic Emergency Braking (AEB), and energy recovery functions. Some models enter limp mode. Depending on the software version or specific repair scenario, this fault code may also correlate with an abnormal brake pedal position sensor (BPS) signal. The IPB system verifies brake system integrity by evaluating both the fluid level and pedal signals.
Causes
— Brake fluid leakage or natural loss: Aging and leaking of the brake wheel cylinder, brake lines, IPB integrated pump body, or reservoir seal causes the fluid level to continuously drop below the threshold.— Brake fluid level sensor fault: A stuck sensor float, damaged Hall element, or failed magnetic float causes the output signal to mismatch the fluid level.— Electrical connection issues: sensor connector oxidation, water ingress (common after wading), pin back-out, or wiring harness damage causing a signal short or open circuit.+2 more →
Actions
— Visual inspection: Open the engine compartment and check if the brake fluid level in the reservoir is below the MIN mark. Inspect the brake fluid color (fluid should be clear and slightly yellow; replace if dark or cloudy).— Leak check: Raise the vehicle. Inspect all four brake calipers, brake hoses, steel line fittings, and the underside of the IPB pump body for wet marks or fluid drips. Focus on freshly wet areas.+5 more →
C004C04›
On BYD new energy vehicles (particularly the E5 and Song series), DTC C004C04 indicates a circuit fault in the Electronic Parking Brake (EPB) right rear wheel actuator, rather than an ESP switch fault as stated in the original documentation. Specifically, the EPB control unit detects an open circuit, short circuit, or abnormal resistance in the right rear parking motor circuit, preventing the motor from completing the clamp/release action. This fault triggers the system protection mechanism. It may cause the right rear wheel to lock mechanically, prevent the EPB from releasing automatically (failing to disengage when shifting into gear and applying the accelerator), and compromise vehicle launch and driving safety. Although the EPB and ESP (Electronic Stability Program) interact during brake management, this code specifically indicates a hardware or wiring fault in the parking brake actuator.
Causes
— EPB actuator motor internal coil burnt out or open circuit: Prolonged motor operation causes overheating, the internal winding opens, and resistance becomes infinite (normal: 1.2-2.0Ω).— Wheel speed sensor signal interference: A loose right rear wheel speed sensor connector, damaged wiring harness, or iron filings on the magnetic encoder ring cause the EPB control unit to receive an unreliable wheel speed signal and incorrectly detect an actuator fault.— CAN communication circuit fault: Worn insulation on the CAN-H/CAN-L wiring harness between the EPB control unit and the vehicle network at the right rear quarter panel causes a short to ground or abnormal signal voltage (deviating from the 2.5V reference).+2 more →
Actions
— Use the BYD VDS diagnostic tool to read the complete EPB system fault codes and freeze frame data. Check for accompanying network fault codes, such as 'loss of communication with EPB', and confirm the vehicle speed, temperature, and other environmental conditions at the time of the fault.— Raise the vehicle and inspect the right rear EPB actuator connector for broken locking tabs, backed-out terminals, water ingress, or oxidation. Measure the motor resistance. Standard: 1.2-2.0 Ω. Infinite resistance indicates an internal motor open circuit.+5 more →
C006102›
DTC C006102 indicates the Intelligent Power Brake (IPB) system received a lateral acceleration (Ay) sensor signal outside the plausible range or with an abnormal status. This sensor typically integrates with the longitudinal acceleration (Ax) sensor and yaw rate sensor into a single inertial sensor module mounted in the center of the vehicle chassis or under a seat. It provides a key input signal for the Electronic Stability Control (ESC) system, Anti-lock Braking System (ABS), and electronic parking system. When this fault triggers, the IPB system cannot accurately obtain the vehicle's lateral dynamic parameters, limiting or disabling the body stability control function. This condition may also trigger a chain reaction fault in the electronic parking system, severely compromising vehicle stability and safety during cornering or emergency evasive maneuvers. The '02' suffix in the fault code indicates a signal plausibility error, meaning the signal value logically conflicts with the vehicle's actual condition or data from other sensors.
Causes
— Internal circuit fault in the inertial sensor (yaw rate sensor) or damaged MEMS sensing element, causing lateral acceleration signal output deviation or distortion.— The sensor mounting bracket is loose, deformed, or misaligned (e.g., not restored after chassis bottoming out or a collision), causing the sensor reference plane to misalign with the vehicle's actual horizontal plane.— Poor contact at the sensor wiring harness connector, backed-out terminals, oxidized or corroded pins, or a damaged wiring harness causing abnormal signal transmission impedance or an intermittent open circuit.+2 more →
Actions
— Use the dedicated diagnostic tool (VDS2000/3000) to read all IPB system fault codes. Confirm if C006202 (longitudinal acceleration signal fault), C006302 (yaw rate signal fault), or C006108 (signal fault) occur simultaneously, and record the freeze frame data.— Visually inspect the inertia sensor condition and installation. Confirm the mounting bracket shows no deformation, the bolts are secure (standard torque 9-11 N·m), and the sensor arrow mark aligns with the vehicle's forward direction.+4 more →
C006208›
DTC C006208 indicates the Electronic Stability Program (ESP) control unit detects an abnormal signal from the Longitudinal Acceleration Sensor (LAS). This sensor, typically integrated within the IPB (Intelligent Integrated Braking System) or ESP hydraulic modulator assembly, monitors the vehicle's longitudinal acceleration (G value) in real time. It provides a critical input signal for ESP vehicle stability control, TCS traction control, and brake force distribution. Fault conditions include signal circuit open or short, sensor signal out of range (±1.5g), signal drift, sensor self-test failure, or lost calibration data. When this fault occurs, the ESP system enters a degraded mode. Automatic Emergency Braking (AEB), Traction Control (TCS), and Electronic Brakeforce Distribution (EBD) functions may be limited or disabled. The ESP/ABS warning lights illuminate on the instrument cluster, severely compromising driving stability and braking safety.
Causes
— Faulty longitudinal acceleration sensor or aged chip inside the IPB assembly (sensor integrates into the IPB module; not a separate component).— Loose IPB wiring harness connector (24-pin or 32-pin), backed-out terminals, corroded pins, or poor contact, especially after water wading or underbody scraping.— Lost sensor calibration data or abnormal calibration (e.g., prolonged battery disconnection, interrupted IPB software upgrade, or failure to perform sensor calibration after chassis repairs)+2 more →
Actions
— Use BYD VDS or a dedicated diagnostic tool to read all DTCs, confirm C006208 is a current fault (Active), and record freeze frame data (vehicle speed, raw longitudinal acceleration value, supply voltage, etc.).— Visually inspect the IPB assembly for impact deformation or brake fluid leakage. Check the wiring harness connector (located on the side of the IPB assembly) for looseness, backed-out terminals, water ingress, or corrosion. Measure the connector latch retaining force.+6 more →
C006108›
DTC C006108 indicates an abnormal signal from the lateral acceleration sensor (AY sensor) in the Electronic Stability Program (ESP) system. The ESP Hydraulic Electronic Control Unit (HECU) typically houses this sensor to monitor the vehicle’s lateral acceleration (lateral G-force) in real time. The sensor provides a key input for the ESP to calculate vehicle dynamic attitude, sideslip tendency, and yaw rate correction. The ECU triggers this fault upon detecting a sensor signal outside the calibrated range (e.g., 0.5-4.5V), excessive signal drift, intermittent interruptions, or logical inconsistencies with yaw rate sensor or wheel speed sensor data. This fault degrades or completely disables active safety functions such as ESP, ABS, and TCS, though the vehicle typically retains basic hydraulic braking. On the E5 model, the lateral acceleration sensor and HECU feature an integrated design. Do not replace the sensor separately; replace the complete HECU assembly.
Causes
— Internal lateral acceleration sensor hardware fault in the ESP hydraulic control unit (HECU) assembly: sensor element aging, cold solder joints, or internal circuit damage causing abnormal signal output.— Wiring harness and connector faults: Water ingress and oxidation at the HECU connector (usually located near the engine compartment firewall), backed-out pins, harness wear causing short or open circuits, or vibration causing poor contact in the chassis harness.— Abnormal installation reference: Loose HECU mounting bolts, deformed mounting bracket, or failure to apply the standard torque (usually 25±5 N·m) after chassis accident repairs, causing the sensor installation angle to deviate from the horizontal reference.+2 more →
Actions
— Initial diagnosis: Use the VDS diagnostic tool to read all fault codes and confirm whether C006108 is a current DTC or a history code; record freeze frame data (vehicle speed, lateral acceleration, steering wheel angle, etc.); check the ABS/ESC warning light status on the instrument cluster.— Visual and installation inspection: Inspect the ESP hydraulic modulator (located on the left side of the engine compartment firewall) for physical damage or fluid leaks. Inspect the mounting bracket for deformation and verify bolt torque meets specifications. Inspect the wiring harness connectors (especially the 24-pin main connector) for water ingress, corrosion, or pin discoloration.+4 more →
C006164›
DTC C006164 indicates the IPB (Integrated Intelligent Braking System) detected an abnormal Lateral Acceleration Sensor (LAS) signal or a sensor fault. The LAS is a core sensor in the ESP/ESC vehicle stability control system. It monitors vehicle lateral acceleration (centrifugal acceleration) in real time, helping the ECU detect unstable conditions such as side slip, fishtailing, or understeer. This fault degrades or completely disables the ESC, ABS, TCS (Traction Control System), and Automatic Emergency Braking (AEB) functions. The vehicle enters Limp Mode, and the instrument cluster simultaneously illuminates the ABS and ESC warning lights. BYD’s new-generation IPB system typically integrates the lateral acceleration sensor into the Inertial Measurement Unit (IMU) inside the IPB assembly, rather than using a separate external sensor. Therefore, this fault usually indicates an internal hardware or communication link issue within the IPB assembly.
Causes
— Hardware damage or signal drift in the IPB assembly lateral acceleration sensor (MEMS chip), typically resulting from long-term vibration, thermal cycling aging, or inherent chip defects.— Abnormal IPB assembly power supply or ground circuit (unstable voltage or poor ground), causing the sensor supply voltage to drop below 9V or exceed 16V, outside the normal operating range.— CAN bus communication fault, including short or open circuits in the CAN-H and CAN-L lines, or abnormal terminal resistance, interrupting communication between the IPB and the VCU/ESP ECU.+2 more →
Actions
— Use the VDS2000/VDS3 diagnostic tool to read all fault codes. Check for accompanying faults such as C006108 (signal plausibility fault) and U100304 (CAN communication fault). Record the lateral acceleration value from the freeze frame data.— Visually inspect the IPB assembly installation. Confirm the fastening torque is 8±2 N·m and the installation angle deviation is within ±2°. Check the wiring harness connector (32-pin plug) for backed-out pins, water ingress, or burn marks.+4 more →
C006202›
DTC C006202 indicates the IPB (Intelligent Integrated Braking System) detected an abnormal longitudinal acceleration sensor signal. This sensor measures the vehicle’s longitudinal acceleration (deceleration) G-value. It provides a key input signal for the coordinated control of Electronic Stability Control (ESC), the Anti-lock Braking System (ABS), Automatic Emergency Braking (AEB), and the energy recovery system. BYD DMi models typically integrate this sensor within the IPB assembly or mount it on the chassis as an independent inertial sensor. A signal fault causes these safety systems to enter a degraded mode or fail, affecting driving stability, particularly during emergency braking and handling on slippery roads.
Causes
— IPB assembly internal longitudinal acceleration sensor hardware fault (chip damage, cold solder joint, or aging drift)— Poor contact, open circuit, or short circuit in the sensor power supply, ground, or signal wiring (especially chassis wiring harness damage after wading or bottoming out)— Outdated IPB control unit software or missing calibration data causes abnormal signal processing.+2 more →
Actions
— Use VDS or a dedicated BYD diagnostic tool to read the complete fault codes and freeze frame data. Check for accompanying DTC C006164 (lateral acceleration) or other IPB-related fault codes. Verify the longitudinal acceleration live data stream reads within ±0.1G while the vehicle is stationary.— Visually inspect the IPB assembly and chassis wiring harness connectors (especially the G03 connector underneath the vehicle) for water ingress, oxidation, looseness, or mechanical damage. Measure the sensor supply voltage (typically 5V or 12V, depending on the specific model year) and the signal wire resistance.+3 more →
C006302›
DTC C006302 indicates the IPB (Intelligent Integrated Braking System) receives an abnormal yaw rate sensor signal. The ESP (Electronic Stability Program) system relies on the yaw rate sensor to detect the vehicle's real-time rotational angular velocity around the vertical axis (such as oversteer or understeer). This fault means the IPB module receives CAN bus message 0x222 with a yaw signal that falls outside the valid range, is missing, or contains a checksum error. This condition forces systems including the ESP, ABS, EPB (Electronic Parking Brake), and Automatic Emergency Braking into a degraded mode or complete failure, severely compromising vehicle dynamic stability control and driving safety.
Causes
— Yaw rate sensor (usually integrated into the IPB or mounted independently): internal circuit fault, component aging, or cold solder joint.— Poor contact, open circuit, short circuit, or oxidation from water ingress in the sensor power supply, ground, or CAN communication circuits.— Internal signal processing circuit fault in the IPB control module or outdated software version causing signal parsing errors.+2 more →
Actions
— Use the VDS diagnostic tool to read all fault codes. Check for accompanying C006102 (lateral acceleration), C006202 (longitudinal acceleration), or U-class communication fault codes to confirm the fault conditions.— Check the IPB system software version. If an update is available, upgrade to the latest version to rule out software defects.+6 more →
C006308›
The yaw rate sensor (also known as the yaw angular velocity sensor) is the core inertial measurement unit of the ESP electronic stability system. It monitors the vehicle's rotational angular velocity around the vertical axis (Z-axis) in real time. DTC C006308 indicates the ABS/ESP control unit detects the sensor's analog or digital output signal continuously exceeds the valid threshold range (typically 0-5V or an abnormal CAN signal), or experiences an abnormal update frequency or checksum error. This fault prevents the ESP from accurately determining the deviation between the vehicle's actual attitude and the driver's steering intent, causing the system to exit the stability control function and trigger a multi-system degraded protection mode. In extreme cases, the vehicle loses electronic assistance during emergency obstacle avoidance or sideslipping on wet or slippery roads, posing a severe safety hazard.
Causes
— Damaged yaw rate sensor chip or cold solder joint inside the ESP hydraulic modulator assembly (most common; many BYD models integrate the sensor into the ESP assembly rather than using a separate external unit).— Poor contact or intermittent connection in the sensor power supply circuit (12V IGN) or ground wire (GND), causing operating voltage fluctuations or momentary power loss.— Sensor signal wire (LIN/CAN or analog signal wire) short circuit to power or ground, open circuit, or signal crosstalk caused by water ingress and oxidation in the connector.+2 more →
Actions
— Use the VDS2000/3000 diagnostic tool to read all fault codes and record freeze frame data. Confirm if C006308 is a current fault and check for accompanying related codes such as C006302/C006382.— Check the relevant warning light status on the instrument cluster. With the vehicle stationary, verify the yaw rate value in the data stream is near 0°/s (within ±5°/s). If the value is fixed at 0 or 126, or is out of range, confirm the fault.+5 more →
C006382›
BYD's IPB (Integrated Brake Control System) defines DTC C006382 as a lateral acceleration sensor (G200) signal plausibility fault, rather than a simple yaw rate sensor fault. This sensor typically mounts beneath the center console or behind the center armrest. It continuously monitors lateral acceleration (in m/s² or G) during cornering or skidding, serving as a core input signal for the ESC (Electronic Stability Control) system to determine the vehicle's dynamic attitude. The IPB control unit deems the signal unreliable and triggers this DTC if the sensor output falls outside the plausible range (does not approach 0 when stationary), exhibits excessive drift, or if the sensor mounting reference plane deviates from the vehicle horizontal plane by more than 3°. Following this fault, active safety functions including ESC, ABS, and Automatic Emergency Braking (AEB) may degrade or fail completely. In extreme cases, the vehicle may lose stability control on curves or slippery surfaces, posing a severe safety risk.
Causes
— Sensor mounting position offset or loose mechanical mounting: Failure to tighten screws to the standard torque (usually 8Nm) after accident repairs or removing the center console or armrest box causes the sensor body to tilt or prevents the arrow mark from pointing directly forward.— Wiring harness connector water ingress and oxidation: After driving through water (especially standing water deeper than 20 cm), a poorly sealed sensor plug near the floor causes terminal oxidation, short circuits, or increased contact resistance.— Control unit calibration data lost: Replacing the low-voltage battery (auxiliary battery), disconnecting power for more than 30 minutes, or updating software clears the sensor zero-point calibration data stored in the IPB control unit, causing an incorrect signal reference.+2 more →
Actions
— Initial visual inspection: Remove the centre armrest box or the trim panel below the centre console. Check the lateral acceleration sensor exterior for physical damage, the mounting bracket for deformation, the connector for water marks or green oxidation, and the retaining screws for looseness.— Diagnostic tool data stream analysis: Use the BYD VDS2000 or Launch X431 to read the fault code freeze frame and check the 'lateral acceleration' value in the data stream. With the vehicle stationary on a level surface, the normal value should be close to 0±0.2 m/s². If the data shows a fixed offset (e.g., 0.8 m/s²) or the value fluctuates erratically, confirm an abnormal sensor signal.+4 more →
C006A01›
This DTC indicates the IPB (Integrated Power Brake) or ESC (Electronic Stability Control) system detects an abnormal parameter configuration status for the yaw rate sensor. Specifically, the control unit cannot correctly identify the sensor identity type, range parameters, or installation direction configuration, causing the system to flag an "unknown sensor type" or "parameter configuration error". This typically occurs when failing to write parameters after replacing the IPB assembly, ESC module, or yaw rate sensor, or when the sensor hardware model does not match the software configuration. The fault degrades or disables functions including Electronic Stability Control (ESC), Anti-lock Braking System (ABS), and Automatic Emergency Braking (AEB), compromising driving safety in extreme cases.
Causes
— Failure to perform sensor parameter configuration (Sensor Configuration) and zero-point calibration (Calibration) using the dedicated diagnostic tool after replacing the IPB assembly, ESC module, or yaw rate sensor.— Installation of an incorrect yaw rate sensor hardware model causes a mismatch between the sensor's actual characteristic parameters and the control unit's pre-stored parameters.— Stored sensor configuration data lost or corrupted after vehicle software reflash, control unit upgrade, or power disconnection.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000/VDS2100) to read the IPB/ESC system fault codes, confirm C006A01 is present as a current fault, and check the status of the ABS and ESC warning lamps on the instrument panel.— Check the physical installation of the yaw rate sensor: verify mounting bolt torque (usually 8-10Nm), mounting surface cleanliness, and that the sensor arrow aligns with the vehicle longitudinal axis. Inspect the wiring harness connector for looseness, backed-out pins, or water ingress corrosion.+5 more →
C006A02›
DTC C006A02 indicates a functional failure or abnormal signal from the combined inertial sensor (typically an integrated yaw rate and lateral/longitudinal acceleration sensor) in the IPB (Intelligent Electro-Hydraulic Braking) system. This sensor typically mounts in the vehicle center tunnel (under the armrest) near the center of gravity. It acts as the core sensing component for the ESC (Electronic Stability Control), ABS (Anti-lock Braking System), TCS (Traction Control System), and AEB (Automatic Emergency Braking) systems. When this fault triggers, the IPB ECU cannot obtain accurate vehicle attitude, lateral acceleration, and yaw rate data, causing these active safety functions to degrade or fail completely. This failure risks a loss of vehicle stability control; therefore, the system classifies it as a Level 3 severe fault.
Causes
— Damage to the internal MEMS chip or signal processing circuit in the combination sensor causes output signal drift or complete signal loss.— Sensor wiring harness open circuit, short circuit, or short to ground/power, especially harness damage near the center tunnel from water ingress, abrasion, or audio/seat modifications.— Loose, deformed, or misaligned sensor mounting bracket (angle offset exceeding ±3°), causing an inertial measurement reference error.+2 more →
Actions
— Use the VDS2000/VDS3100 diagnostic tool to access the IPB system and read the freeze frame data. Verify the vehicle speed, lateral acceleration, and sensor voltage at the time of the fault.— Visually inspect the combined sensor installation under the center tunnel (usually at the gear selector base or under the seat). Verify the fixing bolt torque (standard: 8-10 N·m) and confirm the bracket is not deformed.+5 more →
C006B00›
DTC C006B00 in the BYD IPB (Intelligent Integrated Brake) system indicates the Electronic Stability Program (ESP/ESC) activation time exceeds the designed safety threshold. This fault does not simply mean the system operated too long; it indicates the IPB control module detects vehicle stability control functions (including anti-skid, traction control, and yaw moment control) continuing to operate under non-essential conditions, or the system failing to exit the stability control state. This typically points to signal drift, calibration errors, or wiring faults in inertial measurement units, such as the yaw rate sensor and longitudinal/lateral acceleration sensors. These issues cause the IPB to misjudge the vehicle as continuously unstable. This fault triggers IPB system degradation and may limit or disable functions such as ABS, ESP, and Automatic Emergency Braking (AEB), severely compromising driving safety.
Causes
— Signal drift, failure, or loose mounting of the yaw rate sensor (YRS) or longitudinal/lateral acceleration sensor causes the IPB to continuously receive incorrect vehicle dynamic attitude signals.— Abnormal internal software operation in the IPB intelligent integrated brake control module, an MCU processor fault, or an infinite loop in the low-level driver prevents the system from exiting stability control mode normally.— Failure to perform the sensor calibration procedure after replacing the IPB assembly or repairing the suspension system, or calibration data lost while driving (accompanied by calibration fault codes such as C051D01).+2 more →
Actions
— Read complete fault codes and freeze frame data using the BYD VDS diagnostic tool. Check for accompanying fault codes such as C006A02 (yaw rate sensor signal), C006108/C006208 (acceleration sensor signal), and C051D01 (calibration error). Record key parameters at the time of the fault, including vehicle speed, steering angle, and lateral acceleration.— Check the voltage of the IPB Intelligent Integrated Braking System power supply (constant power, IG power) and ground points (G08, G09, etc.), as well as the resistance (approx. 60Ω) and waveform of the CAN-H/CAN-L lines, to rule out system abnormalities caused by power supply fluctuations or communication faults.+3 more →
C007200›
C007200 is an advanced diagnostic trouble code in the BYD Integrated Power Brake (IPB) system. It indicates an abnormal thermal condition or pressure-temperature correlation in hydraulic brake circuit A (typically the front brake circuit). The system triggers this code based on a combined assessment of real-time master cylinder pressure sensor data, the hydraulic valve body temperature prediction model, and the braking frequency algorithm. The system records this fault when brake fluid temperature exceeds the preset threshold (typically caused by frequent braking, throttling heat generation from internal hydraulic leakage, or high ambient temperatures), or when the pressure sensor signal logically mismatches the temperature model. This fault may degrade ESP/ABS functions, cause abnormal brake pedal feel (soft or hard), and restrict regenerative braking. Severe cases trigger overheat protection and cut off power output.
Causes
— Continuous heavy braking conditions (such as long downhill grades, aggressive driving, or frequent hard acceleration/deceleration) cause heat build-up in the brake fluid.— Aging or worn internal sealing rings in the IPB hydraulic valve body cause internal hydraulic leakage (not externally visible), resulting in throttling heat build-up.— Master cylinder pressure sensor signal drift, zero-point misalignment, or internal sensor fault sending incorrect pressure-temperature correlation data to the ECU.+2 more →
Actions
— Use VDS or a dedicated diagnostic tool to read the DTC freeze frame data. Confirm vehicle speed, brake pressure, calculated temperature, pedal travel, and driving conditions (e.g., energy recovery mode) at the time of the trigger.— Visually check the brake fluid level (between MAX and MIN), brake fluid color (for deterioration or blackening), and external brake lines, hoses, and wheel cylinders for physical leaks.+5 more →
C007204›
DTC C007204 indicates the standard solenoid valve (typically the inlet or outlet valve) inside the ABS/ESC Hydraulic Electronic Unit (HEU) triggered the overheat protection mechanism. The control unit detected the valve body temperature exceeded the safe threshold (typically >120°C) and entered protection mode to prevent valve spool binding or coil burnout. Root causes include: 1) Actual overheating (continuous heavy braking, brake drag, or increased movement resistance from degraded brake fluid); 2) False overheat detection (abnormal valve coil resistance, control unit temperature monitoring circuit failure, or software algorithm error). This fault limits or disables ABS/ESC functions, retaining only basic hydraulic braking. This severely compromises braking safety and requires immediate repair.
Causes
— Short circuit, open circuit, or resistance drift in the ABS hydraulic modulator internal solenoid valve coil, causing abnormal current and overheating.— Continuous heavy braking (such as frequent braking on long descents) causes actual valve body overheating, exceeding heat dissipation capacity.— Brake fluid deterioration, excessive water content, or incorrect fluid type (non-DOT4) increases valve spool movement resistance and generates additional heat.+2 more →
Actions
— Use a dedicated diagnostic tool (such as VDS2000/Launch PAD) to read all fault codes and freeze frame data. Confirm if C007204 is a current fault. Record the vehicle speed, brake pressure, ambient temperature, and other parameters when the fault triggered.— Verify the brake fluid level is between MAX and MIN. Check the brake fluid moisture content (should be <3%) and type (must be DOT4). If necessary, completely replace the fluid and bleed the system.+3 more →
C007500›
DTC C007500 indicates an electrical fault or short circuit in Master Cylinder Position Sensor A within the IPB (Intelligent Power Brake) system. This sensor typically uses a Hall-effect or inductive principle and mounts near the brake master cylinder. It monitors master cylinder piston travel in real time, converting the driver's mechanical braking intent into an electrical signal (typically a 0.5-4.5V analog voltage) and transmitting it to the IPB ECU. The ECU uses this signal to calculate the required brake fluid pressure and controls the motor to build hydraulic pressure. The ECU sets this DTC when it detects the sensor signal voltage continuously exceeding the valid range (short to power >4.8V or short to ground <0.2V), or an abnormal logical relationship between the signal and pedal travel. Setting this DTC causes the IPB system to enter a degraded mode, disable brake energy recovery, retain only basic hydraulic braking, and illuminate the ABS/ESC warning light.
Causes
— Sensor wiring harness worn or crushed, causing a short to power or ground: The IPB assembly is located near the engine compartment firewall. Vibration may cause the wiring harness to rub against sharp body edges, or front compartment repairs may crush the harness, damaging the insulation.— Connector water ingress or oxidative corrosion: During car washing, wading, or in damp environments, poor sealing of the sensor connector (usually located in the middle of the IPB assembly) causes pin oxidation or electrolytic corrosion, resulting in abnormal resistance or a short circuit.— Internal fault in the master cylinder position sensor: Aging of the internal Hall element, cold solder joints, or a coil short circuit causes an abnormal output signal. This fault frequently occurs in high-temperature environments or high-mileage vehicles (>80,000 km).+2 more →
Actions
— Freeze frame analysis: Use a dedicated BYD diagnostic tool (VDS or EDS) to read the fault code freeze frame data. Record the vehicle speed, brake pedal status, battery SOC, and IPB motor status at the time of the fault. Determine whether the fault is intermittent during driving or continuous while stationary.— Visual and wiring harness inspection: Raise the vehicle and inspect the IPB assembly (located at the firewall above the brake pedal) for impact deformation or water marks. Follow the sensor wiring harness (usually exiting from the top of the IPB) and inspect for wear, damaged insulation, or interference with the vehicle body. Closely inspect the rubber grommet at the firewall pass-through.+4 more →
C00A800›
This DTC indicates the Integrated Inertial Sensor (IIS) in the ESP (Electronic Stability Program) system lacks initial calibration, or the calibration data is abnormal or invalid. The Integrated Inertial Sensor integrates a high-precision MEMS accelerometer and gyroscope to monitor the vehicle’s longitudinal acceleration, lateral acceleration, and yaw rate in real time. The ESP uses these core input signals for body stability control, anti-skid calculations, and Automatic Emergency Braking (AEB) decisions. The ECU sets this DTC when it detects a significant deviation between the sensor output and the expected reference, when the calibration data area checksum validation fails, or when the installation attitude angle exceeds the permitted tolerance. This condition forces the ESP system into a degraded mode, restricting or disabling functions such as the Anti-lock Braking System (ABS), Traction Control System (TCS), Vehicle Dynamics Control (VDC), and AUTOHOLD. In extreme cases, this compromises driving safety.
Causes
— Reinstalling the ESP/IPB control unit assembly after accident repairs, chassis removal/installation, or a collision altered the installation angle/level, causing the inertial sensor to lose its reference attitude.— Severe impact to the vehicle chassis (such as bottoming out, a deep pothole impact, or a collision) causing slight physical displacement of the sensor or zero-point drift in the internal MEMS chip.— Failure to perform the initial Sensor Calibration procedure for the new part after replacing the ESP hydraulic modulator assembly, or failure to keep the vehicle perfectly level during calibration.+2 more →
Actions
— Pre-inspection preparation: Park the vehicle on level ground (recommended hoist platform levelness error <0.5°), center the steering wheel, check the ESP/IPB control unit mounting bracket for deformation, and verify the fixing bolt torque meets the specification (usually 8-12 Nm). Confirm the mounting surface is free of debris and the control unit is level.— Fault confirmation: Connect a dedicated diagnostic tool such as BYD VDS or Launch X-431, enter the ABS/ESP system, and read and record all fault codes. Check for C00A800 and accompanying faults such as C006102 (lateral acceleration sensor) and C006202 (longitudinal acceleration sensor).+3 more →
C012104›
DTC C012104 indicates the ABS/ESP electronic control unit (ECU) detected a fault in the solenoid valve relay control circuit. This relay resides inside the hydraulic control unit (HCU) and supplies stable operating power (typically 12V) to the inlet/outlet solenoid valve assembly. The ECU triggers this fault upon detecting an open or short in the relay coil circuit, or abnormal relay contact feedback voltage (such as output voltage dropping below the threshold after the relay energizes). This fault disables active safety functions relying on hydraulic regulation, such as ABS, EBD, ESP, and TCS. The vehicle retains only basic hydraulic braking capability. In models such as the BYD E5, the HCU integrates this relay. The relay is not serviceable separately; replace the complete assembly.
Causes
— Burnt internal relay contacts or an open coil circuit in the Hydraulic Control Unit (HCU/ABS pump) prevents the ECU from engaging the relay normally.— Abnormal power supply, including blown ABS fuse (usually 30A or 40A), low battery voltage (<10V), or loose power supply connection.— Poor ground circuit, especially loose or oxidized HCU ground terminals (G104/G105) or a broken wiring harness, causing unstable relay operating voltage.+2 more →
Actions
— Safety preparation and initial checks: Disconnect the high-voltage system (for new energy vehicles), check if the ABS fuse (30A/40A in the engine compartment fuse box) is blown, measure the battery voltage (should be >12V), and check the ABS/ESP warning light status on the instrument cluster.— Deep diagnostic scan: Use a VDS or Launch diagnostic tool to read all fault codes and check for accompanying wheel speed sensor faults (such as C0035 or C0040). Perform the 'solenoid valve actuation test', listen for the relay engagement sound, and verify the 'valve relay status' in the data stream is 'ON'.+4 more →
C019604›
This DTC indicates a functional fault in the Inertial Measurement Unit (IMU) integrated within the ESP (Electronic Stability Program) hydraulic modulator. This MEMS-based sensor assembly integrates a Yaw Rate Sensor and a Lateral G-Sensor. It monitors the vehicle's real-time rotational angular velocity around the vertical axis and lateral acceleration to provide critical vehicle dynamic attitude parameters for the ESP, TCS, HHC, and AEB systems. Sub-code '04' specifically indicates a signal circuit/range/performance fault or an internal self-test failure. Possible causes include: 1) Physical damage to the sensor hardware (internal silicon structure fracture or cracked solder joints); 2) Operating temperature outside the rated range (-40°C to +85°C); 3) Signal output exceeding valid thresholds (e.g., yaw rate ±75°/s or lateral acceleration ±1.5g); 4) ECU internal A/D converter or power management circuit fault. This fault causes complete failure of the vehicle stability control system. It creates a loss-of-control risk under extreme conditions (such as high-speed cornering or emergency obstacle avoidance) and may compromise the accuracy of the brake energy recovery strategy. This is a safety-critical fault requiring immediate repair.
Causes
— Physical damage, aging, or internal cold solder joints in the ESP hydraulic control unit assembly (HECU) inertia sensor chip, causing signal drift or complete loss of output.— Sensor power supply circuit fault: Includes unstable constant power (B+) or ignition power (IG1) voltage, or excessive ground circuit resistance (>1Ω), causing the sensor reference voltage (typically 5V) to drift.— Module installation issue: The angle between the mounting surface and the vehicle horizontal plane exceeds tolerance (±2° required), or failure to apply the specified tightening torque (usually 8-10Nm) results in an incorrect sensor measurement reference.+2 more →
Actions
— Safety Preparation: For E5 battery electric vehicles, strictly follow high-voltage safety procedures. Disconnect the power battery high-voltage service disconnect, disconnect the 12V battery negative terminal, and wait at least 3 minutes to allow the system to fully discharge.— Initial visual inspection: Check the ESP hydraulic modulator assembly (located on the left side of the engine or front compartment) for physical damage or leaks, mounting bracket deformation, and oxidation, water ingress, or backed-out pins in the wiring harness connector.+7 more →
C024501›
DTC C024501 indicates a general Wheel Speed Sensor Fault in the BYD ABS/ESP system. The ABS control unit (ECU) sets this code when it detects an abnormal or completely lost wheel speed signal from at least one wheel while the vehicle is moving. Specifically, the ECU triggers this DTC if the vehicle speed exceeds 2 km/h and the ECU fails to receive a pulse signal from a wheel speed sensor, or if the speed difference between the affected wheel and the opposite wheel on the same axle (or the reference vehicle speed) exceeds the set threshold (typically 6%) for longer than the specified time (typically 500 ms). This fault forces the Anti-lock Braking System (ABS), Electronic Brakeforce Distribution (EBD), Electronic Stability Program (ESP), Traction Control System (TCS), Auto Hold, and energy recovery systems into a degraded or inoperative mode. This severely compromises braking safety and driving stability. This DTC represents a circuit or signal fault and does not involve a mechanical actuator. However, mechanical or electrical issues with the sensor body, wiring harness, connector, or signal tone ring can cause the fault.
Causes
— Wheel speed sensor component fault: Hall element aging or failure, internal coil open/short circuit, sensor head physical damage, or magnetic degradation, preventing the generation of a valid speed pulse signal.— Wiring harness and connector issues: Chassis vibration chafes the sensor wiring harness insulation, causing a short to ground or intermittent open circuit; connector pins oxidize, loosen, or back out; water ingress after wading causes corrosion, increasing contact resistance.— Abnormal tone ring: Missing teeth, fractures, or deformation (e.g., after an impact), or iron filings, mud, sand, ice, or snow adhering to the tone ring surface, causing abnormal magnetic flux changes and disrupting sensor signal acquisition.+2 more →
Actions
— Fault confirmation and localization: Use VDS or a dedicated diagnostic tool to read the complete fault codes and freeze frame data. Check if a specific wheel sub-fault code (such as C003708) accompanies C024501. Enter live data stream mode and drive the vehicle at 10-30 km/h. Observe the wheel speed signals for all four wheels and identify which wheel signal is abnormal (showing 0 km/h, fluctuating, or differing excessively from the others).— Visual and connection inspection: Raise the vehicle. Check the affected wheel speed sensor connector for looseness, oxidation, or water ingress. Trace the sensor wiring harness routing and check for wear, damaged insulation, or signs of interference with the body. Focus on the harness protection where it passes through body panel holes and moving suspension parts.+4 more →
C040008›
C040008 is a UDS diagnostic protocol chassis system fault code indicating an abnormal communication signal between the EPB (Electronic Parking Brake) control module and the ABS/ESC module. This fault indicates the ABS system received an EPB status signal (e.g., parking motor position, clamping force, switch status, or system ready status) with a validity error, checksum error, signal timeout, or out-of-range value. This fault may cause AUTO HOLD function failure, abnormal Hill Hold Control (HHC) operation, or failure of the electronic parking brake to apply or release. Extreme cases compromise driving safety.
Causes
— EPB control module internal circuit fault: Damaged MCU processor, failed power management chip, or abnormal internal memory data, causing incorrect signal output.— Power supply system fault: unstable EPB module supply voltage (below 9.3V or above 16.9V), loose fuse connection, oxidized relay contacts, or excessive contact resistance in the ground circuit (>1Ω)— CAN bus communication fault: Short or open circuit in Power CAN-H and CAN-L lines, terminating resistor drift (deviation from 60Ω), wiring aging, or external electromagnetic interference causing signal distortion.+2 more →
Actions
— Use a BYD dedicated diagnostic tool (VDS or ED400) to read complete DTC information and freeze frame data. Record key parameters at the time the fault occurred, such as vehicle speed, system voltage, ambient temperature, and gear position.— Check the EPB control module supply voltage: With the ignition switch ON, measure the voltage between the module power terminal and the ground terminal. The standard value is 9.3-16.9V. Measure the ground resistance; it must be less than 1Ω. Check the fuse and relay status.+4 more →
C046008›
DTC C046008 indicates an unreliable or incorrect SAS (Steering Angle Sensor) signal value in the EPS (Electric Power Steering) system 0x11F message. Although originally classified under the ABS/braking system, modern vehicle architectures route the SAS signal via the CAN bus to both the ESP (Electronic Stability Program) and the EPS. The control unit sets this fault when it detects the steering angle sensor signal exceeds the plausible range, exhibits abnormal jumps, experiences a sampling timeout, or fails the logical correlation check with the wheel speed sensor signals (as related code C052801 indicates). This fault limits ESP functionality, causes abnormal steering assistance, or disables the automatic emergency braking system, severely impacting driving stability.
Causes
— Internal Steering Angle Sensor (SAS) damage or signal drift, commonly resulting from mechanical impact to the sensor during a front-end collision.— Poor contact, open circuit, or short circuit in the steering wheel clock spring or SAS wiring harness connector, interrupting signal transmission.— Failed to perform SAS zero-point calibration and maximum steering angle learning using the dedicated diagnostic tool after replacing the steering gear or steering column, or performing chassis repairs.+2 more →
Actions
— Pre-inspection and data collection: Check battery voltage (should be ≥12V), verify the status of all instrument cluster warning lights, use the diagnostic tool to read complete DTCs and freeze frame data, and check for accompanying related fault codes such as C052801 (SAS and wheel speed check abnormal).— Physical inspection: Check the steering wheel clock spring connector for looseness, verify proper SAS sensor installation (especially on accident-repaired vehicles), and inspect the related wiring harness for pinching, damage, or corrosion.+5 more →
C050200›
This DTC indicates the IPB (Intelligent Integrated Braking System) control unit detects an abnormally low-resistance connection between the left front wheel speed sensor (WSS) power supply circuit (typically a 12V DC supply) and body ground (GND), indicating a short to ground. The wheel speed sensor uses a two-wire design (multiplexed power/signal or independent power and ground). When the power supply circuit shorts to ground, the sensor fails to receive normal operating voltage. This causes a complete loss of the left front wheel speed signal and prevents the IPB from monitoring the left front wheel speed. This fault directly degrades or completely disables systems including the Anti-lock Braking System (ABS), Electronic Stability Control (ESC), Traction Control System (TCS), Automatic Emergency Braking (AEB), and Electronic Parking Brake (EPB). The vehicle may enter a safety protection mode (limp mode) and brake pedal feel may change, severely compromising driving safety.
Causes
— Damaged left front wheel speed sensor wiring harness insulation rubs against metal body components (such as the steering knuckle, lower control arm, or fender liner mounting screws) during suspension travel, causing the power wire to short to ground.— Internal breakdown of the wheel speed sensor drive circuit (such as a shorted Zener diode or filter capacitor), causing the power supply pin to short to the housing (ground).— Wheel speed sensor connector seal failure (seal ring aged or improperly installed) allows water or electrolyte ingress, causing a short circuit between the power supply pin and the ground pin.+2 more →
Actions
— Visual inspection: Raise the vehicle, remove the left front wheel, and check the routing of the wheel speed sensor wiring harness near the fender liner, suspension spring seat, steering knuckle, and lower control arm. Inspect for wear, damaged insulation, crushing, or scorch marks. Check the connector for looseness, water ingress, corrosion, or recessed pins.— Voltage measurement: Disconnect the left front wheel speed sensor connector, turn the ignition switch to ON, and measure the voltage between the harness-side power supply pin and ground. Normal voltage is 12V (battery voltage). If the voltage is 0V or very low (<1V), a short circuit exists in the wiring harness or at the IPB. If the voltage is normal, the sensor may have an internal short to ground.+4 more →
C050300›
DTC C050300 indicates a short to battery positive (B+) in the left front wheel speed sensor (WSS) power supply circuit. Normally, the IPB (Integrated Power Brake) supplies 5V or 12V to the wheel speed sensor (depending on sensor type). A "short to battery" condition means the power supply line shorts to a vehicle constant power circuit, or the internal sensor power terminal breaks down to the signal or ground terminal. This causes the control unit to detect an abnormally high voltage (approximately 12V battery voltage). This prevents the IPB from correctly reading the left front wheel speed signal, triggers the safety protection mechanisms of systems such as ABS, ESP, and Automatic Emergency Braking, and disables the related functions.
Causes
— Damaged left front wheel speed sensor wiring harness insulation contacting body power wires (such as headlight power supply, horn wires, etc.), causing a short circuit.— Sensor internal power supply circuit breakdown shorts the power terminal to the housing or signal wire.— Water ingress, corrosion, or bent pins at the wheel speed sensor connector causing the power supply terminal to short to an adjacent power terminal.+2 more →
Actions
— Connect the VDS diagnostic tool, read and record the freeze frame data for DTC C050300, and confirm the vehicle speed and voltage status at the time of the fault.— Turn off the ignition, disconnect the left front wheel speed sensor connector, and check the connector terminals for signs of corrosion, deformation, or water ingress.+4 more →
C050400›
DTC C050400 indicates the IPB (Intelligent Integrated Braking System) control unit detects an "indirect uncertainty" (plausibility fault) in the left front wheel speed sensor signal. This is not a simple sensor open or short circuit. Instead, the control unit algorithm identifies a logical inconsistency between the left front wheel speed signal and the vehicle's actual motion state, the speeds of the other three wheels, and the longitudinal/lateral acceleration sensor data. Symptoms include signal spikes, an abnormal fixed value (such as a constant 1845 km/h), a signal rate of change exceeding physical limits, or intermittent signal loss within specific vehicle speed ranges (usually >60 km/h). This fault triggers degraded protection modes in systems including ABS, ESP, and automatic emergency braking, severely affecting vehicle dynamic stability control.
Causes
— Magnetic encoder target wheel contamination: Iron filings (brake pad wear dust) or oil accumulated on the half shaft magnetic encoder surface distorts the magnetic field signal, causing abnormal square waves or signal loss.— Wheel speed sensor aging: Hall element performance degrades, causing insufficient output signal amplitude. The control unit cannot correctly identify the signal at high rotational speeds.— Intermittent wiring harness fault: Left front wheel speed sensor harness shorts or opens intermittently during steering or suspension travel, or oxidized connector pins or backed-out terminals increase contact resistance.+2 more →
Actions
— Initial diagnosis: Use the VDS diagnostic tool to read the complete fault code freeze frame. Record the vehicle speed and wheel speed data from when the fault occurred. Enter "Live Data Stream" mode and observe the four wheel speed signals. Check whether the left front wheel shows 0 km/h, a fixed abnormal value (such as 1845km/h), or a significant difference from the other wheels.— Basic check: Turn off the ignition switch. Inspect the left front wheel speed sensor connector (usually located near the shock absorber) for looseness, water ingress, or pin oxidation. Measure the sensor resistance (Hall type: approx. 1.0-1.5kΩ; magnetic induction type: approx. 0.8-1.4kΩ). Check the wiring harness for continuity and insulation to ground.+3 more →
C050576›
This DTC indicates the IPB (Integrated Intelligent Braking System) detects a correlation plausibility fault in the left front wheel speed sensor signal. Specifically, the frequency or amplitude of the sensor pulse signal logically conflicts with the actual vehicle motion state, the other three wheel speed signals, or the longitudinal acceleration sensor data, failing the system plausibility check algorithm. This fault typically indicates intermittent sensor signal interruption, electromagnetic interference, magnetic ring (magnetic encoder) demagnetization, or out-of-tolerance mechanical installation clearance. These conditions prevent the ABS/ESC from accurately identifying the actual left front wheel speed, triggering the ABS warning light and ESC OFF light, and degrading the automatic emergency braking system.
Causes
— Open or short circuit in the internal coil of the front left wheel speed sensor (magnetic induction type), or Hall element signal drift, resulting in unstable output signal amplitude.— Deformed sensor mounting bracket, loose retaining bolts, or missing washer causes the air gap between the sensor and magnetic ring to exceed the standard range (0.3-1.2 mm).— Heavy iron filings or mud accumulate on the surface of the wheel hub bearing magnetic encoder (magnetic ring), or the encoder has physical damage or demagnetization.+2 more →
Actions
— Connect the VDS2000/VDS3100 diagnostic tool and read the C050576 freeze frame data. Record the vehicle speed, left front wheel speed, steering wheel angle, and longitudinal acceleration at the time of the fault. Check for other accompanying sub-codes in the C050500-C050599 series.— Raise the vehicle until the wheels are off the ground. Visually inspect the left front wheel speed sensor wiring harness for wear or stretching at the steering knuckle and lower control arm retaining clips. Inspect the connector waterproof sealing ring for aging.+5 more →
C050600›
DTC C050600 indicates the IPB (Intelligent Integrated Braking System) detects an electrical circuit fault in the right front wheel speed sensor (WSS). This is a circuit integrity fault. The ECU detects sensor signal voltage outside the normal threshold (typically 0.1V-4.9V), a short to power or ground, an open circuit, or signal interference. The BYD IPB system uses a two-wire Hall effect or magnetoelectric wheel speed sensor. The ECU continuously monitors the sensor supply current and signal waveform. If the right front wheel speed signal is lost or distorted, the system disables functions relying on wheel speed data, including ABS, EBD, TCS, ESC, and AEB. The vehicle retains basic hydraulic braking capability. This fault illuminates multiple instrument cluster warning lights (ABS/ESC/AEB) and triggers Limp Home mode, which limits power output or disables energy recovery.
Causes
— Physical damage to the right front wheel speed sensor wiring harness: Due to its routing near the steering knuckle, the wiring harness bends repeatedly during suspension travel and steering. This causes internal copper wire fatigue fractures or insulation damage, especially after driving on rough roads or through water.— Sensor connector corrosion or poor contact: Mud and water easily accumulate in the right front wheel area. The sensor plug sealing ring (typically located near the shock absorber or fender liner) ages and fails, causing pin oxidation, short circuits from water ingress, or increased contact resistance (>1Ω).— Wheel speed sensor internal fault: damaged internal Hall element, coil open/short circuit (magnetic type resistance must be 1.0-2.0kΩ; values outside this range indicate failure), or abnormal gap between the sensor head and tone ring due to impact damage (standard gap: 0.3-1.2mm).+2 more →
Actions
— Initial diagnosis: Use VDS2000/3000 or Launch X-431 to read all fault codes. Check for related faults such as C050500 (left front) and C050700 (right rear). Record parameters such as vehicle speed, voltage, and temperature from the freeze frame data.— Visual inspection: Raise the vehicle. Remove the right front wheel and fender liner. Inspect the complete routing of the wheel speed sensor wiring harness from the IPB control unit (located on the engine compartment firewall or above the cabin pedals) to the right front steering knuckle. Check the harness for wear, insulation damage, or crush marks, focusing on the suspension control arm retaining clips and the bend at the steering knuckle.+5 more →
C050800›
DTC C050800 indicates an abnormal short circuit between the right front wheel speed sensor power supply circuit (typically a 12V or 5V reference voltage) and body ground (GND). In the BYD IPB (Integrated Power Brake) architecture, the active wheel speed sensors (Hall-effect or magnetoelectric) require a stable operating voltage from the ECU. When the power supply line shorts to ground, the IPB module detects an abnormal current increase or a voltage drop to near 0V and triggers the fault protection mechanism. This fault causes the loss of the right front wheel speed signal, disabling or degrading functions such as the Anti-lock Braking System (ABS), Electronic Stability Control (ESC), Traction Control System (TCS), and Automatic Emergency Braking (AEB). This hard fault severely impacts driving safety.
Causes
— Right front wheel speed sensor harness insulation damage: Long-term friction and vibration at the steering knuckle, suspension control arm, or body pass-through wears through the harness outer sheath. The internal power wire contacts the metal body, creating a short to ground.— Internal short circuit in the sensor body: A failed Hall element or internal circuit board shorts the power supply pin to the housing. Common causes include sensor aging, overheating, or water ingress corrosion.— Connector water ingress or corrosion: Poor sealing of the right front wheel speed sensor connector (located in the fender liner or engine compartment) allows water to accumulate inside after washing the vehicle or driving through water, causing a short circuit between the power terminal and the ground terminal.+2 more →
Actions
— Safety check and pre-diagnosis: Connect the VDS diagnostic tool and confirm the DTC status is Active. Read the right front wheel speed sensor data stream to confirm no signal output. Check if the IPB power supply fuse is blown (a blown fuse indicates a severe short circuit). Disconnect the IPB and right front wheel speed sensor connectors. Measure the resistance to ground at the sensor-side power supply pin. A reading of less than 1Ω confirms a short to ground.— Wiring harness visual inspection: Raise the vehicle, remove the right front wheel and inner fender liner, and inspect the wiring harness sheath along the entire wheel speed sensor harness routing (from wheel hub bearing → steering knuckle → fender liner → engine compartment) for wear, cuts, or burn marks. Focus on interference points between the harness and the steering knuckle, brake hose, and suspension spring, and check the body pass-through rubber grommet for aging or detachment.+4 more →
C050900›
This DTC indicates a short circuit between the 12V power supply wire and the signal output circuit of the right front (FR) wheel speed sensor, or a direct short from the signal wire to battery positive (B+). In the BYD IPB (Intelligent Integrated Braking System) architecture, the wheel speed sensor is typically a Hall-effect type. Under normal operation, the supply voltage is 12V, and the signal wire outputs a 0.5-4.5V pulse voltage. When the signal wire shorts to the 12V supply, the IPB control unit receives a continuous high-level signal and cannot identify wheel speed pulses. This causes the system to lose the right front wheel speed data or display an abnormal fixed value. This condition triggers the safety protection mechanisms of systems including ABS, ESP, and EHB (Electro-Hydraulic Braking), causing brake assist functions to degrade or fail. Multiple warning lights illuminate on the instrument cluster, severely compromising driving safety.
Causes
— Improperly secured right front wheel speed sensor wiring harness at the fender liner, below the A-pillar, or at the front wheel arch. Prolonged rubbing against the body bracket, steering knuckle, or suspension components damages the insulation, causing the power and signal wires to contact and short circuit.— Sensor connector seal failure allows water ingress after driving through water or high-pressure washing, causing electrolytic corrosion and short circuits between pins; or an improperly seated connector causes pin misalignment and poor contact.— Crushing, bending, or improperly securing the wiring harness during front-end accident repairs or vehicle modifications (such as installing mud flaps or modifying brakes) damages and exposes the internal copper core.+2 more →
Actions
— Connect the BYD VDS diagnostic tool and confirm C050900 is a Current DTC. Read the IPB data stream and check if the right front wheel speed signal displays a fixed high value (such as 8191 rpm or maximum value) or zero. Compare this signal with the other three wheels to confirm the abnormality.— Raise the vehicle to a suitable height. Visually inspect the right front wheel speed sensor connector for looseness, water ingress, and oxidized or deformed pins. Inspect the harness mounting and visual integrity at the fender liner, front wheel arch, below the A-pillar, and firewall pass-through. Verify the clearance between the harness, body metal edges, and suspension mounting bolts.+5 more →
C050A00›
DTC C050A00 indicates the IPB (Intelligent Integrated Braking System) ECU detects the air gap between the right front wheel speed sensor (WSS) and the signal tone ring exceeds the calibrated tolerance range (typically 0.3-1.2mm), or the sensor signal amplitude/phase exhibits intermittent erratic characteristics. This is a plausibility fault, distinct from a direct short or open circuit. The IPB system uses an active Hall-effect wheel speed sensor highly sensitive to the installation air gap. An excessive gap attenuates the signal, while an insufficient gap causes the sensor head to rub against the tone ring. The ECU sets this fault when algorithmic compensation cannot verify wheel speed signal reliability. This fault degrades or disables ABS, ESP, TCS, and Automatic Emergency Braking (AEB) functions. In severe cases, it illuminates the brake system warning lamp continuously.
Causes
— Loose wheel speed sensor mounting, or mud, sand, or foreign matter in the mounting hole, causing the actual air gap to deviate from the standard value.— Excessive axial play or wear in the right front wheel hub bearing causes axial displacement of the integrated signal tone ring (magnetic encoder ring), altering the air gap.— Bottoming out, stone impacts, or long-term wear physically damages the wheel speed sensor head, altering the magnetic field distribution.+2 more →
Actions
— Use VDS2000 or a dedicated BYD diagnostic tool to read complete fault codes, confirm if the fault is current (Present), and record freeze frame data (vehicle speed, temperature, etc.).— Raise the vehicle. Inspect the right front wheel speed sensor exterior and wiring harness connector for damage or water ingress. Inspect the sensor tip for wear marks or attached foreign objects.+6 more →
C050B76›
DTC C050B76 indicates the IPB (Intelligent Integrated Braking System) detects a correlation fault in the right front wheel speed sensor signal. This fault does not indicate a simple signal loss (open circuit). Instead, the sensor pulse signal output logically mismatches actual vehicle dynamics (e.g., other wheel speeds, vehicle speed, acceleration, yaw rate), or the signal characteristics (frequency, amplitude, duty cycle) exceed calibrated thresholds. The IPB algorithm compares the correlation of all four wheel speed sensors. The system sets this code when the right front signal differs excessively from the other wheel speeds, exhibits erratic signal jumps, or experiences an intermittent fault in the sensor power supply or ground circuit. This fault directly affects the Anti-lock Braking System (ABS), Electronic Stability Control (ESC), Automatic Emergency Braking (AEB), and energy recovery functions. It may increase braking distance or cause abnormal brake pedal feel.
Causes
— Right front wheel speed sensor component degradation or an internal coil inter-turn short circuit causes insufficient output signal amplitude or waveform distortion. Signal quality degrades particularly at high temperatures or high wheel speeds.— Abnormal air gap between the sensor and magnetic encoder ring (tone ring) (greater than 1.2 mm or less than 0.3 mm). Common causes include a loose sensor retaining bolt, a deformed bracket, or bearing wear causing axial hub play.— Damage to the magnetic encoder ring in the right front wheel hub unit (demagnetization, cracks, or attached iron filings) causes uneven magnetic flux changes, resulting in signal noise or missing tooth signals.+2 more →
Actions
— Use a diagnostic tool to read freeze frame data. Confirm the vehicle speed, wheel speed values, and IPB supply voltage at the time of the fault. Check for accompanying fault codes (e.g., C050A00, U0121). Clear the fault codes and perform a road test. Monitor the right front wheel speed data stream for sudden fluctuations or loss of synchronization with the other wheel speeds.— Raise the vehicle and visually inspect the right front sensor. Verify the mounting bolt torque (standard 8-12 N·m). Check the wiring harness for stretching at the steering lock positions. Measure the sensor resistance (standard value 1.5-2.5 kΩ at 20°C). Measure the sensor supply voltage (12 V ± 0.5 V with ignition ON).+3 more →
C050C00›
DTC C050C00 indicates the IPB (Integrated Intelligent Brake Control System) detects an electrical fault in the left rear wheel speed sensor (WSS) wiring harness, including an open circuit, short circuit, or short to ground or power. This sensor, typically a Hall-effect or magnetoelectric type, converts wheel speed into an electrical signal and transmits it to the IPB module. The IPB module uses this signal for precise control of systems including ABS, ESC, TCS, EPB, and Automatic Emergency Braking (AEB). A wiring harness fault prevents the IPB from obtaining left rear wheel speed data and triggers a system degraded mode (ABS/ESC functions limited or disabled). In extreme cases, this fault can affect brake force distribution, cause abnormal parking brake operation, or trigger speed-limiting protection, posing a driving safety risk.
Causes
— Loose connection, backed-out terminals, water ingress, or corrosion in the left rear wheel speed sensor wiring harness connector, causing increased contact resistance.— Wiring harness worn, chafed, or completely broken at moving suspension parts (such as near the steering knuckle, control arm, or shock absorber) due to detached retaining clips.— Sensor internal coil burnt out, Hall element failed, or probe damaged.+2 more →
Actions
— Use the VDS2000/VDS3000 diagnostic tool to read the fault code and freeze frame data. Confirm the vehicle speed, road conditions, and related fault codes at the time of the fault. Check if the left rear wheel speed data stream reads 0 or shows abnormal jumps.— Raise the vehicle to a suitable height and visually inspect the entire left rear wheel speed sensor wiring harness. Check the protective sleeve for damage, chafing, or water ingress, particularly where it passes through body holes and near the suspension control arm and shock absorber.+5 more →
C050E00›
DTC C050E00 indicates the IPB (Intelligent Integrated Braking System) or ABS module detects an abnormal short circuit to vehicle ground (GND) in the left rear wheel speed sensor (WSS) power supply circuit (typically the 12V supply line). This supply circuit provides the operating voltage for the Hall-effect or magnetic wheel speed sensor. When a short to ground occurs, the power driver circuit inside the ABS module detects overcurrent or a voltage drop to nearly 0V, triggering the protection mechanism and storing the fault code. This fault causes a missing or abnormal left rear wheel speed signal, forcing active safety functions such as ABS, ESC, TCS, and Automatic Emergency Braking (AEB) into fail-safe mode (conventional braking). The instrument cluster illuminates multiple warning lamps, including ABS, ESC, and EBD. This severely compromises driving safety and creates a risk of wheel lock-up, especially on slippery roads or during emergency braking.
Causes
— Damaged or aged left rear wheel speed sensor wiring harness insulation rubs against metal components (such as the longitudinal beam, suspension bracket, or wheel arch liner) during driving, grounding to the chassis and causing a power wire short to ground.— Short circuit inside the wheel speed sensor body between the power supply pin and the sensor housing or ground pin (usually resulting from water ingress from sensor seal failure, internal coil burnout, or circuit board breakdown).— Water enters the sensor connector (located at the left rear fender or chassis wiring harness connection) due to wading, high-pressure washing, or sealing ring aging, causing an electrolytic short circuit or corrosion-induced conduction between the internal power terminal and ground terminal.+2 more →
Actions
— Connect the VDS or dedicated diagnostic tool and read the freeze frame data for DTC C050E00. Record key parameters at the time of the fault, such as vehicle speed, voltage, and temperature. Clear the fault code and perform a road test to confirm if the fault is persistent.— Raise the vehicle and remove the left rear wheel. Visually inspect the wheel speed sensor for physical damage. Specifically check the sensor connector (usually located near the shock absorber or body wiring harness connection) for water ingress, terminal corrosion, looseness, or damaged wiring insulation.+5 more →
C051000›
DTC C051000 indicates the IPB (Integrated Intelligent Braking System) detected an abnormally low-resistance path between the left rear wheel speed sensor power supply circuit (typically a 5V or 12V reference voltage) and the vehicle main power supply (B+, battery voltage). In automotive electronic diagnostics, "Short to Battery" means the signal wire or power supply wire shorted to the positive 12V power supply. This fault causes the sensor supply voltage to rise abnormally above the rated 5V/12V to the 13-14V battery voltage range, triggering the overvoltage protection mechanism in the IPB control unit. Because the wheel speed signal is a core input parameter for the ABS, ESC, EBD, and Autonomous Emergency Braking (AEB) systems, this fault causes these safety systems to enter a degraded mode or fail completely, posing a severe driving safety hazard. Potential causes include physical damage to the wiring harness, electronic component breakdown inside the sensor, water ingress and corrosion in the connector, or a power management chip failure inside the IPB control unit.
Causes
— Damaged left rear wheel speed sensor wiring harness insulation, particularly in the corrugated conduit section routed between the body and suspension, shorting to an adjacent 12V power wire (such as the tail light or fuel pump power wire).— Wheel speed sensor internal Hall element or capacitor breakdown causes abnormally low impedance between the power supply and signal pins, creating an internal short circuit.— Faulty IPB control unit internal voltage regulation module (LDO or DC-DC) shorts the power supply output terminal directly to the internal battery power supply.+2 more →
Actions
— Use the VDS2000 or VDS3000 diagnostic tool to read the DTC freeze frame data. Record the vehicle speed, throttle opening, and ambient temperature when the fault occurred. Confirm whether the fault is static (code sets at key ON) or dynamic (code sets at a specific vehicle speed).— Raise the vehicle and remove the left rear tyre. Visually inspect the entire wheel speed sensor wiring harness, focusing on the corrugated conduit entry and exit points, the body sheet metal pass-throughs, and the area near the rear differential. Check for signs of harness abrasion, scorching, or discolouration.+6 more →
C051176›
The BYD IPB (Intelligent Integrated Braking System) defines DTC C051176 as "Incorrect Installation Direction of Left Rear Wheel Speed Sensor". This fault does not indicate a simple open or short circuit. Instead, the magnetic pole direction of the Hall-effect wheel speed sensor mismatches the relative position of the tone ring, reversing the output square-wave signal phase or generating an abnormal duty cycle. The IPB control unit triggers this code upon detecting unexpected rising and falling edge timing in the signal waveform, or upon identifying a logical conflict between the left rear wheel speed signal and the other three wheels during vehicle speed calculation. This fault directly disables or falsely triggers the Anti-lock Braking System (ABS), Electronic Stability Program (ESP), Automatic Emergency Braking (AEB), and tire pressure monitoring system (calculated via wheel speed differentials), severely compromising driving safety.
Causes
— Sensor body rotated 180° during installation: Technician failed to align the locating marks when inserting the sensor into the mounting hole after replacing the bearing or brake system, reversing the Hall element magnetic pole direction relative to the tone ring.— Using a non-genuine aftermarket sensor: Some third-party parts have magnetic pole markings opposite to the genuine part, or the internal Hall chip orientation mirrors the genuine part. This causes an incorrect electrical direction despite correct physical installation.— Loose sensor mounting: Retaining bolt not tightened to specified torque (8-10 N·m) or stripped steering knuckle mounting hole threads allow driving vibration to gradually rotate and shift the sensor.+2 more →
Actions
— Connect the VDS2000/BYD dedicated diagnostic tool, read the IPB system fault codes to confirm C051176 is present, and record the freeze frame data (especially vehicle speed and wheel speed values when the fault occurred).— Raise the vehicle to a suitable height and remove the left rear wheel. Visually inspect the wheel speed sensor condition, connector locking tab, and wiring harness routing. Confirm the direction of the arrow mark on the sensor head (it must point toward the wheel center/toothed ring).+5 more →
C051200›
DTC C051200 indicates the IPB (Intelligent Integrated Braking System) detected a persistent or intermittent electrical fault in the right rear wheel speed sensor (RR WSS) circuit. This fault occurs when the IPB module fails to receive a valid wheel speed signal within the specified time, or detects signal voltage/resistance outside the threshold range (typically an open circuit, short to ground, short to power, or signal interference). On vehicles equipped with the IPB (One-box) integrated braking system, such as the BYD Song PLUS DM-i, this fault disables or limits the Anti-lock Braking System (ABS), Electronic Stability Control (ESC), Automatic Emergency Braking (AEB), Hill Hold Control (HHC), and Adaptive Cruise Control (ACC) functions. Additionally, because New Energy Vehicles (NEVs) rely on wheel speed signals to calculate regenerative braking torque, this fault may cause abnormal energy recovery, inaccurate driving range display, and force the drive system into protection mode.
Causes
— Physical damage to the right rear wheel speed sensor wiring harness: Chassis bottoming out, driving through water, or prolonged vibration damages the harness sheath, breaks the wires, or oxidizes the internal copper strands. This damage commonly occurs at stress concentration points where the harness passes the suspension control arm or routes through body apertures.— Connector water ingress and corrosion: Direct high-pressure washing, driving through water, or aging sealing rings allow water into the sensor connector (near the right rear wheel hub) or the IPB module connector (in the motor compartment), causing terminal oxidation and increased contact resistance.— Internal sensor fault: Although the DTC points to the wiring harness, the IPB misinterprets an open circuit (infinite resistance) or short circuit (resistance below 0.5 kΩ) in the internal sensor coil as a circuit fault. Normal magnetic induction sensor resistance is 1.0–1.8 kΩ.+2 more →
Actions
— Initial diagnosis: Use the VDS2000/VDS3000 diagnostic tool to read all fault codes and confirm if C051200 is present as a history or current code. Check the vehicle speed, wheel speed values, and IPB voltage in the freeze frame data. Confirm if the right rear wheel speed showed 0 km/h or abnormal jumps when the fault occurred.— Visual inspection: Raise the vehicle and remove the right rear wheel. Follow the sensor wiring harness routing (from the wheel hub bearing → body side member → IPB module) and check the protective sleeve for wear, breaks, or pinching. Focus on the contact points between the wiring harness and the control arm, shock absorber, and body sheet metal. Check the sensor connector (black 2-pin) and the IPB module connector (32-pin or 48-pin, located on the left firewall in the engine compartment) for water ingress, oxidation, or terminal back-out.+5 more →
C051400›
This DTC indicates the IPB (Intelligent Integrated Braking System) detects an abnormally low-resistance connection between the right rear wheel speed sensor power supply circuit (typically a 12V or 5V reference voltage) and body ground (GND), constituting a short to ground. In the BYD IPB system, the wheel speed sensor is a two-wire active Hall sensor. The ECU supplies operating voltage to the sensor via the power supply line. A short to ground on the power supply line causes: 1) complete loss of the right rear wheel speed signal; 2) the IPB system to trigger limp mode, automatically disabling the dynamic functions of the ABS, ESC, Automatic Emergency Braking (AEB), and Electronic Parking Brake (EPB); 3) potential damage to the internal IPB driver circuit if the short-circuit current is excessive. This is a hard-wire circuit fault, not signal interference or performance degradation. Repair the fault immediately to prevent braking system failure.
Causes
— Right rear wheel speed sensor wiring harness insulation damage: Stones striking the vehicle chassis during driving break the harness sheath, or loose harness retaining clips cause long-term friction against suspension components, exposing the power supply wire copper core and causing it to contact metal body parts.— Wheel speed sensor internal short circuit: Breakdown of the internal Hall element or capacitor causes continuity between the power supply terminal and the sensor housing (ground). Common causes include sensor aging, overheating, or manufacturing defects.— Wiring harness connector water ingress and corrosion: Wading in the right rear wheel area or direct high-pressure spraying during car washing causes the sensor plug seal to fail. This forms an electrolyte conductive path between the pins, causing a short circuit between the power supply pin and the ground pin.+2 more →
Actions
— Safety preparation and fault confirmation: Use VDS or a dedicated diagnostic tool to read all fault codes; confirm if C051400 appears alone or with related wheel speed signal faults; inspect the right rear wheel speed sensor connector for looseness, backed-out pins, or corrosion; verify the vehicle is stationary when the fault occurs (to rule out electromagnetic interference during driving).— Sensor body inspection: Disconnect the right rear wheel speed sensor connector. Use a multimeter to measure the resistance between the sensor-side power supply pin and the ground pin (or sensor metal housing). Normal resistance is greater than 10 MΩ (open circuit). If the resistance is less than 1 Ω, replace the right rear wheel speed sensor. Also measure the resistance between the sensor signal pin and the power supply pin. Normal resistance is 1-2 kΩ (Hall sensor internal resistance).+3 more →
C053D00›
This fault code indicates the IPB (Intelligent Integrated Braking System) detects the hydraulic pressure value from the brake master cylinder pressure sensor falls outside the system-calibrated normal threshold range (too high or too low). The IPB system monitors the driver’s braking intent and hydraulic circuit status in real time via the master cylinder pressure sensor. The system logs a pressure out-of-range fault if the pressure signal voltage falls outside the valid 0.5-4.5V range, or if the pressure value mismatches the pedal travel and wheel cylinder pressure logic. This fault triggers a degraded protection mode, which may limit ABS/ESC functions, disable automatic emergency braking, or cause abnormal brake pedal feel, severely compromising driving safety.
Causes
— Master cylinder pressure sensor inside the IPB integrated module drifted or damaged, causing abnormal signal output.— Brake hydraulic system leak (lines, wheel cylinders, or aged IPB body sealing ring), preventing the system from building or maintaining actual pressure.— Severely low, degraded, or aerated brake fluid causing abnormal pressure transmission and inaccurate sensor readings.+2 more →
Actions
— Safety check and initial assessment: Verify the brake fluid level is between MAX and MIN, check the instrument cluster warning light status (if ABS/ESC lights remain illuminated), and perform a road test to confirm normal brake pedal travel and braking force.— Diagnostic scan: Use VDS or Launch X431 to read the complete fault codes and view freeze frame data (record the pressure value, pedal travel, and vehicle speed at the time of the fault). Analyze whether the pressure is too high (>20MPa abnormal) or too low (<0.5MPa abnormal).+5 more →
C051500›
DTC C051500 indicates the IPB (Intelligent Integrated Braking System) detected a short circuit to battery positive (B+) in the right rear wheel speed sensor power supply circuit. This fault occurs when abnormal electrical continuity develops between the sensor power line (typically a 12V supply) and the vehicle constant power supply or the IPB internal power output stage, causing an abnormal voltage increase or current overload. The IPB control unit monitors the supply circuit voltage and current characteristics. Upon detecting a short circuit, it triggers a protection mechanism and cuts power to the circuit to prevent hardware damage. This fault causes the loss of the right rear wheel speed signal, disabling or degrading ABS, ESP, TCS, EPB, and Automatic Emergency Braking (AEB) functions, which severely compromises driving safety. The '00' suffix in the DTC typically indicates an active, hard fault (non-intermittent).
Causes
— Damaged right rear wheel speed sensor harness insulation: Long-term vibration and chafing damage the harness at the rubber grommet where it passes through the body floor or suspension control arm. The power supply wire contacts an adjacent constant power circuit (e.g., tail light power, fuel pump power), creating a short circuit.— Sensor connector water ingress and corrosion: Vehicle wading, direct high-pressure water jets, or poor sealing causes an internal short circuit, connecting the power supply terminal to an adjacent high-potential terminal or the metal housing.— Wheel speed sensor internal circuit breakdown: Damage to the sensor's internal voltage regulator circuit or Hall element causes a short circuit between the power input terminal and the signal output terminal or housing, creating a reverse short circuit to the power supply circuit.+2 more →
Actions
— Safety preparation and fault confirmation: Use VDS2000 or Launch X431 to read all fault codes. Verify if C051500 is the only code present or if other wheel speed sensor faults, such as C051400 (short to ground), accompany it. Record freeze frame data (vehicle speed, temperature, and voltage at the time of occurrence). Check the IPB software version and confirm there are no related Technical Service Bulletins (TSB).— Visual and connector inspection: Raise the vehicle and remove the right rear wheel. Inspect the wheel speed sensor connector (usually located near the steering knuckle or brake caliper) for water ingress, corrosion, looseness, or deformed pins. Follow the wiring route and inspect the wiring harness sheath for damage, focusing on the bent sections passing through the floor pan and suspension control arm.+4 more →
C051600›
DTC C051600 indicates the IPB (Intelligent Integrated Braking System) detects an intermittent abnormality or insufficient plausibility in the right rear wheel speed sensor signal. Unlike a direct open or short circuit fault, 'indirect uncertainty' means the sensor still returns a signal, but under specific operating conditions (such as a specific vehicle speed range, steering maneuver, or road input), the signal spikes, drifts, or illogically contrasts with the other wheel signals. The IPB system algorithm compares the four-wheel speed differential, longitudinal acceleration, and yaw rate signals. The system triggers this fault when the right rear wheel speed signal duration or amplitude exceeds the plausible confidence interval but has not yet reached the hard fault threshold. This condition typically indicates dynamic sensor-to-tone ring gap variation, electromagnetic signal interference, or an intermittent voltage drop in the sensor power supply or ground, which can cause ABS/ESC function degradation or false activation.
Causes
— Ferromagnetic debris or brake dust accumulated on the right rear wheel speed sensor head changes the effective magnetic permeability of the air gap, causing unstable signal amplitude.— Right rear wheel hub bearing wear causes axial/radial play to exceed tolerance, dynamically changing the relative position between the sensor and tone ring (common on vehicles with >50,000 km).— Repeated bending of the sensor wiring harness in the body-to-rear-wheel transition area (such as inside the sill trim panel or near the rear suspension) causes hidden internal wire breaks and intermittently increases contact resistance.+2 more →
Actions
— Connect the VDS diagnostic tool, enter the IPB system, and read the live data stream. Monitor the right rear wheel speed signal under stationary, accelerating, constant speed, and turning conditions. Check for anomalies such as signal jumps, negative values, or a >3km/h difference compared to the other three wheels.— Raise the vehicle. Visually inspect the right rear wheel speed sensor mounting hole for looseness and the sensor head for oil or metal swarf. Clean the sensor end face and use a feeler gauge to measure the clearance to the tone ring (standard: 0.3-1.2 mm; Song PLUS DM-i standard: approx. 0.8 mm).+4 more →
C051776›
The IPB (Intelligent Integrated Braking System) or ESC (Electronic Stability Control System) triggers this DTC. It indicates a wrong installation direction for the right rear wheel speed sensor. The sensor uses the Hall effect principle; its internal magnetic poles have a specific bias direction to identify the tone ring rotational direction. Installing the sensor opposite to the calibrated direction, or swapping the left and right sensors, produces an output signal polarity opposite to ECU expectations. This prevents the system from correctly interpreting the wheel speed signal. This condition degrades or disables functions such as ABS, ESP, Auto Hold, and Automatic Emergency Braking, representing a brake safety-related functional fault.
Causes
— Mistakenly swapping the left and right rear wheel speed sensors during repair work, or installing the sensor backwards by failing to observe the arrow mark on the sensor housing.— Installing a non-genuine part or a wheel hub bearing unit from a different batch causes a mismatch between the sensor magnetic pole orientation and the tone ring.— During accident repairs, the technician failed to install the sensor in the orientation specified by the workshop manual, or used a refurbished part.+2 more →
Actions
— Use VDS or a dedicated diagnostic tool to read the fault code, confirm C051776 is active, and check the right rear wheel speed data stream for abnormalities (e.g., missing signal, erratic signal, or mismatch with actual vehicle speed).— Raise the vehicle and inspect the right rear wheel speed sensor harness connector for looseness, water ingress, or corrosion. Measure the sensor supply voltage (usually 12V or 5V, depending on the vehicle model).+6 more →
C051D01›
DTC C051D01 indicates an abnormal calibration status of the inertial measurement unit (IMU) inside the IPB (Integrated Power Brake). Specifically, the yaw rate sensor or longitudinal acceleration sensor reference data is lost, offset, or invalid. Integrated inside the IPB control module, this sensor monitors the vehicle’s rotational yaw rate about the vertical axis and its longitudinal acceleration in real time. It provides the core input signal the ESP electronic stability control system uses to calculate vehicle dynamic attitude. The IPB sets this code when it detects the sensor output deviates from the expected calibration reference beyond the threshold, or when it loses the stored calibration parameters. This limits ESP functionality or triggers limp mode; however, normal hydraulic braking usually remains unaffected.
Causes
— Failure to perform the IMU sensor calibration procedure after replacing the IPB assembly, disconnecting the battery, or prolonged battery depletion results in calibration data loss.— Loose IPB control module mounting bracket, insufficient mounting bolt torque, or external impact to the module causes the internal inertial sensor physical reference to shift.— A vehicle software upgrade (OTA or diagnostic tool) updated the IPB control program but failed to synchronously reset or match the calibration data.+2 more →
Actions
— Use a dedicated BYD diagnostic tool (VDS or ED400) to read the complete IPB system fault codes and freeze frame data. Check if related fault codes such as C006A02 (signal error) or C00A800 (not calibrated) accompany C051D01.— Visually inspect the IPB control module for external damage. Verify the module mounting bracket is not deformed. Tighten the fixing bolts to the specified torque (usually 8-10 N·m). Ensure the module mounting surface is parallel to the vehicle body reference surface.+4 more →
C052801›
DTC C052801 indicates the Steering Angle Sensor (SAS) in the Intelligent Integrated Braking System (IPB) detects a steering angle value exceeding the valid system-calibrated range (typically ±720° or ±1440°, depending on vehicle calibration), or the sensor output signal voltage falls outside the normal 0.5-4.5V range. The Electronic Stability Control (ESC) system uses this key input sensor to determine the match between the driver's steering intent and the vehicle's actual yaw rate. When the steering angle value exceeds this range, advanced driver assistance functions including ESC, ABS, Automatic Emergency Braking (AEB), and Lane Keeping may enter a degraded mode or fail completely, severely compromising vehicle handling stability. Potential causes include a damaged sensor, an open circuit in the steering wheel clock spring, a Steering Column Control Module (SCCM) communication fault, an abnormal IPB internal signal processing circuit, or a missing SAS zero-point calibration following chassis repairs.
Causes
— Damaged internal potentiometer or Hall element in the steering angle sensor (SAS), causing the output signal to drift or remain at a fixed out-of-range value.— Broken internal ribbon cable or poor contact in the steering wheel clock spring (Clock Spring), causing an intermittent open circuit in the sensor power supply, ground, or signal wires.— Abnormal CAN bus communication between the steering column control module and the IPB (wiring short circuit, open circuit, or abnormal terminating resistor)+2 more →
Actions
— Connect the BYD VDS2000 dedicated diagnostic tool and read the complete IPB system fault codes and freeze frame data. Confirm if the steering angle sensor real-time value (Steering Angle) displays an invalid value (such as a fixed abnormal value like 8191° or -4096°), and check for related fault codes (such as C052901 Steering Angle Sensor Module Missing).— Check the steering wheel clock spring connector for looseness or corrosion. Use a multimeter to measure the continuity of each clock spring circuit (especially the sensor 12V supply, GND, and signal wires). Turn the steering wheel and observe if the resistance value changes abruptly.+4 more →
C052901›
DTC C052901 indicates a communication interruption or loss of data validity between the IPB (Intelligent Integrated Braking System) control unit and the Steering Angle Sensor (SAS). The steering angle sensor mounts on the steering column and transmits steering wheel angle, rotational speed, and direction information in real time to the IPB, VCU, ADAS, and other modules via the CAN bus. It provides the core input signal for the Electronic Stability Control (ESC), automatic parking, lane keeping, and Autonomous Emergency Braking (AEB) systems. The IPB triggers this fault when it fails to receive a valid steering angle data frame within 500 ms, or detects a sensor response timeout or checksum error. The vehicle then enters a degraded mode: ESC function is limited or disabled, skid control fails, and automatic parking is unavailable. Extreme cases may alter brake assist characteristics, but the system retains basic hydraulic braking.
Causes
— Steering angle sensor internal fault: Damaged Hall effect element, internal MCU crash, or EEPROM data loss prevents valid signal output.— Abnormal steering column wiring harness connection: The steering angle sensor connector below the steering wheel (usually integrated into the combination switch assembly) is loose, has backed-out terminals, or shows water ingress and oxidation; or frequent steering column rotation caused wiring harness wear or breakage.— Power supply and ground fault: 12V battery voltage below 10V, blown sensor power supply fuse, or poor contact in the ground circuit causing sensor initialization failure.+2 more →
Actions
— Diagnostic tool check: Use VDS2000/VDS3000 to access the IPB system, read the complete fault codes and freeze frame data, and check for related faults such as C052B (steering angle sensor signal error) and U0416 (IPB communication fault); view the live data stream to confirm if the steering angle value displays as 'invalid' or remains fixed when turning the steering wheel.— Basic check: Disconnect the 12V battery negative terminal for 5 minutes, then reconnect power and check if the fault code changes to a history code. Inspect the combination switch connector (grey or black 18-pin connector) at the steering column below the steering wheel for looseness, backed-out pins, or water corrosion. Clean and apply conductive grease if necessary.+4 more →
C053B00›
DTC C053B00 indicates an open circuit or abnormal voltage in the ABS solenoid valve power supply circuit inside the IPB (Intelligent Integrated Braking) module. This fault means the ECU detects the power supply line voltage to the ABS hydraulic modulator solenoid valve falls outside the normal range (typically below 9V or above 16V) or has an open circuit. Because the IPB system integrates ABS, ESP, EHB (Electro-Hydraulic Braking), and other functions, an abnormal solenoid valve power supply causes safety functions such as anti-lock braking and vehicle stability control to fail or degrade. The system then enters fail-safe mode. External power supply circuit issues (fuses, wiring harnesses, connectors) or a fault in the IPB internal power management circuit can cause this fault. Repair the system immediately to ensure braking system reliability.
Causes
— IPB/ABS system fuse (usually 30A or 40A) in the front compartment power distribution box is blown, loose, or has poor contact, causing power supply interruption or excessive voltage drop.— IPB module power wiring harness connector (located in the front compartment near the firewall): oxidized, backed-out, or burnt terminals, or water ingress due to poor sealing, causing increased contact resistance.— Poor contact, open circuit, or short circuit due to damaged insulation in the main power harness from the battery to the IPB module, especially harness aging in the high-temperature engine compartment.+2 more →
Actions
— Use the VDS2000/VDS1000 diagnostic tool to read all fault codes. Check if C053B00 occurs with C053C00 (wheel speed sensor) or other communication fault codes, and record the freeze frame data.— Check the ABS, ESP, and brake system warning light status on the instrument panel, perform a brake pedal feel test, and confirm whether the IPB system has entered backup mode (hard pedal).+8 more →
C053C00›
DTC C053C00 indicates the IPB (Intelligent Integrated Brake) system detects one or more wheel speed sensor input signals outside the plausible physical range. Specific conditions include: the sensor reports an equivalent vehicle speed exceeding the theoretical maximum vehicle speed (e.g., a frequency corresponding to over 250 km/h); the signal frequency or amplitude exceeds the ECU calibration threshold; or the four-wheel speed logic mismatches (e.g., one wheel speed reads abnormally higher than the others). This fault triggers the IPB safety protection mechanism, disables functions including ABS, ESC, and Automatic Emergency Braking, and forces the system into degraded mode.
Causes
— Wheel speed sensor body fault (internal coil open/short circuit, Hall element aging, magnetic material degradation)— Mechanical damage to the ABS tone ring (target wheel) (missing or damaged teeth, foreign object jamming, or deformation causing air gap changes)— Abnormal sensor installation gap (gap too large >1.2 mm or too small <0.3 mm, deformed bracket)+2 more →
Actions
— Use the VDS diagnostic tool to read freeze frame data and confirm the specific wheel location of the fault (left front/right front/left rear/right rear) and the vehicle status at the time.— Raise the vehicle. Visually inspect the condition of the affected wheel speed sensor and the integrity of the ABS tone ring (check for missing teeth, cracks, and attached metal debris).+6 more →
C053C76›
DTC C053C76 indicates the IPB (Intelligent Integrated Braking System) detects a wheel speed sensor output signal exceeding the system's defined logical range. This fault is a signal anomaly that may manifest as: 1) Signal frequency/amplitude exceeding physical limits (e.g., vehicle speed above 300 km/h or below 0 with signs of movement); 2) Abnormal signal transition rate (e.g., instantaneous drop from 100 km/h to 0); 3) Signal distortion caused by sensor output noise interference. This fault limits or disables safety functions including ABS, ESC, and automatic emergency braking. The IPB system enters degraded protection mode and illuminates multiple warning lights on the instrument cluster.
Causes
— Incorrect wheel speed sensor installation direction (left/right reversed or front/rear swapped, causing reversed signal polarity or incorrect phase; relatively common on BYD Song PLUS DM-i models)— Abnormal gap between the sensor and magnetic encoder (tone ring) (excessive gap causes a weak signal, insufficient gap causes friction damage, or impact during installation causes misalignment)— Magnetic encoder surface contaminated or damaged (iron filings, mud, or sand accumulation causing signal distortion, or encoder scratches or missing teeth)+2 more →
Actions
— Use the VDS2000 diagnostic tool to read the complete fault codes and freeze frame data, and determine the specific faulty wheel position (left front/right front/left rear/right rear) and the vehicle speed when the fault triggered.— Raise the vehicle and visually inspect the wheel speed sensor installation on the affected wheel: confirm the installation direction is correct (the angled face of the sensor head matches the wheel rotation direction) and check the retaining bolt torque (typically 8-12N·m).+6 more →
C053E00›
DTC C053E00 indicates a short to ground in the signal circuit of IPB (Intelligent Integrated Braking System) master cylinder pressure sensor 1. This sensor monitors brake master cylinder hydraulic pressure in real time and serves as the core feedback component of the brake-by-wire system. The ECU uses this signal to calculate brake assist demand, trigger energy recovery, and control ABS/ESC intervention timing. The ECU sets this fault when it detects the sensor signal voltage remaining continuously below the threshold (typically <0.5 V, normal range 0.5–4.5 V) or an abnormal drop in signal wire resistance to ground. This fault causes abnormal brake pedal feel (too hard or too soft), degrades energy recovery, and forces the ESC/ABS system into a degraded mode (illuminating multiple instrument cluster warning lights). Extreme cases may trigger limp-home mode (speed-limited driving).
Causes
— Physical damage to the wiring harness: Harness sheath in the engine compartment high-temperature area or near the steering mechanism wears or cracks from age, causing the signal wire (usually 0.5-1.0 mm² wire) to short circuit against vehicle body metal.— Connector water ingress and corrosion: Seal failure on the IPB assembly 24-pin main connector or sensor sub-connector. Internal terminals oxidize after driving through water or high-pressure washing, creating a low-resistance path between the signal terminal (pin) and the ground terminal.— Internal short circuit in the sensor body: Damage to the pressure-sensitive element or signal conditioning circuit inside the master cylinder pressure sensor causes the output terminal to short to the housing/ground wire (internal insulation breakdown).+2 more →
Actions
— Initial diagnosis: Read all fault codes using VDS2000/VDI. Check for accompanying codes C053D00 (pressure out of range) or C053F00 (open circuit). Record freeze frame data (vehicle speed, brake pedal travel, and pressure values at the time of the fault).— Visual inspection: Focus on the transition area between the IPB assembly (located on the left side of the engine bay firewall) and the body wiring harness. Check the 24-pin grey connector for water ingress (look for green corrosion on the terminals), and inspect the wiring harness for abrasion where it passes through the firewall grommet.+4 more →
C053F00›
DTC C053F00 indicates an electrical circuit fault in Primary Pressure Sensor 1 within the IPB (Intelligent Integrated Braking System, One-Box brake-by-wire unit). Specifically, the signal circuit, 5V supply circuit, or ground circuit has a short to ground, short to power, or open circuit. This sensor is a core input component of the brake-by-wire system. It monitors brake master cylinder hydraulic pressure or pedal simulator pressure in real time, providing critical data for brake assist, energy recovery, ESC vehicle stability, and AEB automatic emergency braking. When this fault occurs, the IPB immediately enters limp-home mode, potentially causing a loss of brake assist, a hard brake pedal, and complete deactivation of ABS and ESC functions. This severe fault compromises driving safety.
Causes
— IPB wiring harness connector (32-pin or 48-pin plug) seal failure. Water ingress after wading or high-pressure washing causes terminal corrosion and oxidation, resulting in intermittent short or open circuits.— Pressure sensor 1 internal circuit damage (this sensor typically integrates into the IPB assembly and is not replaceable separately), possibly due to overvoltage, overheating, or component aging.— Chassis bottoming out or a detached wiring harness retaining clip causes harness wear, shorting the signal wire to body ground or the 12V power supply wire.+2 more →
Actions
— Safety preparation: Disconnect the low-voltage battery negative terminal, remove the high-voltage service disconnect (MSD), wait at least 5 minutes to ensure high-voltage capacitor discharge, and wear insulated gloves and safety goggles.— Visual inspection: Inspect the IPB assembly exterior at the front compartment firewall. Check the wiring harness connector for looseness, backed-out pins, water stains, white corrosion, or brake fluid leaks. Verify sealing ring integrity.+6 more →
C054100›
DTC C054100 indicates the analog voltage signal from the second pressure sensor (typically the accumulator pressure sensor or master cylinder pressure monitoring sensor) inside the IPB (Intelligent Power Brake) module exceeds the ECU-calibrated upper threshold (typically >4.8V or a corresponding pressure exceeding the system safety limit, such as >22MPa). In the Bosch IPB system used by BYD, this sensor uses the piezoresistive effect to convert hydraulic pressure into a 0.5-4.5V linear voltage signal. The ECU logs an "Out of Range High" fault when it detects this signal voltage remains above the valid physical range over multiple consecutive drive cycles (i.e., the sensor reports an excessively high pressure regardless of actual braking conditions). This fault triggers the IPB system to enter a safety degradation mode: it disables regenerative braking, limits ESC functions, maintains basic hydraulic brake assist, and illuminates the ABS/ESC warning lamps. If Sensor 2 monitors accumulator pressure, sustained high pressure may prevent the motor pump from starting or cause the pressure relief valve to remain open continuously, affecting brake pedal feel and response speed.
Causes
— Ruptured internal pressure sensor diaphragm or short circuit locks the signal output near the 5V reference voltage (sensor hardware fault).— Water ingress, oxidized pins, or backed-out pins at the IPB wiring harness connector (usually located near the engine compartment firewall), causing a short circuit between the sensor signal wire (SIG) and the power wire (+5V or +12V).— IPB accumulator internal pressure rises abnormally and fails to relieve (e.g., accumulator pressure-holding valve stuck in the closed position or blocked oil return port), causing actual pressure to continuously exceed the sensor measurement range.+2 more →
Actions
— Use VDS2000 or the BYD dedicated diagnostic tool to read the DTC freeze frame data. Record the vehicle speed, brake pedal travel, motor pump operating status, and specific pressure values of Pressure Sensor 1 (master cylinder) and Sensor 2 (accumulator) when the fault occurred to determine whether the high pressure is actual or a false high signal.— Verify the brake fluid level is between the MAX-MIN marks. Inspect the brake fluid color and clarity. If the fluid is cloudy, darkened, or contains suspended particles, completely replace it with DOT4 standard brake fluid (dry boiling point ≥230℃) and perform a circulation flush on the IPB system.+5 more →
C054200›
DTC C054200 indicates an electrical signal fault in Pressure Sensor 2 within the IPB (Integrated Power Brake). This sensor typically provides the master cylinder pressure sensor secondary signal or monitors wheel cylinder pressure. The sensor transmits real-time brake pressure data to the IPB-ECU using a 0.5-4.5V analog voltage signal or a PWM digital signal. The ECU logs a short circuit (to ground or power) or an open circuit if the sensor signal voltage remains outside the valid threshold (typically below 0.25V or above 4.75V) for over 200ms. As the BYD IPB utilizes a Brake-by-Wire architecture, the pressure sensor signal serves as a key parameter for calculating brake force distribution, triggering ABS/ESC intervention, and coordinating electro-hydraulic braking with energy recovery. This fault triggers the IPB fail-safe mode, disabling ESC, AEB, Auto Hold, and brake energy recovery. The system retains only basic hydraulic brake assist, increasing the risk of extended braking distances.
Causes
— Damage to the IPB assembly internal pressure sensor 2 body, dry solder joints, or ruptured diaphragm (the sensor integrates with the IPB housing and is not separately replaceable; this is the primary failure mode).— Backed-out terminals, poor contact, or seal failure causing water ingress and corrosion at the IPB wiring harness connector (32-pin or 48-pin, depending on vehicle model), resulting in an intermittent open circuit or short to ground in the signal line.— Low-voltage signal wiring harness wear in the engine compartment high-temperature area or firewall pass-through. Damaged insulation causes a short to body ground, or contact with the 12V power wiring harness causes a short to power.+2 more →
Actions
— Safety preparation: Turn off the ignition and power down the vehicle. Disconnect the 12V battery negative terminal and wait at least 3 minutes for the high-voltage capacitors inside the IPB to discharge completely. Wear insulated protective equipment.— Visual inspection: Inspect the IPB assembly (located near the left shock absorber tower in the engine compartment or at the firewall) for physical damage or brake fluid leaks. Check wiring harness connector X1 (main connector) for secure locking, an intact sealing ring, and signs of water ingress (green corrosion on pins) or burn marks.+5 more →
C054300›
DTC C054300 indicates an abnormal electrical signal from Pressure Sensor 2 in the IPB (Intelligent Power Brake) electro-hydraulic module, specifically a short to power, short to ground, or open circuit in the signal circuit. This sensor monitors brake master cylinder pressure (or wheel cylinder pressure channel 2) and provides a key input signal for ESC (Electronic Stability Control) and brake assist functions. The ECU logs a hardware-level fault when it detects the sensor voltage signal falling outside the calibrated range (typically below 0.3V or above 4.7V, depending on the 5V reference voltage division logic). This fault forces the IPB into a degraded mode, disabling ESC/ESP and Automatic Emergency Braking (AEB) functions. The system may trigger limp mode (reducing brake assist). In extreme cases, the brake pedal hardens or braking distance increases, posing a serious safety hazard.
Causes
— Internal open or short circuit in the pressure sensor: Damage to the pressure-sensitive element or internal conditioning circuit causes an abnormal output signal.— Poor wiring harness connector contact: Backed-out pins, oxidation, or corrosion from water ingress at the 32-pin (or 24-pin) connector on the IPB electro-hydraulic module, causing an intermittent or continuous open circuit.— Wiring harness wear and short circuit: Sensor wiring harness insulation ages in the high-temperature engine compartment and chafes against metal body edges, causing a short to ground or short to power.+2 more →
Actions
— Diagnostic tool check: Use a BYD VDS or Bosch KTS diagnostic tool to read all fault codes and freeze-frame data. Check for accompanying C054200 (Pressure Sensor 1 fault) or other IPB communication faults. Record the vehicle speed and brake pedal status at the time of the fault.— Visual and connector inspection: Disconnect the 12V battery negative terminal. Inspect the electrical connector of the IPB electro-hydraulic module (usually located on the left side of the firewall or at the ABS pump position). Inspect the pins for oxidation or backing out, and check the wiring harness for abrasion or crushing marks, especially the protective sleeve near high-temperature areas in the engine compartment.+4 more →
C055000›
DTC C055000 indicates an internal self-check fault in the ABS electronic control unit (ECU). Specifically, the control module integrated inside the ABS hydraulic modulator assembly detects a hardware or basic software abnormality. This constitutes a 'core-level' ABS system fault, indicating the ECU cannot execute normal anti-lock braking control logic. When triggered, the ABS system forces Fail-Safe Mode. This disables anti-lock braking, EBD (Electronic Brakeforce Distribution), and ESC (Electronic Stability Control) functions, retaining only conventional hydraulic braking. The instrument cluster illuminates the ABS warning light, ESC warning light, and brake system warning light. Some models also display the text prompt 'Please check brake system'. This DTC differs fundamentally from wheel speed sensor signal faults (such as the C003 series). The latter represents an 'input signal abnormality', whereas C055000 represents a 'control unit internal abnormality', involving significantly higher repair complexity and cost.
Causes
— Damaged internal ECU circuit board in the ABS hydraulic modulator assembly: Physical damage to the internal processor, memory, or power management chip causes the self-check procedure to fail.— Abnormal supply voltage: Battery voltage too low (<9V) or too high (>16V), excessive voltage drop in the power supply circuit, or voltage regulator module failure, causing the ECU supply voltage to fall outside the normal operating range (typically requires 12V±0.5V).— Poor ground circuit: An oxidized, loose, or corroded ECU main ground point (usually located in the engine compartment or near the battery negative terminal) causes reference voltage drift, triggering ECU misjudgment or reset.+2 more →
Actions
— Connect the BYD dedicated diagnostic tool (VDS or ED400), read the complete DTC list and freeze frame data, check for accompanying related codes such as C055500 (wheel speed sensor protocol error), and record parameters such as vehicle speed and voltage at the time of the fault.— Check the battery condition: measure the static voltage (should be ≥12.4V), cranking voltage (should be ≥9.6V), and charging voltage (should be 13.5-14.8V). Check the battery terminals for oxidation. Perform a battery load test if necessary.+7 more →
C055164›
DTC C055164 indicates the IPB (Integrated Power Brake) detects a fault in the Longitudinal Acceleration Sensor signal circuit. This sensor monitors longitudinal acceleration (braking deceleration/driving acceleration) and provides key vehicle dynamic parameters to the ESC (Electronic Stability Control), ABS (Anti-lock Braking System), AEB (Autonomous Emergency Braking), and energy recovery systems. When the fault triggers, the longitudinal acceleration signal status bit the IPB receives via CAN message 0x223 indicates an error (such as invalid signal, checksum error, or timeout), preventing the system from accurately determining the vehicle motion state. In severe cases, ESC, ABS, and AEB functions may enter a degraded mode or fail completely. The instrument cluster illuminates multiple brake system warning lamps, and extreme conditions compromise vehicle braking safety and stability control.
Causes
— Inertial sensor wiring harness connector loose, pins backed out, or terminals corroded: Poor contact at the IPB assembly or independent longitudinal acceleration sensor connector (depending on vehicle configuration). This commonly occurs after driving through water, driving on rough roads, or a collision.— Longitudinal acceleration sensor hardware fault: Internal MEMS element damage, zero-point drift, or abnormal signal output causes the output voltage to exceed the IPB recognition range (typically 0.5-4.5V corresponding to ±1.5g).— IPB internal signal acquisition circuit fault: The 5V sensor reference power supply inside the IPB module has a short or open circuit, or a damaged signal acquisition ADC circuit fails to correctly interpret the sensor analog signal.+2 more →
Actions
— Step 1: Fault code freeze frame analysis and preliminary inspection: Use the VDS2000 or DMS diagnostic tool to read the fault freeze frame. Confirm parameters such as vehicle speed, longitudinal acceleration value, and yaw rate when the fault occurred. Check the vehicle history for collisions, water ingress, or modifications. Visually inspect the IPB assembly and wiring harness for damage.— Step 2: Power supply and ground circuit inspection: Disconnect the IPB connector (or independent sensor connector). Check the sensor supply voltage (standard: 5V ± 0.25V). Check the ground wire resistance (should be less than 1 Ω). Confirm the reference voltage is stable without fluctuation. If the voltage is abnormal, repair the wiring harness or replace the IPB.+4 more →
C055500›
This DTC indicates the IPB (Intelligent Integrated Braking System) control module detects a mismatch between the front left wheel speed sensor hardware identifier (HW ID) or signal characteristics and the vehicle configuration parameters (EPC/calibration data). Specifically, when reading the wheel speed sensor ID code, resistance characteristics, or signal waveform parameters via the LIN bus or dedicated wiring harness, the IPB module detects a deviation between the actual characteristic values and the expected theoretical values. This typically occurs when installing non-genuine parts, failing to reconfigure the system after a software upgrade, or when strong electromagnetic interference distorts the sensor signal characteristics. This fault limits or disables the ABS, ESC, EBD (Electronic Brakeforce Distribution), and Automatic Emergency Braking (AEB) functions, severely impacting the vehicle's active safety performance, but does not directly cause mechanical brake failure.
Causes
— Installation of a non-genuine or incorrect specification wheel speed sensor (e.g., mismatched supplier code, polarity, or tooth count), causing a mismatch between the hardware ID and the IPB software calibration.— The IPB control module software version does not match the vehicle configuration (e.g., failing to perform online configuration or write the VIN after replacing the IPB module with one from another model).— An intermittent short or open circuit in the left front wheel speed sensor wiring harness, or oxidized or backed-out connector pins, alters signal transmission characteristics and causes a false 'incorrect sensor type' detection.+2 more →
Actions
— Use the VDS2000/BYD dedicated diagnostic tool to read all DTCs. Check for accompanying code C055600 (right front) or other wheel speed sensor fault codes, and review the vehicle speed, wheel speed values, and system voltage in the freeze frame data.— Check the appearance and installation condition of the left front wheel speed sensor. Confirm the sensor head is free of oil contamination, the tone ring has no deformation or missing teeth, the connector shows no oxidation, backed-out terminals, or signs of water ingress, and the wiring harness has no chafing or short to ground.+6 more →
C055F92›
DTC C055F92 indicates an IPB (Integrated Power Brake) hydraulic subsystem performance fault. This DTC indicates the IPB control unit detects abnormal hydraulic circuit pressure, excessive pressure build-up time, insufficient pressure holding capability, or abnormal hydraulic pump motor operation. The IPB system integrates electric vacuum assist, ESP electronic stability control, and ABS anti-lock braking functions. This fault may reduce brake assist, harden the brake pedal, restrict or disable active safety functions (AEB/ACC), or in extreme cases, trigger the brake system downgrade protection mode. The fault suffix '92' indicates a hydraulic circuit performance deviation or intermittent operating abnormality rather than a complete failure.
Causes
— IPB internal hydraulic pump motor wear or seizure causing insufficient pressure build-up or delayed response, common in high-mileage vehicles or due to internal corrosion caused by overdue brake fluid replacement.— Insufficient, degraded, or air-locked brake fluid; fluid level below the minimum mark or water content exceeding 3% causes abnormal hydraulic compressibility.— Sticking IPB control unit internal solenoid valve (inlet/outlet valve) or aged sealing ring causes abnormal pressure retention or internal leakage.+2 more →
Actions
— Use VDS2000 or a dedicated BYD diagnostic tool to read the complete fault codes and freeze frame data. Record key parameters at the time of the fault, including vehicle speed, master cylinder pressure, and motor current. Check for accompanying wheel speed-related faults such as C003F and C0040.— Visually check the brake fluid reservoir level. Inspect the IPB assembly, four-wheel brake calipers, and brake lines for leaks. Perform a pressure holding test if necessary (pressure drop must be <10 bar over 10 minutes).+5 more →
C055600›
DTC C055600 indicates the IPB (Intelligent Integrated Braking System) control module detects the hardware model or electrical characteristics of the right front wheel speed sensor do not match the system calibration parameters. This is a configuration/calibration fault, not a simple signal fault. By monitoring the sensor resistance, signal voltage range, pulse characteristics, or digital communication protocol, the IPB system detects the installed sensor does not match the vehicle configuration code (VIN-corresponding calibration data). This typically occurs after installing non-genuine parts, installing a sensor from another vehicle model, or if the sensor does not match the wheel hub bearing assembly (some BYD models separate the magnetic encoder bearing from the sensor). When this fault triggers, the IPB enters degraded mode, disables ABS, ESC, Automatic Emergency Braking (AEB), and energy recovery functions, retaining only basic hydraulic braking.
Causes
— Non-genuine aftermarket wheel speed sensor installed; resistance value or signal characteristics do not match factory calibration (original is typically a 1200-1600Ω active sensor; mistakenly installed an 800-1200Ω passive sensor).— Installing a part from another model during right front wheel hub bearing assembly replacement causes a mismatch in the magnetic encoder ring pole count or spacing (e.g., installing a 46-pole Song Pro ring instead of the required 48-pole Song PLUS DMi ring).— Outdated IPB control module software fails to recognize the new sensor communication protocol (common on 2021 Song PLUS DMi models combining early software versions with later improved replacement sensors).+2 more →
Actions
— Use the VDS2000/VDS3000 diagnostic tool to access the IPB system and read the freeze frame data. Verify the deviation range of the sensor signal voltage and resistance from the calibrated values at the time of the fault.— Raise the vehicle and check the right front wheel speed sensor part number (usually stamped on the sensor body). Cross-reference the EPC system to verify the part number matches the vehicle configuration code (e.g., Song PLUS DMi requires the 5A-36301-XX series active sensor).+4 more →
C055700›
DTC C055700 indicates the IPB (Intelligent Integrated Braking System) detects the left rear wheel speed sensor electrical characteristics, signal pulse count, or communication protocol do not match system calibration parameters during self-check or signal monitoring. This fault is not a simple signal loss or short circuit; rather, the system identifies an abnormal sensor "identity". Possible causes include installing a non-genuine wheel speed sensor with incorrect specifications (mismatched resistance, pole count, or Hall element type), an abnormal match between the sensor and the tone ring (magnetic ring), or incorrect IPB control module software configuration (such as flashing configuration data from another vehicle model). This fault directly limits or completely disables functions relying on accurate wheel speed signals, including ABS, ESC, and EPB. In extreme cases, it causes wheel lock-up or skidding during emergency braking, making it a critical fault affecting driving safety.
Causes
— Non-genuine or incorrect wheel speed sensor installed (e.g., using a passive magnetic sensor from a conventional ICE vehicle instead of the BYD-specific Hall-effect sensor, or a mismatched pole count).— The left rear wheel bearing unit (including the magnetic ring/tone ring) does not match the sensor; for example, installing an incorrect specification bearing results in an abnormal number of magnetic poles or abnormal air-gap magnetic field strength.— IPB control module software programming error: programming an incorrect vehicle model configuration code (e.g., writing Tang model wheel speed parameters to a Song model) causes the system to misidentify the sensor type.+2 more →
Actions
— Use the BYD VDS2000/3000 diagnostic tool to read all fault codes and freeze frame data. Confirm if C055700 is a current fault and check for accompanying related fault codes, such as C055600 (front right) and C055800 (rear right).— Check the electronic parts catalog (EPC) and verify the left rear wheel speed sensor part number (Song PLUS DM-i typically uses a 3C-3630100 series Hall-effect sensor). Check the actual vehicle sensor part number, resistance (normally approx. 1.0–1.5 kΩ), and pole count (usually 46 or 48 poles, depending on configuration).+5 more →
C055800›
DTC C055800 indicates the IPB (Integrated Intelligent Braking System) control unit detects a mismatch between the digital signal protocol from the right rear wheel speed sensor (WSS) and the system preset standard. Specifically, the sensor PWM (pulse-width modulation) or square-wave signal exceeds calibrated thresholds for waveform characteristics, duty cycle, frequency range, or voltage amplitude, preventing the control unit from correctly interpreting wheel speed data. Unlike a simple signal loss (open circuit), this protocol-level communication mismatch indicates an incompatible sensor hardware version, signal distortion, or EMC interference. When this fault triggers, wheel speed-dependent systems (ABS, ESC, TCS) enter a degraded mode. On some models, the fault disables the automatic emergency braking system or limits vehicle speed.
Causes
— Wheel speed sensor component fault: Poor thermal stability of the internal Hall element or processing chip distorts the output signal waveform at high temperatures or high speeds, causing protocol verification failure.— Wiring harness and connector fault: Sensor connector pin oxidation or back-out, or damaged wiring harness shielding causing electromagnetic interference and signal distortion during transmission.— Mechanical installation issue: Air gap between the sensor and magnetic encoder ring (tone ring) falls outside the standard range (0.3-1.2mm), or the encoder ring is deformed, dirty, or demagnetized, causing abnormal signal amplitude.+2 more →
Actions
— Initial diagnostic scan: Use VDS or a dedicated diagnostic tool to read the complete fault codes and freeze frame data. Confirm if C055800 is a current fault. Record environmental parameters, such as vehicle speed and temperature, at the time the fault occurred.— Visual and connection inspection: Inspect the right rear wheel speed sensor connector (usually located near the rear suspension) for looseness, water ingress, or oxidation; inspect the wiring harness sleeve for damage, paying special attention to wear-prone areas under the chassis; inspect the magnetic encoder ring for cracks, deformation, or attached foreign matter.+4 more →
C057900›
DTC C057900 indicates the IPB (Integrated Power Brake) electro-hydraulic control module detected a short to ground in the brake booster motor temperature sensor signal circuit. Typically integrated inside the electro-hydraulic brake booster, this temperature sensor uses a negative temperature coefficient (NTC) thermistor to monitor the booster motor operating temperature in real time and prevent overheating damage. The ECU logs a short to ground fault when the sensor signal voltage remains below the calibrated threshold (typically <0.5V) for longer than the set time (e.g., 200ms). This fault triggers the IPB system to enter a degraded safety mode, which may reduce or eliminate brake assist (hard brake pedal), disable the energy recovery system, restrict ABS/ESC functions, and illuminate multiple brake system warning lights. Continued driving under extreme operating conditions may cause a complete loss of brake assist, posing a serious safety risk. Workshop practice on certain vehicle models indicates this DTC may also involve a short to ground in the brake switch signal circuit.
Causes
— Short circuit in the brake booster temperature sensor internal thermistor, or damaged wiring harness insulation.— Signal wiring harness between the IPB electro-hydraulic module and the sensor (usually located near the engine compartment firewall) chafed from vibration or cut by a sharp edge, causing a short to body ground.— Poor sealing of the IPB electro-hydraulic module connector (usually located near the brake master cylinder) causes water ingress, corrosion, or bent pins, shorting the temperature signal pin (such as pin TBD) to the ground pin.+2 more →
Actions
— Use the VDS2000/3000 diagnostic tool to read fault codes, confirm C057900 is a current fault (Active), and record the ambient temperature and sensor voltage values from the freeze frame data.— Visually inspect the IPB electro-hydraulic module and 24-pin (or corresponding model) connector for obvious signs of water ingress, burn marks, pin corrosion, or mechanical damage.+5 more →
C055F00›
DTC C055F00 indicates the IPB (Intelligent Integrated Brake System) detects a hydraulic circuit abnormality. The IPB is BYD’s electro-hydraulic integrated braking system (One-Box architecture), integrating brake boost, ESP, ABS, and EPB functions. This fault occurs when, during a self-check or braking request, the system detects the deviation between the master cylinder pressure sensor feedback and the target pressure exceeds the limit, the hydraulic pump fails to build the required pressure within the specified time, or solenoid valve actuation feedback is abnormal. Possible causes include hydraulic pump motor failure, pressure sensor drift, a sticking solenoid valve, brake fluid leakage/air lock, or an internal control unit sampling circuit fault. When this fault occurs, the system may enter Limp Home mode, limiting brake boost or switching to mechanical backup mode, severely affecting braking performance.
Causes
— Worn carbon brushes or a seized rotor in the internal DC motor (hydraulic pump) of the IPB electro-hydraulic module prevents hydraulic pressure buildup.— Master cylinder pressure sensor (M/C Pressure Sensor) signal drift or internal open circuit; feedback pressure value deviates from the actual value by more than the ±0.5MPa threshold.— Brake line leak or severely low brake fluid level causes system pressure hold test failure (leak rate > 0.1 MPa/s).+2 more →
Actions
— Use the VDS2000/Launch diagnostic tool to read the complete fault codes and freeze frame data. Record key data at the time of the fault, including vehicle speed, master cylinder pressure, motor current, and solenoid valve status.— Visually check the brake fluid level (must be between MAX and MIN). Inspect the IPB unit, four-wheel brake lines, and hose joints for leaks or signs of fluid seepage.+5 more →
C056364›
DTC C056364 indicates the ABS control module inside the IPB (Intelligent Integrated Brake System) detects an internal operating fault. The IPB is BYD's one-box brake-by-wire solution (such as the Bosch IPB or BYD in-house IPB), integrating ABS, ESC, regenerative braking, automatic emergency braking, and other functions. Sub-code 64 usually indicates a control module internal self-test failure, involving a main control chip (MCU) fault, abnormal power supply voltage monitoring, internal memory (Flash/RAM) errors, a solenoid valve drive circuit fault, or a watchdog reset. This fault causes ABS, ESC, TCS, AEB, and other functions to fail or enter degraded mode. The instrument cluster illuminates the ABS and ESC warning lights, and the vehicle may limit power output. The vehicle usually retains basic hydraulic braking (the brake pedal may feel hard).
Causes
— Abnormal internal ECU power supply circuit in the IPB module: Unstable 12V constant power (B+) or ignition power (IGN) voltage, blown fuse, or poor relay contact causes the module supply voltage to drop below 9V or exceed 16V, triggering protection.— Internal hardware fault in the IPB electro-hydraulic module: damaged main control chip, corrupted internal memory data, overheated or burnt solenoid valve driver chip, PCB water ingress and corrosion (especially after car washing or wading)— Wiring harness and connector issues: Loose IPB module plug, backed-out pins, water ingress causing oxidation, or wiring harness wear causing intermittent open/short circuits, affecting power supply, ground, or CAN communication.+2 more →
Actions
— Diagnostic scan: Use VDS2000/3000 or Launch X431 to read complete fault codes, record freeze frame data, and check for accompanying U-class communication faults or power supply fault codes (e.g., C003F00, C004000). Analyze parameters such as vehicle speed and voltage at the time of the fault.— Power and ground check: Measure the voltage at IPB module connector Pin 1 (terminal 30, constant power) and Pin 2 (terminal 15, ignition power); the standard value is 12V ± 0.5V. Measure the resistance between Pin 13/26 (ground) and body ground; it must be <1Ω. Check the IPB-related fuses in the engine compartment fuse box, such as F1/14 and F2/11.+5 more →
C056B00›
DTC C056B00 indicates an abnormal signal from the main pressure sensor (Pressure Sensor 1) inside the IPB (Intelligent Power Brake) module. This sensor typically monitors hydraulic pressure in the brake master cylinder or booster chamber, providing critical input for the ABS, ESC, regenerative braking system (RBS), and electric brake assist functions. The IPB ECU sets this fault when the sensor output voltage falls outside the calibrated range (typically 0.5-4.5V), the signal drift rate is abnormal, or the cross-check difference with a redundant sensor (such as Pressure Sensor 2) exceeds the threshold (e.g., a pressure value corresponding to ±0.3V). When this fault occurs, the vehicle may enter brake assist degraded mode (hard brake pedal), limit ESC/ABS functions, disable automatic emergency braking (AEB), and illuminate multiple brake system warning lamps on the instrument cluster.
Causes
— Damaged or degraded internal pressure sensor element in the IPB integrated electro-hydraulic module causes unstable or inaccurate signal output.— Loose sensor wiring harness connector, backed-out terminals, oxidation from water ingress, or corroded pins causing signal transmission interruption or crosstalk.— Brake fluid contamination (excessive water content or impurities) causes sensor port blockage or internal corrosion.+2 more →
Actions
— Use the BYD VDS2000 dedicated diagnostic tool or Launch X431 to read the complete fault codes. Confirm whether C056B00 is a Current or History fault and record the freeze frame data (key parameters at the time of the fault, including vehicle speed, pedal travel, pressure value, and system voltage).— Perform a preliminary visual inspection: verify the brake fluid level is between MIN and MAX, the brake fluid is clear (not black or milky), the IPB module has no leaks, impact damage, or deformation, and the wiring harness connector is fully locked.+5 more →
C057A00›
DTC C057A00 indicates an abnormally high voltage or a short to power (B+) in the IPB (Intelligent Power Brake) internal brake booster temperature sensor power supply circuit. Integrated within the electronic brake booster, this sensor monitors the operating temperature of the booster motor or electronic control unit in real time to prevent brake performance degradation or motor burnout from overheating. The IPB-ECU logs a power supply short circuit fault when the sensor supply line (typically a 5V reference voltage) continuously exceeds the calibrated threshold (generally above 6.0V or reaching the 12V battery voltage). This fault triggers the IPB system safety protection mechanism. It may limit or completely disable brake assist, degrade ABS/ESP functions, and force the vehicle into Limp Home Mode. The system retains only basic unassisted hydraulic braking. This constitutes a severe fault affecting driving safety.
Causes
— Damaged sensor wiring harness insulation causing a short circuit to 12V constant power (B+) or the ignition power wire.— Breakdown or internal short circuit of the brake booster internal temperature sensor element causes abnormal continuity between the power supply pin and the ground pin or signal pin.— Fault in the IPB electro-hydraulic module internal 5V reference voltage regulation circuit causes abnormally high output voltage.+2 more →
Actions
— Safety preparation: Disconnect the high-voltage system service disconnect switch (for DM-i/EV models), disconnect the 12V battery negative terminal, and wait at least 3 minutes to completely power down the IPB system and release residual pressure.— Fault confirmation: Connect the VDS or dedicated diagnostic tool to read fault codes. Confirm C057A00 is a current fault (Present) and fails to clear. Record freeze frame data. Check for accompanying C057B00 (signal short circuit) or IPB communication fault codes.+6 more →
C057F00›
This DTC indicates the IPB (Integrated Power Brake) ECU detects abnormal power supply voltage to the brake booster motor. Conditions include voltage outside the normal range (9-16V), excessive voltage fluctuation, or power supply interruption. The IPB system uses a motor-driven hydraulic pump to replace the conventional vacuum booster. The ECU sets this fault when it detects an open circuit, short circuit, undervoltage (typically <9V), or overvoltage (>16V) in the motor power supply circuit. This fault reduces or disables the brake assist function. The system may enter Limp Home mode, resulting in a hard brake pedal, increased pedal travel, and an illuminated ABS/ESC warning lamp, severely compromising driving safety.
Causes
— Fault in the internal power management circuit or motor drive chip of the IPB electro-hydraulic control module, resulting in abnormal voltage monitoring.— Severely discharged or aged 12V battery, or generator charging system fault, causing system voltage to drop below 9V.— Poor contact in the IPB power supply circuit, blown fuse (e.g., F1/23 40A), loose relay connection, or damaged power wiring harness.+2 more →
Actions
— Use the VDS2000/VDS3000 diagnostic tool to read the complete fault codes and freeze frame data. Record key parameters at the time of the fault, including vehicle speed, system voltage, and motor current, and determine if the fault is intermittent.— Check the 12V battery status: static voltage must be ≥12.4V and cranking voltage must be ≥9.6V. Verify the alternator output voltage is 13.5-14.5V to rule out a power supply system fault.+6 more →
C058200›
DTC C058200 indicates the supply voltage to the brake booster motor inside the IPB (Intelligent Integrated Braking System / One-box electro-hydraulic brake-by-wire system) falls outside the normal operating threshold set by the ECU (typically 9-16V DC). This brushless DC motor drives the brake master cylinder to generate hydraulic brake assist. A generator regulator fault, a power supply circuit short, or reversed polarity during jump-starting can cause high voltage (>16V). A discharged battery, excessive wiring voltage drop, poor ground connection, or internal module DC-DC power supply chip failure can cause low voltage (<9V). This fault triggers the IPB degraded mode, reducing or completely disabling the brake assist function (hard brake pedal). The fault may also inhibit ABS/ESC/EBD functions. In severe cases, the system illuminates the red brake warning lamp, compromising driving safety.
Causes
— Fault in the DC-DC converter, MOSFET drive circuit, or voltage sampling resistor inside the IPB electro-hydraulic module, causing abnormal motor power supply.— Battery aging, low charge (voltage <11V), or alternator regulator fault causing excessive output voltage (>15.5V)— Poor contact, loose connections, backed-out terminals, or burnt pins in the IPB power supply circuit or fuses (e.g., F1/16, F2/03, or F4/15, depending on vehicle configuration)+2 more →
Actions
— Use the VDS2000 or a dedicated BYD diagnostic tool to read the complete fault codes and freeze frame data. Record the specific voltage, vehicle speed, brake pedal travel, and IPB temperature at the time of the fault to determine whether it is continuous or intermittent.— Measure the battery static voltage (normal 12.4-12.8V) and dynamic voltage (idle 13.8-14.4V, acceleration <15.0V). Check the alternator output waveform to rule out a charging system fault.+3 more →
C058800›
DTC C058800 indicates the signal voltage of the brake booster Motor Position Sensor (MPS) inside the Integrated Power Brake (IPB) electro-hydraulic module falls below the ECU threshold (typically below 0.5V or 10% of the reference voltage). The sensor uses electromagnetic or Hall effect principles to monitor the booster motor rotor position in real time, enabling closed-loop control of the motor torque output and brake assist level. When the ECU detects the sensor voltage remains continuously below the calibrated value, it sets a circuit undervoltage fault. This fault prevents the IPB system from accurately determining the motor position, which limits or disables the electric brake assist function. As a result, the vehicle may enter Limp Home Mode, the brake pedal becomes hard, and the ESC/ABS warning lights illuminate.
Causes
— Motor position sensor internal short circuit or component aging: a short circuit in the sensor's internal coil or a damaged Hall element pulls the output voltage low.— Wiring harness short to ground or connector fault: Damaged sensor wiring harness insulation causes a short to the vehicle body, or water ingress, oxidation, or loose connector pins cause excessive contact resistance.— Abnormal IPB module internal power supply circuit: Internal 5V reference voltage regulator failure or filter capacitor short circuit, causing insufficient sensor supply voltage.+2 more →
Actions
— Fault confirmation and freeze frame analysis: Use VDS or X-431 to read DTC C058800 and freeze frame data. Record parameters such as vehicle speed, voltage, and temperature at the time of the fault. Confirm whether the fault is current (Current) or historical (History).— Visual and connector inspection: Check the IPB module exterior for impact damage and leaks. Disconnect the IPB wiring harness connector and check the pins for corrosion, backed-out pins, and signs of water ingress. Test the connector sealing.+4 more →
C058900›
DTC C058900 indicates the IPB (Intelligent Integrated Braking System) electro-hydraulic control module detected a brake booster motor position sensor signal voltage exceeding the calibrated upper limit (typically >4.8V or 95% of the reference voltage). Typically a Hall-effect or electromagnetic position sensor, this component monitors the booster motor rotor position/travel in real time to enable precise electronic brake assist control (similar to a brake-by-wire i-Booster system). Excessively high voltage saturates the signal at the ECU, preventing it from identifying the actual motor position. This triggers fail-safe mode: the system disables the electronic assist function, the brake pedal becomes hard (mechanical backup remains available), and the ABS/ESC/brake system warning lamps illuminate. This is a hard fault; once triggered, it remains active and does not self-clear.
Causes
— Sensor signal circuit shorted to power supply (+12V or +5V reference voltage): Damaged wiring harness insulation allows contact with a vehicle power wire, pulling the signal voltage high.— Motor position sensor internal short circuit or damage: Sensor Hall element breakdown causes an internal short between the signal terminal and the reference voltage terminal.— IPB control unit (ECU) internal sampling circuit fault: analog-to-digital converter (ADC) front-end protection diode breakdown or voltage divider resistor open circuit, causing abnormal sampling voltage.+2 more →
Actions
— Safety preparation and initial inspection: Disconnect the high-voltage service disconnect (MSD) and wait 5 minutes to discharge the capacitors. Read all DTCs using VDS2000 or Launch X431. Confirm if C058900 appears alone or alternates with C058800 (low voltage) or other codes. Inspect the IPB electro-hydraulic module exterior for impact damage or fluid leaks. Check the motor position sensor connector (usually on the side of the IPB assembly) for looseness or water ingress.— Voltage measurement and wiring checks: Refit the MSD, switch the ignition ON (do not press the brake), and measure the sensor signal wire voltage without unplugging the connector (normal voltage is 0.5–4.5 V, varying with position). If the measured voltage is >4.8 V or close to the reference voltage (5 V), unplug the sensor connector and measure the resistance between the harness-side signal wire and ground: continuity indicates a short to ground. Measure the resistance between the signal wire and the power wire: continuity confirms a harness short circuit. Simultaneously check that the sensor reference voltage (+5 V) output from the ECU is stable.+3 more →
C059400›
DTC C059400 indicates a functional fault in the brake booster motor within the IPB (Intelligent Power Brake) system. This brushless DC motor integrates into the IPB electro-hydraulic module to replace the traditional vacuum booster. It provides electric brake assist based on pedal input and coordinates energy recovery. The IPB control unit sets this code upon detecting abnormal motor current, abnormal speed feedback, a drive circuit fault, or motor mechanical binding. This fault causes a hard brake pedal, reduced brake assist, and increased braking distance. It also degrades or disables functions including ABS, ESC, and Automatic Emergency Braking, severely compromising driving safety.
Causes
— Damaged IPB internal brake booster motor: Motor bearing wear, rotor seizure, or permanent magnet demagnetization prevents normal motor operation or causes abnormal current.— Motor drive circuit fault: Damage to the MOSFET, gate driver chip, or sampling resistor in the IPB internal H-bridge drive circuit causes an abnormal motor drive signal.— Abnormal power supply: Poor contact in the IPB module terminal 30 constant power or terminal 31 ground circuit, loose fuse connection, or voltage fluctuation (below 9V or above 16V), causing unstable motor power supply.+2 more →
Actions
— Use the dedicated diagnostic tool (VDS2000/3000) to read the complete fault codes and freeze frame data. Specifically check for accompanying fault codes such as C059100 (motor voltage too low), C059500 (internal drive fault), or C003700 (pump motor fault). Record parameters at the time of the fault, such as vehicle speed and pedal travel.— Visually inspect the IPB electro-hydraulic module exterior for damage, fluid leaks, or burn marks. Check the master cylinder connection and wiring harness connectors (especially the large 30-pin connector) for looseness, water ingress, or corrosion. Measure the voltage between power (Pin30) and ground (Pin31) to verify it is within 12V±0.5V.+4 more →
C058A00›
DTC C058A00 indicates the brake booster motor position sensor (MPS1) in the IPB (Integrated Power Brake, intelligent integrated braking/One-Box brake-by-wire system) outputs a voltage signal outside the valid operating range calibrated by the ECU (typically 0.5V-4.5V). This sensor uses the Hall effect to monitor the absolute angular position of the booster motor rotor in real time and serves as the key feedback component for closed-loop brake boost control. The ECU sets this fault when the signal voltage remains below the lower limit (<0.2V, short to ground or sensor power loss) or above the upper limit (>4.8V, short to power or internal sensor open circuit) for longer than the calibrated time (typically 200ms-500ms). Upon fault detection, the IPB enters a degraded mode. The system cuts off motor assist, requiring the driver to apply greater pedal force (unassisted braking), but retains basic hydraulic braking functions. Simultaneously, the system illuminates the ABS and ESC warning lamps and disables ADAS functions relying on active braking, such as Automatic Emergency Braking (AEB) and Adaptive Cruise Control (ACC).
Causes
— Aging of the internal Hall element in the motor position sensor or magnet demagnetization causes the output voltage to drift beyond the normal range.— Oxidized or backed-out pins at the sensor harness connector (located on the IPB assembly), or worn wiring harness insulation causing a short to ground, short to power, or open circuit.— IPB ECU internal signal acquisition circuit fault, such as a burnt sampling resistor, damaged ADC module, or abnormal reference voltage source (5V)+2 more →
Actions
— Use the VDS or Launch X-431 diagnostic tool to access the IPB system, read the complete DTC list and freeze frame data, and confirm C058A00 is a current (Active) fault rather than a history fault. Record key parameters at the time of the fault, including vehicle speed, motor speed, and raw sensor voltage values.— Disconnect the low-voltage wiring harness connector from the IPB electro-hydraulic module (located above the ABS pump body). Visually inspect the connector sealing ring for damage or water ingress. Use a special probe to check the motor position sensor power supply pin (usually 5V reference voltage) and signal pin (MPS1 Signal) for oxidation or terminal spread.+4 more →
C058F00›
DTC C058F00 indicates an abnormal coasting regenerative torque signal status in CAN message 0x410 transmitted from the VCU (Vehicle Control Unit) to the IPB (Intelligent Integrated Braking System). In the BYD New Energy architecture, the VCU calculates the target regenerative torque during coasting or braking (typically 0-150 Nm) and transmits it to the IPB via a CAN message. The IPB uses this signal to coordinate motor and hydraulic braking force distribution for energy recovery. This fault indicates the IPB received a regenerative torque signal with a data validation error, an update timeout, or an out-of-range value (such as a negative value or sudden change), or communication synchronization failed between the VCU and IPB. This fault frequently accompanies brake system DTCs such as C055E00 (hydraulic circuit leakage), triggering energy recovery system derating or protective shutdown.
Causes
— Poor contact in the CAN communication line between VCU and IPB, abnormal terminating resistance (standard: 60Ω), or electromagnetic interference causing signal frame loss.— Blocked brake caliper hydraulic line (e.g., foreign object in the right front brake caliper line) or contaminated and degraded brake fluid causes abnormal hydraulic feedback, triggering a VCU calculation error.— Internal CAN receiving circuit fault in the IPB intelligent integrated brake control module, outdated software version, or missing calibration data.+2 more →
Actions
— Use the BYD VDS diagnostic tool to read the complete fault codes. Record any accompanying related fault codes, such as C055E00 (hydraulic circuit leak) and C007200 (pedal signal implausible).— Measure the CAN-H and CAN-L line voltages (standard: CAN-H 2.5-3.5V, CAN-L 1.5-2.5V) and terminal resistance between the VCU and IPB. Check connector conditions in areas prone to water ingress, such as the front passenger A-pillar and firewall.+5 more →
C059000›
This DTC indicates the IPB (Intelligent Power Brake) electro-hydraulic control module detects the brake booster motor drive circuit supply voltage exceeds the calibrated threshold (typically >16V). In BYD DMi models, the 12V low-voltage system powers the IPB, which uses motor direct-drive brake assist (without a vacuum booster). Faults in the DC-DC converter, generator, or IPB internal power management circuit causing voltage increases trigger this DTC. Continuous overvoltage can overheat and damage the IPB internal MOSFETs or motor driver chip. This triggers system protection mode, resulting in a hard brake pedal, reduced brake assist, or restricted ABS/ESC functions. Severe cases force the vehicle into limp mode.
Causes
— DC-DC converter fault: High-voltage to 12V DC-DC module failure generates abnormally high output voltage (>15-16V), exceeding the IPB supply voltage limit.— IPB electro-hydraulic module internal fault: Fault in the IPB internal power regulation circuit, voltage sampling circuit, or motor drive circuit causing actual overvoltage or false overvoltage reporting.— 12V charging system fault: Alternator regulator failure on DMi models or abnormal DC-DC control strategy causes low-voltage system overvoltage charging.+2 more →
Actions
— Fault Confirmation and Data Reading: Use VDS2000/3000 to read all DTCs, freeze frame data (record the actual voltage when the fault occurred), and the live data stream. Confirm if the actual IPB supply voltage continuously exceeds 16V.— Low-voltage system voltage check: Measure the 12V battery static voltage (normal: 12.4–12.8V) and dynamic voltage (startup/charging state, normal: 13.5–14.8V, should not exceed 15.5V) to check for overvoltage.+3 more →
C059100›
This DTC indicates the supply voltage to the IPB (Integrated Power Brake) internal brake booster motor is below the normal operating threshold set by the ECU (typically below 9V or 75% of the nominal value). The IPB system uses a vacuum-free electro-hydraulic assist design. A DC motor drives a hydraulic pump to build brake assist pressure. When motor voltage drops too low, the ECU limits assist torque output to protect hardware. This results in a significantly harder brake pedal, longer pedal travel, and increased braking distance. The IPB internal power management module triggers this fault by monitoring the motor drive circuit voltage in real time. Possible causes include an abnormal external power supply, excessive wiring voltage drop, poor connector contact, or a failed IPB internal DC-DC converter or motor drive circuit. A persistent fault causes the IPB to enter Limp Home mode, limits vehicle speed, and illuminates multiple system warning lights.
Causes
— Poor connection, oxidation, or burnt fuse holder in the IPB assembly main power circuit (constant +B or IGN power) causes voltage drop under high-current conditions (especially at motor startup, when current reaches 30–50 A).— IPB internal power management module (DC-DC converter or pre-driver circuit) fault, failing to output the stable 12V/24V voltage required to drive the motor (some models use a boost drive).— Low-voltage battery aging (increased internal resistance) or unstable DC-DC converter output causes the vehicle 12V system voltage to drop below 11V, triggering IPB low-voltage protection.+2 more →
Actions
— Read freeze frame and fault conditions: Use the BYD dedicated diagnostic tool (VDS or X-431) to read the C059100 freeze frame data. Record the motor voltage, vehicle speed, brake pedal travel, SOC status, and ambient temperature at the time of the fault. Determine whether the fault is intermittent (intermittent voltage drop) or persistent.— Check the external power supply system: Measure the voltage drop across the IPB power supply fuse in the front compartment distribution box (usually F1/40A or F2/60A; refer to the vehicle wiring diagram). With the vehicle started, measure the voltage between IPB connector B (power connector) Pin 1/2 (+B) and body ground. The voltage must remain stable at 13.5-14.5V. Check the fuse holder for burning or terminal spread.+3 more →
C059500›
DTC C059500 indicates an abnormal internal power drive circuit or supply voltage in the IPB (Integrated Power Brake) system. This fault involves abnormal electrical performance of the power management unit (PMU) or DC-DC conversion circuit inside the IPB module, or the external power supply wiring. The IPB controller triggers this DTC when it detects the internal drive voltage exceeds normal thresholds (typically below 9V or above 16V), excessive power supply ripple, or an abnormal internal drive MOSFET/IGBT circuit. This fault can cause vacuum boost simulation failure, a hard brake pedal, energy recovery interruption, and restricted ESC/ABS functions. In severe cases, the vehicle enters limp mode or fails to power up the high-voltage system. This constitutes a critical driving safety fault.
Causes
— Loose connection, oxidation, or corrosion in the IPB module power supply circuits (especially the constant power B+ and ignition power IG1 circuits)— Blown dedicated IPB power supply fuse (usually 30A or 40A) in the engine compartment fuse box, or poor contact at the fuse holder.— Damaged IPB module internal power management chip, DC-DC converter circuit, or pre-driver circuit+2 more →
Actions
— Use the VDS/DTS diagnostic tool to read the fault code, confirm the C059500 status as current or history, and record the freeze frame data (voltage value, temperature, vehicle speed).— Check the vehicle 12V battery voltage and health condition. Verify the static voltage is ≥12.6V and the charging voltage is 13.5-14.5V. Replace the battery if necessary.+8 more →
C059592›
The IPB (Intelligent Power Brake) system triggers this DTC when the internal power drive circuit of the Electrical Booster detects an abnormal power supply. The IPB system integrates the conventional vacuum booster, ABS, ESP, and EPB into a single unit, and uses a motor-driven hydraulic system to generate brake assist. DTC C059592 indicates the control module detects the booster motor supply voltage falls outside the normal threshold (typically 9-16V), or the internal DC-DC conversion circuit, power drive MOSFET, or power management chip operates abnormally. This fault disables or limits the electric brake assist function and significantly stiffens the brake pedal (requiring over 200N of pedal force). Simultaneously, the system triggers safety protection mechanisms, restricting ADAS functions such as Autonomous Emergency Braking (AEB) and Adaptive Cruise Control (ACC), severely compromising driving safety.
Causes
— Low-voltage power supply system fault: Increased internal resistance due to battery aging, insufficient alternator charging, or voltage regulator fault causes voltage to drop below 9V during startup or high-current operating conditions.— Wiring connection fault: Poor contact at the IPB power supply circuit fuse (usually 30A or 40A), loose power connector, oxidized or backed-out terminals, or loose ground points G06/G08 causing excessive circuit resistance.— IPB internal power module fault: Internal DC-DC converter damaged, assist motor drive circuit shorted/open, PCB power components damaged by overheating.+2 more →
Actions
— Use the VDS2000/VDS3000 diagnostic tool to read the complete fault codes and freeze frame data. Record key parameters at the time of the fault, including vehicle speed, voltage, and pedal position. Check for related fault codes such as C059500 and C058200.— Check the vehicle low-voltage power supply system: measure the battery static voltage (should be ≥12.4V), cranking voltage (should be ≥9.6V), and charging voltage (should be 13.8-14.8V). Check the battery internal resistance and State of Health (SOH).+6 more →
C059900›
This fault code indicates the EPB (Electronic Parking Brake) control module detects an uncalibrated system, a communication fault, or an actuator fault. Although some repair data categorizes this code under the IPB (Integrated Power Brake) system, C059900 typically indicates interrupted CAN communication between the EPB control unit and the left and right rear parking motors, an unstable power supply, or lost internal module calibration data. When this fault occurs, the EPB control module cannot accurately acquire motor position signals or execute control commands, causing partial or complete electronic parking brake failure. Symptoms include the inability to release or apply the parking brake, and instrument cluster warnings. Extreme cases compromise driving safety.
Causes
— Poor contact in the EPB control module power supply/ground circuit, especially oxidized or loose ground points G106/G107, or low battery voltage (static <12V)— Open or short circuit in the left or right rear wheel EPB actuator motor wiring harness. Repeated flexing at the door hinge or chassis pass-through commonly breaks the internal copper strands (outer insulation remains intact).— EPB control module internal circuit board corrosion, chip damage, or software calibration data loss, often due to water ingress or voltage fluctuations.+2 more →
Actions
— Use the VDS2000/3000 diagnostic tool to read the complete fault codes. Check for accompanying sub-codes such as C059801 (right rear wheel fault) and C059802 (left rear wheel fault). View the motor current, position, and switch status in the data stream.— Check the battery health status. Measure the static voltage (should be ≥12V) and the voltage after startup (13.8-14.5V). Check the tightening torque and oxidation condition of the EPB control module ground point (usually G106 on the left side of the dashboard or under the center tunnel).+4 more →
C05B000›
DTC C05B000 indicates the IPB (Intelligent Integrated Braking System) detects abnormal pressure or a leak in the L2 hydraulic circuit (typically the right-rear/left-rear brake circuit, depending on vehicle brake line routing). The internal IPB hydraulic pressure sensor triggers this fault upon detecting an inability to maintain L2 circuit pressure or an abnormal pressure drop during pressure build-up. The L2 circuit is the second hydraulic circuit in the dual-circuit braking system and controls brake pressure for specific wheels. If the IPB detects a circuit pressure decay rate exceeding the threshold (typically >3-5 bar/s) or a failure to reach target pressure, it records the fault and enters fail-safe mode. This mode limits or disables functions including ABS, ESC, and Automatic Emergency Braking, while retaining basic hydraulic braking capability. This hard fault affects driving safety; clearing the DTC will not resolve the issue.
Causes
— An aged or damaged internal valve body sealing ring in the IPB electro-hydraulic module causes internal pressure loss (common in vehicles used for over 2-3 years, especially those operating in high-temperature, high-humidity environments).— Physical damage to external pipes or hoses in the L2 circuit (including metal brake pipe corrosion, rubber hose cracking, or loose fittings), causing brake fluid leakage.— Brake fluid contamination or degradation causes the internal IPB solenoid valve to stick and fail to seal properly, resulting in pressure crossover between circuits or internal leakage.+2 more →
Actions
— Connect the VDS or dedicated diagnostic tool to read all fault codes. Check for C05B000 and related fault codes (e.g., C05B001, C055E00), and record the pressure value and vehicle speed from the freeze frame data.— Visually check the brake fluid reservoir level. If the level is significantly below the MIN mark, inspect the L2 circuit (right rear/left rear) lines, hoses, calipers, and IPB unit for wet spots or fluid drips.+5 more →
C05C200›
DTC C05C200 indicates the electric booster motor operating temperature in the IPB (Intelligent Power Brake) integrated brake system exceeds the safety threshold (typically 120°C–130°C). The IPB system uses a brushless DC motor to drive the brake master cylinder and generate hydraulic boost, completely replacing the traditional vacuum booster. When the motor temperature sensor (NTC thermistor) detects an abnormal temperature rise in the motor windings or drive module, the ECU stores this DTC and initiates a protection strategy. This strategy limits motor power output, illuminates the ABS/ESC warning light, and may switch the system to a degraded mode (no boost or hydraulic brake backup). This fault results in a noticeably harder brake pedal, increases required pedal force, and extends braking distance, posing a severe safety hazard during continuous braking or high-speed driving.
Causes
— Brake drag or poor return: Brake caliper piston corrosion, binding guide pins, or improper brake pad installation causes continuous clamping. The motor operates continuously to maintain pressure, generating excessive heat.— Cooling system fault: Mud or sand blocking the cooling air duct at the IPB module installation position, poor heat dissipation inside the compartment, or sustained high ambient temperatures (such as during prolonged aggressive driving or in towing mode).— Abnormal mechanical load: increased master cylinder piston resistance due to degraded, moisture-contaminated brake fluid, partial brake line blockage, or reduced transmission efficiency due to motor bearing wear.+2 more →
Actions
— Freeze frame analysis: Use VDS2000 or a dedicated diagnostic tool to read freeze frame data recorded when the fault occurred, including ambient temperature, motor temperature, brake pressure, and motor current. Verify actual overheating versus a false sensor reading.— Visual and heat dissipation inspection: Inspect the IPB module for impact damage. Clean dust and oil from the heat sink surface. Verify the mounting bracket is free of deformation that causes poor contact with the heat dissipation surface.+5 more →
C05B001›
DTC C05B001 indicates the IPB (Intelligent Integrated Brake System) detects a leak in brake hydraulic circuit L1. The IPB is the BYD brake-by-wire system (One-Box architecture) integrating brake assist, Electronic Stability Control (ESC), and energy recovery functions. Circuit L1 typically refers to the primary brake circuit or a specific wheel cylinder control circuit (e.g., front left wheel circuit). This fault indicates hydraulic system sealing failure. This condition can extend brake pedal travel, cause a non-linear reduction in braking force output, and restrict or disable active safety functions including ABS, ESC, and Automatic Emergency Braking. Due to braking safety risks, the system illuminates multiple warning lights and may limit vehicle power output.
Causes
— Brake caliper (wheel cylinder) piston seal aged, damaged, or improperly installed, causing hydraulic fluid leakage.— Visible leak caused by loose, corroded, or physically damaged steel brake lines or rubber hose fittings.— Worn master cylinder sealing ring or failed valve body seal inside the IPB integrated brake module (internal leakage)+2 more →
Actions
— Park the vehicle safely, disconnect the high-voltage system power supply, and check if the brake fluid reservoir level has dropped abnormally.— Use the VDS2000/3000 diagnostic tool to read the fault code and freeze frame data, and confirm the specific operating conditions of the L1 circuit pressure build-up failure.+7 more →
C05C24B›
The integrated motor drive unit of the IPB (Intelligent Power Brake) electro-hydraulic braking system triggers this DTC. When the internal temperature sensor of the brake assist motor (usually a permanent magnet synchronous motor or brushless DC motor) detects a temperature exceeding the safety threshold (generally 120°C-140°C, depending on software calibration), the ACM (Brake Assist Control Module) records this fault and enables thermal protection mode. In this state, the system may limit or cut off motor assistance, resulting in a noticeably harder brake pedal and longer pedal travel. The driver must build braking force entirely through manual effort. This fault involves functional safety (ISO 26262). The system illuminates the ABS/ESC warning lamp, may disable energy recovery, and forces the vehicle into limp-home mode.
Causes
— Extreme operating conditions: Continuous high-frequency braking on long downhill sections, or repeated hard acceleration and deceleration while towing or fully loaded, causes the motor to operate continuously under high load and generate more heat than the cooling system can dissipate.— IPB control module software defect: Early software versions contain bugs in the thermal management strategy or motor drive PWM control logic, causing abnormal continuous motor operation or overheating under low load.— Brake system mechanical binding: Corroded brake caliper piston causing poor return, brake pad and disc drag, or partially blocked brake fluid line. This forces the motor to continuously output high torque to maintain pressure. The resulting excessive current causes overheating.+2 more →
Actions
— Connect the BYD VDS or Launch X-431 diagnostic tool and read the complete DTC list. Confirm if C05C24B is a current or history code and record the freeze frame data (focus on motor temperature, ambient temperature, brake pressure, and vehicle speed).— Check the IPB assembly software version against the BYD TSB. If a software upgrade solution exists for this fault code, update the ACM control module software to the latest version (such as V2.3 or higher released after 2023).+5 more →
C05CA00›
DTC C05CA00 indicates the IPB (Intelligent Integrated Braking System) electro-hydraulic control module detects the signal voltage from Brake Master Cylinder Piston Position Sensor A exceeds the normal upper limit (typically >4.8V, normal range is 0.5-4.5V). This Hall-effect or potentiometer-type position sensor monitors the travel position of the primary brake master cylinder piston in real time. It provides the IPB ECU with precise pedal depth and hydraulic build-up rate data, enabling regenerative braking, brake assist adjustment, and ESC intervention. High voltage indicates a short to power in the sensor signal circuit, an internal sensor short, an ECU sampling circuit fault, or an abnormally high reference voltage. This fault distorts brake pedal travel recognition, triggers the brake system degraded mode (loss of regenerative braking, pure hydraulic braking), and restricts ABS/ESC functions.
Causes
— Damaged sensor wiring harness insulation shorts the signal wire to +B (common in high-temperature areas of the engine compartment or at frequent bending points near the steering column).— Short circuit in internal Hall element or thick-film resistor of brake master cylinder piston position sensor (sensor fault)— Failure of the internal 5V reference power supply regulator circuit in the IPB electro-hydraulic module causes abnormally high output voltage.+2 more →
Actions
— Connect the VDS diagnostic tool to read the fault codes and freeze frame data. Confirm the vehicle speed, pedal travel, and voltage values when the fault occurred. Clear the fault codes and road test the vehicle to verify if the fault is intermittent.— Disconnect the connector between the IPB electro-hydraulic module and the brake master cylinder position sensor. Check the pins for corrosion, backed-out terminals, or burn marks. Measure the voltage between the sensor-side power supply pin (usually PIN1) and ground (PIN3) to verify a stable 5V (normal: 4.9-5.1V). If the voltage is >5.3V, check the ECU power supply circuit.+4 more →
C05CB00›
This DTC indicates the signal voltage from Master Cylinder Piston Position Sensor A, internal to the Intelligent Integrated Brake System (IPB), falls below the calibrated threshold (typically <0.5V or below the valid range lower limit). The sensor uses Hall effect or potentiometer principles to monitor brake master cylinder piston displacement in real time. It provides the IPB control unit with an accurate pedal travel signal to calculate driver braking demand, coordinate electro-hydraulic brake pressure distribution, trigger regenerative braking, and control active safety functions (ESP/ABS/AEB). Low voltage indicates a voltage drop in the sensor supply circuit (5V reference voltage), a signal wire short to ground, an internal sensor short circuit, or a faulty IPB control unit sampling circuit. This fault causes abnormal brake pedal feel, limited or disabled regenerative braking, and degraded ESP/ABS functions. Extreme conditions trigger brake system fail-safe protection (pure hydraulic braking backup), compromising driving safety.
Causes
— Damage, wear, or internal short circuit of the master cylinder position sensor A body inside the IPB integrated electro-hydraulic brake assembly.— Water ingress, corrosion, or seal failure at the sensor wiring harness connector (located on the side of the IPB assembly) causing the signal wire to short to ground.— Poor connection, excessive voltage drop, or short to ground in the 5V reference voltage circuit between the IPB control unit and the sensor.+2 more →
Actions
— Use a VDS or Launch diagnostic tool to read the IPB live data stream. Confirm if the master cylinder position sensor A voltage remains at 0V or <0.5V. Compare the value with sensor B (if equipped) to verify. Check for accompanying DTCs C05CA00 (overvoltage) or C05CC00 (out of range).— Visually inspect the IPB assembly wiring harness connector (usually located near the brake master cylinder, grey or black plug) for looseness, water ingress, pin corrosion, backed-out pins, or deformation. Clean the connector with electrical contact cleaner, apply conductive grease, and reconnect. Verify the locking tab fully engages.+3 more →
C05CC00›
DTC C05CC00 indicates the master cylinder piston position sensor A signal in the IPB (Integrated Power Brake) exceeds the ECU-calibrated valid range (typically 0.5V-4.5V or the corresponding physical travel range). This Hall effect sensor monitors brake master cylinder piston displacement in real time to calculate driver braking intent, control brake booster motor torque distribution, and coordinate electro-hydraulic blended braking. The IPB module sets this fault when an open circuit, short circuit, or short to power/ground causes the sensor signal voltage to exceed limits, or when actual piston displacement exceeds the physical travel range detectable by the sensor. Upon fault trigger, the vehicle may enter brake backup mode (no assist or limited assist). The system disables regenerative braking, may degrade ABS/ESP functions, and illuminates the brake system warning lamp on the instrument cluster.
Causes
— Loose or corroded wiring harness connector: The wiring harness between the IPB module and the master cylinder sensor routes through a high-temperature area in the engine compartment. This makes the connector susceptible to terminal pin back-out, oxidation, or poor sealing, causing intermittent signal interruption or drift.— Sensor body damaged: Aging Hall element, internal short circuit, or detached magnetic ring fixes the output signal voltage at an extreme value (close to 0V or 5V).— IPB control unit reference voltage abnormal: Module internal 5V regulator circuit fault causes excessively high or low sensor supply voltage.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000/3000) to read the fault code and freeze frame data. Record the vehicle speed, brake pedal travel, and sensor voltage values at the time of the fault. Confirm if the fault is intermittent.— Inspect the wiring harness connector between the IPB electro-hydraulic module and the brake master cylinder sensor (usually located near the ABS pump assembly). Check the terminals for backed-out pins, burning, or water corrosion, and verify normal terminal retention force.+5 more →
C05CD00›
DTC C05CD00 indicates the signal voltage of master cylinder piston position sensor B inside the IPB (Intelligent Integrated Braking System) continuously exceeds the calibrated threshold (typically >4.8V). This Hall-effect position sensor monitors the brake master cylinder piston travel position in real time. It provides the IPB with an accurate brake pedal input signal to enable brake-by-wire assist, coordinated energy recovery, and ESC intervention. This high voltage indicates a short to power in the sensor signal circuit, an internal sensor breakdown short, or an IPB control module sampling circuit fault. This fault forces the IPB into degraded mode, which causes abnormal brake assist (stiff pedal or altered pedal travel), disables the energy recovery system, and limits ESP/ABS functions. In extreme cases, it compromises braking performance. This is a safety-related fault.
Causes
— Damaged master cylinder position sensor B inside the IPB electro-hydraulic module: The sensor is highly integrated with the IPB. A faulty internal Hall element or signal processing circuit causes abnormally high output voltage. This is the most common root cause.— Wiring harness short circuit: The sensor signal wire (typically the standard 5V reference circuit) shorts to the vehicle 12V power wire or 5V reference line, pulling the voltage high.— Connector issue: Water ingress, corrosion, or bent pins at the IPB module connector cause abnormal continuity between the signal and power terminals, commonly after driving through water or high-pressure washing.+2 more →
Actions
— Safety Confirmation and Initial Inspection: Verify the brake fluid level is normal. Inspect the IPB module for physical damage and brake fluid leaks. Check the instrument panel warning light status (ABS/ESP/brake system lights). Use the VDS2000/VDS6000 diagnostic tool to read all fault codes and record freeze frame data. Verify C05CD00 is a current fault, not a history fault.— Data stream analysis: Access the IPB system and read the real-time voltage data of master cylinder position sensor B. Verify if the voltage remains continuously above 4.8V (normal range is typically 0.5-4.5V). Simultaneously check the voltage value of sensor A for comparison. If sensor A is normal and sensor B is abnormal, initially rule out a common power supply issue.+4 more →
C100104›
DTC C100104 has dual definitions across different BYD vehicle platforms. On early pure electric platforms like the E5, this code explicitly indicates an internal CAN hardware communication fault within the ABS control unit. This indicates an abnormality at the physical or data link layer between the ABS module and the vehicle CAN network (powertrain CAN or chassis CAN). The fault can interrupt communication or cause data packet loss in brake-related systems like the ABS, ESP, and EPB. On DM-i and e-Platform 3.0 models like the Song Pro, Tang DM, and Qin Plus, this code typically maps to an abnormal left front wheel speed sensor (WSS) signal or circuit fault. Regardless of the platform, this is a safety-critical braking system fault. The fault degrades or completely disables ABS/ESC functions. The instrument cluster typically illuminates the ABS warning lamp, ESC warning lamp, and parking system fault lamp. CAN hardware faults typically originate from a damaged internal ABS module transceiver, abnormal terminating resistance, or wiring physical layer faults. Wheel speed sensor faults mostly originate from sensor component failure, wiring harness open or short circuits, or an abnormal signal tone ring.
Causes
— Damaged internal CAN transceiver hardware or faulty communication chip in the ABS control unit (early models such as E5)— Internal short circuit, open circuit, or abnormal impedance in the left front wheel speed sensor coil (standard value: 1.0-1.6 kΩ)— Worn or broken wheel speed sensor wiring harness insulation, or water ingress and oxidation at the connector causing excessive contact resistance.+2 more →
Actions
— Use VDS2000 or Launch X431 to read the complete fault code stream. Confirm whether C100104 is a current or history fault. Check for accompanying U-class communication fault codes (such as CAN bus off) or other wheel speed sensor fault codes to initially determine the fault type (CAN hardware or wheel speed signal).— For CAN hardware faults on models such as E5: Check the ABS module power supply (constant power +BAT, ignition IG1), ground (GND), and CAN-H/CAN-L circuit voltages (standard: CAN-H 2.5–3.5 V, CAN-L 1.5–2.5 V, static differential approximately 2.0 V). Measure the chassis CAN termination resistance at the OBD diagnostic port (approximately 60 Ω).+4 more →
C05CE00›
This DTC indicates the master cylinder piston position sensor B circuit voltage in the IPB (Intelligent Power Brake) smart integrated braking system falls below the calibrated threshold (typically <0.5V). The master cylinder position sensor uses a dual-sensor redundant design (sensors A and B) to monitor brake master cylinder piston displacement in real time. It provides brake pedal travel signals to the IPB ECU to calculate driver braking intent and control electro-hydraulic brake assist. Low sensor B voltage prevents the IPB system from accurately identifying the master cylinder position. This triggers the system safety protection mechanism and limits or disables ESP/ABS functions, potentially causing abnormal brake pedal travel, reduced brake assist, or complete loss of brake assist, seriously compromising driving safety. A short to ground in the sensor power or signal circuit, poor wiring contact, or a damaged sensor typically causes this fault.
Causes
— Poor contact at the sensor wiring harness connector, oxidized pins, pin back-out, or corrosion from water ingress, causing excessive signal transmission resistance.— Master cylinder position sensor B power supply circuit (5V reference voltage) short to ground or open circuit, resulting in insufficient operating voltage.— A short to ground in the sensor signal output circuit causes the ECU to detect an abnormally low voltage.+2 more →
Actions
— Use a dedicated diagnostic tool (such as BYD VDS) to read the DTC freeze frame data and confirm the vehicle status and sensor voltage values when the fault occurred.— Disconnect the IPB wiring harness connector. Visually inspect the pins for oxidation, recession, corrosion, or deformation. Clean or repair the connector.+8 more →
C05CF00›
DTC C05CF00 indicates the signal voltage or travel value from Master Cylinder Position Sensor B inside the IPB (Intelligent Integrated Braking System) falls outside the calibrated range (typically 0.5-4.5V or the corresponding physical travel limit). This sensor features a dual-redundant design (Sensors A and B) to monitor brake master cylinder piston displacement in real time, enabling brake pedal travel interpretation, precise brake force distribution, and redundant safety cross-checking. The IPB control unit sets this fault if Sensor B experiences an open circuit, short circuit, mechanical binding, or excessive signal deviation from Sensor A. The fault may cause abnormal brake pedal feel (soft/hard), restricted regenerative braking, ABS/ESC system deactivation, and Automatic Emergency Braking (AEB) failure. In extreme cases, it triggers limp mode (speed-limited driving).
Causes
— Hardware fault in master cylinder position sensor B inside the IPB assembly: damaged internal magnetoresistive element, failed Hall-effect chip, or dry solder joint causing output signal drift or out-of-range values.— Wiring harness and connector issues: poor contact in the Sensor B power supply, signal, or ground circuits; oxidized or annealed terminals; water ingress or moisture in the connector reducing insulation resistance; or wiring harness wear causing a short circuit.— Power supply and ground fault: Unstable IPB controller constant power or ignition voltage (below 11V or above 14V), or a loose ground wire bolt causing excessive contact resistance (>0.1Ω), resulting in sensor reference voltage drift.+2 more →
Actions
— Safety preparation and fault confirmation: Use VDS2000 or a dedicated BYD diagnostic tool to read all fault codes and freeze frame data. Record vehicle speed, pedal travel, and sensor A/B voltage values at the time of the fault. Check the instrument panel warning light status and verify brake pedal force is normal.— Visual and basic inspection: Check the IPB assembly for impact damage and brake fluid leaks; check if the brake fluid level is between MAX and MIN, adding DOT4 brake fluid if necessary; check the IPB mounting bracket tightening torque (standard 25±2Nm) and mounting surface flatness.+7 more →
C05D000›
This DTC indicates the signal difference between dual redundant channels A and B of the Master Cylinder Position Sensor inside the IPB (Intelligent Integrated Braking System) exceeds the diagnostic threshold. For functional safety (ISO 26262), the IPB uses a dual-channel redundant design to monitor brake master cylinder piston travel. When the difference between the two signals continuously exceeds the calibrated value (typically 5%-10%), the system determines the sensor signal is implausible. This fault triggers the brake system limp-home mode, potentially causing a loss of electronic brake assist, a hard brake pedal, ABS/ESC deactivation, and illuminating multiple system warning lights.
Causes
— Master cylinder position sensor internal circuit fault or signal drift causing inconsistent dual-channel output.— Loose mechanical connection, abnormal clearance, or misaligned installation position between the sensor and master cylinder piston.— Water ingress, oxidation, or loose pins at the IPB wiring harness connector (especially the 32-pin or 48-pin main connector) causing signal crosstalk.+2 more →
Actions
— Use VDS or a dedicated BYD diagnostic tool to read the complete DTC list and freeze frame data. Record the vehicle speed, pedal travel, and channel A/B raw signal values at the time of the fault.— Check if the brake fluid level is normal. Inspect the IPB and lines for leaks, deformation, or external damage.+7 more →
C05D200›
This fault code indicates an internal pressure sensor monitoring fault within the IPB (Integrated Power Brake). Specifically, during self-test or operation, the IPB control unit detects the voltage signal from the brake master cylinder pressure sensor (or wheel cylinder pressure sensor, depending on configuration) falls below the calibrated normal operating threshold (typically corresponding to an equivalent voltage for a pressure below 0.1-0.3MPa). Potential causes include sensor drift, an open circuit causing signal loss (reading 0V or extremely low voltage), or an internal IPB hydraulic circuit leak preventing actual pressure buildup. This fault triggers the brake system degradation mode and may disable the ABS, ESC, Automatic Emergency Braking (AEB), and energy recovery functions. Extreme conditions may limit vehicle speed and illuminate multiple warning lights.
Causes
— Damaged or aged master cylinder pressure sensor inside the IPB electro-hydraulic module causes abnormally low output signal voltage.— Open circuit or short to ground in the pressure sensor 5V reference power supply circuit or signal feedback circuit, causing the ECU to detect an abnormally low voltage.— Leakage at the internal IPB brake master cylinder seal or valve body causes the actual pressure value to fall below the sensor threshold during pressure build-up.+2 more →
Actions
— Safety preparation: Confirm the vehicle is stationary and apply the electronic parking brake. Use the BYD VDS or a Launch/Autel diagnostic tool to read the complete fault codes and freeze-frame data. Record the vehicle speed, pedal travel, and pressure values at the time of the fault.— Basic inspection: Verify the brake fluid reservoir level is between MAX and MIN, inspect the exterior of the IPB electro-hydraulic module for leaks or impact damage, and check the relevant chassis wiring harness for damage.+5 more →
C05D300›
C05D300 is a specific fault code for the BYD IPB (Intelligent Power Brake) integrated braking system. It indicates the actual hydraulic pressure detected by the master cylinder pressure sensor exceeds the theoretical expected value the ECU calculates using the brake pedal position sensor (master cylinder stroke sensor A/B). This fault represents a logical mismatch between the pressure signal and the pedal stroke signal. Possible causes include: 1) Pressure sensor drift or damage causing a falsely high signal; 2) Incomplete brake master cylinder piston return generating residual pressure; 3) Hydraulic circuit abnormalities (blockage or internal leakage) causing abnormal pressure transfer; 4) Incorrect brake pedal position sensor signals causing the ECU to miscalculate the expected value; 5) IPB control module software algorithm errors. This fault triggers the brake system degraded mode. It may restrict ABS/ESP functions, cause a hard brake pedal or abnormal pedal travel, and severely compromise driving safety.
Causes
— Brake master cylinder position sensor (especially sensor B) signal drift, damage, or installation misalignment causing abnormal feedback voltage (above the 4.5V standard range)— A sticking brake master cylinder piston, aged and swollen seal ring, or failed return spring prevents residual pressure from fully releasing after pedal release (static pressure > 0.3 MPa).— Sticking hydraulic valve body inside the IPB electro-hydraulic module or partially blocked brake line, causing abnormal pressure build-up and slow pressure release.+2 more →
Actions
— Use the BYD VDS diagnostic tool to access the IPB system and read the complete fault code list (check for accompanying related fault codes such as C05D200, C05CF00, and C055E00). Record the pressure and pedal travel values from the freeze frame data.— Enter data stream mode and monitor the 'master cylinder pressure sensor', 'master cylinder position sensor A', and 'master cylinder position sensor B' values in real time: at rest, the pressure must be 0 MPa and the sensor voltage 0.5-4.5 V; while pressing the pedal, both sensor signals must change linearly and synchronously, and the pressure-to-travel ratio must fall within the standard curve range.+5 more →
C05D309›
This DTC indicates the master cylinder pressure sensor built into the IPB (Intelligent Power Brake) electro-hydraulic module detects a pressure signal exceeding the normal upper threshold set by the ECU (typically >25 MPa or signal voltage >4.8 V). In BYD e-Platform 3.0 and DM-i models, the IPB integrates conventional ESP, ABS, and i-BOOSTER functions, and uses a motor-driven plunger pump to build pressure. The pressure sensor monitors master cylinder pressure in real time for brake force distribution, regenerative braking intensity adjustment, and active braking control. When the sensor signal remains above the calibrated value beyond the set time (typically 200-500 ms), the ECU logs a "pressure too high" fault. This fault restricts ABS/ESP functions, disables Automatic Emergency Braking (AEB), and interrupts regenerative braking. In extreme cases, it triggers a "brake system fault" warning and limits vehicle speed. Determine whether the cause is actual excessive hydraulic pressure (such as a blocked brake line) or a false high-pressure signal caused by sensor drift or a short circuit.
Causes
— Pressure sensor internal short circuit or signal drift: An aging or damaged pressure-sensitive element outputs a fixed high-voltage signal (close to the 5V reference voltage), causing the ECU to falsely detect a high-pressure state.— Sensor wiring harness short to power: Water ingress, wear, or pin misalignment at the IPB harness connector (usually near the firewall) shorts the pressure sensor signal wire (Pin 2 or Pin 3, depending on vehicle model) to the 12V power supply or 5V reference voltage.— IPB hydraulic circuit mechanical fault: Blocked brake master cylinder return port, high-pressure valve stuck in the normally open position, or severely contaminated and crystallized brake fluid preventing pressure release, resulting in abnormally high actual pressure.+2 more →
Actions
— Fault confirmation and freeze frame analysis: Use VDS 4.0 or 5.0 to read all fault codes. Check the 'actual master cylinder pressure' in the freeze frame data (normal: 0-1 MPa during pedal free travel; typically <18 MPa when fully depressed). A reading >25 MPa or 4.9 V without pedal application indicates a sensor or wiring fault. A stiff pedal with high pressure indicates a hydraulic fault. Check for related fault codes such as C05D300 and C05D500.— Circuit continuity and insulation test: Disconnect the IPB assembly connector (48-pin or 32-pin; Song PLUS DM-i uses 48-pin). Measure the resistance between the pressure sensor signal wire (usually Pin 23 or Pin 24; check the wiring diagram for the specific pin) and body ground (must be >1MΩ). Measure the resistance between the signal wire and the 5V reference wire (Pin X) to confirm no short circuit exists. Test the signal wire for a short circuit to the power supply (Pin 1, constant power). Inspect the connector for water ingress, corrosion, or backed-out pins.+3 more →
C05D500›
This DTC indicates an abnormal open-circuit condition in the Master Cylinder Solenoid Valve or its control circuit within the IPB (Integrated Power Brake) intelligent integrated braking system. In the BYD IPB system, the master cylinder pressure valve controls the hydraulic passage between the brake master cylinder and the wheel cylinders. It serves as a key actuator for electro-hydraulic blended braking control, energy recovery, and ABS/ESC functions. The ECU sets this DTC when it detects an open circuit in the valve drive circuit, abnormal valve position feedback, or a mismatch between the actual and commanded valve states lasting beyond the set threshold (typically exceeding 100ms). This fault reduces brake pressure control accuracy and may trigger a brake system degraded mode (entering pure mechanical backup braking or limiting energy recovery). This condition affects brake pedal feel and active safety functions (such as AEB and ACC).
Causes
— Open circuit in the IPB assembly master cylinder pressure solenoid valve coil, or valve mechanically stuck in the open position, causing the ECU to detect an open circuit.— Solenoid valve drive circuit fault on the internal IPB module PCB (e.g., damaged MOSFET driver chip or cold solder joint).— Water ingress and corrosion at the IPB wiring harness connector (especially the 32-pin main plug), pin back-out, or increased contact resistance (>1Ω)+2 more →
Actions
— Connect the VDS2000 diagnostic tool, read the complete fault codes and freeze frame data, and confirm the fault frequency (current/historical). Check for accompanying fault codes (such as other C05Dxx series pressure valve faults) and record the vehicle speed and brake pressure values at the time of the fault.— Perform a visual inspection: inspect the IPB assembly exterior for brake fluid leaks or impact damage; inspect the wiring harness connector (located at the front left of the motor compartment) for looseness or water ingress; measure the IPB supply voltage (constant power +B, standard 12-14V) and ground wire resistance (standard <0.5Ω) using a multimeter.+5 more →
C080001›
For BYD new energy vehicles (specifically E5, Qin, Tang, and Song models equipped with Bosch or Continental ESP systems), DTC C080001 indicates a fault in the ESP (Electronic Stability Program) lateral acceleration sensor or its power supply circuit. Although the fault description reads "voltage below range", this specifically means the lateral acceleration sensor supply voltage falls below the ECU threshold (normal range: 4.5V–5.5V), or the sensor output signal voltage remains below the valid range (0.5V–4.5V). Consequently, the ECU cannot obtain accurate vehicle lateral acceleration data. This condition causes active safety functions (ESP, ABS, EBD) to fail or enter a degraded mode, severely compromising vehicle stability during cornering or driving on wet and slippery surfaces.
Causes
— Lateral acceleration sensor internal circuit short or damage causes excessive operating current, pulling down the supply voltage.— Fault in the 5V reference voltage output circuit of the ESP control unit (or internal ECU of the ABS hydraulic modulator), failing to provide a stable sensor power supply.— Oxidation, looseness, or backed-out pins at the sensor harness connector cause excessive contact resistance, reducing actual voltage at the sensor.+2 more →
Actions
— Use the diagnostic tool to read the DTC freeze frame and confirm parameters such as vehicle speed and voltage at the time of the fault. Inspect the battery voltage and charging system for normal operation, and verify the static voltage is greater than 12.4V.— Check the power supply (terminal 30), ground (terminal 31), and ignition switch-controlled power supply (terminal 15) at the ESP control unit (usually located in the engine compartment or cabin). Verify the voltage is above 12V and the ground resistance is less than 1Ω.+3 more →
C080002›
This DTC indicates the ABS (Anti-lock Braking System) electronic control unit detects an operating supply voltage outside the calibrated allowable range (typically 9.5V-16V). In the BYD E5, the 12V low-voltage system powers the ABS module. The DC-DC converter steps down voltage from the high-voltage battery pack to provide this supply. If the module detects voltage that is too high (>16V, risking internal ECU circuit damage) or too low (<9V, reducing control accuracy), it logs DTC C080002. This condition may trigger system protection mechanisms, causing ABS, EBD, ESC, and Automatic Emergency Braking functions to fail or enter a degraded mode. Troubleshoot this fault immediately, as it affects braking safety.
Causes
— An aged, sulfated, or internally shorted 12V low-voltage battery causes voltage fluctuations or increased internal resistance, resulting in a sudden voltage drop under high-current loads, such as ABS pump motor operation.— DC-DC converter fault: Output voltage regulation failure causes excessive (>15V) or unstable low-voltage system voltage.— Poor contact, oxidized or loose terminals, or a burnt fuse holder in the ABS module power supply circuit (constant power B+, ignition power IG1), causing excessive circuit voltage drop.+2 more →
Actions
— Connect the diagnostic tool and read the DTC freeze frame data. Confirm the specific voltage value when the fault occurred (to determine if it is a high-voltage or low-voltage fault) and related information such as vehicle speed and ABS pump operating status.— Measure the 12V battery static voltage (standard 12.4V-12.6V) and load voltage (turn on headlights and air conditioning; should be >12.0V). Use a battery tester to test the CCA value and internal resistance to determine if the battery needs replacement.+5 more →
C104400›
DTC C104400 indicates the IPB (Integrated Power Brake) system detects an incomplete or insufficient hydraulic brake line bleeding procedure. The IPB system uses internal pressure sensors to monitor the hydraulic pressure build-up characteristics of each brake wheel cylinder. When the system detects air in the lines (abnormal compressibility) or identifies an incorrectly executed bleeding procedure, it triggers this fault code and enters fail-safe mode. This fault restricts ABS/ESP functions, causes abnormal brake pedal travel (spongy pedal), and derates or disables the Automatic Emergency Braking (AEB) function, severely impacting braking safety and driver assistance system performance.
Causes
— Failure to perform the standard bleeding procedure after brake system repairs (replacing brake fluid, brake hoses, brake calipers, or brake pads), or manual interruption of the bleeding process.— Battery voltage dropped below 12V or diagnostic communication interrupted during the IPB electro-hydraulic module internal bleeding procedure, causing calibration data write failure.— Using non-dedicated bleeding equipment (such as traditional pedal bleeding) fails to trigger the IPB active pressure-building bleed mode, preventing the system from recognizing the bleeding completion status.+2 more →
Actions
— Pre-check: Confirm brake fluid level is between MAX and MIN, inspect four-wheel brake lines for leaks, measure battery voltage (≥12.5V), and verify normal diagnostic tool communication.— Enter bleeding mode: Use the BYD VDS or Bosch dedicated diagnostic tool to access the IPB system → Special Functions → Hydraulic Brake Bleeding/Refill Procedure. Strictly follow the prompted sequence (usually right rear, left rear, right front, left front).+3 more →
C108008›
C108008 indicates the Hill Hold Control (HHC) system detects an abnormal clutch/start interlock signal. In the BYD E5 battery electric vehicle, this fault does not refer to a conventional mechanical clutch. Instead, it indicates the ABS/ESP control unit fails to receive the correct brake pedal-gear interlock logic signal (the combined signal the system uses to determine if the vehicle is in a 'ready to move off' state). The HHC system relies on the brake switch signal, gear position signal (P/R/N/D status), and wheel speed signals. When the control unit detects a released brake pedal while the gear signal or brake interlock signal contradicts the hill hold release logic, it logs a clutch signal fault. This fault disables the hill start assist function. The vehicle may roll backward on a slope when the driver transitions from the brake pedal to the accelerator pedal. The fault also illuminates the ABS/ESC fault warning lamp and compromises driving safety.
Causes
— Poor contact, burnt internal contacts, or misaligned installation of the brake pedal position sensor (brake switch), causing an intermittent signal or abnormal voltage.— Abnormal signal from the gear selector position sensor (especially the P-gear lock switch); fails to correctly indicate the Neutral/Drive position status.— Loose wiring harness connectors, oxidation due to water ingress, or backed-out pins between the ABS/ESP control unit and the brake switch or gear position sensor, interrupting signal transmission.+2 more →
Actions
— Connect the BYD dedicated diagnostic tool (VDS or ED-400), read the freeze frame data for DTC C108008, and record the vehicle speed, brake pedal status, gear position, and longitudinal acceleration value when the fault occurred.— Visually inspect the brake pedal position sensor (brake light switch) mounting. Check the wiring harness connector for looseness or disconnection. Measure the switch continuity and voltage signal with the pedal pressed and released (voltage normally switches between 12V/B+ and 0V).+5 more →
C104C04›
DTC C104C04 indicates a signal failure in the brake pedal position detection switch or internal mode switch within the Integrated Power Brake (IPB) system. In the BYD brake-by-wire architecture, the IPB monitors this switch signal to identify driver braking intent and trigger hydraulic pressure build-up. Switch failure prevents the IPB from accurately identifying pedal travel status, forcing the system into Limp Home mode with limited brake assist. This condition may cause a stiff brake pedal, increased braking distance, and disabled ESC/ABS functions, constituting a severe fault that compromises driving safety.
Causes
— Internal carbon track wear or contact oxidation in the brake pedal position sensor (primary/secondary) causing signal interruption.— Mechanical binding, spring fatigue, or seal failure of the internal button switch mechanism in the IPB electro-hydraulic module— Water ingress and corrosion at the wiring harness connector (especially at the pass-through between the engine compartment and cabin), causing the signal wire to short to ground.+2 more →
Actions
— Use the VDS diagnostic tool to read the DTC freeze frame data and record the pedal travel value, vehicle speed, and system voltage when the fault occurred.— Check the physical connection of the brake pedal position sensor (located above the pedal bracket). Measure the voltages at sensor pin 1 (+5V reference voltage) and pin 2 (signal output) to verify the output voltage changes linearly with pedal travel (normal range: 0.5-4.5V).+3 more →
C106600›
DTC C106600 indicates missing or incorrect Steering Angle Sensor (SAS) calibration data, or that the calibration procedure was never performed. This sensor typically resides within the steering column or ESP control unit and monitors the steering wheel's absolute angle, rotation direction, and angular velocity in real time. It serves as a core input signal for the Electronic Stability Program (ESP/ESC), Electric Power Steering (EPS), and Automatic Emergency Braking (AEB) systems. The system triggers this fault code upon detecting a calibration data validation failure, or a significant deviation between the sensor's output angle and the theoretical zero position during straight-line driving (typically required to be within -5° to +5°). Consequently, the ESP/ESC function enters a degraded or failure mode. This may cause the vehicle to lose skid control during emergency avoidance maneuvers or on slippery roads; however, basic hydraulic braking functions typically remain unaffected.
Causes
— Failure to perform the steering angle calibration procedure after replacing the steering gear, steering column, steering wheel, or ESP control unit.— After a vehicle collision, chassis geometry changes or the steering angle sensor physical mounting position shifts, causing zero position mark misalignment.— Loss of calibration data stored in the ECU non-volatile memory following a prolonged battery disconnection, abnormal system power supply voltage, or control unit software upgrade.+2 more →
Actions
— Pre-inspection preparation: Park the vehicle on level ground, adjust tyre pressures to standard values, confirm the steering wheel is in the mechanical centre position (visually verify the front wheels are straight or remove the steering wheel to check alignment marks), and clear unrelated fault codes.— Data stream reading: Use the BYD VDS or a generic diagnostic tool to access the Chassis/ABS/ESP system and read the Steering Angle Sensor (SAS) live data stream. Verify the angle value is between -5° and +5° when the vehicle is driving straight. If the deviation is too large, perform a mechanical adjustment or calibration.+4 more →
C108C08›
DTC C108C08 indicates the ABS control unit detects a logic error or implausibility fault in the reverse switch signal (Signal Invalid). In the BYD E5, the HHC (Hill Hold Control) system monitors the reverse signal in real time to determine vehicle travel direction. When the vehicle is in R gear, the reverse switch closes (signal = '1'), and the HHC system activates the hill reverse assist logic. If the ABS module detects a '1' reverse signal while the vehicle moves forward (vehicle speed > 0), or a '0' signal while reversing in R gear, it registers a signal fault. This fault disables the HHC function in reverse mode. The vehicle risks rolling back when reversing on a slope because the system releases braking force prematurely. Simultaneously, the system illuminates the ABS/ESC fault warning lamp, disables specific body stability functions, and enters a safety fallback mode.
Causes
— Reverse switch internal contacts are burnt, oxidized, or mechanically stuck, preventing the switch from closing or opening properly.— Water ingress, loose connection, or backed-out pins at the reverse switch connector, causing excessive contact resistance or an intermittent open circuit in the signal circuit.— Reverse signal circuit (usually from BCM or shift controller to ABS module) shorted to ground, shorted to power, or wiring harness chafed or broken.+2 more →
Actions
— Connect the VDS diagnostic tool, enter the ABS system, and read the 'Reverse switch status' and 'Current gear' data stream parameters. Compare these with the actual gear selector position to confirm signal synchronization. Simultaneously check for accompanying U-class communication fault codes.— Visually inspect the reverse gear switch mounting condition (located near the motor controller or on the shift mechanism assembly) and connector sealing. Check specifically for signs of water ingress and green oxidation on the terminals. If necessary, clean and spray with WD-40 electronic contact cleaner.+5 more →
C1102›
DTC C1102 indicates the ABS (Anti-lock Braking System) electronic control unit (ECU) detects an operating voltage below the minimum system-calibrated threshold (typically 9V-10.5V, depending on vehicle calibration). This fault indicates an abnormal power supply to the ABS hydraulic modulator assembly, potentially causing active safety systems including ABS, ESP (Electronic Stability Program), EBD (Electronic Brakeforce Distribution), and Automatic Emergency Braking (AEB) to enter a degraded mode or fail completely. In BYD new energy vehicles, this fault typically results from a discharged 12V low-voltage battery, excessive voltage drop in the power supply circuit, high ground circuit resistance, or an internal ABS ECU power management module failure. This critical fault compromises driving safety and requires immediate repair.
Causes
— 12V low-voltage battery aging, low charge, or performance degradation (SOC below 30% or SOH below 80%, static voltage below 12.4V)— Loose connection, oxidation, or corrosion in the ABS hydraulic modulator assembly power supply circuit, or a blown ABS fuse (usually 30A/40A/60A) or poor fuse contact in the front compartment power distribution box.— Loose, oxidized, or paint-covered ABS ECU ground points causing increased ground resistance (common ground points: G101 left front side member, G102 firewall)+2 more →
Actions
— Basic power supply check: Measure the 12V battery static voltage (≥12.4V) and dynamic voltage (≥13.5V after engine start or in READY mode). Check the battery terminals and ABS fuses (FB-02 or ABS1/ABS2) for oxidation and verify the tightening torque (8-10 N·m).— ABS module power supply check: Set the ignition switch to ON. Use a multimeter to measure the voltage between the ABS module power supply pin (e.g., B04-1/25) and body ground. If the voltage is below 10V, measure the power supply harness voltage drop in segments (from battery positive terminal → front compartment power distribution box → ABS module connector).+3 more →
C1200›
DTC C1200 indicates the ABS control unit (ECU) detects an electrical integrity fault in the left front wheel speed sensor (WSS) circuit, specifically a short to ground, short to power, or open circuit in the signal line. This sensor is typically a two-wire magnetic or Hall effect type. During normal operation, it transmits either an AC voltage signal proportional to wheel speed (magnetic type, amplitude varying from 0.1V-3V depending on speed) or a square-wave digital signal (Hall effect type) to the ABS ECU. The ECU triggers this code when it detects sensor resistance outside the calibrated range (typically 1.0-1.6kΩ), abnormal signal line voltage (continuous 0V or 12V/B+ voltage), or signal interruption time exceeding the threshold. This fault causes the Anti-lock Braking System (ABS), Electronic Brakeforce Distribution (EBD), Electronic Stability Program (ESP), Traction Control System (TCS), and Autonomous Emergency Braking (AEB) functions to fail or enter a degraded mode. The fault illuminates the ABS, ESP, and tire pressure/brake system warning lights on the instrument cluster, severely compromising vehicle active safety.
Causes
— Wheel speed sensor damage: Open internal coil, inter-turn short circuit, or burnt Hall element. Prolonged high temperatures, vibration, or aging typically cause this. Resistance reads infinite or falls far outside the standard range (<500Ω or >2kΩ).— Wiring harness and connector faults: frequent bending during steering breaks internal copper wires in the left front wheel wiring harness (intermittent connection); loose plug; oxidized or backed-out terminals; or poor plug sealing after chassis water ingress causes a short circuit or corrosion.— Abnormal sensor installation gap: Sensor not fully seated, loose retaining bolt, or bushing wear causing a tone ring gap that is too large (>1.5mm) or too small (<0.3mm); deformed tone ring, missing teeth, or contamination (covered with metal filings or mud).+2 more →
Actions
— Preliminary visual inspection: Raise the vehicle. Check the left front wheel speed sensor connector for looseness and the housing for damage. Inspect the wiring harness protective sleeve at the fender liner and suspension control arm for wear or water ingress. Remove any dirt and corrosion from inside the connector.— Sensor resistance measurement: Disconnect the left front wheel speed sensor connector. Use a multimeter to measure the resistance between the two sensor terminals. The standard value is 1.0-1.6 kΩ (at 20°C). If the reading is OL (open circuit) or 0 Ω (short circuit), replace the sensor.+4 more →
C1201›
DTC C1201 indicates the ABS control unit detects that the left front wheel speed sensor signal's rate of change or amplitude exceeds the calibrated threshold. Specifically, the sensor's square-wave output signal exhibits sudden frequency changes, intermittent interruptions, or abnormal voltage fluctuations, preventing the ABS module from accurately calculating the real-time left front wheel speed. This fault can trigger false ABS activation (pump operates without braking input), restrict Electronic Stability Program (ESP) functionality, disable Automatic Emergency Braking (AEB), and in extreme cases, limit power output on some BYD new energy vehicles equipped with torque vectoring control. Classified as a "plausibility fault," it differs from open or short circuit faults by focusing on dynamic signal quality monitoring.
Causes
— Inter-turn short circuit in the left front wheel speed sensor internal coil, or magnetic core aging, causing signal amplitude attenuation.— The air gap between the sensor and the reluctor ring exceeds the standard range (normal: 0.3-0.8 mm), usually due to excessive wheel hub bearing axial play or a deformed sensor bracket.— Ferromagnetic debris (such as brake wear dust or road metal fragments) adhering to the tone ring surface, or missing teeth or deformation on the tone ring.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS or X-431) to read complete DTCs and freeze frame data. Confirm vehicle speed and ABS operating status at the time of the fault, and check for accompanying C1200 (circuit fault) or other wheel speed sensor fault codes.— Raise the vehicle. Check the left front wheel speed sensor for physical damage, the connector for oxidation or water ingress, and the wiring harness for signs of abrasion. Clean metal shavings from the sensor head.+4 more →
C1202›
DTC C1202 indicates that during continuous monitoring, the ABS/ESC control unit (ECU) detects that the left front wheel speed sensor (WSS) input signal remains at 0 km/h or outputs no pulse signal. In the Bosch/Continental ABS systems of BYD E1/E2/E3/Yuan series models, this code specifically indicates the left front electromagnetic induction or Hall-effect wheel speed sensor fails to transmit a valid square-wave or sine-wave signal to the ECU. This causes the ECU to classify the wheel as "stationary" or "signal missing". This fault triggers the system fail-safe mode, limiting or disabling the Anti-lock Braking System (ABS), Electronic Brakeforce Distribution (EBD), Electronic Stability Control (ESC), Traction Control System (TCS), and Cooperative Regenerative Braking System (CRBS). This severely impacts vehicle stability and braking safety. ISO/SAE standards and some Japanese vehicles (such as Toyota) define C1202 as a brake master cylinder reservoir fluid level fault. However, the fault code system for the specified BYD models clearly maps this code to an abnormal wheel speed sensor signal input.
Causes
— Open or short circuit in the wheel speed sensor internal coil, or Hall element failure, preventing the generation of an induced signal.— Water ingress, oxidation, loose connection, or terminal back-out at the sensor wiring harness connector, causing an open circuit or excessive contact resistance in the signal circuit.— Abnormal sensor installation gap (exceeding 1.2 mm or too small, causing wear), or tone ring (signal disc) deformed, missing teeth, dirty, or jammed by foreign matter.+2 more →
Actions
— Connect a BYD ED400 or Launch/Autel diagnostic tool. Read the fault codes to confirm if C1202 is a current or history code. Check if the left front wheel speed in the data stream remains at 0 km/h, and record the freeze frame data.— Visually inspect the left front wheel speed sensor connector for looseness or water ingress. Inspect the wiring harness for wear or pinch marks at the fender liner and steering knuckle retaining clips. Clean iron filings and mud from the sensor tip and tone ring surface.+6 more →
C1203›
DTC C1203 indicates the ABS detects an electrical fault in the right front wheel speed sensor (WSS) circuit, specifically a signal line short to power/ground or open circuit. The sensor typically uses Hall effect or electromagnetic induction principles, providing pulse signals to the ABS control unit (ECU) to calculate wheel speed. The ECU triggers this fault when it detects a continuously abnormal signal voltage (e.g., 0V or 12V, instead of the normal 0.5-4.5V fluctuation range) or fails to receive pulse signals from the passing tone ring. This causes active safety systems such as ABS, ESC, and EBD to fail or enter a degraded mode. In severe cases, it may affect the coordinated operation of the energy recovery system because the vehicle control system cannot accurately determine the real-time speed and slip ratio of the right front wheel.
Causes
— Internal open or short circuit in the sensor body: Damaged Hall element, burnt coil, or internal circuit board failure due to water ingress or high temperatures, resulting in a constant output signal or complete loss of signal.— Wiring harness connector fault: Water ingress or mud and sand erosion at the right front fender liner sensor plug causes pin oxidation, backed-out pins, or seal failure, resulting in intermittent poor contact or a short circuit.— Wiring insulation damage: Long-term vibration and chafing of the sensor wiring harness at the steering knuckle, suspension control arm, or body pass-through damages the insulation, causing a short to body ground or to an adjacent power wire.+2 more →
Actions
— Initial inspection: Raise the vehicle and visually inspect the right front wheel speed sensor connector (usually located near the shock absorber or on the steering knuckle) for looseness, water ingress, or corrosion. Inspect the wiring harness retaining clips at the fender liner and suspension moving parts for detachment and signs of wear.— Sensor body inspection: Disconnect the connector and use a multimeter to measure sensor resistance (electromagnetic type is typically 1-2 kΩ; Hall type requires a powered test). Compare the data with the left front wheel sensor. Check the sensor head for iron filings or physical damage.+3 more →
C1204›
DTC C1204 indicates the ABS/ESP control unit detected the right front wheel speed sensor output signal change rate (acceleration/deceleration rate) exceeds the configured system threshold (typically ±8-12m/s²). Unlike simple signal loss (C1203) or a static zero signal (C1205), this fault indicates the signal is present but exhibits severe non-linear fluctuations, sudden jumps, or sawtooth distortion. The control unit monitors the wheel speed difference between adjacent sampling cycles to determine if the change is physically plausible (plausibility check). Upon detecting an abnormal jump, the system deems the wheel speed signal unreliable and triggers a degraded protection mode for the ABS, ESP, TCS, EPB, and other systems. This limits or disables related functions to ensure braking safety. Common causes include electromagnetic interference affecting the sensor signal, dynamic gap changes between the sensor and the magnetic encoder, or intermittent failure of the magnetoresistive element inside the sensor.
Causes
— An intermittent short circuit or poor connection in the right front wheel speed sensor wiring harness within the suspension travel range causes signal transmission resistance to fluctuate.— Metal filings, oil sludge, or physical scratches on the surface of the built-in magnetic encoder (tone ring) in the right front wheel hub unit, distorting the magnetic field modulation signal.— Degraded thermal stability of the wheel speed sensor's internal magnetoresistive element (Hall IC or MR element) causes output signal drift at high temperatures.+2 more →
Actions
— Connect the VDS2000 or Launch X431 diagnostic tool. Read the complete DTCs and freeze frame data. Record the vehicle speed, deceleration, and system voltage when the fault occurred. Check for related fault codes such as C1203 (open circuit) or C1205 (signal zero).— Raise the vehicle to a suitable height and visually inspect the right front wheel speed sensor installation. Verify the fixing bolt torque meets the specification (usually 8-12 N·m). Inspect the wiring harness corrugated conduit for wear, crushing, or water ingress throughout the full suspension travel.+3 more →
C1205›
DTC C1205 indicates the ABS/ESC control module continuously detects 0 V (no signal state) from the right front wheel speed sensor. In BYD new energy vehicles, the control module logs an open circuit or sensor failure because the variable reluctance or Hall-effect sensor fails to transmit a valid sine or square wave signal to the ECU. This fault forces the Anti-lock Braking System (ABS), Electronic Stability Control (ESC), Automatic Emergency Braking (AEB), Auto Vehicle Hold (AVH), and energy recovery systems into a degraded or failed mode, and illuminates the ABS/ESC warning lamps on the instrument cluster. Unlike DTC C1204 (excessive signal variation/intermittent fault), C1205 represents a continuous signal loss, typically indicating a hard circuit fault or a damaged sensor.
Causes
— Right front wheel speed sensor internal coil open circuit, burned out Hall element, or internal circuit fault (infinite resistance or 0Ω)— The sensor wiring harness is chafed or broken in high-vibration chassis areas (such as near the suspension control arm), or oxidized connector terminals, terminal back-out, or water ingress corrosion cause poor contact.— Worn or loose wheel hub bearing causing the gap between the sensor and the tone ring (magnetic ring) to exceed tolerance (normal: 0.3-1.2 mm), or loose sensor mounting bolt causing sensor displacement.+2 more →
Actions
— Connect the VDS diagnostic tool to read the DTC freeze frame. Confirm the right front wheel speed data stream remains at 0 km/h and the fault code does not clear to rule out intermittent interference.— Raise the vehicle and visually inspect the right front sensor, wiring harness sleeve, and connector for damage, water ingress, oil contamination, or signs of physical impact.+5 more →
C1206›
DTC C1206 indicates the ABS control module detected an electrical integrity fault (open or short circuit) in the left rear wheel speed sensor circuit. The sensor is typically a two-wire magnetic inductive or Hall effect type. During normal operation, it sends the ABS module either an AC voltage signal that varies with wheel speed (magnetic inductive type, amplitude increases with speed, approximately 0.1V-5V) or a square-wave digital signal (Hall effect type). The module triggers this fault when it detects infinite resistance in the sensor wiring (open circuit), a short to ground or power, or a continuously abnormal signal voltage (below 0.5V or above 4.5V) exceeding the set threshold (typically 2-5 seconds). This fault causes a loss of the left rear wheel speed signal, forces the ABS, EBD, ESC, TCS, and Automatic Emergency Braking (AEB) systems into a degraded mode, and limits the energy recovery system. In extreme cases, it causes uneven brake force distribution or vehicle skidding.
Causes
— Wheel speed sensor internal coil open or short circuit: Prolonged exposure to high temperatures and vibration can cause the internal copper winding to break from thermal fatigue or damage the insulation layer, creating an inter-turn short circuit. This manifests as a resistance value outside the standard range (typically 1.0kΩ-2.0kΩ for BYD models).— Wiring harness and connector faults: The chassis wiring harness may rub against the body bracket over bumps, damaging the outer insulation and causing an open circuit or intermittent poor contact. Aging connector seals allow water ingress, causing pin oxidation and corrosion (especially common after water wading or in high-humidity environments) and interrupting signal transmission.— Abnormal sensor installation gap or damaged tone wheel (reluctor ring): Loose sensor mounting bolts cause an excessive air gap (standard gap is typically 0.3-1.0 mm). Metal shavings or mud on the tone wheel teeth, tone wheel deformation, or missing teeth cause insufficient signal amplitude, resulting in a false circuit fault.+2 more →
Actions
— Initial Inspection and Verification: Use VDS or a dedicated diagnostic tool to read the complete fault code stream and confirm if C1206 is a current fault (Active). Check for other wheel speed sensor or high-voltage system fault codes. Raise the vehicle and visually inspect the left rear wheel speed sensor and wiring harness for physical damage, signs of water ingress, or loose installation.— Sensor resistance measurement: Disconnect the left rear wheel speed sensor connector and use a multimeter to measure the resistance between the two sensor terminals. The standard value is 1.0kΩ-2.0kΩ (at 20℃). Infinite resistance indicates an open circuit. Resistance near 0Ω indicates a short circuit. Replace the sensor if the resistance deviates significantly from the standard value. Measure the insulation resistance between the sensor and the vehicle body ground. The resistance must exceed 10MΩ; otherwise, a short to ground exists.+4 more →
C1207›
DTC C1207 indicates the torque sensor signal change rate in the Electric Power Steering (EPS) system exceeds the normal threshold. This sensor monitors the magnitude and direction of torque the driver applies to the steering wheel, and steering angle changes. When the sensor signal experiences sudden changes, drift, intermittent interruption, or a change gradient exceeding the calibrated limit, the EPS control unit cannot accurately calculate the required steering assist and triggers fail-safe mode. This fault causes a sudden loss of steering assist, heavy steering, or intermittent assist. In extreme cases, steering wheel binding may occur, severely compromising driving safety. This fault typically illuminates the EPS warning light and may limit vehicle speed.
Causes
— Torque sensor internal damage, aging, or signal drift— Torque sensor 8-pin black connector loose, backed-out terminal, oxidized, or poor contact— Sensor wiring harness short circuit, open circuit, chafing, or electromagnetic interference+3 more →
Actions
— Use the dedicated diagnostic tool to read the fault code and record freeze frame data. Check for related fault codes such as C1B0E00 and C106600.— Check the torque sensor (black 8Pin) connector for a secure connection. Inspect the terminals for backing out, oxidation, corrosion, or bending.+5 more →
C120700›
DTC C120700 indicates the hydraulic pump motor inside the IPB (Integrated Power Brake) fails to return to its initial mechanical position (Home Position) within the specified time (typically 200-500 ms) after completing brake boost pressure build-up or an ABS/ESC control action. This fault stems from a malfunction in the motor mechanical return mechanism, Hall position sensor signal feedback, or ECU closed-loop control logic. Upon setting this DTC, the IPB enters Limp Home Mode, resulting in a stiff brake pedal and reduced brake assist. The system disables ABS/ESC active intervention and retains only basic hydraulic braking, severely compromising driving safety.
Causes
— Excessive carbon brush wear or a burnt commutator in the IPB electro-hydraulic module's internal DC motor causes the motor to seize in one position and fail to rotate.— Motor position sensor (usually a dual Hall sensor) signal drift, damage, or connector water ingress and oxidation prevents the ECU from identifying the actual position.— Mechanical binding inside the IPB hydraulic unit, such as piston seal aging and swelling or jamming caused by brake fluid impurities, resulting in excessive motor load.+2 more →
Actions
— Use the VDS2000/3000 diagnostic tool to read all fault codes and freeze frame data. Confirm C120700 is a current fault (Current DTC) and record parameters such as vehicle speed and pedal travel at the time of occurrence.— Visually inspect the IPB assembly exterior and confirm no brake fluid leakage or signs of impact deformation. Inspect wiring harness connectors C1 and C2 for backed-out pins, oxidation, or water ingress, and measure the clip retaining force.+5 more →
C2A1700›
DTC C2A1700 indicates the pressure compensation value in the IPB (Intelligent Power Brake) internal hydraulic circuit exceeds the normal ECU-calibrated threshold. Specifically, during pressure holding or build-up in the L1 hydraulic circuit (master cylinder primary circuit or a specific wheel cylinder circuit), the compensation frequency or amount the system requires to maintain target pressure constantly exceeds normal values. Delayed pressure build-up or pressure fluctuations usually accompany this condition. The ECU triggers this fault upon detecting abnormal hydraulic system compressibility (e.g., air ingress) or an internal leak, which forces the system to overwork to maintain pressure. This represents a self-check anomaly within the IPB electro-hydraulic control module. A persistent fault can cause abnormal brake pedal travel, restrict ABS/ESC functions, or disable Automatic Emergency Braking (AEB), posing a driving safety hazard.
Causes
— Air in the brake hydraulic system: Incomplete bleeding after replacing brake fluid or repairing brake lines, or poor sealing at line connections drawing in air. This increases hydraulic compressibility and causes the IPB motor to frequently compensate for pressure.— IPB electro-hydraulic module internal pressure sensor fault: L1 circuit pressure sensor signal drift or failure sends incorrect pressure values to the ECU, causing the system to falsely detect an overcompensation state.— Brake fluid contamination or deterioration: Excessive water content (>3%) or impurities in the brake fluid cause valve body binding and seal swelling, compromising normal hydraulic circuit sealing.+2 more →
Actions
— Use the VDS2000/Launch X431 diagnostic tool to read the complete fault codes, verify if C2A1700 is a current fault (Active), and read the Freeze Frame data to record vehicle speed, pressure value, and pedal travel when the fault occurred.— Check if the brake fluid reservoir level is between MIN and MAX. Check the brake fluid color and moisture content using a brake fluid moisture tester. If the moisture content is >2.5% or the color is cloudy, replace with DOT4 low-viscosity brake fluid.+5 more →
C1208›
On BYD E Series and Yuan Series models, DTC C1208 indicates the left rear wheel speed sensor (RLWSS) signal voltage to the ABS/ESP control module is 0V. The control module detects no wheel speed pulse signal for over 100ms, indicating an open circuit, a short to ground, or a failed sensor. The wheel speed signal is a core input parameter for the Anti-lock Braking System (ABS), Electronic Brakeforce Distribution (EBD), Traction Control System (TCS), and Electronic Stability Control (ESC). A missing signal forces these safety systems into fail-safe mode (limp mode), halts their operation, and illuminates multiple warning lights. In generic OBD-II definitions for Bosch ABS systems, C1208 typically indicates "Inlet Valve Coil Rear Circuit Short To Battery". However, some BYD battery electric vehicles redefine this code as a left rear wheel speed sensor signal fault. Consult the vehicle-specific workshop manual during repair.
Causes
— Left rear wheel speed sensor internal coil open circuit or damaged (abnormal resistance; normal: 1.0-1.5kΩ)— Sensor wiring harness wear, breakage, or short to ground in the suspension travel area, especially after driving on rough roads.— Aged sensor connector seal allows moisture intrusion and pin oxidation, causing poor contact or signal interruption.+2 more →
Actions
— Connect the VDS or Launch diagnostic tool. Read and confirm DTC C1208 and freeze frame data. Verify if the left rear wheel speed remains at 0 km/h, and check for accompanying fault codes such as C1209 (right rear).— Raise the vehicle. Visually inspect the left rear wheel speed sensor installation and wiring harness routing. Closely inspect the wiring harness sleeve near the shock absorber and body pass-through hole for wear and exposed wires.+5 more →
C1209›
BYD DTC C1209 indicates the ABS system detected an electrical fault in the right rear wheel speed sensor (RR Wheel Speed Sensor) circuit, specifically an open circuit, short to ground, or short to power in the signal line. In new energy vehicles, the wheel speed signal not only controls ABS/ESC braking but also directly affects the motor regenerative braking strategy, driving range calculation, and automatic emergency braking (AEB) function. This fault causes a lost or abnormal right rear wheel speed signal, forcing the ABS into fail-safe mode. This disables anti-lock braking, traction control, and vehicle stability functions, and may trigger regenerative braking derating, creating a safety hazard.
Causes
— Open or short circuit in right rear wheel speed sensor internal coil (sensor aging or overheating damage)— Loose wiring harness connector, backed-out terminals, or seal failure causing water ingress and corrosion (common after chassis water exposure)— Sensor wiring harness insulation worn through, shorted to body ground, or broken signal wire.+2 more →
Actions
— Read freeze frame data using the diagnostic tool. Verify vehicle speed and wheel speed status when the fault occurred to rule out intermittent interference.— Raise the vehicle. Visually inspect the right rear wheel speed sensor condition, installation, and wiring harness routing. Check for obvious damage.+6 more →
C121208›
DTC C121208 indicates the variant coding stored in the ESP (Electronic Stability Program) control unit mismatches the actual vehicle hardware configuration or contains corrupted data. In BYD new energy vehicles, the ESP hydraulic modulator assembly (integrated ECU) stores model-specific configuration parameters, including key data such as the vehicle platform (E5/Song/Tang, etc.), powertrain type (BEV/PHEV), tire specifications, brake system version, and steering system type. The ESP module triggers this DTC upon detecting abnormal internal variant coding, such as data loss, a checksum failure, or a mismatch with vehicle information on the CAN bus. This software or data configuration fault typically causes no mechanical damage but forces the ESP system into a degraded mode or causes complete failure, compromising vehicle stability control. In extreme cases, ABS/ESP functions become unavailable, though conventional hydraulic braking generally remains unaffected.
Causes
— Incorrect ESP control unit software version or interrupted flashing process causing data corruption in the variant code area.— Failure to configure vehicle Variant Coding using the dedicated diagnostic tool after replacing the ESP hydraulic modulator assembly.— Vehicle battery disconnection, low voltage, or improper jump-starting caused configuration data loss or checksum failure in the ESP control unit EEPROM.+2 more →
Actions
— Connect the BYD dedicated diagnostic tool (ED400/ED600), access the ABS/ESP system, and read the complete fault codes and freeze frame data. Confirm if C121208 appears alone or alongside other communication or hardware fault codes.— Check the ESP control unit software version. Compare it against the BYD technical bulletin to confirm if it is a known defective version. Download the latest software package if necessary.+4 more →
C12F909›
DTC C12F909 indicates a blockage or abnormal flow in the internal hydraulic circuit of the IPB (Intelligent Integrated Braking) system. The IPB system integrates the traditional vacuum booster with the ESP and uses a motor-driven hydraulic unit to provide brake boost. The ECU sets this fault when it detects an abnormal pressure difference between the master cylinder and the wheel cylinders, hydraulic pump current exceeding the threshold, or solenoid valve flow deviating from the calibrated value. Potential causes include a blocked brake fluid passage, a sticking solenoid valve, hydraulic pump wear, or internal seal failure. When this fault occurs, the IPB enters a degraded mode that retains basic hydraulic braking but disables energy recovery and automatic emergency braking. Extreme cases may cause a hard brake pedal or increased braking distance.
Causes
— Brake fluid contamination or crystallization: Prolonged failure to replace brake fluid causes excessive moisture content (>3%), oxidizing the aluminum valve body or swelling the sealing ring, resulting in a stuck valve spool.— Internal fault in the IPB electro-hydraulic module: metal debris jams the integrated solenoid valves (IN/OUT valves), or DC motor-driven plunger pump wear causes pressure build-up failure.— Physical blockage in the hydraulic line: Brake hose inner wall delamination, wheel cylinder corrosion, or failure to clean the lines during brake fluid replacement caused contaminants to enter the IPB master cylinder.+2 more →
Actions
— Connect the VDS diagnostic tool to read all fault codes, verify if C12F909 is active, and check the Master Cylinder Pressure and Motor Current in the freeze frame data.— Check the brake fluid reservoir level and condition: inspect the brake fluid for cloudiness, darkening, or sediment. Test the fluid using a brake fluid moisture tester. If the moisture content is >3% or the fluid has deteriorated, replace all fluid with DOT4 brake fluid.+4 more →
C2A2000›
DTC C2A2000 indicates that during pressure compensation, IPB (Intelligent Integrated Braking System) hydraulic Circuit C detects a compensation amount exceeding the internal ECU threshold (typically 15–20% above the rated compensation amount). In the BYD One-Box brake-by-wire architecture, "Circuit C" specifically refers to the master cylinder pressure compensation circuit or the high-pressure accumulator maintenance circuit. When the system attempts to maintain or build brake pressure, the ECU logs excessive compensation if it detects an excessively long motor-driven hydraulic pump compensation time, an abnormally high compensation frequency, or a compensation pressure gradient outside the calibrated range. This typically indicates an internal hydraulic circuit leak (poor solenoid valve sealing), abnormal brake fluid compressibility (air ingress or contamination), pressure sensor feedback drift, or reduced hydraulic pump volumetric efficiency. This fault triggers the braking system to enter a degraded mode (backup braking mode), limits ABS/ESC functions, and may increase brake pedal travel and braking distance. This is a Level 2 fault affecting driving safety.
Causes
— Aged, deformed, or binding internal solenoid valve seal in the IPB electro-hydraulic control module causes high-pressure fluid to leak internally from circuit C to the low-pressure side, forcing the system to continuously compensate for pressure.— Severely contaminated brake fluid (water content >3% or containing impurities) causes valve body sealing surface corrosion and poor lubrication, increasing internal leakage.— Signal drift or intermittent open circuit at the Circuit C pressure sensor (master cylinder pressure sensor) sends a false low-pressure signal to the ECU, causing the system to misjudge and continuously increase pressure to compensate.+2 more →
Actions
— Use VDS2000 or a dedicated BYD diagnostic tool to read the complete DTC list. Check for accompanying C2A1700 (hydraulic circuit overcompensation), C2A1F00 (circuit A overcompensation), or pressure sensor fault codes, and analyze the fault correlation.— Check that the brake fluid reservoir level is between MAX and MIN. Use a brake fluid tester to check the brake fluid color and moisture content. If the moisture content is >2.5% or the fluid is dark and cloudy, completely replace it with DOT4 standard brake fluid.+5 more →
P056023›
This DTC indicates the IPB (Intelligent Integrated Braking System) detected an abnormal main power supply and automatically switched to UBB (Ultracapacitor Backup Battery) power mode to maintain basic braking functions. Common causes include low voltage in the 12V low-voltage system (<9V), poor contact in the power supply circuit, abnormal DC-DC converter output, or an internal IPB power management fault. In this mode, the system limits or disables advanced functions such as ABS, ESC, and Automatic Emergency Braking, retaining only basic hydraulic braking capability. The brake pedal may feel harder. This Level 2 fault affects driving safety.
Causes
— 12V low-voltage battery aging, depletion, or capacity degradation causes the voltage to fall outside the IPB operating threshold (usually <9V or >16V).— Poor contact in the IPB power supply circuit, including backed-out pins, oxidation, or burn damage at the connectors between the front compartment distribution box and the IPB (GJK01, etc.), or loose ground points (G301/G08).— Abnormal or fluctuating DC-DC converter output voltage (hybrid/battery electric vehicles), causing unstable low-voltage system power supply and failing to meet IPB main power requirements.+2 more →
Actions
— Use the BYD VDS diagnostic tool to read the complete fault codes and freeze frame data. Check the actual supply voltage (Battery_Voltage), backup power supply status, and historical fault records in the IPB data stream.— Check the 12V low-voltage battery status: measure the static voltage (should be ≥12.4V) and the cranking/driving dynamic voltage (should not be <9V). If necessary, perform a battery State of Health (SOH) inspection and a charging test.+4 more →
P056024›
DTC P056024 indicates the IPB (Integrated Power Brake) detects a switch or attempted switch to the UBVR (Unified Backup Voltage Regulator) power supply mode. In the BYD IPB system, the UBVR is the internal backup power management unit. When the main power supply (typically constant 12V power) experiences a voltage drop, instability, or failure, the system triggers a redundant power supply mechanism to maintain critical braking functions. This DTC indicates: 1) abnormal main power supply voltage causing an automatic system switch; 2) a fault in the UBVR switching circuit; 3) an internal power management logic error within the IPB module. This fault may affect functions including ABS, ESC, and Automatic Emergency Braking, risking degraded braking performance.
Causes
— Aging or undercharged low-voltage battery (12V battery) causes a sudden voltage drop during startup or driving, triggering backup mode.— Poor contact, loose connection, or corrosion in the IPB module power supply circuit, causing intermittent interruption of the supply voltage.— DC-DC converter fault (DM-i models) causes unstable high-voltage to low-voltage output, failing to meet IPB operating voltage requirements.+2 more →
Actions
— Use the VDS2000/3000 diagnostic tool to read the complete fault code stream, confirm whether P056024 is a current or history fault, and check the system voltage in the freeze frame data.— Measure the low-voltage battery static voltage (should be ≥12.4V) and dynamic voltage during startup/driving (should stabilize at 13.5-14.5V). Check the battery state of health (SOH). Charge or replace the battery if necessary.+3 more →
P056200›
The BYD IPB (Intelligent Power Brake) system logs DTC P056200 for abnormal supply voltage. This code is a manufacturer-specific extension of P0562. The fault indicates the IPB control module detects the 12V system voltage remaining below the normal operating threshold (typically 9.5V-10V, depending on the software version). Because the IPB system uses electro-hydraulic servo braking technology, its motor pump, solenoid valves, and ECU require highly stable voltage. Insufficient voltage causes key safety functions, including the Anti-lock Braking System (ABS), Electronic Stability Control (ESC), and Autonomous Emergency Braking (AEB), to fail or degrade. In DM-i hybrid models, this fault typically relates to an abnormal DC-DC converter (which supplies the 12V system from the high-voltage battery), rather than a traditional alternator failure. This is a safety-critical fault. When triggered, the IPB enters degraded mode and illuminates multiple system warning lights on the instrument cluster.
Causes
— 12V low-voltage battery is aged, discharged, or has increased internal resistance, and cannot maintain stable IPB voltage under high-load conditions (especially during automatic emergency braking or frequent braking).— DC-DC converter fault or low output voltage preventing the high-voltage system from properly charging the 12V battery (specific to new energy vehicles; output must remain at 13.8V-14.5V).— Poor connection in the IPB module power supply circuit, oxidized fuse holder, or burnt relay contacts, causing excessive voltage drop under high-current operating conditions.+2 more →
Actions
— Use the VDS2000/3000 diagnostic tool to read the complete fault codes and freeze frame data. Specifically record the system voltage value, vehicle speed, and brake pedal status when the fault occurred. Confirm whether the fault is persistent or intermittent.— Measure the 12V battery static voltage (should be ≥12.4V) and dynamic load voltage (≥11.5V with headlights and air conditioning on). Use a battery tester to measure the CCA value and internal resistance to determine the battery state of health. Replace the battery if SOH < 70%.+5 more →
P056216›
P056216 is a BYD IPB (Intelligent Power Brake) extended fault code. It indicates the IPB control module detects its supply voltage remaining continuously below the internal threshold (typically 9V-10V; normal operating voltage is 12V±0.5V). As the core brake-by-wire component, the IPB provides electro-hydraulic brake assist, coordinates energy recovery, and controls ESC and ABS functions. Insufficient supply voltage reduces brake assist motor torque, causing a stiff brake pedal and extended braking distances. This condition can also degrade or deactivate ESC and ABS functions, severely compromising driving safety. This fault code typically triggers the IPB warning light, the ABS warning light, and a "Please check the braking system" message.
Causes
— Low-voltage battery aging or depletion: The 12V battery in BYD hybrid/EV models (typically AGM or EFB) reaches the end of its service life or deeply discharges, causing voltage to drop below 9V during cold starts or high electrical loads.— Poor contact in the IPB power supply circuit: Backed-out terminals or loose connections at the power supply connector from the front compartment power distribution box to the IPB module (usually located near the bulkhead), or fuse holder oxidation increasing contact resistance and causing a voltage drop.— Front compartment power distribution box internal fault: Burnt relay contacts or a broken internal copper busbar inside the distribution box causes unstable output voltage at the IPB power supply terminal.+2 more →
Actions
— Fault Confirmation and Freeze Frame Analysis: Use VDS or a dedicated diagnostic tool to read the fault code. Review the freeze frame data for the specific voltage value when the fault occurred (e.g., Battery Voltage: 8.2V). Verify vehicle speed, mileage, and other conditions at the time of the fault to determine if the issue is a static battery discharge or a dynamic power supply fault.— Low-voltage battery condition check: Measure the battery static voltage (must be ≥12.4V). Perform an internal resistance test (CCA value must be ≥70% of the rated value). Check the battery terminals for oxidation or looseness. If the voltage is below 12V or the internal resistance is too high, replace the battery with a genuine AGM battery first.+6 more →
P056300›
DTC P056300 indicates the IPB (Intelligent Power Brake) ECU detects its 12V supply voltage exceeds the system-calibrated safety threshold (typically 16V-18V, depending on vehicle calibration). In BYD DM-i and other new energy vehicles, the IPB system integrates electro-hydraulic brake assist, ESC, ABS, and automatic emergency braking. This fault means the IPB module detects an abnormally high input voltage, which can damage internal solenoid valve coils, motor drive circuits, or sensors. As a result, the system stores the fault code and may enter a degraded protection mode, limiting or disabling ESC/ABS functions. This causes a hard brake pedal and increased braking distance, severely compromising driving safety. Distinguish this code from engine management system DTC P0563: DTC P056300 applies specifically to the IPB system. Typical causes include abnormal DC-DC converter output, IPB internal voltage monitoring circuit faults, or poor circuit grounding.
Causes
— DC-DC converter voltage regulation failure: On DM-i models, the DC-DC converter converts the high-voltage battery output to 12V low voltage. If the internal regulation circuit fails, the output voltage may exceed 15V or even rise above 16V, causing the IPB to report an overvoltage fault.— Internal fault in the IPB electro-hydraulic module: The voltage monitoring circuit (A/D converter) inside the IPB ECU drifts or fails, falsely reporting excessively high voltage while the actual measured external voltage is normal.— Abnormal contact resistance in the power supply circuit: Loose, oxidized, or poorly contacting IPB power wiring harness connectors (such as plugs A03 and B02), or corroded or insufficiently torqued ground points (G101, G102, etc.) cause the reference ground potential to drift and the ECU to detect a relative voltage increase.+2 more →
Actions
— Read freeze frame data: Use the VDS2000 or Launch X-431 diagnostic tool to read the DTC freeze frame. Record the specific voltage value (Voltage_Battery_Value), vehicle speed, time, and system status when the fault occurred to determine whether the fault is continuous or intermittent.— Measure high and low-voltage system voltages: With the vehicle in the Ready state, measure the voltage across the battery positive and negative terminals using a multimeter (normal: 13.5-14.5 V). Simultaneously read the actual IPB supply voltage (IPB_Voltage) in the VDS data stream. Compare the two values to check for circuit voltage drop or monitoring errors.+3 more →
P060400›
DTC P060400 indicates a read/write checksum error in the RAM (Random Access Memory) of the IPB (Integrated Power Brake) control unit. This fault represents an ECU internal memory integrity self-test failure, indicating the IPB module detected abnormal data storage or retrieval in its internal working memory during the power-on self-test. The IPB uses RAM as the critical storage medium during operation to store temporary variables, fault counters, system status flags, and real-time control parameters. This fault forces the IPB into a degraded mode and may restrict or completely disable the ABS, ESP, Automatic Emergency Braking (AEB), and Electronic Parking Brake (EPB) functions, severely compromising vehicle active safety. Simply clearing the code usually does not resolve this fault; it typically indicates substantial hardware damage or a severe firmware error.
Causes
— Hardware damage or aging of the internal RAM chip in the IPB electro-hydraulic control unit. Semiconductor physical defects, electrostatic breakdown, or long-term thermal cycling stress typically cause memory cell failure.— Abnormal IPB ECU power supply system, including battery voltage fluctuation, unstable ignition power (IGN), or poor ground connection, causing RAM bit flips or data loss during read/write operations.— Defective or outdated IPB control software/firmware with memory management vulnerabilities or an overly sensitive RAM self-check algorithm, causing false faults or an actual memory leak that triggers hardware protection.+2 more →
Actions
— Connect the BYD VDS2000/3000 diagnostic tool to the vehicle. Read the complete fault code stream to confirm if P060400 is present and is a current fault (Active). Record environmental parameters, such as voltage and temperature, from the Freeze Frame data.— Execute the 'Clear DTCs' operation, perform an ignition cycle (OFF-ON-OFF), and observe if the fault code immediately reappears. If the fault is intermittent, check the IPB supply voltage (constant B+ should be 12.5-14.5V, IGN power supply stable) and ground resistance (<0.5Ω). Monitor for voltage drops using an oscilloscope.+3 more →
P060500›
DTC P060500 indicates a self-check error in the read-only memory (ROM/Flash) inside the Intelligent Power Brake (IPB) electro-hydraulic control module. This internal control module fault means the IPB ECU detected a checksum error, data corruption, or physical hardware fault during the start-up self-check. This affects the non-volatile memory (typically Flash ROM or EEPROM) storing the brake control program, calibration data, and fault information. The IPB is the core component of the BYD One Box brake-by-wire system. It integrates conventional ABS, ESC (Electronic Stability Control), EPB (Electronic Parking Brake), Automatic Emergency Braking (AEB), and energy recovery functions. A ROM error forces the IPB system into a safety fallback mode (limp home). This mode may fully or partially disable ESC, AEB, and EPB functions, retaining only basic hydraulic braking capability and severely compromising driving safety. Common causes include software corruption, hardware defects, abnormal power loss, electromagnetic interference, or physical memory damage from prolonged high-temperature exposure.
Causes
— IPB electro-hydraulic module internal software corruption, program crash, or checksum verification failure (e.g., interrupted software flashing process).— IPB control unit hardware fault, such as ROM chip cold solder joint, physical damage, or internal circuit aging.— A discharged 12V low-voltage battery, unstable voltage, or momentary power loss causes the IPB module to reset abnormally and corrupt ROM data.+2 more →
Actions
— Use the VDS2000/VDS3000 dedicated diagnostic tool to read the complete fault codes, freeze frame data, and IPB system status to verify if the fault is continuous.— Check the 12V low-voltage battery voltage (static ≥12.4V, starting ≥11V, charging ≥13.5V) to verify power supply system stability and rule out voltage fluctuations.+6 more →
P060600›
In the BYD IPB (Intelligent Power Brake) system, DTC P060600 indicates a self-check failure of the ECU control processor inside the electro-hydraulic brake module. Specifically, the microcontroller unit (MCU) inside the IPB assembly detects a core component failure during the power-on self-test (POST) or runtime monitoring. This indicates an anomaly in the CPU arithmetic unit, internal RAM/ROM, clock oscillator circuit, power supply monitoring circuit, or watchdog reset circuit. The IPB system integrates critical functions including brake boost, Electronic Stability Control (ESC), Anti-lock Braking System (ABS), and regenerative braking force distribution. Consequently, this fault results in a hard brake pedal (loss of electric brake boost), complete failure of ESC/ABS functions, and disabled Automatic Emergency Braking (AEB). In extreme cases, the fault triggers brake system degradation protection and forces the vehicle into limp mode. This constitutes a hardware-level or low-level software fault; clearing the DTC will not resolve the issue.
Causes
— Abnormal IPB supply voltage: Unstable 12V constant power or IGN power supply, or excessive fuse/relay contact resistance causes internal ECU voltage to drop below 9V or exceed 16V, triggering a processor protection fault.— IPB ECU internal hardware damage: physical damage to the main control chip (e.g., Infineon or Renesas MCU), PCB cold solder joints, stalled crystal oscillator, Flash memory bad blocks, power management IC (PMIC) failure.— Software malfunction: IPB control program infinite loop, memory overflow, watchdog reset failure, or software version defects causing intermittent program crashes (common in early software versions).+2 more →
Actions
— Fault Confirmation and Freeze Frame Analysis: Use VDS2000 or Launch X431 to read all fault codes. Confirm whether P060600 is a current (Active) or historical (Historic) code. Record key freeze frame parameters such as vehicle speed, supply voltage, and temperature. Check for accompanying fault codes such as U0100 (Lost Communication with IPB).— Basic circuit check: Turn off the ignition switch. Measure the voltage between pin 1 (constant power 30) of the IPB module 24-pin connector and body ground (should be 12V ± 0.5V). Measure the voltage at pin 8 (ignition power 15) with the ignition switch in the ON position. Measure the resistance between pins 23/24 (ground) and body ground (should be less than 1Ω). Check the condition of IPB-related fuses, such as F1/23 and F2/11 in the engine compartment fuse box, and the relay contacts.+4 more →
P060700›
DTC P060700 indicates a functional fault in the internal control processor (MCU/ECU) of the IPB (Intelligent Power Brake). This fault stems from a hardware-level or low-level software abnormality, specifically involving a main control chip calculation error, memory checksum failure, watchdog timeout reset, or internal bus communication interruption. As a core braking component on BYD e-Platform 3.0 and DM-i models, the IPB integrates ESP, ABS, EBD, energy recovery, and brake assist functions. This fault causes brake assist failure (hard brake pedal), loss of ESC/ABS functions, and Automatic Emergency Braking (AEB) deactivation. It may also trigger limp-home mode (speed-limited driving). When this fault occurs, the IPB enters a safety protection state and defaults to pure hydraulic braking. This severe fault compromises driving safety.
Causes
— Internal ECU hardware damage in the IPB electro-hydraulic module: cold solder joints on the main control chip (Infineon or NXP series), corrupted memory (Flash/EEPROM) data, or peripheral circuit component failure (capacitors, crystal oscillators), typically resulting from batch hardware defects or long-term vibration.— Power supply system fault: Unstable voltage (below 9V or above 16V) in the IPB power supply circuit (constant power B+, ignition IG1), loose or oxidized ground terminals, or low battery charge causing abnormal processor reset.— Software operation fault: IPB control program version bug (such as early Song PLUS DM-i V1.2) causes excessive CPU load or memory overflow under specific operating conditions (such as frequent energy recovery switching + emergency braking).+2 more →
Actions
— Initial diagnostic scan: Use BYD VDS2000/VDS3000 to read all DTCs. Confirm if P060700 is a current fault (Active). Check for accompanying fault codes (e.g., U1000 communication fault, C1234 brake pressure sensor fault). Record freeze frame data (vehicle speed, brake pressure, and voltage values at the time of the fault).— Power supply and ground check: Disconnect the IPB module connector. Measure the voltage at pin 1 (terminal 30, constant power) and pin 2 (terminal 15, ignition power) (standard: 12.6 ± 0.3 V). Check the ground resistance at pins 5-8 (must be less than 1 Ω). Use an oscilloscope to monitor the voltage drop during engine start. Confirm if the voltage falls below 9 V and triggers the fault.+4 more →
P060B00›
DTC P060B00 indicates a performance fault in the A/D (analog-to-digital) conversion control module inside the IPB (Intelligent Power Brake/Integrated Power Brake) system ECU. The IPB ECU uses the A/D converter to acquire real-time analog signals from the brake pedal travel sensor, brake master cylinder pressure sensor, wheel cylinder pressure sensor, motor current sensor, and temperature sensor. It converts these into digital signals for the processor to calculate brake force distribution and regenerative braking coordination. The ECU triggers this DTC if its self-check detects reference voltage drift in the A/D conversion circuit, reduced sampling accuracy, conversion logic errors, or if the internal monitoring circuit detects abnormal A/D conversion timing. This fault forces the braking system into a safety fallback mode (limp mode) and may restrict or disable ABS, ESC, Automatic Emergency Braking (AEB), and parking system functions. This is a brake safety-critical fault.
Causes
— Hardware fault in the IPB ECU internal A/D converter chip, reference voltage source, or signal conditioning circuit (aging, overvoltage breakdown, or cold solder joint)— Abnormal IPB supply voltage (overvoltage, undervoltage, or severe fluctuation in the vehicle 12V power supply system) causes unstable A/D conversion reference voltage Vref.— External sensor wiring short circuit (short to 12V power supply or short to ground) causing A/D input port overload damage or clamping.+2 more →
Actions
— Use VDS2000 or the latest diagnostic tool to read the complete fault code freeze frame. Check for accompanying CXXXXX-series pressure sensor or position sensor fault codes. Record the current IPB software version number and hardware version.— Check the IPB electro-hydraulic module power supply voltage: Measure constant power (+B), ignition power (IG1), and the ground wire (GND). Verify static voltage is 12.0-12.6V, dynamic voltage is at least 10.5V, ground resistance is less than 0.5Ω, and there is no voltage drop or ripple voltage.+4 more →
P060C00›
In the BYD IPB (Integrated Power Brake) system, DTC P060C00 indicates an internal control module main processor performance fault or internal self-test failure. This fault isolates to a calculation error, clock fault, memory checksum failure, or internal bus communication interruption within the core processor (MCU) of the ECU built into the IPB electro-hydraulic module. Because the IPB system integrates key functions including ABS, ESP, EPB, Automatic Emergency Braking (AEB), and energy recovery, this fault can cause brake assist failure, restricted ESC operation, and unavailable AEB, posing serious safety risks. The vehicle typically enters brake system degraded mode (limp mode).
Causes
— Hardware damage or performance degradation of the internal main processor (MCU) in the IPB electro-hydraulic module, commonly involving cold solder joints after prolonged high-temperature exposure or sustained heavy-load operation.— Abnormal IPB module supply voltage. Unstable battery voltage, excessive voltage drop in the power supply circuit, or poor ground connection causes the processor operating voltage to fall below the rated value (outside the 9-16V range).— Corrupted IPB control software, a Flash memory data checksum error, or a defective software version causes the internal monitoring program to trigger fault protection.+2 more →
Actions
— Use the BYD VDS2000/3000 diagnostic tool to access the IPB system. Read all fault codes and freeze frame data. Check for accompanying fault codes such as P060B00 (A/D conversion fault) and C155200 (ECU fault). Record parameters such as vehicle speed, voltage, and temperature when the fault occurred.— Check the IPB electro-hydraulic module power supply: measure the voltage and resistance of Terminal 30 constant power (B+), Terminal 15 ignition switch power (IGN), and the ground wire (GND). Verify the voltage is within 12V±0.5V and the ground resistance is less than 1Ω. Check the fuse and relay status.+4 more →
P229900›
P229900 is a BYD-specific fault code for the IPB (Intelligent Integrated Braking System). It indicates a signal logic mismatch between the brake pedal stroke sensor (BPS) and the accelerator pedal stroke sensor (APS), specifically an abnormal zero-point calibration (failure to return to zero). In the IPB system, these two sensor signals must meet interlock logic: when the vehicle is stationary without pedal application, both sensors must simultaneously read zero; during operation, they must meet "brake priority" or "one-pedal" logic. This fault indicates the IPB-ECU detects a non-zero output from the BPS or APS under expected zero-position conditions, or a mismatch in their signal change rates. This fault triggers a safety protection mechanism, potentially causing regenerative braking failure, false Automatic Emergency Braking (AEB) activation, or limited power output (limp mode), severely compromising driving safety.
Causes
— Brake pedal position sensor (BPS) zero-point drift or internal potentiometer wear causes the sensor to output a non-zero voltage signal with the pedal released (normal reference value is approximately 0.5V).— Accelerator pedal position sensor (APS) main and secondary signal channels (APP1/APP2) synchronization deviation, or lost zero-point calibration data, commonly occurring after disconnecting the battery without performing the reset procedure.— Faulty ECU sampling circuit inside the IPB electro-hydraulic module causing an AD conversion error for the BPS signal, or abnormal software logic evaluation.+2 more →
Actions
— Connect the VDS2000/VDS3000 diagnostic tool, enter the IPB system, and read the freeze frame data. Record the BPS voltage (normal range 0.4-0.6V) and APS percentage (expected <5%) at the time of the fault to determine which sensor deviated from the zero position.— Execute the 'IPB Sensor Zero Point Calibration' function (path: IPB System → Special Functions → Sensor Zero Point Learning). Follow the prompts to complete the zero-position self-learning for the brake and accelerator pedals, and verify the data stream returns to normal.+3 more →
P25C600›
DTC P25C600 indicates a short to ground in the BLM (Brake Load Module) temperature sensor signal wire inside the IPB (Integrated Power Brake). In the BYD Song PLUS DM-i One-Box braking system, the BLM typically refers to the brake motor or brake fluid temperature monitoring unit. When the ECU detects the temperature signal voltage remaining below the set threshold (near 0V), it identifies a signal wire short to vehicle ground. This fault prevents the IPB from accurately monitoring key component temperatures. To prevent system overheating or degraded braking performance, the ECU triggers a safety protection mode, disables or limits electro-hydraulic brake assist, and illuminates the ABS, ESC, and brake system warning lamps. Because this fault affects a core braking safety function, the system classifies it as a Level 3 severe fault.
Causes
— Chassis scraping or vibration wear damaged the insulation on the BLM temperature signal wire in the IPB-to-body wiring harness, shorting it to body metal.— Insulation failure of the IPB assembly internal temperature sensor or a dry solder joint on the PCB causes the signal wire to short to housing ground.— Water ingress or oxidation in engine compartment or chassis connectors (such as the BJG02 or IPB 32-pin connector) causes a short to ground between pins.+2 more →
Actions
— Connect the VDS2000/VDS3000 diagnostic tool, read the complete fault codes and freeze frame data, and confirm P25C600 is a current fault accompanied by an illuminated IPB-related warning lamp. Record environmental data such as vehicle speed and temperature at the time of the fault.— Raise the vehicle and visually inspect the IPB assembly (located on the left side of the front compartment firewall) and wiring harness. Check harness contact points with sharp body edges and verify retaining clips are secure. Inspect for obvious damage, water ingress, or burn marks.+4 more →
U007300›
DTC U007300 indicates a communication failure or Bus-Off condition on the IPB (Intelligent Integrated Braking System / One-Box Integrated Braking System) private CAN bus. As the core control unit of the braking system, the IPB uses the private CAN bus (typically a 500 kbps high-speed CAN) to exchange real-time data with key modules such as the Vehicle Control Unit (VCU), Electronic Stability Control (ESC), Electronic Parking Brake (EPB), and Gateway Module (GWM). This data includes safety-critical information such as wheel speed signals, brake pedal travel, brake force demand, and system status. If the IPB detects its CAN controller has transmitted over 255 consecutive error frames, or detects continuous abnormal dominant or recessive bus levels, a terminating resistor mismatch, or severe signal integrity degradation, it triggers the Bus-Off protection mechanism, stores this DTC, and enters Limp Home mode. The vehicle loses active safety functions such as ABS, ESC, and Automatic Emergency Braking (AEB), retaining only basic hydraulic braking capability. This severe fault compromises driving safety (Severity Level 3).
Causes
— Damage to the internal CAN transceiver (TJA1043 or equivalent chip) in the IPB control module or an abnormal power supply (3.3V/5V reference voltage drift) causes signal levels to deviate from the standard range (CAN-H: 2.5-3.5V, CAN-L: 1.5-2.5V).— Private CAN bus wiring harness physical layer fault: Vibration wear causing a short circuit between CAN-H and CAN-L, a short to ground, or an open circuit in the chassis wiring harness; or connector water ingress, oxidation, pin back-out, or excessive contact resistance (>5Ω), particularly at the 32-pin main IPB connector in the engine compartment.— Gateway controller routing function failure or CAN branch line fault between the IPB and the Gateway, preventing the IPB from establishing effective communication with the vehicle CAN network (Powertrain CAN/Body CAN).+2 more →
Actions
— Fault freeze frame capture: Use the BYD dedicated diagnostic tool (VDS2000/VDS2100) to read the complete DTC snapshot data. Record parameters at the time of the fault, including vehicle speed, SOC, bus load rate, and IPB supply voltage. Check for accompanying related fault codes, such as U012200 (Lost Communication With ESC) and U014100 (Lost Communication With BCM).— Basic circuit check: Check the voltage drop of the IPB module constant power (B+), ignition switch power (IG1/IG2), and ground wires (G101/G102) (should be <0.5V). Check the continuity of fuses FB11 (10A), FB12 (15A), etc., and the contact condition of the fuse sockets to rule out a controller reset caused by momentary power interruption.+5 more →
U010004›
U010004 is an ISO 14229 CAN bus communication fault code. It indicates the ESP (Electronic Stability Program) module detects a data validation error (CRC error), sequence error, or abnormal Data Length Code (DLC) when receiving a CAN data frame from the ECM (Engine Control Module, or the Vehicle Control Unit [VCU] / Motor Control Unit [MCU] in New Energy Vehicles). This compromises data integrity. Unlike U0100 (communication timeout), this fault indicates a physical connection exists but the data content is corrupted. On BYD hybrid and battery electric platforms, this prevents the ESP from obtaining accurate motor torque, speed, or engine operating condition information. This condition can trigger brake system downgrade mode (limiting ABS/ESP functions), disrupt energy recovery and brake coordination control, and in severe cases, cause power interruption or limp mode.
Causes
— CAN bus physical layer fault: CAN-H and CAN-L lines shorted together, open, or shorted to power/ground, compromising signal integrity.— ECM/EMS module internal CAN transceiver damaged: a faulty internal communication chip transmits error frames or corrupts data packets.— ESP module CAN receive circuit fault: ESP-side CAN controller or transceiver is faulty and misinterprets normal data as invalid.+2 more →
Actions
— Read the complete fault codes using the diagnostic tool: confirm if U010004 is a current or history code, check the ECM/VCU and other modules (TCU, BMS) for related communication fault codes, and analyze the freeze frame data recorded when the fault occurred.— Measure CAN bus physical layer parameters: Use a multimeter to measure the voltage to ground for CAN-H (approx. 2.6-2.8 V) and CAN-L (approx. 2.2-2.4 V). Measure the termination resistance (measure across the circuit after disconnecting power; standard value is approx. 60 Ω, 120 Ω for a single module). Use an oscilloscope to check the waveform for distortion, spikes, or abnormal bit width.+4 more →
U01000A›
DTC U01000A indicates the Intelligent Integrated Brake System (IPB) or vehicle network detects an integrity check failure or abnormal data content in Engine Control Module (ECM) data packets during CAN communication. Unlike a simple loss of communication (U0100), this fault indicates a normal physical connection where ECM-transmitted data frames contain CRC errors, data overflows, illegal values, or sequence anomalies. Causes include ECM internal memory (RAM/ROM) faults, program runaway, a damaged CAN transceiver, or strong electromagnetic interference. In the DM-i hybrid architecture, abnormal ECM data prevents the IPB from accurately acquiring engine torque, speed, and operating status. This directly affects the brake energy recovery strategy, ABS/ESP coordinated control, and overall vehicle power distribution, posing a safety hazard.
Causes
— Defective ECM software version or corrupted calibration data causing periodic transmission of incorrect data frames.— Unstable ECM supply voltage (burnt main relay contacts, increased battery internal resistance, poor ground connection), causing abnormal module operation or reset.— Electromagnetic interference, physical damage to the wiring harness, or abnormal terminating resistance on the powertrain CAN bus (PT-CAN) causes data transmission errors.+2 more →
Actions
— Use the BYD VDS diagnostic tool to read the complete fault codes and freeze frame data. Check if U01000D (ECM communication timeout), U010001, or other communication faults accompany this code. Record environmental parameters such as vehicle speed and voltage when the fault occurred.— Check the ECM basic power supply and ground: Measure constant power (B+), ignition switch power (IG), and the main ground point. Verify the voltage is stable at 12V±0.5V and ground resistance is less than 1Ω. Check if the ECM main relay engages normally and inspect the contacts for burning.+4 more →
U01000B›
U01000B is a CAN communication fault code for BYD e-Platform 3.0 models (such as the Seal 6 DM-i and Song PLUS DM-i). This fault code indicates the IPB (Integrated Intelligent Braking System) detects a data integrity error when receiving the 0x240 message from the VCU (Vehicle Control Unit). Specific errors include incorrect message byte length, CRC (Cyclic Redundancy Check) errors, non-continuous or abnormal Alive Counter jumps, or key signal values exceeding the valid range. This powertrain CAN network communication fault may limit regenerative braking, cause abnormal electro-hydraulic braking coordination, and in severe cases, trigger the braking system degraded protection mode, compromising driving safety.
Causes
— Poor contact, short circuit, or open circuit in the powertrain CAN bus line between the VCU and IPB, causing abnormal data frame transmission.— Outdated VCU software or an internal algorithm defect causes incorrect CRC calculation or abnormal counter logic in the generated 0x240 message.— Internal communication chip fault or software parsing error in the IPB receiving module, causing a false data corruption report.+2 more →
Actions
— Use the BYD VDS 1000/2000 diagnostic tool to perform a full system scan. Record the U01000B freeze frame data (including vehicle speed, voltage, and CAN signal status at the time of the fault) and accompanying fault codes.— Check the power supply circuits (constant B+, ignition IG) and ground points G103/G104 for the VCU (located in the front compartment or cabin) and the IPB (located in the motor compartment near the brake master cylinder). Verify the voltage is stable at 12V±0.5V and ground resistance is less than 1Ω.+6 more →
U01000C›
DTC U01000C indicates a power CAN bus communication timeout between the IPB (Integrated Intelligent Braking System) and the Front Motor Controller (FMC). Timeout 6 specifically refers to the loss of a specific cyclic message, typically the 0x240 network management message. As the main braking control unit, the IPB requires real-time front motor speed, torque, and temperature data to coordinate the seamless transition between motor regenerative braking and hydraulic mechanical braking. If the communication interruption exceeds the set threshold (typically >100ms), the IPB triggers this fault and enters a degraded mode. This mode disables regenerative braking and may restrict ESC/ABS to basic functions; however, conventional hydraulic braking remains available. This network communication fault may result from an offline Front Motor Controller, a CAN bus physical layer anomaly, or an IPB receiver module failure.
Causes
— Front motor controller (MCU) low-voltage power supply fault. Causes include: blown 12V constant power fuse (e.g., F1/14), missing IGN wake-up signal, or open high-voltage interlock circuit causing the controller to enter sleep mode.— CAN bus physical layer fault: CAN-H and CAN-L lines between the IPB and front motor shorted together, shorted to ground/power, or open; or terminating resistor drift (standard value 60Ω, measured value outside the 40-80Ω range).— Front motor controller internal fault: Damaged CAN transceiver chip, main control MCU crash, or software infinite loop prevents periodic transmission of the 0x240 status message.+2 more →
Actions
— Initial diagnostic scan: Use VDS2000/3000 to read the complete DTC snapshot. Confirm whether U01000C is a current or historical fault. Check for accompanying network faults, such as U0101 (TCU communication fault). Record the vehicle speed and bus load rate at the time of the fault.— Power supply system troubleshooting: Measure voltage at pin BXX-XX (constant power BAT) on the front motor controller low-voltage connector; voltage must be 12V±0.5V. During startup, voltage at pin BXX-XX (IGN wake-up) must be >11V. Check continuity of fuses F1/14, F2/03, etc., and relay engagement status in the engine compartment fuse box.+4 more →
U01000D›
U01000D is a BYD-specific subtype of ISO standard communication fault code U0100 (suffix 0D is a hexadecimal identifier). It indicates a failure to receive a valid data frame via the CAN network between the IPB (Intelligent Power Brake system) and the ECM (Engine Control Module) within a specific cycle (typically 100ms-500ms, depending on calibration). This triggers the timeout counter to reach its threshold (6th timeout). In the DM-i hybrid architecture, the IPB must retrieve real-time engine torque, engine speed, and brake energy regeneration request status from the ECM. Communication interruption degrades the brake energy regeneration function, disables ESC coordinated control, and in severe cases, triggers Limp Home mode. The basic hydraulic braking function remains available.
Causes
— Intermittent open circuit, short circuit, or short to ground/power in the ECM or IPB CAN-H/CAN-L circuits, especially due to damaged wiring harness sheathing in high-temperature areas of the engine compartment.— ECM power supply circuit fault (including constant power B+ and ignition switch power IG1/IG2) or excessive ground circuit resistance (>1Ω), causing intermittent ECM restarts.— CAN bus termination resistance deviation between IPB and ECM (standard value 60Ω, allowable range 58-62Ω), or branch line length exceeding 0.3m causing signal reflection.+2 more →
Actions
— Use the VDS1000 or DiLink diagnostic tool to perform a 'Vehicle Scan', record the U01000D freeze frame data, and confirm the vehicle speed, SOC, and communication status bits at the time of the fault.— Check ECM connector BYD-121PIN (located at the front left of the engine compartment) and the IPB connector (located in front of the engine compartment firewall). Confirm no backed-out pins, oxidation, or signs of water ingress. Apply electronic contact protectant and reconnect.+5 more →
U010104›
U010104 is a powertrain CAN bus communication fault code indicating the ABS (Anti-lock Braking System) control unit cannot establish normal communication with the TCU (Transmission Control Unit / Motor Control Unit) via the CAN bus. Although the BYD E5 pure electric model uses a fixed-ratio reducer instead of a conventional transmission, the TCU designation typically refers to the drive motor control unit (MCU) or the reducer control module. This fault prevents the ABS system from obtaining real-time powertrain data, such as motor speed, torque output, and gear position status. This data loss restricts regenerative braking and disrupts ESC (Electronic Stability Control) coordination. Severe cases may trigger limp mode or cut power output. Information exchange between the ABS and TCU is critical to vehicle dynamic control; repair this fault immediately.
Causes
— TCU power supply system fault: Blown TCU power fuse (usually 15A or 20A), open power supply circuit, or poor contact, preventing normal TCU operation.— CAN bus physical layer fault: Powertrain CAN-H or CAN-L line shorted to ground or power, wiring harness open circuit, abnormal terminating resistance (standard value: 60Ω), or poor contact at branch nodes.— TCU control unit internal fault: damaged internal CAN transceiver, main control chip failure, software crash, or outdated software version causing a communication protocol mismatch.+2 more →
Actions
— Fault Confirmation and Freeze Frame Reading: Use a VDS2000 or Launch X431 diagnostic tool to read all fault codes and freeze frame data. Confirm if U010104 is a current fault. Check for accompanying communication fault codes (such as U0100 or U0121). Record parameters such as vehicle speed and voltage at the time of the fault.— TCU power supply and ground check: Disconnect the TCU connector and measure the voltage between the TCU power supply pin (constant +B) and body ground. Standard value: 10-16V (20-32V for 24V systems). Check the continuity of the TCU ground wiring harness (resistance < 1Ω) and verify the power supply fuse status.+5 more →
U010108›
U010108 is a BYD-specific extended fault code and a subclass of the U0101 communication fault series. It indicates the ABS (Anti-lock Braking System) control unit detects a data integrity check failure when receiving CAN messages from the TCU (Transmission/Drive Control Unit; in E5 battery electric vehicles, this typically refers to the motor controller MCU or transmission management unit). Although the ABS module receives the CAN signal from the TCU, the message contains a CRC checksum error, a non-continuous Live Counter, a byte length violating protocol specifications, or out-of-range key signal values (such as motor speed, output torque, or gear status). This prevents the ABS from accurately obtaining real-time powertrain parameters, affecting regenerative braking and ESC (Electronic Stability Control) coordination. In severe cases, the system triggers Limp Home mode and limits motor power to ensure safety.
Causes
— Internal software defect in the TCU/MCU control unit or hardware clock drift causing abnormal timing or checksum values in transmitted CAN messages.— CAN bus physical layer interference (short circuit due to wiring harness wear, electromagnetic interference, or abnormal terminating resistance), resulting in data frame bit errors or loss during transmission.— TCU supply voltage fluctuations (low auxiliary battery charge, unstable DC-DC output) or excessive ground circuit resistance causes CAN signal level offset and sampling errors at the receiving end.+2 more →
Actions
— Use the VDS1000 diagnostic tool to perform a full vehicle scan and confirm if U010108 is a current active fault. Check for accompanying U0101 (Lost Communication With TCU) or U0073 (CAN Bus Off) codes, and record the freeze frame data.— Check the power supply voltage (+B, IG1) and ground wires of the TCU (located in the front compartment) and the ABS control unit (located near the engine compartment firewall). The voltage must be 12V ± 0.5V, and the ground resistance must be less than 1Ω. On E5 models, inspect the mating connector between the front compartment wiring harness and the body wiring harness for oxidation.+3 more →
U011187›
DTC U011187 indicates the Body Control Computer (BCC) failed to receive CAN message ID 0x44A (hexadecimal) from the Battery Management System (BMS) via the air conditioning controller (acting as a gateway/relay node). This battery status information frame typically contains key thermal management parameters, including total battery voltage, total current, SOC, highest/lowest cell voltage, and temperature. This fault represents a gateway communication interruption between the thermal management sub-network and the body control network. The interruption prevents the BCC from obtaining real-time battery status to coordinate thermal management actuators, such as air conditioning compressor speed, PTC heating, and cooling fans. Consequently, this can cause battery temperature control failure, range estimation deviation, or abnormal coordination between the air conditioning system and battery cooling.
Causes
— Air conditioning controller internal gateway forwarding function failure or software fault prevents correct relay of the BMS 0x44A message.— Poor contact, open circuit, short circuit, or abnormal terminating resistor in the CAN_H/CAN_L wiring harness between the BMS and A/C controller (Powertrain CAN) or between the A/C controller and BCC (Body CAN)— An internal BMS control module fault causes an abnormal 0x44A message transmission cycle or stops transmission.+2 more →
Actions
— Use VDS2000 or the latest diagnostic tool to read all vehicle DTCs. Check for accompanying U-class communication fault clusters (e.g., U0141, U0291). Record freeze frame data and environmental conditions at the time of the fault.— Check the power supply voltage to the BMS, air conditioning controller, and BCC (12V/B+ must be greater than 11V), and verify the ground points are secure. Measure the ground resistance; it must be less than 1Ω. Inspect the body control-related ground wires for burning or looseness.+4 more →
U011887›
DTC U011887 is a U-category CAN bus communication fault indicating a subnet communication interruption between the AC Controller and the Battery Cooling Controller (BCC). In the BYD Qin EV300 architecture, the air conditioning system uses an independent CAN subnet. The BCC manages the battery pack liquid cooling system, controlling components such as the battery cooling water pump and the battery cooler three-way valve. The AC Controller requires real-time cooling demand and status information from the BCC to coordinate refrigerant distribution between the cabin air conditioning and the battery cooling system. The AC Controller triggers this DTC when it fails to receive valid CAN messages from the BCC for a continuous period (typically multiple message cycles of 100–200 ms). These messages include IDs containing signals for battery cooling requests, temperature, and flow rate. This fault forces the thermal management system into a degraded mode. This limits battery cooling capacity, which may reduce fast charging speeds or cause battery overheating. The air conditioning system may also forcibly restrict cooling output or enter limp-home protection mode. However, this fault typically does not cause a complete vehicle breakdown.
Causes
— A/C sub-network CAN wiring harness fault: CAN-H or CAN-L circuit open, short to ground, short to power, or poor connection due to the high-temperature, high-humidity environment in the front compartment, especially wiring harness corrosion caused by wading or mud and water ingress near the right front wheel arch (common BCC mounting location).— BCC power supply or ground fault: blown BCC constant power (+B) fuse, poor relay contact, or loose or oxidized ground point (G point), causing the controller to intermittently lose power or reset, preventing CAN communication.— Poor connector contact: An aged sealing ring on the BCC 24-pin (or 32-pin) connector causes terminal back-out, oxidation, and water ingress corrosion on the pins (especially CAN communication pins), interrupting signal transmission.+2 more →
Actions
— Freeze frame analysis: Use VDS2000/3000 or a BYD dedicated diagnostic tool to read the fault freeze frame. Confirm the vehicle speed, ambient temperature, and air conditioning status at the time of the fault to determine if it is an intermittent fault (e.g., on rough roads or after driving through water).— Basic power supply check: Disconnect the BCC connector and measure the voltage at the BCC power supply pins (usually Pins 1/2 are +B, Pins 3/4 are ground). The voltage should be 12V±0.5V, and the ground resistance should be less than 1Ω. Inspect the BCC-related fuse in the front compartment power distribution box (e.g., F1/16 15A) for a blown element or poor contact.+5 more →
U012604›
DTC U012604 indicates a CAN bus communication interruption or data frame reception timeout between the Steering Angle Sensor (SAS) and the ABS/ESP control unit. From a network communication perspective, the ESP module logs this fault if it fails to detect a valid CAN message (whose ID typically contains steering angle, angular velocity, and fault status signals) from the SAS within the preset monitoring period (typically 100-200ms). The SAS is the core sensor of the vehicle stability control (ESC/ESP) system, providing driver steering intent information. Communication failure prevents the ESP from calculating the yaw moment correction, triggering system downgrade protection. ESC/ABS functions may completely deactivate or enter limp mode. This failure simultaneously affects ADAS functions relying on the steering angle signal, such as the Electronic Parking Brake (EPB), Automatic Emergency Braking (AEB), and lane keeping. This powertrain CAN (PT-CAN) or chassis CAN (Ch-CAN) network communication fault is typically sporadic and intermittent. Loose wiring connections, electromagnetic interference, or intermittent module lockups commonly cause this issue.
Causes
— Abnormal SAS module power supply or ground: Includes a blown fuse, excessive voltage drop in the power supply circuit (less than 9V or greater than 16V), or oxidized ground terminals causing excessive contact resistance (greater than 1Ω), which causes intermittent module resets or unstable CAN transceiver operation.— CAN bus physical layer fault: CAN-H and CAN-L line open or short circuit (shorted together, to power, or to ground), poor connection or backed-out pin at a wiring harness junction (such as the instrument panel joint connector), or terminating resistor drift (normal: 60 Ω; abnormal: below 40 Ω or above 80 Ω).— Steering wheel angle sensor module fault: internal MCU crash, CAN transceiver chip damage, sensor element failure (photoelectric encoder or magnetoresistive element fault), or software version defect causing periodic communication interruption.+2 more →
Actions
— Fault Confirmation and Freeze Frame Analysis: Use VDS2000/Launch X431 to read all fault codes. Confirm whether U012604 is a Current or History code. Record freeze frame data, including vehicle speed, steering angle, and power supply voltage. Clear the fault codes and road test the vehicle to reproduce the fault.— SAS module power and ground measurement: Disconnect the battery negative terminal. Unplug the SAS module connector (located below the steering column). Measure the voltage to ground at PIN1 (constant power B+) and PIN2 (ignition power IGN) (should be 12V ± 0.5V). Measure the resistance to ground at PIN3 (ground) (should be less than 0.5Ω). Check the connector for water ingress or oxidation.+4 more →
U012608›
DTC U012608 indicates the ABS/ESP control unit receives an abnormal CAN bus data frame or detects a checksum failure from the Steering Angle Sensor (SAS). This fault is a communication data integrity error, not a simple signal timeout. The ABS module flags "corrupted data" when it detects a CRC error in the SAS data packet, an abnormal Data Length Code (DLC), or a signal value outside the physically reasonable range. This fault causes the vehicle's Electronic Stability Program (ESP), Traction Control System (TCS), and Automatic Emergency Braking (AEB) to enter a degraded mode or fail completely. Some models trigger power limitation (limp mode), severely compromising driving safety.
Causes
— Internal damage to the Steering Angle Sensor (SAS) causing incorrect data frame transmission or signal drift.— Sensor wiring harness connector oxidized, loose, or corroded by water ingress (common in flood-damaged or water-exposed vehicles), causing CAN signal transmission interference.— Chassis CAN bus (powertrain CAN) circuit short to ground, short to power, or poor connection affecting data communication quality.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS or EDT) to read all fault codes. Confirm if U012608 is a current or historical fault, and check for accompanying communication fault codes such as U010008 and U014004.— Inspect the appearance of the steering angle sensor below the steering wheel and the connector connection. Check the connector pins for oxidation, backed-out pins, or signs of water ingress. Clean with electrical contact cleaner if necessary.+5 more →
U012E87›
This DTC indicates a data communication interruption between the air conditioning controller (AC ECU) and the electronic fan controller (typically the integrated control module for the condenser fan or radiator fan). In the BYD thermal management system architecture, the AC ECU sends fan speed control commands (based on A/C pressure and coolant temperature) to the electronic fan via the CAN or LIN bus, and receives fan operating status, speed feedback, and fault information. If the communication signal drops continuously for more than the set time threshold (typically 500ms-1s), the system records DTC U012E87. This fault prevents the fan from adjusting speed on demand, potentially reducing A/C cooling efficiency and causing insufficient heat dissipation for the high-voltage system (motor, battery, and power electronics). In extreme cases, the system triggers motor over-temperature protection or limits power output; however, under most operating conditions, the vehicle remains drivable for a short time.
Causes
— Electronic fan wiring harness connector is loose, oxidized, corroded by water ingress, or has backed-out pins, causing poor communication signal contact or an intermittent open circuit.— Electronic fan controller internal PCB damage, burnt power supply chip, CAN transceiver fault, or software crash— Open or short circuit in the CAN/LIN communication line between the A/C controller and fan (including short to ground or power)+2 more →
Actions
— Use the VDS2000/3000 diagnostic tool to read all fault codes and freeze frame data. Verify if U012E87 is a current fault. Check for associated power supply fault codes (e.g., B12C series) or communication fault codes (e.g., U01 series). Record parameters such as vehicle speed and temperature when the fault occurred.— Perform a visual inspection: Open the motor compartment and inspect the electric fan wiring harness connector (usually located above or beside the fan assembly) for looseness, water ingress, mud, sand, or obvious signs of corrosion; check if the relevant high-current fuse (usually 30A-40A) in the fuse box has blown.+4 more →
U014008›
DTC U014008 indicates a CAN data communication integrity check failure between the ABS/ESC control unit and the vehicle gateway controller. Data frames sent by the ABS module to the gateway over the Powertrain CAN bus contain CRC errors, out-of-sequence frames, abnormal Data Length Codes (DLC), or protocol format mismatches. Consequently, the gateway determines the received brake system status data is corrupted. This fault triggers the brake system fail-safe strategy, degrading or completely disabling functions such as ABS, ESC, EBD, and Autonomous Emergency Braking (AEB). Simultaneously, the gateway sends multi-system fault warnings to the instrument cluster, severely compromising driving safety.
Causes
— Internal CAN transceiver chip failure or software checksum algorithm error in the gateway controller prevents it from correctly parsing ABS data frames.— Physical damage (abrasion, crushing) to the Power CAN line between the ABS/ESC control unit and the gateway, water ingress and oxidation in the connector, or excessive contact resistance, compromising signal integrity.— ABS/ESC module software bug (e.g., calibration defect in early E5 versions) or internal CAN controller hardware fault continuously sending incorrectly formatted data frames.+2 more →
Actions
— Use the VDS2000/VDS3000 diagnostic tool to read the complete DTC list. Confirm whether U014008 is a current (Active) or historical (History) fault code, and record freeze frame data parameters such as vehicle speed, voltage, and temperature.— Check the power supply voltage (constant B+, ignition IG1 power) and ground resistance of the gateway controller (on the BYD E5, typically below the left side of the dashboard or near the front compartment power distribution box) and the ABS module. Verify ground resistance is less than 1Ω and voltage is 12-14V.+4 more →
U0146-00›
DTC U0146-00 indicates a Controller Area Network (CAN) communication interruption between the airbag control unit (SRS ECU) and the vehicle gateway module. In BYD Qin series models, the Body Control Module (BCM) typically integrates the gateway, coordinating data exchange among the powertrain CAN, comfort CAN, and chassis CAN. The system triggers this fault when the SRS fails to receive the gateway handshake signal or data frame within the specified cycle (typically 250ms). This forces the airbag system into a degraded mode, preventing normal airbag deployment, seatbelt pretensioning, or high-voltage cutoff activation during a collision. It may also affect the vehicle’s collision signal recording function. This network communication fault does not involve electrical failures within the SRS components themselves, but it directly disables the passive safety system.
Causes
— Gateway module (BCM) power supply circuit fault: Includes poor contact at the constant power (B+), ignition switch power (IG) or ground wire, or a blown fuse, preventing normal gateway operation.— CAN network circuit fault: Open or short circuit in the CAN-H and CAN-L wiring harness between the SRS and gateway, or terminating resistor drift (normal: 60Ω), causing signal transmission failure.— Internal gateway module fault: Damaged BCM internal CAN transceiver, software crash, or lost configuration data prevents forwarding of SRS data frames.+2 more →
Actions
— Full diagnostic scan: Use the VDS2000/VDS3000 diagnostic tool to read all vehicle DTCs. Check for accompanying codes such as U0100 (lost communication with engine) and U0121 (lost communication with ABS) to determine if the issue is a single system fault or a gateway bus failure. Verify the SRS software is the latest version.— Power and ground check: Measure the constant power (B+, should be 12V), ignition power (IG, should be 12V in the ON position), and ground resistance (should be <1Ω) at the gateway module (located below the left side of the dashboard). Check if the SRS-related fuses in the dashboard power distribution box, such as F1/15 and F2/3, are blown.+3 more →
U0146›
DTC U0146 indicates a loss of communication between the airbag control unit (SRS ECU) and the vehicle gateway controller (Gateway Control Module). The gateway acts as the data exchange hub between different vehicle CAN bus networks (such as powertrain CAN, comfort CAN, and chassis CAN) and routes information between control units. When the SRS system cannot communicate with the gateway, the airbag system becomes isolated. It cannot receive critical signals from other systems (such as crash signals, vehicle speed signals, and high-voltage interlock status). Additionally, during a collision, it cannot send commands through the gateway to other systems (such as cutting off the high-voltage power supply, unlocking the doors, and turning on the hazard lights). This may degrade or disable crash protection functions, creating a serious safety hazard.
Causes
— Gateway Controller (GWC) power supply or ground circuit fault causing intermittent or permanent power loss to the gateway.— Physical damage to the CAN bus wiring (chafing, crushing, water ingress) causing a short circuit, open circuit, or excessive contact resistance in CAN-H and CAN-L.— Gateway controller internal hardware fault or outdated software version causing a communication protocol mismatch.+2 more →
Actions
— Perform a full vehicle scan using the VDS2000/VDS1000 diagnostic tool. Record the communication status and fault codes of all modules, and determine whether the communication fault affects a single module or multiple modules.— Check the power supply (constant BATT, ignition IG1) and ground (GND) of the gateway controller (usually located under the dashboard or center tunnel). Measure the voltage; it must be within 12V±0.5V, and ground resistance must be less than 1Ω.+6 more →
U014604›
DTC U014604 indicates a CAN communication timeout between the IPB (Integrated Brake Control System) and the Gateway controller. In BYD new energy vehicles, the gateway acts as the core hub of the vehicle CAN network, coordinating data exchange among the Powertrain, Chassis, and Body networks. The IPB system (one-box brake-by-wire solution) retrieves real-time vehicle status information via the gateway (e.g., motor torque, vehicle speed, regenerative braking requests, and VCU coordination commands) while simultaneously transmitting key data, such as brake pedal travel, wheel speed, and braking status, to other systems. When a communication timeout occurs, the IPB enters a degraded protection mode. This can cause regenerative braking failure, limit Electronic Stability Control (ESC) functionality, and cause Automatic Emergency Braking (AEB) to trigger falsely or fail. In severe cases, the instrument cluster illuminates multiple warning lights, including ABS, ESC, and parking system indicators, compromising driving safety.
Causes
— Gateway or IPB controller power supply/ground fault, including blown fuses, relay failures, connector oxidation, or terminal back-out causing unstable supply voltage.— CAN bus circuit fault, including CAN-H or CAN-L line open circuit, short circuit (to power, to ground, or to each other), excessive contact resistance, or abnormal terminal resistance (standard value: 60Ω±5Ω).— Internal control module fault, including a damaged built-in CAN transceiver chip in the gateway or IPB, control program crash, or incompatible software version.+2 more →
Actions
— Initial diagnosis: Use the dedicated diagnostic tool to read all vehicle fault codes. Record U014604 and any accompanying fault codes (such as U014608, U0120). Check the vehicle for a history of water ingress, modifications, or accident repairs. Visually inspect the relevant connectors.— Power supply system check: Measure the constant power (B+), ignition power (IGN), and ground point voltages at the gateway module (usually located under the center console or integrated into the BCM) and the IPB (located in the engine compartment). Verify the voltages are within 12V±0.5V. Check fuse F2/15 (10A) and related fuses for good contact.+7 more →
U014608›
DTC U014608 indicates a CAN communication data length error between the Intelligent Power Brake (IPB) system and the vehicle gateway. In the UDS diagnostic protocol, U0146 indicates abnormal communication with the Body Control Module (BCM) or gateway. The suffix '08' specifically indicates an invalid data frame length or a Bus Off state. This fault occurs when the data packet length sent by the IPB module mismatches the gateway module reception protocol, or when an abnormal CAN physical layer signal causes a data frame parsing failure. Because the IPB controls brake boost, energy recovery, and Electronic Stability Control (ESC), this fault may limit ABS/ESP functions, cause abnormal brake pedal feel, and disable Automatic Emergency Braking (AEB). Severe cases compromise driving safety. When this fault occurs, the vehicle typically enters a degraded mode, limiting specific driver assistance functions.
Causes
— Internal CAN transceiver fault in the IPB module or software version defect causing the module to transmit abnormal-length data frames.— Gateway controller (Gateway) internal fault; fails to correctly parse brake system data sent by the IPB.— Poor contact, short circuit, or open circuit in the gateway wiring between the brake system CAN bus (powertrain network) and the body CAN bus.+2 more →
Actions
— Use the BYD VDS diagnostic tool to read all fault codes, check for accompanying communication faults such as U0140 and U0121, and record freeze frame data.— Check the IPB module power supply: Measure the voltage at connector K148 pin 1 (constant power) and pin 6 (IGN power); voltage should be 12 ± 0.5 V. Measure the ground resistance at pin 5; resistance should be less than 1 Ω.+5 more →
U014987›
DTC U014987 indicates a communication link interruption between the battery thermal management controller (usually integrated into the Battery Management System (BMS) or a separate thermal management control unit) and the battery thermal circuit electric coolant pump. This pump drives battery coolant circulation and typically uses LIN bus (CAN bus on some models) for digital communication. The controller triggers this fault when it fails to receive pump status feedback signals (such as speed, temperature, or fault status) within a specified period (generally 100-200ms), or when it cannot send control commands (such as target speed requests). This fault forces the battery thermal management system into open-loop control or degraded mode, limiting fast-charging power and power output. Extreme cases may trigger battery high-temperature protection.
Causes
— Electronic water pump power supply circuit fault: Includes a blown 15A/20A fuse, an open power supply circuit, or a poor connection, preventing the water pump control module from operating properly.— LIN/CAN communication circuit fault: short to ground, short to power, open circuit, or excessive contact resistance (>5Ω). Faults typically occur at harness bends near the battery pack or the firewall wiring pass-through.— Electric water pump assembly fault: damaged internal brushless motor drive circuit, seized motor rotor, damaged LIN transceiver chip, or internal overheat protection activated.+2 more →
Actions
— Use the VDS diagnostic tool to read all fault codes. Confirm if U014987 is a current fault, check for accompanying communication fault codes, and view the freeze frame data (record parameters such as battery temperature and requested coolant pump speed at the time of the fault).— Visually inspect the electric water pump condition and installation. Verify there is no coolant leakage, abnormal noise, or mechanical damage to the wiring harness. Specifically inspect the low-voltage connector at the front of the battery pack to verify it is fully locked and free of water ingress.+5 more →
U0155-00›
U0155-00 is a CAN bus communication fault code indicating interrupted data communication between the airbag control unit (SRS ECU) and the instrument cluster. In the BYD CAN network architecture, the SRS module transmits airbag status, system fault information, and collision trigger signals in real time to the instrument cluster via the powertrain CAN or body CAN bus. The SRS sets this fault code if it fails to receive a response message from the instrument cluster within the predetermined cycle (usually 250ms-500ms) or detects a bus physical layer fault. This fault may prevent the instrument panel from normally illuminating the SRS fault warning lamp and, in extreme cases, affects the safety warning function during a collision. It classifies as a Level 2 safety-related fault.
Causes
— Instrument cluster power supply system fault (blown instrument cluster fuse, poor connection in IGN power circuit, open circuit in constant +B power circuit)— CAN bus physical layer fault (CAN-H to CAN-L short, short to ground or power, open circuit, or excessive contact resistance)— Poor module ground (loose, oxidized, or corroded instrument cluster or SRS ground point causing increased signal circuit impedance)+2 more →
Actions
— Use VDS2000 or a dedicated BYD diagnostic tool to perform a full-vehicle DTC scan. Confirm if U0155-00 is the only code present or if other U01XX series communication faults accompany it to determine if it is a single-point fault.— Check the instrument cluster power supply: Measure the voltage at instrument cluster connector terminal 30 (constant +B) and terminal 15 (IGN). Standard value: 12V ± 0.5V. Check the continuity of instrument cluster-related fuses such as FB-02 and FB-22.+6 more →
U0155›
U0155 is an ISO 15031 CAN bus communication fault code. It indicates a CAN communication interruption between the SRS airbag system (or other vehicle control units) and the instrument cluster control unit (IPC/ICU). In BYD New Energy Vehicles (NEVs), the instrument cluster displays vehicle speed and battery level, and also shows airbag status, fault warning lamps, and seat belt reminders. This fault means the SRS module fails to receive a response message from the instrument cluster within 500ms, or the message checksum fails. A physical layer fault in the Powertrain CAN or Body CAN bus can cause this issue, resulting in a blank instrument cluster display, a continuously illuminated airbag warning lamp, and an abnormal odometer display. In extreme cases, this fault affects normal airbag deployment logic during a collision because the system cannot confirm the instrument cluster warning lamp status.
Causes
— Instrument cluster control unit power supply circuit fault (blown fuse, open IGN power circuit) or poor ground connection (loose G201/G202 ground points), preventing normal instrument cluster operation.— CAN bus physical layer fault: short circuit between CAN-H and CAN-L, short to ground or power, or open circuit (commonly at dashboard wiring harness bends or pin back-out at A-pillar connectors X202/X203)— Instrument cluster internal CAN transceiver (TJA1043 or compatible chip) is faulty, or main control MCU crashed and fails to respond to bus requests.+2 more →
Actions
— Use the VDS or ED400 diagnostic tool to read all DTCs. Confirm if U0155 is a current or historical fault and record the freeze frame data (vehicle speed, voltage, etc. at the time of occurrence). Check for accompanying U01xx series communication fault codes (such as lost communication with the BMS or ABS) to determine if the fault isolates to the instrument cluster or indicates a bus failure.— Visually inspect the instrument cluster display for a black, distorted, or frozen screen. Check the instrument panel fuses (F1/14, F2/11, etc., depending on the model). Measure the voltage at pin 1 (B+ constant power), pin 2 (IGN power), and the ground pin of instrument cluster connector X101. Verify the power supply is ≥12V (or low-voltage system ≥12V on high-voltage models) and the ground resistance is <1Ω.+4 more →
U016487›
ISO 15031 defines fault code U0164 as 'Lost Communication With HVAC (Air Conditioning Control Module)'. Sub-code 87 is a BYD-specific identifier indicating the BCC (Battery Cooling Controller/Body Control Computer) failed to receive key CAN messages from the air conditioning controller within a 500ms monitoring cycle: ID 0x1DB (ambient temperature, soft shutdown request) or 0x3CF (cabin compressor speed request, A/C request status). This fault indicates a communication interruption between the HVAC sub-network (HVAC-CAN) and the Powertrain CAN or BMS network. This interruption prevents the thermal management system from coordinating the electric compressor, PTC heater, and battery cooling circuit. The system may trigger thermal management derating protection (power limitation or A/C disabled), but typically does not cause immediate vehicle immobilization.
Causes
— Abnormal HVAC controller power supply: Causes include a blown F1/15 fuse in the dashboard fuse box, burnt terminals, backed out pins or poor connections at the IGN ignition signal wire, or a loose ground wire, causing intermittent power loss to the module.— CAN bus physical layer fault: Short or open circuit in the A/C sub-network CAN-H and CAN-L lines, terminating resistor deviation (normally approx. 60Ω), or wiring harness chafing and insulation damage at instrument panel frame bends.— HVAC module hardware fault: internal PCB water ingress and corrosion (often due to a blocked A/C drain hose causing condensate backflow), damaged CPU or CAN transceiver chip, software version mismatch (protocol conflict after OTA update)+2 more →
Actions
— Use the VDS2000/3000 diagnostic tool to read all DTCs. Check for accompanying DTC U0140 (Lost Communication with BCM) or B12C2 (Compressor Controller Fault). Read the data stream to confirm the HVAC module online status and communication voltage.— Check HVAC controller power supply: Measure voltage across fuse F1/15 in the fuse box (should be 12V±0.5V), check IGN signal wire voltage stability over bumps (should be >11V), and measure ground resistance (should be <1Ω).+5 more →
U025387›
U025387 is a U-category network communication DTC. It indicates a CAN bus communication interruption between the Vehicle Control Unit (VCU) or thermal management controller and the Electric Air Conditioning Compressor Controller (ACCM). This fault indicates the main control unit failed to receive valid messages (such as status, speed, and fault data) from the compressor controller within the predetermined cycle (typically 100ms-500ms). This represents a control link communication loss rather than a mechanical failure of the compressor itself. The fault completely disables the air conditioning system (no cooling/heating). This failure subsequently triggers battery thermal management degradation (limiting fast charge power and affecting battery life) and causes insufficient motor cooling (triggering high-temperature protection and power reduction). Severe cases restrict EV functions or prevent the vehicle from starting.
Causes
— Loose front compartment wiring harness connector, backed-out terminals, or poor contact: High temperatures (such as sun exposure) cause thermal expansion and contraction, forcing connector terminals (such as B28 and the front compartment wiring harness mating connector) to back out, oxidize, or develop poor contact, resulting in intermittent communication loss.— Electric compressor controller power supply or ground fault: blown fuse, relay failure, open power supply circuit, or loose ground point, causing controller power loss and communication failure.— CAN network physical layer fault: short or open circuit in powertrain CAN or thermal management sub-network wiring; abnormal terminating resistance (normal: approx. 60Ω; abnormal: 120Ω or open circuit); electromagnetic interference causing signal distortion.+2 more →
Actions
— Fault confirmation and data recording: Use the VDS2000/3000 diagnostic tool to read all fault codes. Confirm whether U025387 is a current fault (Active) or a history fault (History). Record the freeze frame data (ambient temperature, battery temperature, vehicle speed, etc.). Clear the fault codes and road test the vehicle to confirm if the fault reoccurs.— Low-voltage wiring harness and connector inspection: Disconnect the battery negative terminal. Check the electric compressor low-voltage wiring harness connectors (focusing on the front compartment harness interface connector and right domain controller Port E). Verify pins are not backed out, bent, corroded, or burnt. Measure voltage at the power supply pins (+B, IG) (12V±0.5V) and resistance at the ground pins (<1Ω).+4 more →
U025487›
U025487 (U0254-87, where 87 is a BYD custom sub-code meaning "signal/information missing or incorrect") indicates interrupted CAN communication between the air conditioning control module (ACU) and the PTC (Positive Temperature Coefficient) heater controller. The PTC is the core high-voltage component of the new energy vehicle heating system (typically operating at 200-750V, 3-6kW). It converts electrical energy into heat, replacing conventional engine waste heat. This fault means the ACU cannot send power regulation commands (PWM or CAN signals) to the PTC or receive PTC feedback regarding high-voltage interlock status, IGBT temperature, operating current, and fault codes. This causes complete failure of the air conditioning heating function (no warm air). In low-temperature environments, this may affect front windshield defrosting and cabin heating, but typically does not affect vehicle drive functions. The communication interruption occurs because the ACU fails to receive a valid CAN frame from the PTC node (Node ID typically in the 0x180-0x1FF range) for 3-5 consecutive message cycles (typically 200-500ms), triggering a timeout.
Causes
— PTC controller low-voltage power supply fault: Causes include a blown 12V constant power (B+) fuse (usually F2/15A in the front compartment fuse box), a faulty ignition switch power (IGN) relay, or a loose or oxidized ground point (G301/G302 on the front compartment longitudinal beam). This prevents the controller from initializing the CAN transceiver.— CAN network physical layer fault: Short circuit, open circuit, or poor connection in the CAN-H (orange/black) and CAN-L (orange/brown) wiring harness of the air conditioning sub-network (Comfort CAN or HVAC CAN), or drift or disconnection of the terminating resistor (120Ω), causing signal reflection or bus failure.— Internal PTC controller fault: Damaged internal CAN transceiver chip (e.g., TJA1041/1051), failed 3.3V/5V power management IC, or crashed main MCU unable to respond to bus requests.+2 more →
Actions
— Fault confirmation and freeze frame analysis: Use VDS2000/3000 or a BYD dedicated diagnostic tool to read the fault code and confirm if U025487 is a current fault (Active). Record freeze frame data, including ambient temperature, PTC outlet coolant temperature, and high-voltage status, to determine if the fault occurs only during high-voltage power-on or heater activation.— Basic power supply and ground check: Disconnect the PTC controller low-voltage connector (usually 8-12 pins, located near the heater core). Measure the voltage to ground at pin 1 (B+ constant power) and pin 2 (IGN); the voltage should be 12.0-14.5V. Measure the resistance to ground at pins 4/5 (GND); the resistance should be <1Ω. Check the PTC fuse in the front compartment fuse box and inspect the ground points on the left/right front longitudinal beams for oxidation.+3 more →
U025900›
U025900 indicates the IPB (Intelligent Integrated Braking System/Intelligent Power Braking System) failed to receive a valid message or heartbeat signal from the VCU (Vehicle Control Unit) via the powertrain CAN bus within the calibrated time window (typically 100-200ms). In the BYD DM-i hybrid architecture, the VCU acts as the primary vehicle controller. It calculates the regenerative braking torque request in real time and sends it to the IPB. The IPB then coordinates the distribution ratio between electric motor braking and hydraulic braking based on this request. Upon a communication timeout, the IPB determines it has lost communication with the VCU and enters fail-safe/limp-home mode. The IPB forcibly cancels regenerative braking and retains only basic hydraulic brake assist (vacuum or electric assist, depending on the IPB type) while triggering an ABS/ESC system fault warning. This U-category communication fault indicates a network or physical layer connection anomaly rather than a functional failure of the braking actuators. However, it severely impacts regenerative braking efficiency and braking coordination.
Causes
— VCU power supply system fault: Causes include a blown VCU constant power fuse (usually EF17/EF18 or a high-current fuse above 30A in the front compartment fuse box), burnt relay contacts, poor power circuit connection, or loose ground wire. These faults cause intermittent VCU restarts or freezing, preventing continuous CAN message transmission.— Powertrain CAN bus physical layer fault: Open or short circuit (shorted together, to power, or to ground) in the CAN_H and CAN_L lines between the VCU and IPB; excessive contact resistance (backed-out pins, water ingress oxidation); or abnormal terminating resistance (120Ω in parallel should measure 60Ω) causing signal reflection.— VCU software fault or hardware damage: damaged VCU internal CAN transceiver chip, MCU crash (program runaway), abnormal Watchdog reset, or software version bug causing an abnormal message transmission cycle.+2 more →
Actions
— Fault Confirmation and Freeze Frame Analysis: Use the VDS2000/VDS3000 diagnostic tool to read the complete fault codes and freeze frame data. Record the vehicle speed, SOC, gear position, and brake pedal status at the time of the fault. Determine if the fault is intermittent or current. Check for accompanying U01xx series communication fault codes.— VCU power supply and ground check: Check the VCU constant power fuse (e.g., EF15/EF16 30A) and IGN power supply fuse in the front compartment power distribution box. Measure the voltage drop across the fuses (should be <0.1V). Check the tightening torque of the VCU ground bolt (usually located on the front left longitudinal beam or firewall; standard: 10-12N·m). Measure the supply voltage at the VCU connector pins (should be 9-16V, fluctuation <0.5V).+5 more →
U030000›
In the BYD IPB (Intelligent Power Brake) integrated braking system, U030000 indicates the brake control unit (IPB ECU) internal software is incompatible with the vehicle network configuration. Specifically, the IPB module software version number, Calibration Verification Number (CVN), or configuration word (Coding) does not match the vehicle VCU, Gateway, and other CAN nodes. This prevents the brake control strategy from loading normally or causes verification failure. The fault triggers the system safety protection mechanism, restricting regenerative braking, Automatic Emergency Braking (AEB), and ESC functions. Severe cases cause a hard brake pedal, limit brake assist, or force the vehicle into limp mode. This functional fault compromises driving safety.
Causes
— Incorrect IPB ECU software version (mistakenly flashed software package for another vehicle model, model year, or trim level)— Failure to perform online matching, coding, and anti-theft synchronization after replacing the IPB assembly with a salvaged or used unit.— Interrupted software flashing (battery voltage below 12V, unstable OBD connection, or diagnostic tool crash) corrupted the program block.+2 more →
Actions
— Use VDS2000 or a BYD dedicated diagnostic tool to read the fault code. Confirm U030000 is a current fault, not a history fault. Record the current IPB software version number (e.g., BGM+ version number) and hardware part number.— Check the IPB ECU power supply (constant power 30+B, ignition switch IG power), ground points (G101/G102), and CAN-H/CAN-L voltages (recessive 2.5V, dominant 3.5V/1.5V) to rule out power supply fluctuations as the cause of software checksum errors.+4 more →
U040100›
U040100 is a U-class network communication fault code indicating "Invalid data received from Engine Control Module (ECM)". In the BYD DM-i hybrid architecture, the IPB (Intelligent Integrated Brake System) receives real-time parameters from the ECM via the powertrain CAN bus—including engine speed, output torque, and operating status—to coordinate the distribution ratio between regenerative and mechanical braking. If the IPB detects an ECM data frame checksum error, data outside the physically reasonable range, a communication protocol version mismatch, or a data update timeout, it logs "ECM data corrupted" and stores this fault code. This fault can force the IPB into a degraded mode, resulting in regenerative braking failure, restricted ESC function, and abnormal brake pedal feel. In extreme cases, it triggers a "Brake System Fault" warning and limits vehicle power output, severely compromising driving safety.
Causes
— Poor contact in the ECM power supply/ground circuit: loose fuse connections or oxidized/loose ground points G101/G102 cause unstable ECM operating voltage, resulting in the ECM sending corrupted data frames.— Powertrain CAN bus physical layer fault: Short or open circuit in the twisted pair between the ECM and gateway, terminal resistance drift (normal: 60Ω), or oxidized connector pins (e.g., water ingress oxidizing the connector near the firewall).— ECM software fault: Flash data corruption due to interrupted flashing, software version mismatch with VCU/IPB (e.g., ECM is V1.02 and VCU is V2.1), or lost calibration data.+2 more →
Actions
— Safety pre-check and fault confirmation: Connect the VDS diagnostic tool to read all fault codes and freeze frame data. Record the frequency and environmental conditions of U040100 (e.g., concurrent communication faults like U0100). Check the instrument warning light status, and confirm if the vehicle exhibits reduced power or abnormal braking.— Basic circuit check: Check ECM fuses (EF03/EF04, etc.), relays, and connector conditions. Measure ECM supply voltage (constant power B+ should be 12V ± 0.5V, IGN power normal). Measure resistance to ground at ground points G101/G102; resistance must be less than 1Ω. Check engine compartment wiring harness for abrasion or signs of water ingress.+4 more →
U043204›
DTC U043204 indicates a communication timeout between the IPB (Intelligent Integrated Braking System) control unit and the MMx_TX module (Multi-axis Acceleration Sensor). The MMx module monitors the vehicle’s lateral and longitudinal acceleration, providing critical dynamic data for ESP, Automatic Emergency Braking (AEB), Electronic Brakeforce Distribution (EBD), and the brake energy recovery system. The IPB main control unit triggers this fault if it fails to receive valid acceleration data within the specified communication cycle (usually 200 ms), or if the received data frame contains a checksum error or abnormal length. The system enters a safety fallback mode, limiting or disabling advanced functions such as ESP and AEB. The vehicle usually retains basic hydraulic braking, allowing cautious driving to a repair facility.
Causes
— Multi-axis acceleration sensor (MMx) power supply circuit fault (5V reference voltage abnormal or missing) or poor ground point connection, causing the sensor to fail to initialize normally or operate continuously.— Physical damage, open or short circuit in the CAN bus communication lines, or backed-out pins, oxidation, or corrosion from water ingress in key intermediate connectors (e.g., KJG05, BJA01) causing excessive contact resistance.— Multi-axis acceleration sensor damaged (internal MEMS chip failure, cold solder joint, moisture ingress due to seal failure, or performance degradation from physical impact)+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS1000/DiLink) to read complete fault codes and freeze frame data. Verify if U043204 is a current fault and check related fault codes (e.g., U012187, U043208, C003500) to assist fault isolation.— Visually inspect the multi-axis acceleration sensor (usually located under the center console, at the bottom of the center armrest, or under the front seats) for mounting condition, external damage, and connector connection. Confirm there are no signs of physical impact.+6 more →
U043208›
DTC U043208 indicates a private CAN network communication fault in the IPB (Intelligent Power Brake) system. Specifically, the IPB control unit detects an integrity check failure when receiving data frames from the MMx_TX module (Inertial Measurement Unit, IMU). This fault involves data link layer errors, including received byte length mismatching the DBC definition (expected 8 bytes, actual length abnormal), Cyclic Redundancy Check (CRC) errors, Alive Counter discontinuity or abnormal jumps, and signal values exceeding the physically valid range (e.g., lateral acceleration >4g or yaw rate >300°/s). The IMU provides vehicle lateral acceleration, longitudinal acceleration, and yaw rate signals, serving as the core sensor for ESC (Electronic Stability Control), ABS (Anti-lock Braking System), and AEB (Automatic Emergency Braking). This fault prevents the IPB from obtaining accurate vehicle body attitude data and triggers the brake system degraded protection mode. Symptoms include restricted ESC function, altered ABS intervention logic, or disabled Automatic Emergency Braking. The system usually retains basic hydraulic braking functions.
Causes
— Inertial Measurement Unit (IMU) internal chip fault or firmware corruption, causing abnormal output data frame format or CRC calculation error.— Physical layer fault in the private CAN bus between the IPB and IMU, including loose connections, oxidized pins, damaged shielding causing electromagnetic interference (EMI), or terminating resistor deviation (typically 120Ω) causing signal reflection.— Outdated IPB Intelligent Power Braking control unit software or a faulty hardware CAN transceiver prevents correct parsing of the new IMU data protocol.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000/VDS2100) to read the complete fault code tree. Check for related faults such as U043204 (communication timeout) or C0035 (lateral acceleration sensor fault). Record the vehicle speed, yaw rate, and IMU raw signal status at the time of the fault from the freeze frame data.— Check the IMU installation status: Verify the IMU retaining bolt torque (typically 8-12 N·m), inspect the mounting surface for deformation, and verify the sensor level error is <2°. A mounting angle deviation causes the system to misinterpret the gravity component as lateral acceleration.+5 more →
U055A00›
U055A00 is a CAN bus communication protocol layer fault code. It indicates the IPB (Intelligent Integrated Braking System/One-Box) detects that the data frame length (DLC) of a received VCU (Vehicle Control Unit) CAN message does not match the specified protocol, or the data payload length check fails. This network communication data link layer error means the VCU transmitted an abnormal message structure (e.g., sending 6 bytes instead of the protocol-specified 8 bytes, or using incorrect padding bytes). In Song PLUS DMi models, the VCU and IPB communicate via the chassis CAN or powertrain CAN to transmit key signals such as vehicle speed, torque request, and regenerative braking level. If the data length is incorrect, the IPB cannot correctly interpret the vehicle status. This can trigger braking system downgrade protection, limit ESC, ABS, and regenerative braking functions, and severely compromise driving safety.
Causes
— VCU software defect or version mismatch: The VCU control program contains a bug causing the transmitted CAN frame data length field to mismatch the actual payload, or the VCU contains incorrectly flashed vehicle model configuration data.— IPB software version too old: Brake system software is incompatible with the new VCU communication protocol, causing standard data frame parsing logic errors.— CAN network physical layer fault: Electromagnetic interference on the powertrain CAN bus, loose wiring connections, or an abnormal terminating resistor corrupts the data frame length field during transmission.+2 more →
Actions
— Use the BYD VDS1000/VDS2000 diagnostic tool to read complete fault codes and freeze frame data. Record key parameters at the time of the fault, such as vehicle speed, gear position, and CAN communication load. Check for accompanying communication fault codes (such as U01A0 or U0100).— Check the VCU and IPB software version numbers. Log in to the BYD TPI (Technical Product Information) system and check for a software upgrade bulletin for this fault code. Confirm software compatibility between both control units.+5 more →
U058504›
U058504 indicates a private CAN or powertrain CAN communication timeout fault between the IPB (Intelligent Integrated Braking System) and the TCU (Transmission Control Unit). In the BYD DM-i architecture, the IPB requires real-time key data from the TCU, including motor torque, vehicle speed, gear position, and regenerative braking requests, to coordinate brake force distribution and regenerative braking. The IPB triggers this fault if it fails to receive a valid data frame from the TCU within a 500ms monitoring period (normal message cycle is 10-20ms), or if it receives data checksum errors for more than 10 consecutive frames. This fault disables the regenerative braking function and forces the ESC/ABS into degraded mode. In extreme cases, it triggers the powertrain Limp Home mode, limiting vehicle speed.
Causes
— Loose connection or oxidation in the TCU power supply or ground circuit, causing intermittent TCU resets (inspect TCU constant power fuse F1/16, IG2 power F2/08, and ground points G201/G202)— Open or short circuit in CAN-H (orange/black) or CAN-L (orange/brown) wiring between IPB and TCU, or wiring harness chafing at the firewall grommet (common fault point on Song PLUS DM-i)— A damaged internal TCU CAN transceiver chip or software crash prevents response to IPB communication requests.+2 more →
Actions
— Use the VDS2000/VDS3000 diagnostic tool to read all network fault codes. Check for accompanying U01xx-series communication faults in other modules. Enter 'Network Topology' to confirm if the TCU is offline.— Measure the terminal resistance between OBD diagnostic connector pin 6 (CAN-H) and pin 14 (CAN-L) (Standard: 60 ± 3 Ω; disconnect battery before measuring) and the static voltage (CAN-H: 2.6 V, CAN-L: 2.4 V).+5 more →
U058508›
DTC U058508 indicates abnormal CAN communication data between the IPB (Intelligent Integrated Braking System) and the TCU (Transmission Control Unit). Specifically, the TCU data frames received by the IPB contain checksum errors, implausible data logic, or communication timeouts. This fault affects critical data exchange between the powertrain and braking systems. The TCU cannot provide the IPB with accurate gear state, torque request, motor speed, or vehicle speed signals, preventing the braking system from coordinating the switching logic between energy recovery and hydraulic braking. Potential causes include corrupted internal TCU EEPROM data, CAN bus physical layer interference, logic errors resulting from an abnormal TCU power supply, or parsing errors at the IPB receiver. When triggered, this fault may limit vehicle power output, disable the energy recovery function, and illuminate the ABS/ESC warning light. In severe cases, the vehicle enters Limp Home Mode.
Causes
— TCU internal program runaway or corrupted EEPROM data causes an abnormal frame structure or checksum error in the transmitted CAN signal.— Intermittent short circuit, open circuit, or excessive contact resistance in the CAN-H/CAN-L wiring harness between the TCU and IPB, especially at the firewall, high-temperature areas of the engine compartment, or chassis wiring harness bends.— Unstable voltage in the TCU power supply circuit (constant B+ or IGN power), or oxidized or loose ground points (such as G303/G304), causes abnormal TCU operating timing.+2 more →
Actions
— Use the BYD VDS2000 diagnostic tool to read all DTCs. Check for accompanying communication faults such as U059508 (MG communication fault). Verify freeze frame data at the time of the fault, such as vehicle speed and gear position.— Check TCU power supply fuses F1/9 (constant power) and F2/2 (IGN power). Measure the voltage at TCU connector pin 1 (B+) and pin 2 (IGN). Verify the voltage is within 11–14 V and fluctuates less than 0.5 V.+6 more →
U100004›
DTC U100004 indicates the control module detects the CAN bus is in a "Bus Off" state. In the BYD E5 battery electric vehicle, the ABS system reports this DTC. It indicates the ABS control unit CAN controller automatically shuts down communication due to an error counter overflow (typically caused by continuous bus errors or interference) to protect the bus from a faulty node. Consequently, the ABS module cannot exchange data with the vehicle network (including the gateway, VCU, and instrument cluster). This disables functions such as the anti-lock braking system and electronic stability control (ESC) and illuminates multiple instrument panel warning lamps. On some other models (such as the S6), U100004 may also indicate a transmission control module (TCU) communication fault, but the core mechanism remains a communication interruption between the control unit and the CAN bus.
Causes
— A damaged internal CAN transceiver chip in the ABS control unit or a cold solder joint prevents sending or receiving CAN signals.— Chassis CAN bus circuit (CAN-H/CAN-L) shorted to power, shorted to ground, or shorted together, causing bus blockage.— Abnormal power supply voltage to the ABS control unit (battery voltage too high/too low) or poor ground connection, causing abnormal communication module operation.+2 more →
Actions
— Use the BYD VDS diagnostic tool to read all fault codes. Confirm whether U100004 is a current or history code, and check for accompanying communication fault codes such as U100308 (EPB CAN communication timeout).— Check the ABS control unit power supply: Measure the constant power (B+) and ignition power (IG) voltages. Voltages must be within 12V±0.5V. Ground resistance must be less than 1Ω.+5 more →
U100308›
This DTC indicates abnormal communication between the EPB (Electronic Parking Brake) control module and the vehicle chassis CAN network (Chassis CAN). Technical details: 1) The EPB module fails to receive valid data frames from the ABS/ESP, VCU, or gateway module within the preset monitoring period (typically 100ms), triggering a timeout counter overflow; 2) Received CAN messages fail the CRC check, contain an abnormal Data Length Code (DLC), or trigger a Bus-Off state. On the BYD E5, the EPB system relies on the CAN bus to receive the vehicle speed signal (from the ABS), brake pedal status, gear position information, and power mode signal. Communication interruption causes the EPB auto-release/Auto Vehicle Hold (AVH) function to fail. Extreme cases may trigger Limp Home mode, though the system usually retains the mechanical emergency release function. This fault belongs to the chassis network communication category. Prioritize inspecting the physical layer wiring.
Causes
— CAN bus physical layer fault: Includes short circuit between CAN-H and CAN-L, short to 12V power supply/ground, open circuit, or excessive contact resistance (>1Ω). Common causes include wiring wear at the firewall grommet or the floor harness under the door sill trim, and connector water ingress and oxidation after driving through water.— Abnormal terminal resistor matching: The E5 model chassis CAN bus uses standard 120 Ω terminal resistors located in the ABS control unit and the gateway controller (integrated into the instrument panel distribution box or a standalone module). Total parallel resistance must measure 60 Ω. Resistance deviations exceeding 10% (e.g., poor connections causing resistance >70 Ω or <50 Ω) cause signal reflection and bit errors.— EPB control module internal fault: Damaged internal CAN transceiver (e.g., NXP TJA1042 chip), crystal oscillator clock drift shifting the sampling point, or failed filter capacitor in the module power supply circuit (12V to 5V) causing excessive power supply ripple.+2 more →
Actions
— DTC Confirmation and Freeze Frame Analysis: Use a BYD VDS2000 or Launch X-431 diagnostic tool to read all DTCs. Distinguish between Current and History codes. Record the vehicle speed, system voltage, ambient temperature, and bus load rate from the freeze frame data. Check for accompanying multi-module communication faults (e.g., U1003, U0308, U0101). If present, prioritize troubleshooting the gateway and bus physical layer over individual modules.— EPB module power supply and ground reference check: Disconnect the EPB control module connector (located under the center armrest or near the rear axle motor). Measure the constant power (B+, Pin 30); it must be 12.6V ± 0.3V (static). Measure the ignition power (IGN, Pin 15); it must be >12V with the ignition ON. Measure the resistance between the ground wire (GND) and the vehicle body; it must be <1Ω. Inspect fuses EF05/EF06 (E5 model) in the instrument panel power distribution box for blown elements or poor connections. Verify the power supply waveform ripple is <100mV.+4 more →
U1004-00›
DTC U1004-00 indicates a short to ground in the CAN bus communication circuit of the BYD vehicle's airbag system (SRS). In the BYD Qin series network architecture, the SRS ECU communicates in real time with the vehicle control unit, instrument cluster, and other modules via the CAN bus (typically powertrain CAN or body CAN). If either CAN_H (high line, usually orange/black) or CAN_L (low line, usually orange/brown) shorts to body ground (GND) due to damaged insulation, water corrosion, or mechanical damage, the short pulls the differential bus signal voltage low and prevents normal transmission of communication messages. This fault forces the SRS system into fail-safe mode, illuminates the airbag warning lamp on the instrument cluster, and prevents proper coordination between the seat belt pretensioners, crash sensors, and airbag deployment circuits. This creates a severe safety hazard where the airbags fail to deploy during a collision.
Causes
— Water ingress or terminal corrosion at the SRS ECU wiring harness connector. Driving through water, washing the vehicle, or a blocked sunroof drain tube causes water to flow under the center console (the typical SRS ECU location on Qin series models), shorting the CAN terminals to ground.— During front-end accident repairs or dashboard removal/installation, the metal frame and sheet metal pinch the wiring harness, damaging the insulation and causing the CAN line to contact the body ground point.— Chassis bottoming out or scraping split the floor wiring harness sleeve, causing the SRS communication harness to contact a sharp frame edge and short to ground.+2 more →
Actions
— Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes for the SRS system high-voltage capacitor to discharge fully, preventing accidental airbag deployment.— Fault confirmation: Use the BYD VDS or Launch X431 diagnostic tool to read the DTC. Confirm U1004-00 is a current fault that will not clear. Record the freeze frame data.+7 more →
U1005-00›
DTC U1005-00 indicates a short circuit between the Supplemental Restraint System (SRS) Controller Area Network (CAN) communication line and vehicle power (+B). In BYD Qin series models, the Airbag Control Module (ACM) communicates with the vehicle network via the CAN bus. When the CAN-H or CAN-L line shorts to constant power or ignition power, the short pulls the bus voltage up to 12V (battery voltage), distorting the CAN signal and interrupting communication. This prevents the airbag system from receiving crash sensor signals or triggering airbag deployment, and may affect safety-related functions such as the seat belt pretensioners and the airbag warning lamp. Because the CAN bus uses differential signal transmission, a short to power disrupts communication across the entire CAN network segment (typically including the instrument cluster and BCM). This serious fault endangers driving safety.
Causes
— Wiring harness wear in the engine compartment or cabin damages CAN and power wire insulation, causing them to contact each other, especially in high-wear areas such as the firewall pass-through and under the seat rails.— Airbag Control Module (ACM) internal transceiver circuit fault or CAN pin short to power. Internal module component breakdown usually causes this.— After vehicle wading or heavy rain, water ingress and corrosion in SRS system connectors (such as floor harness connectors and under-seat connectors) cause a short circuit between the CAN line pins and power supply pins.+2 more →
Actions
— Use VDS2000 or a dedicated diagnostic tool to read all fault codes. Confirm U1005-00 is a current fault, not a history fault. Check for accompanying U1004 (CAN short to ground) or other SRS communication fault codes.— Disconnect the battery negative terminal and wait 3 minutes. Perform the high-voltage power-down procedure (for EV models). Remove the airbag control module (located in the center tunnel or under the instrument panel). Visually inspect the connector for water ingress, corrosion, or burn marks.+6 more →
U1004›
In BYD new energy vehicles, DTC U1004 typically indicates "loss of communication with the Vehicle Control Unit (VCU)" or "powertrain CAN bus off". Some SRS system documentation defines it as "CAN short to ground". This fault indicates a physical layer abnormality in the Controller Area Network (CAN) communication bus. Specifically, the insulation resistance to ground for CAN-H (high line) or CAN-L (low line) decreases or shorts completely. This pulls the bus differential signal voltage down to ground potential, preventing normal data frame transmission. Consequently, this interrupts communication between the VCU or airbag control unit and other key vehicle modules, such as the Battery Management System (BMS), Motor Control Unit (MCU), and Instrument Cluster Unit (ICU). The interruption triggers the fault protection mechanism, forcing the vehicle into limp mode (speed limited to 20-40 km/h) or inhibiting the Ready state, severely compromising driving safety. In the SRS system, this fault also disables passive safety systems such as the airbags and seat belt pretensioners.
Causes
— Abnormal VCU or SRS control unit power supply circuit: blown VCU power supply fuse in the front compartment fuse box (usually F1/23 or F2/08, 15A), burnt relay contacts, or wiring harness chafed at the firewall or floor causing a short to ground.— CAN bus physical layer damage: Power CAN or Comfort CAN wiring harness chafing against air conditioning lines or sharp body edges; waterproof seal aging causing water ingress and corrosion after wading (common at gateway module GWC or VCU connectors); connector pin back-out, oxidation, or excessive contact resistance.— Internal control module fault: CAN transceiver chip breakdown in the VCU, gateway controller (GWC), or airbag control unit; power management circuit fault causing abnormal 12V output to the CAN line; or module failing to enter sleep mode and continuously occupying the bus.+2 more →
Actions
— Use VDS or a dedicated diagnostic tool to read the full DTC data stream. Confirm whether U1004 is a current (Active) or historical (History) fault. Record accompanying fault codes (e.g., U0100, U0110, B1C00) and preliminarily determine if the issue is a VCU communication fault or an SRS system fault.— Check the power supply and ground for the VCU (usually located under the front passenger floor) or the SRS control unit. Measure the constant power (B+) and ignition switch (IG) voltages; the readings must be 11-14V. Measure the ground point resistance; it must be less than 0.5Ω. Check the relevant fuses in the front compartment power distribution box. If a fuse is blown, measure the downstream circuit resistance to ground to locate the short circuit.+5 more →
U1005›
DTC U1005 indicates the vehicle SRS (Supplemental Restraint System/airbag system) control module detects a short circuit between its CAN communication bus (including CAN-H and/or CAN-L lines) and the vehicle positive power supply (12V battery voltage or high-voltage system power supply). Normally, the CAN bus voltage to ground measures approximately 2.5V (recessive state) and 3.5V/1.5V (dominant state). A short to power pulls the CAN bus voltage up to 12V, completely interrupting communication between the SRS system and the vehicle Powertrain CAN or Body CAN. Because safety-critical subsystems (airbag system, seat belt pretensioners, crash sensors, and seat occupancy detection) rely on the CAN bus for data exchange and trigger command transmission, this fault prevents the airbag system from deploying normally during a collision. This constitutes a Level 1 severe fault affecting occupant life safety.
Causes
— Worn or split insulation on the SRS control module wiring harness causes the CAN-H or CAN-L wire to short directly to a power wire (constant or ignition power). This commonly occurs below the steering column, near the seat slide rails, or at bends in the sill wiring harness.— Vehicle wading, a blocked sunroof drain hose, or high-pressure washing of the interior caused water ingress at the SRS control module connector (usually located under the lower center console or beneath the center armrest box), resulting in an electrolytic short circuit between the pins.— During accident repairs or unauthorized aftermarket modifications (e.g., dash cams, seat heaters, audio systems), improperly securing the wiring harness allows the instrument panel bracket, seat mounting bolts, or metal trim edges to cut the harness, causing a short circuit to the vehicle power supply.+2 more →
Actions
— Use the BYD dedicated diagnostic tool (VDS2000/3000) to read all fault codes and freeze frame data. Verify U1005 is a current fault (Active) that will not clear, and check for accompanying B1xxx series SRS sensor faults or U01xx communication faults.— Perform the high-voltage power-down procedure (for new energy vehicles) or disconnect the 12V battery negative terminal. Wait 3 minutes for the capacitors to discharge, then disconnect the SRS control module connector (typically under the center console or center tunnel). Use a multimeter to measure the resistance from connector terminals CAN-H (orange/black) and CAN-L (orange/brown) to the battery positive terminal. Normal resistance is greater than 1 MΩ. A resistance below 10 kΩ indicates a short circuit.+4 more →
U1332-00›
DTC U1332-00 indicates the airbag control unit (SRS ECU) receives an abnormal or timed-out vehicle speed signal via the body CAN bus (B-CAN). This fault occurs when the SRS module fails to receive a valid vehicle speed data frame from the instrument cluster or ABS/ESP module within the predetermined cycle, preventing the airbag system from determining collision severity based on real-time vehicle speed. This safety system communication fault compromises the collision safety strategy, potentially causing airbag deployment timing deviations during high-speed collisions or false deployments during low-speed collisions.
Causes
— Instrument cluster internal CAN communication module or gateway fault prevents transmission of the vehicle speed signal to the B-CAN network.— The internal CAN transceiver in the SRS control unit is damaged and cannot receive or decode vehicle speed data frames.— B-CAN network physical layer fault, including water ingress and oxidation at the G10/M40 connector, wiring harness damage causing short or open circuits, or excessive contact resistance.+2 more →
Actions
— Use the dedicated diagnostic tool to read the fault code and record freeze frame data. Confirm the vehicle speed, time, and environmental conditions when the fault occurred.— Visually inspect the vehicle speed display on the instrument cluster to determine if the fault is a signal source issue (no display on the instrument cluster) or a data transmission issue (instrument cluster operates normally but the SRS reports a fault).+7 more →
U2ABC16›
DTC U2ABC16 indicates the electric air conditioning compressor high-voltage load circuit detects an input voltage below the normal operating threshold (typically below 420VDC). In the 2019 BYD Qin EV thermal management system, the high-voltage battery pack (nominally 500V+) powers the electric compressor through the high-voltage power distribution box. This fault indicates the compressor controller detects insufficient bus voltage to maintain normal compressor startup or operation during self-check or running. This fault triggers a protective compressor shutdown, causing air conditioning cooling failure. In extreme cases, it may affect battery thermal management (liquid cooling system), but typically does not directly cause a vehicle breakdown. The root cause involves an abnormality in the high-voltage power supply circuit, Battery Management System (BMS) voltage monitoring, or the compressor controller internal voltage sampling circuit.
Causes
— Traction battery pack SOC too low or excessive cell voltage difference: When the total battery pack voltage is below 420V or cell voltage is below 3.0V, the BMS limits power output, causing insufficient power supply to the compressor.— High-voltage distribution box compressor contactor welded closed or making poor contact: Oxidation or ablation of the contactor contacts increases contact resistance, causing an excessive voltage drop during compressor startup.— Electric compressor controller (IPM module) internal fault: Controller internal bus voltage sampling circuit fault, precharge circuit failure, or IGBT drive fault causing a false low-voltage report.+2 more →
Actions
— Safety Preparation: Wear insulated gloves, disconnect the low-voltage battery negative terminal, wait 5 minutes, confirm the high-voltage system is de-energized (voltage <60V), and hang a warning sign.— Read freeze frame: Use VDS or ED400 to read the bus voltage, battery SOC, and lowest cell voltage at the time of the fault to confirm whether it is a genuine low voltage condition or a sampling fault.+6 more →
U1332›
DTC U1332 indicates the airbag control unit (SRS ECU) receives an abnormal or interrupted vehicle speed signal via the CAN bus. In BYD new energy vehicles, the ESP electronic stability system (or IPB intelligent integrated braking system) typically generates the vehicle speed signal and transmits it to the SRS module via the chassis CAN or powertrain CAN bus. The SRS system relies on the vehicle speed signal for crash algorithm decisions: at low speeds, it may trigger only the seat belt pretensioners without deploying the airbags, while at high speeds, it requires multi-stage airbag coordination. CAN bus communication interruptions, signal source module failures, or SRS module receiving circuit faults trigger this code. This fault causes the airbag system to enter a degraded mode, which may prevent correct deployment during a collision or cause the warning lamp to remain illuminated.
Causes
— Fault in the ESP/ESC control unit (or IPB Intelligent Integrated Braking System) preventing vehicle speed signal generation or transmission.— Open circuit, short circuit, or high contact resistance in the CAN-H or CAN-L line between the SRS control unit and the gateway/ESP.— Gateway module (GW) fault causing vehicle speed signal forwarding failure across network segments.+2 more →
Actions
— Use VDS2000 or a BYD dedicated diagnostic tool to read fault codes. Confirm if U1332 is a current or history fault, and check for accompanying U-class communication fault codes (e.g., U1100 series).— Check the vehicle 12V battery voltage and SRS system fuses (typically located in the dashboard fuse box, e.g., F1/11, F2/16). Verify the power supply voltage is normal (12-14V).+5 more →
U2ABB17›
DTC U2ABB17 indicates the electric compressor controller (PCU) detects the input DC high voltage exceeds the permitted operating threshold (typically 110%-120% of the rated voltage). For example, on the 2019 Qin EV, the system triggers this fault when the high-voltage battery pack voltage exceeds approximately 420-450V or the compressor internal bus voltage reading exceeds the safe range. This fault acts as a high-voltage safety protection mechanism for the thermal management system. Upon detecting abnormally high voltage, the compressor actively disconnects the high-voltage relay to protect the IGBT power module and motor insulation. Actual battery pack overvoltage, voltage sampling circuit drift, high-voltage interlock circuit faults, or control software logic errors can cause this fault. Determine whether the condition is a genuine voltage abnormality or a signal detection fault.
Causes
— High traction battery voltage at end of fast charging: During DC fast charging above 90% SOC, the battery pack voltage approaches full-charge voltage (about 420V-450V). If the BMS fails to limit the charging voltage correctly, or the compressor overvoltage threshold is too low, the system triggers protection.— Electric compressor controller (PCU) internal voltage sampling circuit fault: voltage divider resistor aging, ADC converter drift, or filter capacitor failure causes the sampled value to exceed the actual value.— Poor contact in the high-voltage wiring harness: Compressor high-voltage connector is poorly connected, burnt, or loose, generating instantaneous overvoltage spikes during load changes (back EMF when disconnecting an inductive load).+2 more →
Actions
— Read freeze frame data: Use the VDS2000/3000 diagnostic tool to read detailed data at the moment the fault occurred, including compressor high-side voltage, total battery pack voltage, SOC, current direction, and compressor operating status. Confirm if a genuine overvoltage condition exists.— Measure actual high-voltage system voltage: Use an insulation tester and a multimeter to measure the total traction battery voltage. Compare this value with the BMS voltage and compressor reported voltage in the diagnostic tool data stream. A deviation exceeding 5V indicates a faulty sampling circuit.+5 more →

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