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B16A3-00

DTC B16A3-00 indicates an internal self-check failure or core function fault within the airbag control unit (SRS ECU) — Seal U

Safety System

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.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1SRS ECU internal hardware fault (damaged MCU processor, memory data checksum error, or capacitor aging causing internal power supply ripple to exceed specifications)
  • 2Abnormal vehicle battery voltage (prolonged under-voltage below 10.5V or charging system fault causing voltage to exceed 16V), resulting in unstable ECU power supply or current surge during startup.
  • 3SRS-CAN bus physical layer fault (short between CAN-H and CAN-L, short to ground or power, or terminating resistor drift causing signal reflection interference)
  • 4Internal short circuit in the crash sensor (front crash sensor, side impact pressure sensor, or central acceleration sensor) sends an incorrect diagnostic signal to the ECU.
  • 5Vehicle water ingress or high humidity causes oxidation of SRS ECU connectors (especially under-floor wiring harness connectors), resulting in intermittent contact resistance or signal crosstalk.
What To Do
  • 1
    Use BYD dedicated diagnostic tool VDS2000 or VDS1000 to perform a full vehicle scan. Confirm B16A3-00 is a current fault (Active) rather than a history fault, and record the vehicle status from the freeze frame data (vehicle speed, ignition cycle count, battery voltage).
  • 2
    Check the battery state of health (SOH) and static voltage (standard: above 12.6V). Measure the generator output voltage (13.8-14.8V) to rule out power system fluctuations causing false faults.
  • 3
    Disconnect the 12V battery negative terminal (follow high-voltage safety procedures and wait 3 minutes for capacitor discharge). Check the SRS ECU connector (usually located under the center console, with black/yellow markings) for oxidized pins, backed-out pins, or signs of water ingress. Measure the voltage drop between the power supply pins (constant power +B, ignition IG1) and ground (must be less than 0.1V).
  • 4
    Measure the SRS-CAN bus resistance (disconnect the ECU connector and measure the resistance between diagnostic port pins 6 and 14, or between CAN-H and CAN-L at the ECU side; standard value approx. 60 Ω) and voltage (CAN-H 2.6 V, CAN-L 2.4 V). Check for a short to ground or power.
  • 5
    Disconnect the front impact sensors (located on the front longitudinal beams), B-pillar side impact sensors, and seat occupancy sensor one by one. Observe if the fault code changes to rule out an ECU protective error caused by a peripheral short circuit.
  • 6
    If circuit measurements are normal, update the SRS ECU software to the latest version (e.g., firmware V2.3 or later released after 2018). After the update, perform 'Crash Sensor Zero Point Calibration' and 'System Configuration Writing' (enter the VIN and vehicle configuration code).
  • 7
    If the fault persists, replace the SRS ECU assembly (part number usually starts with 5A-, such as 5A-5820100). After installing the new part, perform Online Coding to deactivate transport mode and execute an airbag system Cycle Test to confirm no fault codes are present.
Real-World Cases
BYD DTC AI Analysis

2017 Qin EV300 SRS ECU internal memory fault

✓
At 82,000 km, the SRS lamp stayed on constantly. Retrieved active fault code B16A3-00; freeze frame data showed battery voltage at 11.8 V (low) when the fault occurred. Checked ECU power supply: normal. Attempted software upgrade, but the ECU did not respond. Disassembled the ECU and found cracked solder joints on the internal EEPROM chip (93C66), causing loss of configuration data. Replaced the SRS ECU assembly, performed online coding and sensor calibration. Fault resolved.
BYD DTC AI Analysis

2017 Qin 100: SRS system failure after water ingress

✓
Vehicle waded through approximately 30 cm of water. After repairs, the instrument cluster displayed an airbag fault. Retrieved DTC B16A3-00 and multiple collision sensor communication faults. Found water inside the SRS ECU connector at the centre of the floor pan; pins had oxidised, showing green corrosion. Cleaned the connector and dried the wiring harness. Measured the CAN bus and found a short to ground (0.2 V). Replaced the wiring harness connector and applied waterproofing. The DTC became intermittent and has not returned after clearing.
BYD DTC AI Analysis

2018 BYD Qin EV450: Aftermarket modifications causing CAN bus interference

✓
Owner installed a non-OEM dashcam and tapped power from the SRS fuse. The SRS warning lamp illuminated intermittently while driving. Diagnostics showed an intermittent B16A3-00 fault. Measurements found the aftermarket device generated pulse voltage spikes at startup, causing SRS-CAN signal interference. Restored the original vehicle circuit, rewired the dashcam to ACC power, and added a filter capacitor. The fault has not recurred.
BYD DTC AI Analysis

2017 BYD Qin 80: Cannot clear DTCs after collision repair

✓
After a front-end collision, the front bumper and left fender were replaced. After the repair, the SRS light stayed on with DTC B16A3-00. Inspection found the left front impact sensor incorrectly installed (poor grounding due to insufficient torque), and the SRS ECU had recorded a collision event (Crash Locked). Replaced the left front impact sensor and installed it to the specified torque (8.5 N·m). Used a diagnostic tool to perform 'Crash Data Reset' and 'ECU Unlock'. System returned to normal.
BYD DTC AI Analysis

2017 BYD Qin EV300: Aging auxiliary battery triggers false alarm

✓
Vehicle was hard to start after sitting parked for 3 days, and the SRS warning light came on. A battery capacity test showed only 32% remaining, with voltage dropping to 9.2V during cranking, triggering DTC B16A3-00. Replaced the AGM battery (60Ah) and checked the alternator charging current. The fault code cleared but returned intermittently. Eventually traced the cause to a drifted low-voltage protection threshold in the SRS ECU. Updating the ECU software to the latest version permanently fixed the fault.
Other Seal U Fault Codes
B1108For 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.B110811This 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.B1109DTC 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.B110913DTC 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.B110AThis 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.
Data confidence: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.