AU
B169B-00

DTC B169B-00 indicates an internal self-diagnostic fault or severe communication error within the airbag control unit (SRS ECU) — Seal 6 EV

Safety System

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.

The B169B-00 fault code on the Seal 6 EV indicates an internal fault or communication error in the airbag control unit (SRS ECU), disabling all airbags and seat belt pretensioners. Severity is medium. Causes include voltage surges damaging the ECU circuit board or loose power connections. Repair involves checking wiring or replacing the ECU at an authorised dealer. Typical repair cost data is available from 4 recorded cases.
4
Cases Logged
5
Causes
Likely Causes — Seal 6 EV
  • 1SRS ECU internal circuit board damage due to voltage surges (e.g., reversed polarity during jump-starting or charger surges), long-term thermal cycling causing cracked solder joints, or internal capacitor aging causing power supply filtering failure.
  • 2Abnormal power supply: Battery voltage remains too low (<9V) or too high (>16V) for an extended period; loose connection in the IGN power circuit; poor fuse contact; or oxidation at ground point G201 (left side of instrument panel) causing reference voltage drift.
  • 3CAN bus communication fault: Short or open circuit in CAN-H (orange/black) or CAN-L (orange/brown) wiring between the SRS ECU, gateway, and vehicle control unit; abnormal terminating resistance (120Ω); or bus voltage outside standard range (CAN-H 2.5-3.5V, CAN-L 1.5-2.5V).
  • 4Corrupted software or calibration data: Interrupted flashing process, calibration data checksum failure, or physical damage to Flash memory prevents the ECU from loading the correct airbag deployment algorithm and crash threshold parameters.
  • 5External environmental factors: Vehicle wading causes water ingress into the SRS ECU (its mounting location below the A/C evaporator housing makes it susceptible to moisture), minor collision damage fails to manifest immediately, or strong electromagnetic interference (such as high-power radio equipment) causes an abnormal CPU reset.
What To Do
  • 1
    Diagnostic tool check: Use the VDS2000 or a dedicated BYD diagnostic tool to access the SRS system and read the Freeze Frame data. Confirm whether B169B-00 is a current (Active) or historical (History) fault. Record the vehicle speed, battery voltage, temperature, and other parameters at the time of the fault. Check for accompanying fault codes (such as U-prefix communication faults or B16XX series sensor faults).
  • 2
    Power supply and ground check: Turn off the ignition switch. Measure the voltage to ground at pin 16 (constant B+) and pin 15 (IGN) of the SRS ECU connector. 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).
  • 3
    CAN bus inspection: Disconnect the SRS ECU connector. Measure the resistance between CAN-H and CAN-L (approximately 60Ω, two 120Ω terminating resistors in parallel). Check for short circuits between CAN-H and ground, CAN-L and ground, and CAN-H and CAN-L. Use a CAN analyzer to capture the waveform. Verify normal dominant levels (CAN-H 3.5V / CAN-L 1.5V) and recessive levels (2.5V). Check for abnormal bit stuffing errors.
  • 4
    ECU inspection: Remove the SRS ECU located under the center console / behind the glovebox (exact location varies by model; on Qin series models, it is usually on the right side of the A/C evaporator housing). Inspect the exterior for water marks, burn damage, cracks, or impact deformation. Measure the output of the internal ECU voltage regulator chip (this typically supplies a 5V reference voltage to the sensors). If the voltage is abnormal, confirm internal ECU damage. Note: Never dismantle the ECU housing (due to safety sealing and explosion-proof requirements).
  • 5
    Replacement and matching: If the ECU is faulty, replace it with a new SRS ECU with the same part number (e.g., HA2E-5810000A, depending on the vehicle model). Before installation, disconnect the negative battery terminal for more than 5 minutes. After installation, connect the diagnostic tool and perform 'Online Matching' and 'Coding'. Enter the vehicle VIN and airbag configuration parameters (such as side and knee airbag presence). Perform 'System Self-check' to clear fault codes and run a simulated ignition test (use the diagnostic tool to execute the 'Collision Output Test' function; this operation flashes the airbag warning lamp but does not deploy the airbags).
  • 6
    Road test verification: Restore the vehicle, power it on, and confirm the airbag warning lamp turns off after 6 seconds. Conduct a road test over bumpy roads and through turns to confirm the fault code does not recur. Use the diagnostic tool to read the live data stream. Verify sensor voltages, crash signal status, and CAN communication status are normal. Inform the customer the SRS system is operating normally and the airbag system was inactive during the repair.
Real-World Cases
BYD DTC AI Analysis

Qin EV450 SRS fault light on after charging

✓
A 2018 BYD Qin EV450 displayed 'Check SRS System' on the instrument cluster after the owner used a non-genuine DC fast charger. Technicians retrieved DTC B169B-00. They found oxidation on the SRS ECU connector. Power supply voltage measurement during fast charging showed a momentary spike to 16.8 V, triggering the ECU's internal overvoltage protection. They replaced the SRS ECU, installed a zener diode protection circuit, and updated the BMS software to limit charging voltage fluctuations. Fault resolved.
BYD DTC AI Analysis

Qin 100 airbag warning light stays on after water ingress.

✓
2017 BYD Qin 100. The vehicle waded through water about 40 cm deep, after which the airbag warning light stayed on. The diagnostic scanner retrieved DTCs B169B-00 and B1650-00 (left impact sensor fault). Disassembly revealed water had entered the SRS ECU mounting location (below the evaporator case) and green corrosion on the circuit board. Replaced the ECU and wiring harness connector, then resealed the area by installing a waterproof cover and applying sealant. Fault resolved. Recommend checking the air conditioning drain hose for blockages.
BYD DTC AI Analysis

ECU communication failure after accident repair

✓
After a front collision repair on a Qin EV300, DTC B169B-00 appeared and could not be cleared. Inspection found the accident deformed the front bulkhead and displaced the SRS ECU mounting bracket, cracking the ECU housing slightly and putting the internal gyroscope sensor out of calibration. The accident also crushed the CAN wiring harness, damaging the insulation and causing an intermittent short circuit. Replaced the SRS ECU, repaired the wiring harness, corrected the installation position, performed online matching, and the fault cleared.
BYD DTC AI Analysis

Software flash failure locked the ECU

✓
During an SRS software upgrade on a Qin 80 at the dealership, the diagnostic tool disconnected, causing the flash to fail and triggering DTC B169B-00. The ECU entered boot mode (flashing protection mode) and could not communicate via standard methods. Using a dedicated programming power supply to maintain stable voltage, the technician accessed engineering mode, re-flashed the underlying software, restored calibration data, and resolved the fault. This case emphasises that a regulated power supply must be used during flashing; power interruption is strictly prohibited.
Other Seal 6 EV 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.B1737DTC 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.B173BDTC 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.
Common problems reported for Seal 6 EV →Seal 6 EV overview →
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.