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B169B-00

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

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 Qin Plus indicates an internal fault or communication error within the airbag control unit (SRS ECU), disabling all airbags and pretensioners. Severity is medium. Common causes include internal circuit board damage from voltage surges or thermal cycling, and abnormal power supply from voltage spikes or poor connections. Repair involves checking wiring or replacing the ECU at an authorized dealer. Typical repair cost data is available based on 4 recorded cases.
4
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Internal SRS ECU circuit board damage: Voltage surges (such as reversed polarity during jump-starting or charger surges), long-term thermal cycling causing cracked solder joints, or aging internal capacitors causing power supply filter failure.
  • 2Abnormal power supply: Prolonged low (<9V) or high (>16V) battery voltage, loose IGN power circuit connection, poor fuse contact, or oxidized ground point G201 (left side of instrument panel) causing reference voltage drift.
  • 3CAN 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 terminal resistance (120Ω), or bus voltage outside standard values (CAN-H 2.5-3.5V, CAN-L 1.5-2.5V).
  • 4Software or calibration data corrupted: An interrupted flashing process, calibration data checksum failure, or physical damage to the Flash memory prevents the ECU from loading the correct airbag deployment algorithm and crash threshold parameters.
  • 5External environmental factors: vehicle wading causing water ingress into the SRS ECU (installation below the air conditioning evaporator makes it susceptible to moisture), minor post-collision damage not immediately apparent, or strong electromagnetic interference (such as high-power radio equipment) causing an abnormal CPU reset.
What To Do
  • 1
    Diagnostic scan: 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 parameters at the time of the fault, such as vehicle speed, battery voltage, and temperature. Check for accompanying fault codes (such as U-prefix communication faults or B16XX-series sensor faults).
  • 2
    Power and ground check: Turn off the ignition. 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. Inspect fuses SB11 (10A, instrument panel power distribution box) and SB15 (15A) for blown elements or poor contact. Check the power supply waveform with an oscilloscope to rule out excessive ripple voltage (>100mV).
  • 3
    CAN bus inspection: Disconnect the SRS ECU connector and 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 the dominant level (CAN-H 3.5V / CAN-L 1.5V) and recessive level (2.5V) are normal, and check for abnormal bit stuffing errors.
  • 4
    ECU main unit inspection: Remove the SRS ECU located under the center console / behind the glovebox (exact location varies by model; on the Qin series, it is usually on the right side of the A/C evaporator box). Inspect the exterior for water stains, burn marks, cracks, or impact deformation. Measure the output of the ECU internal voltage regulator chip (it typically supplies a 5V reference voltage to the sensors). An abnormal reading confirms internal ECU damage. Note: Never disassemble the ECU housing (due to safety sealing and explosion-proof requirements).
  • 5
    Replacement and matching: If the ECU is damaged, replace it with a new SRS ECU with the same part number (e.g., HA2E-5810000A or specific to the vehicle model). Before installation, disconnect the negative battery terminal for at least 5 minutes. After installation, connect the diagnostic tool and execute 'Online Matching' and 'Coding'. Input the vehicle VIN and airbag configuration parameters (e.g., presence of side and knee airbags). Execute 'System Self-check' to clear fault codes and perform a simulated ignition test. Use the diagnostic tool to run the 'Crash Output Test' function. This operation flashes the airbag warning lamp but does not deploy the airbags.
  • 6
    Road test verification: Restore the vehicle, start the engine, and confirm the airbag warning lamp turns off after 6 seconds. Perform a road test over bumpy roads and through turns to confirm the fault code does not return. Use the diagnostic tool to read the live data stream. Verify sensor voltages, crash signal status, and CAN communication status are normal. Finally, inform the customer the SRS system is operating normally and emphasize 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 Qin Plus 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.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.B110BDTC 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.B173A1ADTC 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.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 Qin Plus →Qin Plus 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.