AU
B169F00

DTC B169F00 indicates the Airbag Control Unit (SRS ECU) detected a severe fault during its internal self-test — Qin Plus

Safety System

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.

The B169F00 fault code on the Qin Plus indicates the airbag control unit (SRS ECU) has detected a severe internal fault during self-testing, triggering a degraded mode that may disable airbags and seat belt pretensioners. Severity is medium. Common causes include internal hardware failure or power supply issues like low battery voltage or poor connections. Visiting an authorised dealer is recommended. Typical repair cost data is available.
4
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1SRS ECU internal hardware fault: Main control chip (MCU) damage, internal accelerometer signal processing circuit fault, ignition driver transistor breakdown, or memory data checksum failure.
  • 2Power supply system fault: battery voltage below 9V or above 16V; poor contact at the dedicated SRS fuse (usually 10A or 15A); loose connection in the ECU constant power (B+) or ignition power (IG) circuit; corroded ground terminal causing reference voltage drift.
  • 3CAN network communication fault: A short 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.
  • 4Corrupted software or calibration data: missing program segments due to interrupted flashing, uncleared latched crash data, or calibration data (Coding) mismatch with vehicle configuration.
  • 5Environmental factors: internal ECU moisture (water ingress or A/C condensate leakage), thermal fatigue cracking of circuit board solder joints (long-term high-temperature environment), electromagnetic interference causing processor program runaway.
What To Do
  • 1
    Perform a deep scan using the BYD VDS2000/3000 diagnostic tool. Record all fault codes and freeze frame data. Check specifically for accompanying B16XX series sensor faults or U-class communication faults.
  • 2
    Perform a power integrity check: measure the battery resting voltage (should be ≥12.4V), check the continuity and terminal fit of the SRS fuse in the instrument panel fuse box (F1/16 or F2/08, depending on vehicle model), measure the voltage to ground at ECU connector terminals B01-1 (B+) and B01-2 (IG), and measure the resistance to ground at B01-3 (GND) (should be <1Ω).
  • 3
    Communication line inspection: Disconnect the ECU connector. Measure the terminating resistance between CAN-H (B01-12) and CAN-L (B01-13) (should be ≈60Ω) and voltage to ground (CAN-H ≈2.6V, CAN-L ≈2.4V) to rule out wiring short or open circuits.
  • 4
    Perform software update: If the wiring is normal, update the SRS ECU software (SVM code: SRS_xxx). After updating, perform coding and calibration, including the seat occupancy sensor (OCS) and seat belt pretensioner configuration.
  • 5
    Component replacement and verification: If the fault persists, replace the SRS ECU (verify part number by vehicle model, e.g., E2 is EG-3636100). Perform online immobilizer matching and safety configuration programming on the new ECU. After replacement, use a dedicated resistor to simulate the crash sensor and perform a static ignition test. Finally, perform real-vehicle crash calibration verification.
Real-World Cases
BYD DTC AI Analysis

Qin EV SRS ECU CAN communication fault causing intermittent warning

✓
The airbag warning light would intermittently illuminate whilst driving and clear after an ignition cycle. A VDS scan revealed DTC B169F00 and multiple U-class communication fault codes. In-depth inspection found the bolt at SRS ECU earth point G106 (below left A-pillar) had loosened, causing unstable power supply when driving over bumps and triggering the internal voltage monitoring circuit into fail-safe mode. Re-tightened the earth bolt, cleared the fault codes, and monitored for one week with no recurrence.
Original source ↗
BYD DTC AI Analysis

E2 BEV SRS ECU memory data corruption repair

✓
After accident repairs, we replaced the airbag but the SRS warning light stayed on. The diagnostic tool read code B169F00, which returned after clearing. Inspection found the high current surge during the accident damaged the EEPROM data area inside the ECU. We fitted a new SRS ECU (Part No. EG-3636100A) and used VDS for online configuration: write VIN, configure seat type (5-seat/7-seat), match seatbelt pretensioner resistance (2.0Ω±0.1Ω). The system then passed the self-test.
BYD DTC AI Analysis

Model E3 SRS ECU internal short circuit after water exposure

✓
The airbag warning light stayed on after driving through water. Diagnosis showed DTC B169F00. Disassembly revealed the SRS ECU mounted beneath the centre console. A blocked air conditioning drain hose had caused condensate accumulation, and the aged ECU housing seal allowed water ingress. Opening the ECU showed corrosion on the circuit board and oxidised chip pins. Replaced the ECU, repaired the air conditioning drain hose, cleaned the wiring harness connectors, and applied anti-corrosion treatment. Fault resolved.
BYD DTC AI Analysis

The software update interruption corrupted the SRS ECU program.

✓
During an OTA update at the dealership, insufficient vehicle battery voltage (11.2V) aborted the SRS system flash. At the next start-up, the SRS warning light stayed on and the system logged DTC B169F00 that would not clear. An attempt to enter Boot mode for low-level reflash failed, indicating damaged Flash memory blocks. After replacing the SRS ECU, a dedicated regulated power supply (14V/30A) maintained voltage stability during the reflash of the latest software (Ver 3.2.1) and collision sensor calibration. This resolved the fault.
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.