AU
B169D-00

DTC B169D-00 indicates the airbag control unit (SRS ECU) detects an internal fault or abnormal system communication — Atto 3

Safety System

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.

The B169D-00 fault code on the Atto 3 indicates an internal fault or communication error within the airbag control unit (SRS ECU), which manages crash detection and deployment. This medium-severity issue typically stems from ECU hardware damage or power supply faults. It requires immediate attention at an authorised dealer to restore critical safety systems. Typical repair cost data is available based on 5 recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1SRS ECU internal hardware fault: Damage to the control module internal CPU, memory chip, or power regulation circuit causes the self-check program to fail.
  • 2Power supply and ground fault: Unstable voltage or excessive voltage drop in the constant power (+BAT) or ignition switch power (+IG) supply, or ground harness contact resistance exceeding the limit (>10Ω), causing abnormal ECU power supply.
  • 3CAN bus communication fault: Short circuit, open circuit, or abnormal terminal resistance in the CAN-H/CAN-L lines between the SRS ECU, vehicle gateway, and instrument cluster (normally 60 Ω in parallel), interrupting data exchange.
  • 4Wiring harness connector issue: Water ingress and oxidation in the ECU plug, terminal back-out, or poor contact, especially after wading or washing the vehicle.
  • 5Software or data corruption: Abnormal ECU internal calibration data, abnormal crash threshold parameters, or software version defects cause the system to falsely detect a hardware fault.
What To Do
  • 1
    Use a BYD VDS2000 or Launch X431 diagnostic tool to access the SRS system, read and record all DTCs and freeze frame data, and confirm B169D-00 is a current (Active) fault, not a history fault.
  • 2
    Check the SRS ECU exterior and installation condition. Confirm there is no physical damage or signs of water ingress. Check the wiring harness connector (usually located under the centre console or central tunnel) for looseness, water ingress, or oxidized pins.
  • 3
    Measure the ECU power supply voltage: Use a multimeter to verify the +B terminal (constant power) voltage is 12.0-14.5V, the +IG terminal (ignition ON) voltage matches battery voltage, and the ground terminal to vehicle body resistance is <1Ω.
  • 4
    Check the CAN communication lines: disconnect the ECU connector, measure CAN-H and CAN-L voltage to ground (normal: approx. 2.5V), measure the resistance between the two wires (normal: 60Ω±5Ω, due to parallel 120Ω terminating resistors), and check for short or open circuits.
  • 5
    Perform software diagnostics: Reflash or upgrade the SRS ECU software (requires the BYD dedicated diagnostic tool and the latest software package) to eliminate false reports from software defects.
  • 6
    Replace the SRS ECU: If wiring measurements are normal and software flashing fails, replace the airbag control module (verify the part number by vehicle model, e.g., Qin EV450 is...). After replacement, perform coding and immobilizer matching.
  • 7
    System calibration and testing: After replacing the ECU, perform crash sensor zero-point calibration, test seat belt pretensioner and airbag circuit resistance, and finally perform a simulated crash signal test (using the special tool) to confirm the fault code clears and the instrument cluster airbag warning light turns off.
Real-World Cases
BYD DTC AI Analysis

Qin EV300 intermittent SRS ECU fault after water wading

✓
A 2017 Qin EV300 presented with an intermittent 'Check SRS System' warning on the instrument cluster, along with intermittent DTC B169D-00. Investigation revealed the vehicle had been driven through flood water. The SRS ECU is located beneath the centre tunnel; upon disassembly, water staining was found inside the ECU connector and minor oxidation on the pins. Cleaning the connector and applying conductive paste temporarily cleared the fault, but it returned after one week. Measurement identified corrosion on the ECU ground wiring harness following water ingress, causing contact resistance to increase to 15Ω. Replacing the ground wiring harness and resealing the connector permanently resolved the fault.
BYD DTC AI Analysis

Qin 100 B169D-00 fault after accident repair

✓
After front collision repairs on a 2017 Qin 100, the airbag warning light stayed on, storing DTC B169D-00. Inspection found the front impact sensor wiring harness had been damaged in the crash. The repair shop used a non-genuine harness, causing CAN bus signal interference. The SRS ECU detected the communication fault and triggered a protective fault. Replaced the front impact sensor harness with a genuine part, confirmed no noise on the CAN bus waveform, cleared the DTCs, and the system returned to normal.
BYD DTC AI Analysis

Qin EV450 software version defect causes false positive

✓
A 2018 BYD Qin EV450 developed a B169D-00 fault code after a service. The vehicle had no collision history, and a wiring inspection found no abnormalities. Using a VDS diagnostic tool, technicians found the ECU was running an early software version (V1.02) with a known self-check logic defect. They upgraded the ECU software to V1.05, which cleared the fault code automatically. The fault has not returned. This software issue is common in some 2018 production batches. Resolve it via an OTA update or a dealer visit for the software upgrade.
BYD DTC AI Analysis

Battery discharge caused abnormal SRS ECU voltage

✓
A long-parked Qin 80 had a severely discharged battery (voltage <9V). After a jump start, multiple warning lights illuminated on the dashboard, including the airbag light. The scan tool retrieved DTC B169D-00. The ECU self-check had failed due to the low voltage. We fully charged the battery (voltage restored to 12.8V) and cleared the codes; the fault did not return. We recommended the owner check the battery State of Health (SOH) to prevent false ECU faults from voltage instability.
BYD DTC AI Analysis

ECU incompatibility fault after aftermarket airbag replacement

✓
A workshop replaced the driver airbag on a Qin EV300 with an aftermarket unit. Afterwards, the instrument cluster airbag warning light came on and the system stored DTC B169D-00 along with multiple airbag circuit faults. The shop found the aftermarket igniter resistance was 1.2 Ω, while the OEM specification is 2.0 Ω ± 0.3 Ω, causing the ECU to detect a system fault and activate protection mode. After installing a genuine driver airbag, the technician used a scan tool to run the 'replace airbag component' reset procedure. The fault codes cleared and the system returned to normal operation.
Other Atto 3 Fault Codes
P0AA6Hybrid Battery Voltage System Isolation FaultB1108For 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.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.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.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.
Common problems reported for Atto 3 →Atto 3 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.