AU
B169800

DTC B169800 indicates an internal fault or communication failure in the airbag control unit (SRS ECU) — Atto 3

Safety System

DTC B169800 indicates an internal fault or communication failure in the airbag control unit (SRS ECU).

As the core control module of the airbag system, the SRS ECU monitors crash sensor signals, processes crash algorithms, and controls airbag and seat belt pretensioner deployment.

This DTC indicates the ECU self-check detected an internal processor fault, memory error, power supply fault, or CAN communication interruption with other modules (such as the Vehicle Control Unit or Body Control Module).

This fault poses a severe safety risk and may cause the airbags to fail to deploy or to deploy inadvertently during a collision.

Repair immediately.

The B169800 fault code on the Atto 3 indicates an internal fault or communication failure in the airbag control unit (SRS ECU), posing a medium severity safety risk that may prevent proper airbag deployment or cause inadvertent deployment. Common causes include power supply issues (voltage outside 9-16V range) or internal hardware failure. Visit an authorised dealer immediately for diagnosis and repair. Typical repair cost data is available based on 4 recorded cases.
4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Poor contact in the SRS ECU power supply or ground circuit, or abnormal voltage (below 9V or above 16V)
  • 2SRS ECU internal hardware fault (processor, memory, or internal sensor damage)
  • 3CAN bus communication fault (loss of communication between SRS ECU and vehicle network, or signal interference)
  • 4SRS ECU software outdated or calibration data missing/corrupted.
  • 5Short or open circuit in the communication line between the crash sensor and the SRS ECU.
What To Do
  • 1
    Use the BYD VDS or a dedicated diagnostic tool to read the complete fault codes and freeze frame data. Confirm if B169800 is a current or historical fault, and check for accompanying communication fault codes (such as codes starting with U).
  • 2
    Check the instrument panel SRS warning light status (solid or flashing). Disconnect the battery negative terminal for 5 minutes, then restore power. Perform a system self-check and observe if the fault code reappears.
  • 3
    Check the SRS ECU power supply and ground: Measure the voltage and resistance at ECU connector terminal 1 (constant power B+), terminal 2 (ignition switch power IG), and the ground terminal. Ensure the voltage is 9-16V and the ground resistance is less than 1Ω.
  • 4
    Check CAN bus communication: Measure CAN-H and CAN-L voltages (CAN-H approximately 2.6-2.8V, CAN-L approximately 2.2-2.4V) and terminating resistance (approximately 60Ω) at the diagnostic interface or SRS ECU connector to rule out open or short circuits in the wiring.
  • 5
    Check the SRS ECU connector and wiring harness: inspect for water ingress, corrosion, deformed pins, backed-out pins, or harness damage. Pay special attention to wiring harness connections after front-end collision repairs.
  • 6
    If the wiring is normal, upgrade or reprogram the SRS ECU software (using the latest software version). If the fault persists, replace the SRS ECU assembly. After replacement, perform online programming, write the configuration code, and perform a system self-check.
Real-World Cases
BYD DTC AI Analysis

BYD Qin Pro EV: SRS warning light came on while driving, logged DTC B169800

✓
The SRS warning light on the dashboard suddenly came on while driving normally. Connected a VDS diagnostic tool and read current fault code B169800 (SRS ECU fault) and stored fault U0155 (lost communication with instrument cluster). Inspection revealed the vehicle had recently had an aftermarket audio system installed, and the centre console had been removed and reinstalled. Removed and inspected the SRS ECU, located under the centre console on the central tunnel, and found the ECU power connector not fully seated, causing intermittent power loss from vibration while driving. Reseated the connector and secured the wiring harness. Cleared the fault codes; the SRS light went out. Road tested for 50 km with no recurrence of the fault.
Original source ↗
BYD DTC AI Analysis

BYD Han EV reports DTC B169800 after accident repair; code will not clear.

✓
Front-end collision. Replaced front bumper and impact sensors. After repairs, airbag warning light stayed on. Read DTC B169800. Inspection found slight deformation of the SRS ECU housing, no cracks. Measured ECU power supply and ground: normal. CAN communication: normal. ECU internal self-test failed. Determined shock wave from collision damaged internal accelerometer or processor in SRS ECU. Replaced with new SRS ECU. Performed online programming via VDS, wrote VIN and configuration parameters. Ran system self-test: passed. Fault cleared.
Original source ↗
BYD DTC AI Analysis

BYD e2 intermittently reports SRS ECU fault

✓
The owner reported the SRS warning light occasionally comes on, sometimes clearing after cycling the ignition. The diagnostic scanner retrieved intermittent DTC B169800. Inspection found the vehicle had been through water, with water accumulation marks at the SRS ECU mounting bracket beneath the floor. Removed the ECU and found slight oxidation inside the connector. Cleaned the ECU and harness connectors, dried internal moisture with compressed air, and applied electrical contact protectant. Also found the ECU ground wire attachment point rusted; sanded the ground terminal and retightened. Followed up for one month post-repair, no recurrence.
Original source ↗
BYD DTC AI Analysis

BYD Tang DM sets DTC B169800 after battery pack replacement

✓
After replacing the power battery pack at the dealership, the airbag warning light illuminated during handover. Retrieved DTC B169800. Investigation found the 12V battery had been disconnected for too long during the repair, and the technician had disconnected the SRS ECU connector to gain access. A communication timeout occurred after reconnection. Performed SRS reconfiguration and calibration using VDS, cleared the DTC, and the system returned to normal. Root cause: ECU data loss after power disconnection, requiring system reconfiguration.
Original source ↗
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.