AU
B167900

DTC B167900 indicates a logic error or communication protocol mismatch in the parameter data transmitted from the left rear side impact sensor (typically installed in the left C-pillar or rear door frame area) to the SRS airbag control unit — Atto 3

Safety System

DTC B167900 indicates a logic error or communication protocol mismatch in the parameter data transmitted from the left rear side impact sensor (typically installed in the left C-pillar or rear door frame area) to the SRS airbag control unit.

This is not a simple circuit fault (such as an open or short circuit).

Instead, specific identification parameters uploaded by the sensor (such as part number ID, calibration zero offset value, sensitivity coefficient, or communication checksum) exceed the SRS ECU storage range or fail verification.

Possible causes include: - Incorrect sensor configuration (e.g., failing to write parameters after accident repairs) - Corrupted parameter data stored in the sensor's internal ASIC chip - LIN/CAN bus communication interference causing data frame errors - Unstable sensor supply voltage causing abnormal analog-to-digital conversion This fault prevents the SRS system from confirming sensor data reliability.

The system may enter a degraded mode, disabling window airbag or side curtain airbag deployment and significantly reducing side impact protection.

The B167900 fault code on the Atto 3 indicates a communication error between the left rear side impact sensor and the airbag control unit, where sensor parameters fail validation. Severity is medium. Common causes include wiring wear at the C-pillar or connector corrosion. Visit an authorised dealer for repair. Typical repair cost data is available based on 5 recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Prolonged bending at the C-pillar or rear door hinge causes internal wire wear or poor contact in the left rear side impact sensor wiring harness, resulting in power supply or signal voltage drift.
  • 2Oxidized pins, backed-out pins, or sealing ring failure at the sensor connector (yellow waterproof connector), causing increased contact resistance or an intermittent open circuit.
  • 3Water seeps into the left rear sensor mounting hole during vehicle wading or washing, causing moisture damage to the parameter storage unit on the sensor internal circuit board.
  • 4Failure to perform 'SRS Sensor Configuration' or 'Crash Sensor ID Registration' using the dedicated diagnostic tool after non-genuine parts replacement or accident repairs, resulting in a parameter mismatch.
  • 5Electromagnetic interference on the communication bus (LIN line or low-speed CAN) between the left rear sensor and SRS ECU, or an abnormal terminating resistor causing signal reflection.
What To Do
  • 1
    Safety Preparation: Disconnect the negative battery terminal and wait at least 3 minutes to discharge the SRS capacitor. Use the VDS2000 or a dedicated diagnostic tool to read all fault codes. Confirm B167900 is a current fault (Active) and check for an accompanying B167800 (hardware fault) or communication fault codes.
  • 2
    Physical inspection: Remove the left rear C-pillar trim panel and sill trim panel to locate the side impact sensor (yellow marking). Visually inspect the sensor housing for impact marks, cracks, or water ingress. Disconnect the connector. Inspect the pins for oxidation, backing out, or deformation. Verify the integrity of the connector sealing ring.
  • 3
    Circuit measurement: Use a multimeter to measure the sensor harness-side connector: 1) power wire (usually 12V, resistance to ground >10MΩ); 2) ground wire (<0.5Ω); 3) LIN wire (voltage approximately 9-11V, no short to ground or power). Use an oscilloscope to capture the LIN bus waveform and confirm communication messages are complete and undistorted. Compare measurements with right rear sensor data.
  • 4
    Component replacement and configuration: If the wiring harness is normal, replace the left rear side impact sensor (use only genuine parts). After installation, perform the 'SRS system configuration' procedure (write the sensor ID and calibration parameters). Some models require performing the 'impact sensor zero-point calibration'. This step requires BYD factory diagnostic authorization.
  • 5
    Verification and testing: Reconnect all components and restore power. Clear the fault code, start the vehicle, and verify the instrument cluster airbag warning lamp turns off. Use a diagnostic tool to read the data stream. Confirm the left rear sensor acceleration value is 0±0.5g when the vehicle is stationary and responds normally to door tapping. Perform a system self-check cycle and confirm B167900 does not return.
Real-World Cases
BYD DTC AI Analysis

Qin Pro DM: Left rear C-pillar wiring harness wear causing sensor parameter drift

✓
After wading through water, the airbag warning light came on the dash. Retrieved current fault code B167900. Inspection found the wiring harness retaining clip missing below the left rear C-pillar. The harness had chafed against the metal bracket over time, wearing through the insulation. Rainwater ingress caused an intermittent short to ground on the LIN line (resistance about 200 Ω). Sensor supply voltage dropped from 12 V to 7 V, causing the uploaded acceleration parameters to exceed the SRS ECU validation limits. Repair: Repaired the damaged wiring (replaced a 20 cm section), re-wrapped with waterproof tape, installed a new harness retaining clip, cleared the fault codes, and performed sensor calibration. Fault resolved.
BYD DTC AI Analysis

E2 EV: Sensor parameters not configured after rear bumper replacement

✓
The vehicle was rear-ended. After the workshop replaced the left rear side impact sensor (aftermarket), the instrument cluster kept displaying an airbag fault. VDS2000 read DTC B167900. The data stream showed the left rear sensor ID as 'FF FF FF FF' (unprogrammed). The aftermarket sensor had not been pre-programmed, and the technician did not run the configuration procedure. Fix: Replaced the sensor with an OEM part, accessed 'SRS System Configuration' via the diagnostic tool, wrote the VIN-matched sensor ID and impact threshold parameters, and cleared the DTC. The system returned to normal.
BYD DTC AI Analysis

Qin EV: Oxidised sensor connector caused intermittent parameter errors

✓
The customer reported the airbag warning light illuminating intermittently, particularly during rain or after washing the vehicle. The diagnostic scanner showed intermittent fault code B167900. Removing and inspecting the left rear C-pillar sensor connector revealed green copper corrosion inside the yellow connector. Pin contact resistance jumped from 0.5Ω to over 15Ω when moving the wiring harness. Long-term parking in a humid environment aged the sensor connector seal, allowing water ingress. Repair: Cleaned the connector pins with precision electrical contact cleaner, replaced the waterproof seal, and applied conductive grease. Fault resolved. Check other sensor connectors on vehicles from the same production batch.
BYD DTC AI Analysis

Qin Pro petrol variant: LIN bus interference causing data frame errors

✓
After installing aftermarket ambient lighting, the instrument cluster occasionally displayed the airbag warning light. Diagnostics found DTC B167900 alongside multiple body LIN communication fault codes occurring simultaneously. Inspection revealed that the installer had cut into the wiring near the left B-pillar to draw power, interfering with the SRS sensor LIN bus signal. An oscilloscope showed significant glitches in the LIN waveform, causing CRC checksum failures of the parameter packets sent by the sensor. To resolve the issue, we removed the non-compliant aftermarket wiring, repaired the factory wiring harness insulation, fitted ferrite cores at both ends of the SRS sensor LIN line to suppress interference, cleared the fault codes, and monitored for a week without recurrence.
BYD DTC AI Analysis

Internal IC damage in the E3 sensor caused fixed parameter errors.

✓
The vehicle had no collision history, but the airbag warning light suddenly illuminated while driving. Pulled DTC B167900 but it would not clear. Checked wiring harness, connectors, and power supply — all normal. Swapped the sensor to a different position; the fault moved to that position, confirming the original sensor was faulty. Disassembled the faulty sensor and found a cold solder joint on the internal MEMS chip, causing the zero-bias acceleration output to remain fixed at 2.3g (normal: 0g). This exceeded the ECU's ±0.5g tolerance, causing the ECU to log a 'parameter error'. Fix: Replaced the left rear side impact sensor assembly, ran the system self-test, and resolved the fault. Analysis: batch production quality issue with the sensor.
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.