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 — Qin Plus

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.

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Cases Logged
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Causes
Likely Causes — Qin Plus
  • 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.
  • 2Terminal oxidation, backed-out terminals, or sealing ring failure at the sensor connector (yellow waterproof connector), causing increased contact resistance or intermittent open circuit.
  • 3Water entered the left rear sensor mounting hole during water wading or vehicle washing, causing moisture damage to the parameter storage unit on the sensor's internal circuit board.
  • 4Failure to perform 'SRS Sensor Configuration' or 'Crash Sensor ID Registration' with the dedicated diagnostic tool after installing non-genuine parts or performing 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 the SRS ECU, or abnormal terminating resistance causing signal reflection.
What To Do
  • 1
    Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes to discharge residual power from the SRS capacitor. Use VDS2000 or a dedicated diagnostic tool to read the complete 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. Locate the side impact sensor (yellow marking). Visually inspect the sensor housing for impact marks, cracks, or water ingress. Disconnect the connector. Check the terminals for oxidation, backing out, or deformation. Inspect the connector sealing ring integrity.
  • 3
    Circuit measurement: Measure the sensor-side harness connector using a multimeter: 1) Power wire (typically 12V, resistance to ground >10MΩ); 2) Ground wire (<0.5Ω); 3) LIN wire (voltage approximately 9-11V, no short to ground or power). Capture the LIN bus waveform using an oscilloscope to verify the communication messages are complete and undistorted. Measure the right rear sensor data for comparison.
  • 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 a 'crash sensor zero-point calibration'. This step requires BYD manufacturer 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 light turns off. Use the 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-test cycle and confirm B167900 does not reappear.
Real-World Cases
BYD DTC AI Analysis

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

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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

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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

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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

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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 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.B110811This DTC indicates a short circuit in the air conditioning system PM2.5 air quality sensor (rapid detector). Specifically, abnormal continuity exists between the sensor power supply circuit or signal output circuit and body ground or battery positive. This causes the control module (ACU/air conditioning controller) to detect abnormal current or a voltage signal outside the valid range (typically 0V or supply voltage). The PM2.5 sensor monitors internal and external particulate concentrations, providing the data the automatic air conditioning system uses to switch between fresh air and recirculation modes. A short circuit disables the air quality monitoring function. This fault may force the air conditioning system into recirculation protection mode and trigger related thermal management system faults, as the air conditioning system acts as a key actuator in vehicle thermal management. In severe cases, the short circuit current can damage the internal sampling circuit of the air conditioning controller or overheat the wiring harness.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.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.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.
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.