AU
B167500

DTC B167500 indicates a communication interruption or data anomaly between the Airbag Control Unit (ACU) and the Left Rear Side Impact Sensor (typically mounted in the left C-pillar, left rear door frame, or rear seat side panel area) — Atto 3

Safety System

DTC B167500 indicates a communication interruption or data anomaly between the Airbag Control Unit (ACU) and the Left Rear Side Impact Sensor (typically mounted in the left C-pillar, left rear door frame, or rear seat side panel area).

This sensor communicates with the ACU via a LIN bus or dedicated CAN line to monitor collision acceleration at the left rear of the vehicle.

The ACU sets this code when it fails to receive a valid data frame from the sensor within a set cycle (typically 100-500ms) or receives data with a checksum error.

This safety-critical fault prevents the side curtain airbag (CAB) and left rear side airbag from triggering accurately during a side impact, or in extreme cases, causes unintended airbag deployment.

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Cases Logged
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Causes
Likely Causes — Atto 3
  • 1Loose, oxidized, or poor contact at the left rear side impact sensor wiring harness connector (commonly results from water leaking through an aging left rear door frame seal, or failing to fully seat the connector after removing and installing the C-pillar trim panel).
  • 2Internal fault in the sensor body (damaged MEMS accelerometer chip, LIN transceiver fault, or internal voltage regulator circuit failure)
  • 3Wiring harness open or short circuit (prolonged bending, water ingress, or rodent damage to the main wiring harness inside the sill trim causes a LIN wire short to ground or power, or a short between the signal wire and shielding layer)
  • 4Airbag Control Unit (ACU) internal LIN driver chip fault or software communication protocol stack error
  • 5Sensor power supply or ground circuit fault (blown fuse or loose ground points G301/G302 causing excessive voltage drop below the 9V operating voltage)
What To Do
  • 1
    Use the VDS2000 or a dedicated BYD diagnostic tool to access the SRS system, read all DTCs, and record the freeze frame data. Check for accompanying fault codes such as B1676 (sensor not connected) and verify the ACU software is up to date.
  • 2
    Remove the left C-pillar trim panel or left rear door seal and locate the left rear side impact sensor (part number usually starts with 5A-). Visually inspect the connector for looseness and the pins for oxidation or discoloration. Measure the voltage between pin 1 (power) and pin 2 (ground) at the sensor connector. The voltage should be 9-16V.
  • 3
    Disconnect the sensor connector. Measure the resistance between the harness-side LIN wire (usually pin 3) and ground (should be >1 MΩ), and check for a short to power. Measure the LIN bus waveform using an oscilloscope. The normal waveform shows a 12 V pull-up, with a regular 0-12 V square wave during communication. If the waveform is a straight line or shows noise, repair the wiring.
  • 4
    If the circuit voltage and waveform are normal, measure the sensor resistance or verify by substitution: replace the sensor with a known-good unit of the same model, clear the fault code, and execute the 'Crash Sensor Calibration' procedure. Perform a road test or simulate vibration to confirm if the fault recurs.
  • 5
    If the fault persists after replacing the sensor, check the wiring harness continuity from the ACU to the sensor (focus on intermediate connectors J302/J303 inside the left sill trim panel). Repair the wiring harness if necessary. If the wiring harness is intact, this indicates an internal ACU fault. Replace the airbag control unit and rewrite the configuration code.
  • 6
    After repair, use the diagnostic tool to perform 'SRS System Self-learning' and 'Crash Sensor Zero Point Calibration'. Confirm all sensor communication statuses are 'Online' and the instrument cluster airbag warning lamp is off. Perform a side impact simulation test (lightly tap the vehicle body near the sensor) and confirm the data stream is normal.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Water leak at left C-pillar caused sensor connector oxidation on Qin Pro DM

✓
A 2019 Qin PRO DM arrived with the airbag warning light illuminated. VDS scan retrieved DTC B167500. Removing the left C-pillar trim panel revealed the rear windscreen seal had perished, allowing water ingress that caused severe oxidation and blackening of the terminals inside the left rear side impact sensor connector (white 3-pin). Replaced the rear windscreen seal, cleaned the connector and sensor pins with electronic cleaner, applied conductive grease, and reinstalled the components. Fault resolved.
BYD DTC AI AnalysisFrom Chinese market (translated)

Aftermarket reversing camera installation caused a LIN bus short circuit

✓
2018 Qin Pro petrol variant. While retrofitting a reversing camera, the owner accidentally pierced the SRS wiring harness sleeve with a screw when routing cables through the left C-pillar, causing the LIN wire of the left rear side impact sensor to short to earth. Symptoms: airbag warning light permanently illuminated; diagnostic tool unable to communicate with the sensor. Repair: stripped back the harness insulation, repaired the damaged LIN wire, re-wrapped with waterproof tape; the system returned to normal after clearing fault codes.
BYD DTC AI AnalysisFrom Chinese market (translated)

Internal chip failure in sensor body

✓
A Qin PRO DM with 30,000 km and no collision history intermittently displayed B167500. Inspection found normal voltage at the sensor connector (12.4 V), with occasional interruptions in the LIN bus waveform. Replaced the left rear side impact sensor (part number 5A-3638400) and performed the sensor calibration procedure; the fault did not recur. Disassembled the original sensor and found a cold solder joint on the internal PCB.
BYD DTC AI AnalysisFrom Chinese market (translated)

Outdated ACU software caused false communication alerts.

✓
2019 BYD Qin Pro. The airbag warning light on the instrument cluster intermittently illuminated when driving over rough roads. Retrieved stored DTC B167500. Checked the wiring harness and sensors; all were normal. Measured LIN line resistance and waveform; both were normal. Reviewed the Technical Service Bulletin (TSB) and found that the ACU software on this batch had the communication fault tolerance threshold set too tight. Updated the ACU software to the latest version V2.3.1. Fault resolved.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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. Sources: [1]