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) — Seal U

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.

4
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Loose, oxidized, or poor contact at the left rear side impact sensor wiring harness connector (commonly due to water ingress from an aging left rear door frame seal, or an improperly seated 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 panel causes a LIN line 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 9V operating voltage)
What To Do
  • 1
    Use VDS2000 or the BYD dedicated diagnostic tool to access the SRS system. Read the complete DTCs and record the freeze frame data. Check for accompanying fault codes such as B1676 (sensor not connected). Verify the ACU software is the latest version.
  • 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) on the sensor connector. The voltage must be 9-16V.
  • 3
    Disconnect the sensor connector. Measure the resistance to ground on the harness-side LIN wire (usually pin 3) (should be >1 MΩ) and check for a short to power. Use an oscilloscope to measure the LIN bus waveform. A normal waveform shows a 12V pull-up and a regular 0-12V square wave during communication. If the waveform is a straight line or shows noise, repair the circuit.
  • 4
    If 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 type, 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 between the ACU and 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) to 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 Seal U 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. Sources: [1]