AU
B167800

This DTC indicates the SRS electronic control unit detects a functional fault in the Left Rear Side Impact Sensor (mounted in the lower left B-pillar or inside the left rear quarter panel) — Seal U

Safety System

This DTC indicates the SRS electronic control unit detects a functional fault in the Left Rear Side Impact Sensor (mounted in the lower left B-pillar or inside the left rear quarter panel).

Specifically, the ECU receives no valid acceleration signal, the signal exceeds the normal threshold (typically 0.5-4.5V), or the system detects an open or short circuit.

This sensor monitors side-impact acceleration on the left rear of the vehicle.

The ECU uses this signal to determine whether to deploy the left curtain airbag and rear side airbag.

When this fault occurs, the system enters fail-safe mode, illuminates the airbag warning light, and disables the related side airbags, significantly increasing the risk of occupant protection failure during a side collision.

3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1The piezoelectric accelerometer or signal processing IC inside the sensor body is damaged, causing output signal drift or no signal.
  • 2Water ingress and oxidation in the harness connector at the base of the left B-pillar (common after car washes or wading) causes increased contact resistance or a short circuit in the signal wire.
  • 3Body wiring harness broken at the B-pillar hinge bend, or incorrect harness routing after accident repairs, causing an open circuit.
  • 4Loose or detached sensor mounting bracket, or external impact to the sensor, causing internal inertial measurement unit misalignment.
  • 5SRS ECU internal sampling circuit fault (uncommon; confirm after ruling out wiring faults)
What To Do
  • 1
    Use the BYD VDS3000 diagnostic tool to read the complete fault codes and freeze frame data. Check for accompanying sub-fault codes such as B167711 (short to ground) or B167712 (short to power). Record the vehicle speed and ambient temperature at the time of the fault.
  • 2
    Disconnect the battery negative terminal and wait at least 90 seconds to ensure the SRS capacitor discharges completely. Remove the left lower B-pillar trim panel and the left rear door sill trim panel. Visually inspect the crash sensor exterior for cracks and verify the installation torque marks align (standard torque is usually 8-10 N·m).
  • 3
    Disconnect the sensor 2-pin connector. Check the terminals for oxidation, backed-out pins, or signs of water ingress. Clean the terminals with electrical contact cleaner and apply conductive grease.
  • 4
    Measure voltage on the wiring harness side: With the ignition ON, the signal wire to ground voltage should be approximately 2.5V (reference voltage), and the power wire should measure 12V battery voltage; measure insulation to confirm the signal wire to ground resistance is greater than 1MΩ.
  • 5
    If the circuit is normal, remove the sensor and measure its static resistance (typically 2.0-3.0 kΩ; refer to the workshop manual). Lightly tap the sensor while observing the resistance. If the resistance does not change, the sensor has internal damage.
  • 6
    Replace the left rear side impact sensor (Note: On some high-trim models, execute the 'Replace Crash Sensor' configuration procedure in VDS and write the sensor serial number). Reconnect the wiring harness and verify the waterproof rubber seal is intact.
  • 7
    Reconnect the battery, clear the fault code, and perform the SRS system self-check (approx. 10 seconds). Confirm the warning lamp turns off, then use the dedicated diagnostic tool to read the live data stream. Lightly tap near the sensor mounting position to verify the acceleration signal changes.
  • 8
    Perform a road test to confirm no intermittent fault codes reappear on bumpy roads. Finally, check and clear all historical fault codes.
Real-World Cases
BYD DTC AI Analysis

Left rear sensor intermittently reporting fault after wading

✓
2018 Qin Pro DM. Owner reported the airbag warning light would intermittently come on during rain or after washing. VDS scan showed active code B167800. Removed the left B-pillar lower trim, found water inside the sensor connector and green copper corrosion on the pins. Traced to deteriorated door seals allowing water ingress along the wiring harness. Cleaned harness terminals, replaced the sensor (internally moisture-damaged), rewrapped the harness and adjusted the waterproof tape position. Fault resolved.
BYD DTC AI Analysis

Open circuit in wiring harness following accident repair caused fault

✓
2019 Qin Pro (petrol). After a left rear side collision, an independent workshop repaired the vehicle. After delivery, the airbag light stayed on. Diagnosis found current DTC B167800 and no voltage at the sensor terminals. Tracing the wiring harness revealed a clamping plate had crushed it during the inner B-pillar repair, breaking the power wire. Repair involved soldering and heat-shrinking the harness, rerouting the wiring to avoid the crush point, and clearing the fault code. The system returned to normal.
BYD DTC AI Analysis

Sensor ageing caused signal drift

✓
The SRS warning light suddenly came on in a 2018 Qin Pro DM with 120,000 km and no collision history. The diagnostic scan tool displayed code B167800. Checked the wiring harness and connectors and found no faults. Measured the sensor's static resistance and found it normal. However, oscilloscope monitoring revealed abnormal noise in the signal output. Determined this was due to internal accelerometer degradation in the sensor. Replaced the left rear side impact sensor and performed the sensor matching procedure. 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.