AU
B166711

DTC B166711 indicates a short to ground in the signal circuit of the airbag system (SRS) left side impact sensor — Atto 8

Safety System

DTC B166711 indicates a short to ground in the signal circuit of the airbag system (SRS) left side impact sensor.

This sensor typically mounts inside the driver-side B-pillar trim panel and detects left-side impact acceleration.

The SRS control unit sets this fault when it detects abnormal voltage to ground on the sensor signal wire (continuous low level) or a resistance value below the threshold.

This fault causes the airbag system to enter fail-safe mode.

During a side collision, the left side airbag and left curtain airbag may fail to deploy.

The instrument panel continuously illuminates the airbag warning light.

The BYD diagnostic protocol defines the DTC suffix '11' as 'Shorted to Ground', distinguishing it from '00' (open circuit/not connected) or other fault types.

5
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Left B-pillar wiring harness worn or crushed: During long-term vehicle use, frequent door operation causes the wiring harness inside the B-pillar to rub against the metal body frame. Damaged insulation shorts the wire to body ground.
  • 2Sensor connector water ingress or corrosion: Driving in rain, improper car washing, or poor window seals allow water to seep into the left B-pillar, causing oxidation or a short circuit at the sensor connector terminals.
  • 3Side impact sensor internal fault: Damage to the internal piezoelectric element or circuit board shorts the signal terminal to ground, causing an abnormal drop in resistance (normal: 2-3kΩ).
  • 4Wiring harness damage after a left-side collision: The vehicle sustained a left-side collision, and incomplete wiring harness repairs during servicing caused the signal wire to short to ground.
  • 5Left Domain Controller (G09) connector fault: Communication line between the Left Domain Controller and the SRS control unit, or the sensor power/signal line, shorts to ground at the connector.
What To Do
  • 1
    Connect the VDS diagnostic tool to the vehicle OBD port, read the SRS system fault codes, confirm DTC B166711 (left side impact sensor short to ground) is present, and record the freeze frame data.
  • 2
    Switch off the ignition and remove the driver-side B-pillar lower trim panel (requires removing the seat belt pretensioner trim panel) to expose the left side impact sensor assembly.
  • 3
    Visually inspect the sensor wiring harness for obvious damage or pinch marks. Focus on areas where the harness contacts metal body edges. Use a multimeter to measure the signal wire to ground resistance (Normal: greater than 10kΩ; Short circuit: close to 0Ω).
  • 4
    Disconnect the sensor connector and check the terminals for water ingress, corrosion, or backed-out pins. Clean the terminals with electrical contact cleaner and blow dry. If necessary, apply conductive grease to improve contact.
  • 5
    Measure the sensor body resistance: Disconnect the sensor and measure the resistance between the sensor signal terminal and ground. The normal value is 2-3kΩ. If the resistance is too low or near 0Ω, the sensor has an internal short circuit. Replace the sensor.
  • 6
    If the sensor is normal but the circuit is shorted, repair the damaged wiring harness insulation (wrap with heat-shrink tubing or insulating tape) and re-secure the wiring harness to prevent contact with vehicle body metal.
  • 7
    Replace the left side impact sensor (confirm the part number for the specific model, such as Qin PLUS DM-i, Yuan PLUS, etc.), securely connect the plug, and reinstall the B-pillar trim.
  • 8
    Reconnect the VDS, clear the fault code, and perform the SRS system self-check procedure. Confirm B166711 does not reappear, the instrument cluster airbag warning light turns off, and the system returns to normal.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

B-pillar wiring harness wear caused a short circuit in a BYD Qin PLUS DM-i.

✓
Vehicle: BYD Qin PLUS DM-i 2021. Symptom: Intermittent airbag warning light, more frequent in rain. Diagnosis: VDS scan: SRS DTC B166711 (left side impact sensor short to earth). Removed driver side B-pillar trim. Found sensor harness chafed at the centre retaining clip, copper exposed and contacting body earth, causing a signal wire short to earth. Repair: Repaired the damaged harness: cut out the damaged section, re-soldered the wires, and insulated with double-layer heat shrink tubing. Rerouted harness clear of metal body panels, and secured to eliminate strain. Cleared fault codes; fault resolved.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Water ingress caused corrosion of the sensor connector on the BYD Yuan Plus.

✓
Vehicle: BYD Yuan PLUS (ATTO 3/SC2E). Symptoms: Airbag warning light constantly illuminated; no collision history. Diagnosis: VDS read DTC B166711. According to the workshop manual, this indicates a left side impact sensor short to ground. Removed and inspected the left B-pillar trim panel and found the sensor connector seal had deteriorated; the pins showed green copper corrosion and water staining, causing a short between the signal and ground terminals. Repair: Cleaned the connector terminals with electronic contact cleaner, blow-dried them, applied conductive grease, fitted a new waterproof seal, and added waterproof tape to the connector where necessary. After the repair, cleared the DTC. System self-test passed.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Song PLUS DM-i side impact sensor internal fault

✓
Vehicle: BYD Song PLUS DM-i. Symptom: Dashboard displays "Airbag System Fault" with the warning light constantly illuminated. Diagnosis: Connected a VDS scanner and retrieved DTC B166711. Checked the sensor wiring harness and found no faults. Disconnected the sensor plug and measured the sensor body resistance, finding only 0.3kΩ (well below normal 2-3kΩ). Determined the sensor had an internal short to ground. Solution: Replaced the left B-pillar side impact sensor assembly (part number to be confirmed against VIN). Reconnected the plug, ensuring full engagement (audible click). Cleared DTCs with VDS, performed SRS self-test, and confirmed the fault was resolved.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin EV wiring harness improperly repaired after collision

✓
Model: 2019 BYD Qin EV. Symptoms: Airbag warning light illuminated on the instrument cluster after a minor scrape on the left side. Diagnosis: VDS scan showed DTC B166711. Accident repair records indicated previous panel beating on the left B-pillar. Removing the interior trim revealed the wiring harness had been poorly bundled during the repair, with the signal wire insulation worn through and grounding against the body. Repair: Re-routed and tidied the B-pillar wiring harness, repaired the damaged conductor (cut and spliced, or replaced the entire section), applied double-layer protection with insulating tape and heat-shrink tubing, and secured the harness with safe clearance from metal edges. Cleared the fault codes and verified the repair.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD E2 left domain controller connector fault

✓
Vehicle: 2019 BYD E2. Symptom: Airbag warning light illuminating intermittently, more frequent on rough roads. Diagnosis: Scanned with VDS and retrieved DTC B166711. Inspected the left B-pillar sensor and wiring, found no faults. Traced the circuit to the left domain controller (G09) and discovered a terminal pin had backed out in connector G09-X1, causing the signal wire to short to earth against the bodywork. Repair: Repaired the backed-out terminal, fully seated the connector, and secured the wiring harness with cable ties to relieve strain. Cleared the fault codes and road-tested; the fault did not return.
Other Atto 8 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]