AU
B176F11

DTC B176F11 indicates the airbag control unit (SRS ECU) detects an abnormally low-resistance connection between the left rear seat belt pretensioner (squib) circuit and body ground (typically <2Ω) — Atto 8

Safety System

DTC B176F11 indicates the airbag control unit (SRS ECU) detects an abnormally low-resistance connection between the left rear seat belt pretensioner (squib) circuit and body ground (typically <2Ω).

The pretensioner is a pyrotechnic actuator with a normal resistance of approximately 2.0-3.0Ω.

A short to ground causes the SRS system to identify a safety risk in this circuit and trigger fail-safe mode.

This mode immediately cuts power to the pretensioner circuit, illuminates the airbag warning lamp, and disables left rear pretensioner deployment during a collision.

It may also affect the normal deployment logic of the entire airbag system.

This is a hard DTC.

The SRS ECU continuously logs the code while the short circuit exists.

Repair the fault immediately to maintain passive safety system integrity.

4
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Wiring harness chafing under the left rear seat: Fore-and-aft seat adjustment or trapped objects damage the pretensioner wiring harness insulation, causing a short circuit to the vehicle metal frame.
  • 2Inner B-pillar wiring harness interference: The wiring harness retaining clip inside the left rear B-pillar trim panel detached, causing the harness to rub against a sharp sheet metal edge and short to ground.
  • 3Connector water ingress and corrosion: Rear floor water exposure or interior cleaning allows water to enter the pretensioner connector (usually located under the seat or at the base of the B-pillar). Electrolytic corrosion between the pins causes a short to ground.
  • 4Pretensioner body internal fault: Insulation failure of the internal squib creates continuity between the pyrotechnic chamber and the housing, causing an internal short to ground.
  • 5Improper repair procedures: Fixing screws piercing or pinching the wiring harness during seat cover installation, seat heater retrofitting, or interior trim removal and installation, causing a hidden short circuit.
What To Do
  • 1
    Safety Preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 2
    Read freeze frame: Use the VDS2000/VDS3000 diagnostic tool to read environmental data (temperature, vehicle speed, voltage) at the time of the fault to confirm if it is an intermittent fault.
  • 3
    Visual inspection: Remove the left rear seat. Inspect the pretensioner wiring harness (yellow sleeve) under the seat frame for signs of wear, crushing, or damage. Inspect the connector at the bottom of the B-pillar for water ingress or green corrosion.
  • 4
    Resistance measurement: Disconnect the SRS ECU and pretensioner connectors. Use a multimeter to measure the resistance to ground of the pretensioner-side wiring harness. Normal resistance is ∞ (infinity). A reading <10Ω confirms a short to ground.
  • 5
    Section-by-section troubleshooting: If the wiring harness appears normal, use the sectional isolation method. Gradually peel back the harness sleeve from the pretensioner end to the ECU end to locate the short circuit. Focus inspection on the seat slide rail mounting bolt areas and the protective rubber grommets where the harness passes through sheet metal holes.
  • 6
    Component test: If the wiring harness is normal, directly measure the pretensioner resistance. Normal value: 2.0 ± 0.3 Ω. If the resistance is <1 Ω or shows continuity to ground, replace the left rear seat belt pretensioner assembly.
  • 7
    Repair verification: After repairing the wiring harness (apply double-layer heat-shrink tubing for insulation) or replacing the component, reconnect all connectors, clear the fault code, perform and pass the SRS system self-diagnosis, and perform a full-range seat adjustment test to ensure no interference.
Real-World Cases
BYD DTC AI Analysis

Qin Pro DM left rear seat rail wear caused pretensioner short circuit

✓
Vehicle at 30,000 km with the airbag warning light constantly illuminated. VDS scan showed DTC B176F11. Disassembly found the pretensioner wiring harness (yellow) pinched by the bolt washer at the rear mounting point of the left rear seat rail. Long-term seat adjustment wore through the harness insulation, exposing the copper core to the seat frame (ground). Fix: Loosened the seat rail mounting bolts, pulled out the damaged harness, wrapped it with high-temperature tape and enclosed it in corrugated tubing, rerouted the harness clear of the rail travel range, then retightened the bolts and installed a rubber protective grommet. Cleared the DTC; SRS system returned to normal.
BYD DTC AI Analysis

E2 EV B-pillar water ingress caused pretensioner connector corrosion and short circuit.

✓
Southern region vehicle. Airbag warning light came on after heavy downpour; DTC B176F11. Found damp carpet at base of left rear B-pillar. Removed B-pillar trim and found pretensioner connector (2-pin yellow plug) had water staining and green copper corrosion. Measured resistance between pin 1 (ground) and pin 2 (pretensioner circuit) at only 0.8Ω. Cause: Perished sunroof drain hose joint at upper B-pillar allowed water to track down trim into lower connector. Repair: Replaced sunroof drain hose joint. Cleaned connector pins with electrical contact cleaner, dried with compressed air, and applied conductive paste. Confirmed insulation resistance to ground >10MΩ. Reassembled and cleared fault.
BYD DTC AI Analysis

False pretensioner short-circuit warning after seat cover replacement on Qin EV

✓
Customer reported the airbag warning light came on while driving after installing leather seat covers at an external auto trim shop. VDS detected DTC B176F11. Inspection revealed the installer used long self-tapping screws penetrating the seat foam to secure the covers; screw tips pierced the yellow sleeve of the pretensioner harness, shorting to ground. Repair: Removed improperly installed screws. Found wiring damage with 2 locations of exposed conductors. Cut out damaged section, soldered connections, and applied double-layer heat-shrink tubing. Relocated mounting points to avoid harness routing. Advised owner to avoid SRS wiring paths during modifications.
BYD DTC AI Analysis

BYD Qin Pro Fuel Pretensioner Body Internal Short Circuit Replacement Case

✓
The vehicle had no accident history, but intermittently set DTC B176F11—sometimes returning hours after clearing. Visual check of the wiring harness showed no damage. Pretensioner body resistance measured 0.3Ω with continuity to ground, indicating the internal squib igniter insulation had broken down. Removed the left rear seatbelt pretensioner (requires seat assembly removal), installed a new assembly (part number possibly 4C-XXXXXX), and torqued the mounting bolts to 7-9 N·m. Reconnected and the fault cleared permanently. Returned part analysis confirmed an internal manufacturing defect caused premature failure.
Other Atto 8 Fault Codes
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.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 overview →
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.