AU
B176A

DTC B176A indicates the SRS (Supplemental Restraint System) detects a resistance of 0 ohms in the left rear seat belt pretensioner circuit — Qin Plus

Safety System

DTC B176A indicates the SRS (Supplemental Restraint System) detects a resistance of 0 ohms in the left rear seat belt pretensioner circuit.

Normally, as a pyrotechnic device, the pretensioner resistance ranges from 1.5–3.0 Ω (depending on vehicle configuration).

A resistance of 0 indicates a short in the circuit, typically a short to ground or an internal short within the pretensioner.

This causes the Airbag Control Unit (ACU) to identify a pretensioner circuit fault.

During a collision, the left rear seat belt pretensioner may fail to deploy, severely compromising rear occupant restraint protection.

This fault also illuminates the instrument cluster SRS warning light and may lock the entire airbag system, preventing other airbags from deploying normally.

4
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Left rear seat belt pretensioner wiring harness short to ground (long-term chafing from seat adjustment damaged the wiring harness insulation inside the B-pillar trim).
  • 2Internal short circuit, water ingress corrosion, or poor terminal contact in the pretensioner connector (usually a yellow waterproof connector) resulting in a shorted connection.
  • 3Internal short circuit in the seat belt pretensioner assembly (internal igniter bridge wire short circuit or pyrotechnic component fault)
  • 4Internal detection circuit fault in the SRS control unit (ACU) causes a false resistance reading of 0.
  • 5Driving through water, deep interior cleaning, or a sunroof leak causes water ingress and a short circuit in the connector below the B-pillar.
What To Do
  • 1
    Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 2
    Locate the component: Remove the left rear B-pillar lower trim panel, then locate the left rear seat belt pretensioner (usually integrated into the bottom of the seat belt retractor) and its yellow connector.
  • 3
    Isolation measurement: Disconnect the pretensioner connector. Use a multimeter to measure the resistance directly between the two terminals on the pretensioner body. Check if the resistance is 0Ω (normal: 1.5-3.0Ω).
  • 4
    Harness inspection: If component resistance is normal, measure the resistance between both harness-side terminals and body ground to check for a short to ground. Also check for a short circuit between the harness wires.
  • 5
    Visual inspection: Inspect the wiring harness routing down the B-pillar, focusing on wear-prone areas near the seat rails and under the carpet. Check the wiring harness for damage, crushing, or signs of water ingress.
  • 6
    Connector handling: If the connector shows water ingress or corrosion, clean it with electrical contact cleaner, dry thoroughly, and apply conductive grease. Replace the waterproof sealing ring if necessary.
  • 7
    Component replacement: If confirming a short circuit in the pretensioner itself, replace the left rear seat belt assembly (the pretensioner is usually not available separately). If the wiring harness is damaged, repair or replace the wiring harness.
  • 8
    System reset: Restore all connections and turn on the power. Use VDS or a dedicated diagnostic tool to clear the fault code. Perform the SRS system self-check procedure. Verify B176A does not return and the SRS warning lamp turns off.
Real-World Cases
BYD DTC AI Analysis

Worn B-pillar wiring harness caused pretensioner short circuit

✓
A 2020 BYD Qin Pro EV had the SRS warning light constantly illuminated. Technicians retrieved DTC B176A. Removing the left rear B-pillar trim revealed the seatbelt pretensioner harness rubbing against the seat rails below the B-pillar. Long-term friction had worn through the insulation, exposing the copper wire and causing a short to ground against the body shell. Resistance measured 0Ω. Repair: Repaired the damaged harness (rewrapped with insulation tape and sleeved with corrugated tubing), adjusted the harness position to prevent seat interference, and replaced the damaged pretensioner connector terminals. After clearing the fault codes, the SRS system returned to normal.
BYD DTC AI Analysis

Pretensioner connector shorted from water ingress after wading

✓
2019 BYD Song MAX. Owner reported the SRS warning light illuminated suddenly after driving through a flooded section. Fault code B176A. Inspection found damp carpet in the left rear. Removed the B-pillar trim to find clear water staining inside the yellow pretensioner connector; terminals were oxidised and blackened, shorting the signal wire to ground. Resistance measured 0 ohms. Repair: Dried the wiring harness and connector with compressed air, cleaned the oxidised terminals with electronic cleaner, applied waterproof conductive grease, and replaced the connector seal. Traced the water ingress to a blocked sunroof drain tube; cleared the blockage to resolve the fault.
BYD DTC AI Analysis

Internal short circuit in pretensioner after accident repairs

✓
A 2021 BYD Tang was involved in a minor collision on the left rear side. After accident repairs, the instrument cluster displayed DTC B176A. Inspection showed no external damage to the left rear seatbelt pretensioner, but resistance measured 0Ω (normal is approximately 2.0Ω). Disassembly revealed the internal igniter's bridge wire had shorted from the collision impact. Pretensioners are single-use safety devices; the internal short was unrepairable even though the unit did not deploy. Fix: Replaced the left rear seatbelt assembly (includes pretensioner), ran the seatbelt pretensioner resistance learn procedure with a diagnostic tool (required on some models), cleared the fault code. System self-test passed.
BYD DTC AI Analysis

Intermittent short circuit causing intermittent B176A

✓
A 2019 BYD Yuan EV came in with the SRS warning light intermittently illuminating. Scanning revealed historic DTC B176A; current status was normal. The technician found the left rear seatbelt pretensioner connector slightly loose—driving on bumpy roads caused the terminals inside to intermittently contact and short. Inspection also revealed the connector locking tab broken, resulting in poor sealing. Repair: Replaced the pretensioner wiring harness connector with a new unit featuring the locking tab, re-crimped the terminals, and ensured a secure connection. Used an oscilloscope to monitor the pretensioner circuit resistance waveform and confirmed no abnormal fluctuations before delivery. One-week follow-up confirmed the fault had not reoccurred.
Other Qin Plus 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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Qin Plus →Qin Plus 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.