AU
B176F-00

DTC B176F-00 indicates the SRS (Supplemental Restraint System) ECU detects an abnormal electrical connection between the left rear seat belt pretensioner drive circuit and the vehicle power supply (B+) — Qin Plus

Safety System

DTC B176F-00 indicates the SRS (Supplemental Restraint System) ECU detects an abnormal electrical connection between the left rear seat belt pretensioner drive circuit and the vehicle power supply (B+).

The pretensioner consists of an igniter and a gas generator, with a normal resistance of 2.0-3.0Ω.

Damaged wiring harness insulation, misaligned connector pins, or an internal pretensioner short circuit cause the ECU to detect an abnormally high circuit voltage (approaching 12V battery voltage) and trigger this DTC.

This fault may result in: 1) Failure of the left rear pretensioner to deploy during a collision, compromising occupant protection. 2) Unintended pretensioner deployment in extreme cases, causing occupant injury. 3) The SRS entering fail-safe mode, disabling all vehicle airbags.

The B176F-00 fault code on the Qin Plus indicates a high-severity SRS fault where the left rear seat belt pretensioner circuit is shorted to vehicle power. This can prevent correct pretensioner operation, trigger SRS fail-safe mode, or in rare cases cause unintended deployment. Common causes include damaged wiring insulation under the rear seat or near the B-pillar, and corroded or bent connector pins. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Qin Plus
  • 1Worn insulation on the pretensioner wiring harness under the left rear seat or near the B-pillar contacts the body power wire (constant power or ignition power), causing a short circuit.
  • 2Water ingress, oxidation, or bent pins in the pretensioner connector (usually located under the seat or inside the B-pillar trim) cause a short circuit between the power and signal terminals.
  • 3Insulation failure of the igniter coil inside the left rear seat belt pretensioner causes an internal short to power.
  • 4During vehicle modifications (such as adding seat heating or ambient lighting), technicians mistakenly connect the pretensioner wiring harness in parallel with the power wire or pierce the harness insulation.
  • 5SRS ECU internal driver circuit fault (MOSFET breakdown) causing false short-circuit detection (low probability)
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 2
    Visual inspection: Remove the left rear seat and lower B-pillar trim panel. Inspect the pretensioner wiring harness (usually in a yellow sleeve) for wear, crushing, or burn marks. Focus on the harness section within the seat slide rail travel range.
  • 3
    Connector check: Disconnect the pretensioner connector. Inspect the pins for corrosion, water ingress, or deformation. Measure the voltage to ground at the harness-side connector terminals to check for abnormal 12V voltage.
  • 4
    Component test: Use a digital multimeter to measure the pretensioner body resistance (must remain stable between 2.0-3.0 Ω). If the resistance is 0 Ω or infinite, or if the multimeter detects continuity to the power supply, replace the pretensioner assembly.
  • 5
    Wiring harness repair: If the wiring harness is damaged, repair it with high-temperature insulating tape (or replace the entire wiring harness). Maintain at least a 10 cm distance from the power cable to prevent electromagnetic interference.
  • 6
    System reset: Reconnect all connectors and the battery. Use VDS2000 or a BYD dedicated diagnostic tool to clear the fault code. Perform 'SRS system self-check' and 'configuration writing' (if installing a new component).
  • 7
    Function verification: Perform an ignition cycle test to confirm the fault code does not return. Observe whether the airbag warning light turns off after the self-test. Finally, perform a road test.
Real-World Cases
BYD DTC AI Analysis

BYD Qin EV450 left rear seat rail chafed through wiring harness causing short circuit

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2018 Qin EV450, 42,000 km. Constant airbag warning light. DTC B176F-00. The pretensioner harness under the left rear seat had chafed against the slide rail mounting bolt edge during fore/aft adjustment, wearing through the insulation. The copper core contacted the seat heater power wire (red, 12V constant). Replaced the entire yellow harness from the floor harness to the pretensioner (PN 4C-5823456) and added retaining clips to prevent contact with metal edges. Cleared the DTC; system returned to normal.
BYD DTC AI Analysis

Qin 100 rear seat water ingress caused connector short circuit

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2017 BYD Qin 100. After heavy rain, water pooled in the left rear footwell and wasn't cleaned up. DTC B176F-00 set intermittently. Tore down the B-pillar and found the 2-pin pre-tensioner connector underneath had taken on water. Electrolytic corrosion between the pins produced verdigris, dropping insulation resistance between the power and pre-tensioner drive pins below 200 Ω (normal: infinite). Fix: Cleaned the connector with electronic cleaner, blew it dry, applied conductive grease, replaced the waterproof seal, and cleared the door drain holes to stop it happening again.
BYD DTC AI Analysis

Incorrect wiring of aftermarket seat heater caused fault

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The owner had a heating pad installed on the left rear seat at a third-party workshop. The technician incorrectly spliced the heating pad power feed into the pretensioner wiring harness, mistaking the yellow wiring for the seat power supply. This caused the pretensioner circuit to connect directly to 12V power. The vehicle immediately set code B176F-00 at power-up, and the code could not be cleared. Repair actions: Removed the unauthorised modification, replaced the damaged pretensioner (internal igniter likely damaged by high-voltage impact), restored the factory wiring layout, and explained to the owner that the SRS system prohibits unauthorised modifications.
BYD DTC AI Analysis

Pretensioner internal coil aged and short-circuited

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A Qin EV300 with 80,000 km and no accident history suddenly set DTC B176F-00. Harness visual inspection revealed no damage. With the connector disconnected, the harness side showed no short to power, but the pretensioner terminals measured 0.5Ω to case. Internal igniter coil insulation had degraded and shorted. Replaced the left rear seatbelt assembly (includes pretensioner, PN 4C-6912345). Fault resolved. Note: Pretensioners are single-use components; even without deployment, internal materials can degrade after long-term use.
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.