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+) — Seal 6 EV

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 Seal 6 EV indicates a high-severity SRS fault where the left rear seat belt pretensioner circuit may be shorted to vehicle power. Common causes include damaged wiring insulation under the rear seat or near the B-pillar, or water, corrosion, or bent pins in the pretensioner connector. Stop DIY work on SRS parts and 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 — Seal 6 EV
  • 1Worn pretensioner wiring harness insulation under the left rear seat or near the B-pillar contacts the body power supply wire (constant power or ignition power), causing a short circuit.
  • 2Water ingress, oxidation, or bent pins at the pretensioner connector (usually located under the seat or inside the B-pillar trim), causing a short circuit between the power and signal terminals.
  • 3Insulation failure of the internal igniter coil in the left rear seat belt pretensioner, causing an internal short to power.
  • 4During vehicle modifications (such as installing seat heating or ambient lighting), technicians accidentally connected the pretensioner wiring harness in parallel with the power supply wire or pierced 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 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, pinching, or burn marks. Focus on the harness section within the seat slide rail travel range.
  • 3
    Connector check: Disconnect the pretensioner connector and inspect the pins for corrosion, water ingress, or deformation. Measure the voltage to ground at the harness-side connector terminals to check for an abnormal 12V voltage.
  • 4
    Component test: Use a digital multimeter to measure the pretensioner body resistance (must remain stable between 2.0-3.0Ω). If the resistance is 0Ω or infinite, or if the multimeter measures continuity to the power supply, replace the pretensioner assembly.
  • 5
    Wiring harness repair: If the wiring harness is damaged, repair it using high-temperature insulating tape (or replace the entire harness section). Keep the harness at least 10cm away from the power cable to avoid electromagnetic interference.
  • 6
    System reset: Reconnect all connectors and the battery, use VDS2000 or the BYD dedicated diagnostic tool to clear the fault code, and perform 'SRS system self-check' and 'configuration write' (if installing a new component).
  • 7
    Function verification: Perform an ignition cycle test to confirm the fault code does not return. Verify 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 Seal 6 EV 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.B1737DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.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 Seal 6 EV →Seal 6 EV 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.