AU
B176B-00

This DTC indicates the SRS (Supplemental Restraint System) control unit detects the left rear seat belt pretensioner ignition circuit resistance is below the normal system-calibrated threshold (the standard value is typically 2 — Qin Plus

Safety System

This DTC indicates the SRS (Supplemental Restraint System) control unit detects the left rear seat belt pretensioner ignition circuit resistance is below the normal system-calibrated threshold (the standard value is typically 2.0Ω±0.3Ω; values below 1.0Ω trigger this code).

The pretensioner uses a pyrotechnic igniter to tighten the seat belt during a collision, removing slack between the webbing and the occupant.

Low resistance indicates a potential short circuit.

Possible causes include a wiring harness short to ground, bridged connector pins, an internal short in the pretensioner igniter, or a faulty internal sampling circuit in the SRS control unit.

This fault forces the airbag system into a degraded mode.

The left rear pretensioner may fail to deploy during a collision or deploy unintentionally without a collision, severely compromising passive safety.

3
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Water ingress, oxidation, or bent pins at the left rear seat belt pretensioner connector (usually located inside the lower B-pillar trim panel or under the seat) causing a short circuit.
  • 2Damaged wiring harness insulation between the pretensioner and the SRS control unit contacts vehicle body metal, causing a short to ground; chafing commonly occurs at the seat slide rail or B-pillar wiring hole.
  • 3Aging or damage to the pretensioner internal squib causes an internal short circuit and permanently low resistance.
  • 4Foreign objects (such as metal toys or liquids) corroded or crushed the wiring harness under the rear seat, causing a short circuit.
  • 5Fault in the SRS control unit internal A/D conversion circuit or sampling resistor causing a false alarm (less common, but requires inspection).
What To Do
  • 1
    Use a dedicated diagnostic tool (such as BYD ED400 or Launch X431) to read the complete SRS fault codes. Confirm if B176B-00 is a Current or History code and record the freeze frame data.
  • 2
    Perform the safe power-down procedure: turn off the ignition, disconnect the negative battery terminal, and wait at least 3 minutes to fully discharge the SRS system capacitors and prevent accidental deployment.
  • 3
    Remove the left rear lower B-pillar trim panel (or seat back side panel), locate the yellow seat belt pretensioner connector, and visually inspect for signs of water ingress, green corrosion, deformed pins, or loose pins.
  • 4
    Test using the dedicated SRS system load simulator (Dummy Load): Disconnect the pretensioner connector and connect the simulator to the wiring harness side (leading to the SRS control unit). The simulator should display normal resistance. If measuring the wiring harness side directly shows abnormally low resistance (<1Ω), diagnose a short circuit in the wiring harness.
  • 5
    Inspect the insulation integrity along the pretensioner wiring harness routing (through the lower B-pillar and floor wiring channel to the center tunnel). Carefully inspect the wiring harness near the seat slide rail for wear or exposed wires caused by long-term seat adjustment.
  • 6
    If the wiring harness tests normal, the pretensioner unit is faulty. Replace the left rear seat belt assembly (including the pretensioner retractor). Never remove the pretensioner module separately.
  • 7
    After installing the new component, restore all connections, reconnect the battery, use the diagnostic tool to clear the fault code, and perform the 'SRS system self-check' or 'igniter resistance learning' procedure.
  • 8
    Perform a simulated road test (including bumpy roads). Confirm the airbag warning light turns off and the system generates no new fault codes. Finally, reinstall the interior trim panel.
Real-World Cases
BYD DTC AI Analysis

Water ingress in the B-pillar connector caused a short circuit.

✓
A 2017 Qin EV300 came in with the airbag warning light on after driving in heavy rain. Read DTC B176B-00 (current). Removed the lower left rear B-pillar trim and found standing water inside the yellow pretensioner connector, along with green corrosion between the pins. Multimeter showed 0.6Ω to ground at the harness side, confirming a short caused by water intrusion. Cleaned the connector thoroughly with electronic cleaner, dried it, applied conductive grease for waterproofing, and reconnected. The code cleared and the system returned to normal. Recommend inspecting the B-pillar trim seal for deterioration that may be allowing water ingress.
BYD DTC AI Analysis

Wiring harness chafed at seat track, short to earth

✓
Airbag warning light illuminated intermittently after frequent adjustment of the left rear seatback angle. DTC B176B-00 stored as intermittent. Inspection found the pretensioner harness insulation chafed through at the seat hinge-to-slide rail junction, with exposed copper wire contacting the seat frame and causing a short to ground. Repaired by cutting out the damaged harness section, soldering in an extension wire, and protecting with corrugated tubing. Rerouted the harness away from the seat movement path, ensuring sufficient slack without contacting metal components. Fault resolved.
BYD DTC AI Analysis

Internal short circuit in pretensioner after accident repair

✓
A Qin 100 persistently set DTC B176B-00 after accident repair and the code would not clear. Inspection found the left rear seat belt had been replaced with a salvage part. After ruling out wiring harness faults using a dedicated load simulator, we measured the pretensioner body resistance directly: 0.4Ω, far below specification. This confirmed an internal short in the igniter. We replaced the left rear seat belt assembly with a new genuine unit (including pretensioner), performed 'Configure New Module' and 'System Calibration' via the diagnostic tool, and cleared the fault code. Never use salvage parts from accident vehicles or measure airbag/pretensioner resistance directly; always use the substitute load method.
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.