AU
B176C1B

DTC B176C1B indicates the airbag control module (SRS ECU) detects the left rear seat belt pretensioner circuit resistance exceeds the calibrated upper limit (typically >5 — Qin Plus

Safety System

DTC B176C1B indicates the airbag control module (SRS ECU) detects the left rear seat belt pretensioner circuit resistance exceeds the calibrated upper limit (typically >5.0Ω, normal range 2.0-3.5Ω).

The pretensioner is a pyrotechnic safety device containing an internal resistance wire and propellant.

The ECU determines its readiness by continuously monitoring the circuit current.

Excessive resistance usually indicates a high-resistance connection in the circuit, a partial open circuit, or aging of the internal pretensioner coil.

This condition can prevent the pretensioner from deploying correctly during a collision, seriously reducing the effectiveness of the occupant restraint system.

This fault is a hard fault in the passive safety system.

It generally illuminates the instrument cluster SRS warning light continuously and triggers a warning chime on some models.

The B176C1B fault code on the Qin Plus indicates excessive resistance in the left rear seat belt pretensioner circuit, which may stop the pretensioner working correctly in a crash. This is a medium-severity SRS safety fault and usually turns on the airbag warning light. Common causes include poor contact or corrosion at the yellow under-seat SRS connector, or an aging pretensioner coil. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Oxidation or partial open circuit of the pretensioner internal resistance wire: Prolonged use may cause micro-cracks or oxidation at the weld points of the pretensioner internal coil, causing the resistance value to drift higher.
  • 2Poor contact at the yellow SRS connector under the seat: Water ingress, oxidation, or frequent removal and installation increases terminal contact resistance at the dedicated airbag connector under the left rear seat (usually located on the inner side of the seat rail).
  • 3Seat slide rail wiring harness fatigue fracture: On Qin PRO models, folding or adjusting the left rear seat fore/aft repeatedly bends the wiring harness at the slide rail, causing the copper wire to partially fracture without fully breaking, creating a high-resistance condition.
  • 4Seat modifications or seat cover installations compress the wiring harness: During aftermarket leather seat modifications, seat foam or retaining clips pinch or damage the pretensioner wiring harness, reducing the conductor cross-sectional area.
  • 5SRS ECU internal sampling circuit fault: In very rare cases, a malfunction in the airbag control module A/D conversion circuit or internal sampling resistor triggers a false high resistance reading.
What To Do
  • 1
    Safety preparation: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 2
    Visual inspection: Remove the left rear seat cushion. Inspect the dedicated yellow SRS connector under the seat (usually marked AIRBAG) for looseness, water ingress, or green oxidation. If necessary, use a special probe to check terminal tension.
  • 3
    Harness continuity test: Disconnect the SRS ECU and pretensioner connectors. Use a multimeter to measure the harness resistance between the pretensioner connector and the ECU connector. Normal resistance is <1Ω. If resistance is >2Ω, check for a break inside the harness sleeve at the seat slide rail.
  • 4
    Pretensioner unit measurement: Measure resistance directly at the pretensioner connector (standard value 2.0-3.0 Ω). If the measured value is >4.0 Ω or shows OL (open circuit), confirm a pretensioner unit fault.
  • 5
    Replacement verification: Connect a 2.7Ω dedicated substitute resistor into the circuit, connect the battery, and clear the fault code. If the fault code changes to 'B176C-00 Resistance too low' or disappears, this confirms a faulty original pretensioner, not a wiring issue.
  • 6
    Component replacement: If confirming a pretensioner fault, replace the left rear seat belt assembly (BYD typically supplies pretensioners integrated with the seat belt retractor and does not provide them separately). During installation, route the wiring harness correctly and leave sufficient slack to prevent bending.
  • 7
    System calibration: Use the VDS2000 or MDI600 diagnostic tool to clear the fault code, execute the 'SRS System Configuration' and 'Sensor Calibration' procedures, and perform an ignition cycle test to confirm the warning light turns off.
Real-World Cases
BYD DTC AI Analysis

Worn seat rail wiring harness causes intermittent warning on Qin Pro DM

✓
A 2018 Qin PRO DM with 60,000 km displayed an intermittent "Check SRS System" warning on the instrument cluster, logging DTC B176C1B. Inspection revealed damaged wiring harness sheathing at the left rear seat rail; one of two internal wires was fractured 90% through, held by only a few remaining copper strands. The owner frequently folded the rear seats to carry loads, bending the harness repeatedly at the rail corner and causing metal fatigue. Repaired the harness, added abrasion-resistant corrugated tubing, and relocated the mounting point to increase the bend radius. Fault resolved.
BYD DTC AI Analysis

Oxidized connector on water-damaged vehicle caused resistance drift

✓
2019 Qin Pro petrol. Water entered beneath the left rear seat due to a blocked sunroof drain, triggering DTC B176C1B. Disassembly revealed water stains and verdigris inside the SRS connector below the seat; terminal oxidation pushed contact resistance to 8.5Ω. Repair: Cleaned the terminals with electronic contact cleaner and precision electrical lubricant, restoring normal resistance at 2.3Ω. Cleared the drain tube, applied waterproof silicone grease at the connector, and verified the seal remained intact to prevent further water ingress.
BYD DTC AI Analysis

Aftermarket leather seats pinched the wiring harness, causing high resistance.

✓
One week after having leather seats fitted at an out-of-town trim shop, the SRS warning light illuminated. A scan revealed DTC B176C1B. Inspection found the left rear pretensioner harness wrapped too tightly in the seat foam and pinched at the seat frame edge, deforming the harness. The internal conductors remained intact, but the reduced effective cross-section increased resistance to 4.8Ω. Repair: Rerouted the harness to avoid sharp seat frame edges, wrapped it in foam to prevent direct compression, and confirmed resistance had returned to 2.1Ω. Fault cleared.
BYD DTC AI Analysis

High-mileage case of internal pretensioner coil degradation

✓
A commercial Qin PRO DM with 280,000 km had a persistent B176C1B code that would not clear. Wiring checked out normal; direct measurement at the pretensioner plug showed 6.2Ω (well outside specification). Dismantling the seat belt retractor revealed micro-cracks in the pretensioner’s internal resistor wire solder joints from long-term vibration, increasing contact resistance. Replaced the left rear seat belt assembly (part number: XXXXX-XXXXX). Post-installation resistance measured 2.2Ω and the system self-test passed.
BYD DTC AI Analysis

Loose connector causing intermittent fault

✓
The SRS warning light occasionally illuminated on rough roads but worked normally on smooth surfaces. DTC B176C1B showed 'History/Intermittent' status. Inspection found the left rear SRS connector fully seated, but the internal locking tab had fractured. Vehicle movement made the connector shift slightly, causing poor contact. Special probe testing showed terminal retention force below 1N. Replaced the wiring harness terminal (part number: XXXX-XXXX) and repaired the connector housing, ensuring the locking mechanism remained intact. Road testing confirmed the fault did not return.
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.