NO
AU
B176C-00

This DTC indicates the airbag control unit (SRS ECU) detects the left rear seat belt pretensioner igniter resistance exceeds the calibrated threshold (normal range is typically 1 — Atto 3

Safety System

This DTC indicates the airbag control unit (SRS ECU) detects the left rear seat belt pretensioner igniter resistance exceeds the calibrated threshold (normal range is typically 1.6-2.4Ω; the DTC triggers when detected resistance is >3.0Ω or an open circuit occurs).

As a key actuator in the passive safety system, the pretensioner uses the igniter to detonate the gas generator during a collision, instantly tightening the seat belt to eliminate slack between the belt and the occupant.

Excessive resistance indicates high impedance or a potential open circuit in the igniter circuit.

This condition can prevent pretensioner deployment during a collision, severely compromising occupant restraint protection.

This is a hard DTC.

While the fault remains active, the system triggers a continuous warning and illuminates the airbag warning lamp.

Some models may also limit power output or disable specific assistance functions.

5
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Wear on the left rear seat folding mechanism caused the wiring harness to break internally.

✓
A 2018 Qin EV450 had the airbag warning light permanently on. DTC B176C-00. Found the left rear seat had been frequently folded for carrying cargo. Removing the seat revealed the pre-tensioner harness at the folding hinge had intact insulation but 90% of the internal copper strands were fractured, leaving only minimal contact and causing resistance to read 4.2Ω. Fix: Cut out the damaged harness section. Reconnected with 0.5mm² high-temperature wire using soldered joints. Protected the repair with double-layer heat shrink tubing and corrugated conduit. Rerouted the harness to avoid interference with the folding mechanism. Fault cleared.
BYD DTC AI Analysis

C-pillar connector oxidation causing increased contact resistance

✓
2017 BYD Qin 80. Owner reported intermittent SRS warning light, occasionally clearing after bumps. Scan tool showed stored DTC B176C-00 with resistance at 2.8Ω (threshold). Removed and inspected the left rear C-pillar pretensioner connector; found green oxidation on the terminals and a loose lock. Cause: Previous water wading allowed moisture into the C-pillar connector. Fix: Cleaned the terminals with electrical contact cleaner, applied copper-powder conductive grease, and replaced the connector lock (or the complete connector). Resistance measured 1.9Ω after tightening. Fault has not returned.
BYD DTC AI Analysis

Pretensioner unit resistance drift due to aging

✓
2017 BYD Qin EV300, 6 years old. Airbag warning light stayed on with DTC B176C-00. Infinite resistance at the pre-tensioner connector; 5.6 Ω measured directly across the pre-tensioner terminals—well above spec. Disassembled the pre-tensioner: internal igniter bridge wire oxidised and fractured. Natural ageing of the pre-tensioner, related to coastal high-humidity conditions. Replaced the left rear seatbelt pre-tensioner assembly (part number matched to VIN). Resistance normal after replacement. Coded and configured with the diagnostic tool (some models require writing the new pre-tensioner serial number). Fault resolved.
BYD DTC AI Analysis

Wiring harness connector not fully locked after accident repair

✓
A Qin 100 involved in a left-rear collision set DTC B176C-00 one month after 4S repairs. Diagnosis showed the pretensioner had fired in the crash (but went unrecorded), or the shop had only replaced the seatbelt assembly without fully locking the connector. In reality, the technician seated the plug during repair but missed the audible click; vibration worked it loose, causing poor contact of approximately 3.5Ω. Re-plugging the connector until the locking tab fully engaged cleared the fault immediately. After any SRS repair, run a 'pull test' to verify the connector locks.
BYD DTC AI Analysis

SRS ECU internal sampling circuit false positive

✓
2018 Qin EV450 repeatedly set DTC B176C-00. Measured pretensioner and wiring harness resistance: 1.8Ω (within spec), continuity good, no oxidation. Replaced the left rear seat pretensioner and wiring harness; fault persisted, appearing randomly at power-on. Found slight water ingress on SRS ECU connector pins from a windscreen leak dripping onto the ECU. Dried the connector, sealed the leak (lower windscreen trim panel), and cleared the codes. Monitored for one week with no recurrence. Confirmed intermittent ECU detection circuit fault. If the fault recurs, replace the airbag control unit.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
Data confidence: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.