AU
B176E-00

DTC B176E-00 is an SRS (Supplemental Restraint System) fault code indicating a short to body ground (GND) in the left rear seat belt pretensioner drive circuit — Atto 8

Safety System

DTC B176E-00 is an SRS (Supplemental Restraint System) fault code indicating a short to body ground (GND) in the left rear seat belt pretensioner drive circuit.

The pretensioner is a pyrotechnic actuator containing an igniter and gas generant.

During a collision, the SRS ECU triggers the pretensioner.

The resulting explosive force rapidly tightens the seat belt, removing slack between the occupant and the belt.

This fault code indicates a short to ground (resistance below the threshold, typically <2Ω) in the wiring harness between the SRS ECU and the left rear pretensioner, or within the pretensioner itself.

This causes the ECU to detect an abnormal current path.

Upon detecting this fault, the SRS system illuminates the airbag warning lamp and enters fail-safe mode.

This disables the left rear pretensioner and any linked side airbag functions, severely compromising crash safety performance.

The B176E-00 fault code on the Atto 8 indicates a high-severity SRS fault: a short to body ground in the left rear seat belt pretensioner drive circuit. This can disable the left rear pretensioner and related airbag functions, reducing crash protection. Common causes include chafed wiring in the left rear sill trim or water-damaged connectors under the rear seat. 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 — Atto 8
  • 1Wiring harness chafing inside the left rear sill trim: After prolonged vehicle use, the seat belt pretensioner wiring harness (typically routed along the B-pillar or sill) rubs against metal body edges. This damages the insulation and causes the core wire to contact the body ground.
  • 2Water ingress in connector under left rear seat: Interior cleaning, wading, or a blocked sunroof drain causes water to accumulate in the left rear carpet. Water enters and corrodes the pretensioner wiring harness connector (usually located under the seat or near the C-pillar), causing a short circuit between pins or between a pin and the housing.
  • 3Pretensioner assembly internal fault: Internal igniter insulation breakdown, or the internal bridge wire contacts the housing, causing an abnormal drop in resistance to ground on either wire.
  • 4Post-accident repair issues: After a left-rear collision or interior trim removal, the technician failed to correctly secure the wiring harness, causing the seat slide rail to pinch the harness or a screw to pierce it, resulting in a short to ground.
  • 5SRS ECU internal drive circuit fault: A breakdown short circuit in the left rear pretensioner channel of the ECU internal ignition driver chip (such as MC33797 or similar ASIC) triggers a false external short circuit diagnosis (relatively rare but requires inspection).
What To Do
  • 1
    Safety preparation: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 90 seconds (to ensure the SRS capacitor discharges completely). Wear an anti-static wrist strap. Do not take direct measurements near the airbag/pretensioner using a standard multimeter resistance setting.
  • 2
    Visual inspection: Remove the left rear sill trim panel, lower B-pillar trim panel, and left rear seat. Check the pretensioner wiring harness (yellow harness, usually with a shorting clip) for obvious damage, crushing, water stains, or burn marks. Focus on the seat slide rail fixing bolts and the wiring harness pass-through grommet.
  • 3
    Connector inspection: Disconnect the connector between the SRS ECU and the left rear pretensioner (usually located at the junction of the floor harness and seat harness). Inspect the terminals for corrosion, deformation, or water ingress. Clean with compressed air and measure the terminal insulation to ground.
  • 4
    Wiring harness insulation measurement: Use a megohmmeter or the high-resistance setting of a multimeter to measure the resistance of each of the two pretensioner harness wires (from the ECU end to the pretensioner end) to body ground. Normal resistance is infinite (>1MΩ). A resistance <10kΩ indicates a short to ground.
  • 5
    Pretensioner unit test: Disconnect the pretensioner connector and install a dedicated airbag resistor simulator (2Ω/0.25W) in place of the pretensioner. Clear the fault code and power on. If the fault code disappears, the pretensioner unit has an internal short circuit; replace the pretensioner. If the fault remains, the problem is in the wiring harness or ECU.
  • 6
    Locating the short circuit: After confirming a wiring harness short circuit, use the 'section-by-section elimination' method. Start at the ECU end and strip back the wiring harness corrugated conduit section by section. Focus on inspecting contact points between the wiring harness and the vehicle body metal. Repair damaged insulation and apply heat-shrink tubing for reinforced protection. Replace the entire floor wiring harness if necessary.
  • 7
    System verification: After repair, reconnect all components. Use the BYD dedicated diagnostic tool (VDS2000 or ED400) to perform 'SRS System Self-Diagnosis' and 'Crash Sensor Calibration'. Confirm B176E-00 no longer appears, verify the instrument cluster airbag warning light turns off, and finally perform a road test for verification.
Real-World Cases
BYD DTC AI Analysis

Water ingress in left rear carpet of water-wading vehicle caused pretensioner short circuit.

✓
A 2017 Qin EV300 came in with the airbag warning light on after driving in heavy rain. DTC B176E-00 stored. The left rear sunroof drain hose had detached, allowing water to accumulate under the left rear carpet. The pretensioner harness connector under the seat showed severely oxidized pins with green copper corrosion. Resistance from the pretensioner side plug to ground measured only 0.8Ω. Replaced the sunroof drain hose, cleaned and dried the connector with electronic cleaner and a heat gun, applied conductive protectant, and reinstalled it. Fault resolved.
BYD DTC AI Analysis

Aftermarket seat modification pinched wiring harness, causing short circuit

✓
A 2018 Qin EV450 owner self-installed a left rear seat heating pad. When reinstalling the seat after disassembly, the owner failed to route the pretensioner wiring harness (yellow) into its designated slot, leaving it pinched by the seat slide rail mounting bolt. Over time, the bolt head wore through the insulation, exposing the conductor to the seat frame (ground). During diagnosis, the fault code appeared intermittently whenever the left rear seat moved. Repaired by cutting out the damaged harness section, soldering in an extension wire, and rerouting and securing the harness to its retaining clips per the standard layout. Fault cleared.
BYD DTC AI Analysis

Pretensioner connector not fully seated after accident repair

✓
A 2017 Qin 100 sustained left rear damage in a scrape; an independent workshop replaced the left rear door and B-pillar trim. One month post-repair, DTC B176E-00 set. Inspection found the pretensioner connector (below the B-pillar) was not fully locked, the waterproof seal had shifted, and internal metal terminals were tilted, with one terminal touching the connector housing (ground). Replaced the pretensioner harness connector (terminals deformed beyond repair), ensured the connector clip fully engaged, and wrapped the joint with waterproof tape. Fault resolved.
BYD DTC AI Analysis

Pretensioner internal igniter insulation breakdown

✓
A 2017 Qin 80 with no accident history. The SRS warning light suddenly illuminated while driving, logging DTC B176E-00. Checked the wiring harness—no damage or water ingress; harness-to-ground insulation measured normal. Disconnected the pretensioner connector and measured resistance from both pins to the metal housing; one pin showed continuity to ground (0.3Ω). This indicated the pretensioner internal igniter insulation had broken down. Replaced the left rear seatbelt assembly (pretensioner integrated with seatbelt, not available separately), wrote the SRS system configuration, and cleared the fault.
Other Atto 8 Fault Codes
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.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.