AU
B176211

DTC B176211 indicates the SRS (Supplemental Restraint System) ECU detected a short to ground in the left front side curtain airbag deployment circuit — Atto 3

Safety System

DTC B176211 indicates the SRS (Supplemental Restraint System) ECU detected a short to ground in the left front side curtain airbag deployment circuit.

Specifically, the SRS ECU continuously monitors the airbag inflator circuit voltage and resistance through its internal diagnostic circuit.

When the ECU detects the circuit voltage remaining below the threshold (near 0V) or an abnormally low resistance (well below the normal 2.0-3.0Ω range), it identifies a short to ground.

This fault prevents the side curtain airbag from deploying normally during a collision and may disable the entire SRS system (entering fail-safe mode), posing a severe safety hazard.

5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Wiring harness chafing inside the left A-pillar, B-pillar, or C-pillar trim panels: The side curtain airbag wiring harness routes along the left roof side rail and runs down through the A-pillar and B-pillar to connect to the SRS ECU. Prolonged vehicle vibration or previous trim removal and installation can damage the harness insulation, causing the copper wire to contact the vehicle body metal and create a short circuit.
  • 2Water ingress or corrosion in the upper seat side airbag connector: On some models, the side curtain airbag connector is located below the left B-pillar or near the C-pillar. Vehicle wading, a clogged and leaking sunroof drain tube, or improper car washing can oxidize and short-circuit the connector pins.
  • 3Side curtain airbag module internal igniter fault: Damaged insulation on the igniter bridge wire inside the airbag inflator causes a short circuit to the housing (ground). Airbag inflator housing damage or aging usually accompanies this condition.
  • 4Internal SRS ECU drive circuit fault: A damaged ignition drive transistor or monitoring circuit inside the control unit for the corresponding airbag falsely detects an external short circuit, or the ECU has an internal ground fault.
  • 5Wiring harness damage caused by vehicle modifications or accident repairs: Drilling during ambient lighting or audio system installation damages the harness insulation, or improperly securing the harness during accident repairs causes it to rub against sharp body edges.
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor. Wear an anti-static wrist strap. Use the BYD VDS2000/VDS2100 diagnostic tool to read complete fault information and record freeze frame data (DTC status: current/history, vehicle speed and temperature at the time of the fault, etc.).
  • 2
    Visual inspection and wiring harness check: Remove the left A-pillar trim, left B-pillar upper trim, and front headliner section. Inspect the side curtain airbag wiring harness (usually a yellow conduit) for obvious damage, crushing, or burn marks. Focus on sheet metal holes and retaining clips where the harness passes through. Inspect the connector below the left B-pillar (if equipped) for looseness, water ingress, or terminal corrosion.
  • 3
    Electrical measurement verification: Disconnect the left front curtain airbag connectors at the airbag and the ECU. Use a multimeter to measure the resistance between the two pins on the airbag-side connector (normal: 1.5–3.0 Ω). Measure the resistance from each pin to body ground (normal: infinite; fault: continuity or low resistance). Measure the voltage to ground on the ECU-side wiring harness (normal: standby voltage, approx. 5 V or 12 V; short circuit: 0 V).
  • 4
    Isolation confirmation: If the measurement indicates a short circuit, bypass the original wiring harness using a jumper wire and connect a known-good airbag simulator (2Ω resistor) directly to the ECU terminal. Clear the fault code and power on for testing. If the fault disappears, the original wiring harness is shorted. If the fault remains, suspect an internal ECU fault.
  • 5
    Repair and verification: If the wiring harness is damaged, wrap it with waterproof tape or replace the harness section. Route the harness away from sharp edges and secure it firmly. If the connector is faulty, clean or replace the connector. If the airbag module has an internal short circuit, replace the left front side curtain airbag assembly. If the ECU is faulty, replace the SRS ECU and perform coding configuration. After repair, clear the DTC and perform an SRS system self-check (turn the ignition switch ON; the SRS warning lamp should illuminate for 6 seconds and then turn off). Finally, perform a road test to verify the repair.
Real-World Cases
BYD DTC AI Analysis

E2 side curtain airbag short circuit after water ingress

✓
A 2019 BYD E2. The owner reported the SRS warning light on constantly. Retrieved DTC B176211 (current status). The vehicle had waded through water approximately 30 cm deep one week prior. Removed the left B-pillar lower trim panel and found obvious water stains inside the side curtain airbag connector; the pins were oxidised and green. Cleaned and dried the connector; harness-to-ground resistance measured normal. Replaced the connector and waterproofed it to eliminate the risk completely. Fault resolved. Advised the owner to check the sunroof drain hose for blockages.
BYD DTC AI Analysis

Aftermarket ambient lighting install damaged Qin EV wiring harness

✓
2020 Qin EV. Owner fitted interior ambient lighting at an auto accessory shop; next day the SRS warning light came on. DTC B176211. Inspection found the installer had drilled through the side curtain airbag harness conduit when mounting the light strip to the left A-pillar, damaging the wire insulation and shorting it against the A-pillar metal. Cut out the damaged section, soldered and heat-shrunk the repair, then rerouted the wiring clear of the modified parts. Cleared the fault. Maintain safe clearance between modification work and airbag harnesses.
BYD DTC AI Analysis

Wiring harness not properly secured after E3 accident repair

✓
2020 BYD E3. SRS warning light illuminated after left-front collision repairs at a non-authorised workshop involving replacement of the left front fender and outer A-pillar panel. DTC B176211. Inspection found the technician failed to secure the side curtain airbag wiring harness with the original retaining clips during reinstallation. The harness sagged and interfered with the left front door lock rod; prolonged friction wore through the insulation, causing a short to ground. Replaced the damaged harness section and resecured the harness per standard procedure (using special clips, maintaining >10 mm clearance from moving parts). Fault resolved.
BYD DTC AI Analysis

SRS ECU internal driver chip failure

✓
2019 BYD Qin EV, no accident history, no modifications. SRS warning light suddenly illuminated with DTC B176211. Measured left front side curtain airbag harness: airbag resistance normal at 2.1Ω, harness insulation to ground good (infinite). ECU output voltage abnormal at 0V instead of normal 5V standby voltage. Disconnected the airbag and connected an external 2Ω dummy resistor; fault persisted. Diagnosed internal drive/monitoring circuit failure in the corresponding SRS ECU channel. Replaced the SRS ECU, performed VIN coding and configuration coding. Fault resolved.
BYD DTC AI Analysis

Side curtain airbag module internal igniter short circuit

✓
2019 E2. SRS warning light illuminated on startup after overnight parking; DTC B176211. Wiring harness inspection showed no damage, connectors normal. Disconnected airbag connector and measured resistance from airbag unit pins to housing. One pin showed continuity to the airbag metal housing (0.5Ω), indicating an internal short in the inflator igniter bridge wire to housing. Replaced left front side curtain airbag assembly (requires removal of front headliner section and left C-pillar trim). Torqued retaining bolts to specification (typically 7–9 N·m). Fault resolved.
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: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.