AU
B1631

DTC B1631 indicates a short to ground in the front passenger side airbag ignition circuit — Atto 3

Safety System

DTC B1631 indicates a short to ground in the front passenger side airbag ignition circuit.

In the BYD SRS (Supplemental Restraint System), this fault code indicates the airbag control unit (ACU) detects an abnormally low resistance (typically <1Ω) between the front passenger side airbag (usually installed in the seat side or door trim panel) ignition wiring and body ground.

Normal airbag circuit resistance should measure between 2.0 and 3.0Ω.

This fault means: 1) the airbag may fail to deploy during a collision, resulting in a loss of side impact protection; 2) extreme cases pose a risk of unintended deployment; 3) the SRS system enters fail-safe mode, illuminating the instrument panel airbag warning light and potentially disabling other airbag functions.

This hard short circuit requires immediate repair to ensure occupant safety.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Front passenger side airbag module internal igniter short circuit: Moisture, aging, or manufacturing defects caused both terminals of the internal squib to short to the housing.
  • 2Wiring harness wear or compression causing a short to ground: Long-term friction or compression damages the airbag wiring harness insulation at the seat rail, door hinge, or under the carpet, causing contact with vehicle body metal.
  • 3Connector water ingress or corrosion: Poorly sealed airbag connectors under the seat or B-pillar allow water ingress after car washing or wading, causing a short circuit between terminals or to ground.
  • 4SRS control module (ACU) internal fault: Damaged internal ACU drive circuit falsely reports a short circuit fault code.
  • 5Improper repair procedures: During recent seat cover replacement, door repair, or seat repair, tools pierced the wiring harness or technicians failed to fully seat connectors, causing a short circuit.
What To Do
  • 1
    Safe power-down: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to completely discharge the SRS system capacitors and prevent accidental airbag deployment.
  • 2
    Visual inspection: Check the front passenger seat side airbag (or door airbag) for external damage. Inspect the yellow SRS wiring harness under the seat and inside the B-pillar trim for wear, crushing, or puncture marks.
  • 3
    Connector inspection: Disconnect the airbag connector (use a shorting clip or wait for capacitor discharge). Check terminals for oxidation, water ingress, or deformation. Measure resistance to ground on the harness side; it must be infinite.
  • 4
    Airbag module test: Measure airbag module resistance using a dedicated SRS tester or multimeter (high-impedance mode only). Normal value is 2.0-3.0 Ω. If resistance is close to 0 Ω, replace the airbag.
  • 5
    Wiring harness continuity test: Measure continuity and insulation to ground of the airbag wiring harness in sections between the ACU and the airbag. Repair the damaged wiring harness or replace the wiring harness assembly.
  • 6
    System reset and verification: Reconnect all components, restore power, use the VDS diagnostic tool to clear the fault code, perform an SRS system self-check, confirm B1631 does not return, and verify the airbag warning light turns off after the self-check.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Song Pro DM remote driving failure and steering angle sensor abnormality

✓
Symptoms: Remote driving function inoperative; no response from directional buttons. Diagnosis: VDS retrieved DTC B163100 (steering wheel angle signal abnormal). Root cause: steering wheel angle sensor not recalibrated after replacing the airbag (including clock spring), resulting in abnormal signal output. Solution: Recalibrated the steering wheel angle sensor using VDS. Cleared the DTC and the remote driving function returned to normal.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Tang DM: Engine self-starting in EV mode and erratic instrument cluster

✓
Symptoms: While driving in EV mode, engine started automatically, instrument cluster fault messages were erratic, recovered after power cycling. Diagnosis: VDS2000 scan found communication faults in multiple systems. Steering system logged DTC B163100 (steering angle sensor signal abnormal). Inspected the sensor connector — discovered oxidation and poor contact. Measured the wiring and detected intermittent voltage fluctuations. Resolution: Cleaned connector terminals and applied conductive grease. Reconnected and secured the wiring harness. Calibrated the steering angle sensor, which resolved the fault.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Song Pro petrol: Intermittent HDC and tyre pressure monitoring warnings

✓
Symptoms: While driving, the instrument cluster intermittently displayed "Check HDC System" and "Check Tyre Pressure Monitoring System" warnings, and the warning lights came on intermittently. Diagnosis: A VDS scan found DTC B163100 (steering angle sensor related) and a body control module communication fault. Inspection confirmed a software abnormality and a loose connector on the right body domain controller, causing steering angle sensor signal processing errors. Resolution: Re-secured the right body domain controller connector, flashed the controller to the latest software version, and recalibrated the steering angle sensor. The fault cleared.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Song MAX: Difficulty shifting gears and ESP system warning

✓
Symptoms: Intermittent difficulty shifting gears; unable to shift out of Park with the brake pedal pressed. Dashboard displayed "Check ESP system" and "Check brake system". Diagnosis: VDS read DTC B163100 (steering angle sensor signal abnormal) and a brake pedal switch fault. The steering angle sensor was misaligned, and the signal deviation affected ESP and consequently the shift logic. Resolution: Reinstalled the steering angle sensor correctly, calibrated it, and tightened the brake pedal switch connector. Gear shifting returned to normal.
Original source ↗
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. Sources: [1]