AU
B163A1A

This fault code indicates the front passenger side airbag igniter circuit resistance measures 0 ohms, indicating a Short to Ground fault — Atto 3

Safety System

This fault code indicates the front passenger side airbag igniter circuit resistance measures 0 ohms, indicating a Short to Ground fault.

Normal airbag igniter resistance in the SRS (Supplemental Restraint System) is typically 1.5-3.0 Ω.

A 0 ohm reading indicates a direct ground path in the circuit.

Damaged wiring harness insulation contacting ground, shorted connector terminals, or an internal short circuit in the airbag module igniter can cause this condition.

This fault triggers the SRS control unit fail-safe mode, illuminates the airbag warning light, and can prevent the passenger side airbag from deploying during a collision, severely compromising occupant side impact protection.

BYD E2/E3 and similar models use seat-integrated side airbags; frequent seat adjustment easily causes wiring harness fatigue damage.

5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Front passenger seat side airbag wiring harness worn and short-circuited (seat rail crushing or long-term fatigue damaged the insulation, causing a short to ground)
  • 2Short circuit at the yellow SRS connector under the seat due to water ingress, corrosion, or poor terminal contact (common after vehicle wading or improper interior cleaning).
  • 3Side airbag module (inflator) internal igniter short circuit failure (manufacturing process defect or aging)
  • 4SRS control unit internal detection circuit fault (control unit ECU chip damage or sampling resistor fault; relatively rare)
  • 5Wiring harness crushed or pinched during front passenger seat modification, removal, or installation, exposing the wire core and causing a short to ground.
What To Do
  • 1
    Use the BYD dedicated diagnostic tool (VDS2000/VDS2100) to read the complete DTCs and freeze frame data. Confirm B163A1A is currently present and is a static fault. Record the environmental data at the time the fault occurred.
  • 2
    Disconnect the battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor for safe operation. Never measure the airbag circuit directly while powered on.
  • 3
    Inspect the front passenger seat side airbag wiring harness (especially the yellow connector and harness sleeve at the seat-to-body connection) for wear, damaged insulation, or crush marks. Focus on the area near the seat slide rail mounting points.
  • 4
    Disconnect the SRS connector under the seat (yellow plug, usually with a shorting bar). Bridge the circuit using a dedicated airbag load tool (2Ω simulated resistor). Power on the vehicle and read the fault codes. If the fault changes to 'resistance too high' or disappears, the circuit is normal and the fault is in the airbag module. If the fault remains, check the harness for continuity to ground.
  • 5
    Use a multimeter to measure the resistance to ground at both ends of the airbag wiring harness (measure the SRS ECU end and the airbag end separately) to check for a short to ground. Focus the inspection on the wiring harness near the seat slide rail and inside the B-pillar trim panel.
  • 6
    If the wiring harness is damaged, repair it with high-temperature insulating tape or replace the wiring harness. If the airbag module has an internal short circuit, replace the front passenger side airbag module (replace the seat trim or side airbag assembly simultaneously, depending on vehicle structure; never disassemble the airbag module).
  • 7
    Reconnect all connectors, ensure the yellow SRS plug locks into place (listen for a 'click'), and verify correct installation of the short-circuit protection piece.
  • 8
    Connect the battery. Clear the fault code using the diagnostic tool. Run the SRS system self-diagnosis procedure and read the igniter resistance value. Confirm DTC B163A1A does not reappear and the airbag warning light turns off. Finally, perform a seat fore-and-aft adjustment test to confirm no wiring harness interference.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD E2 seat rail crushed wiring harness, causing short circuit

✓
The vehicle came into the workshop with the airbag warning light on solid on the instrument cluster. DTC B163A1A was read. Inspection revealed the front passenger seat was an aftermarket add-on, and the wiring harness had been routed incorrectly during installation. Removing the seat showed the side airbag harness crushed by a seat rail mounting bolt, with its copper core in direct contact with the metal seat frame, causing a short to ground. Repair: Replaced the damaged harness section, re-routed the wiring, added corrugated tubing for protection, and made sure the harness would not be pinched throughout the full range of seat adjustment. After the repair, the airbag light went out and the system returned to normal.
BYD DTC AI AnalysisFrom Chinese market (translated)

Water ingress corrosion in the passenger-side airbag connector of a BYD Qin EV.

✓
A 2019 Qin EV developed an illuminated airbag warning light after driving through flood water during a heavy rainstorm. The scan tool showed DTC B163A1A. Inspection found water ingress marks on the carpet and green copper corrosion inside the yellow SRS connector under the front passenger seat. Electrolyte conduction between the terminals caused a short circuit. Disconnected the connector, cleaned the terminals thoroughly with electronic contact cleaner, blew them dry, applied conductive grease, and replaced the waterproof seal. Checked body drain holes for blockages and cleared rear door drain channels. Cleared the fault codes and road-tested; the fault did not return.
BYD DTC AI AnalysisFrom Chinese market (translated)

Frequent seat adjustment caused wiring harness fatigue fracture in E3 commercial vehicle.

✓
A BYD E3 rideshare vehicle with 120,000 km logged DTC B163A1A. Due to commercial use, frequent forward and backward adjustment of the front passenger seat caused the protective sleeve of the airbag wiring harness between the seat and body to crack. Internal wires suffered insulation damage from repeated flexing, with multiple cores shorting to ground. Inspection during repair revealed clear fatigue fracture characteristics where the harness exits the protective sleeve. Fix: Replaced the entire seat wiring harness assembly (including the airbag circuit), adjusted harness mounting points to increase slack, and securely fastened the protective sleeve. No recurrence after one month of post-repair monitoring.
BYD DTC AI AnalysisFrom Chinese market (translated)

Replaced the passenger seat side airbag module to resolve the internal short circuit.

✓
Following a minor side impact, the front passenger side airbag deployed normally. After the dealership replaced the airbag module with a new one and cleared the DTCs, the airbag warning light illuminated again the next day with DTC B163A1A returning. Checked the wiring harness – normal. Used a dedicated resistance tester to directly measure the new airbag module. Resistance: 0.2 Ω (normal is approximately 2.0 Ω), indicating a parts quality issue (internal igniter short circuit). Replaced with another genuine airbag module; resistance measured 1.9 Ω. Installed it, completely eliminating the fault. Recommendation: After replacing an airbag module, always directly measure its resistance to confirm part quality.
BYD DTC AI AnalysisFrom Chinese market (translated)

Misdiagnosed SRS control unit internal sampling circuit fault case

✓
Multiple repairs failed to resolve DTC B163A1A on a BYD E2. Replaced the wiring harness and airbag module, but the fault persisted. Checked the drive signal from the SRS ECU to the airbag using an oscilloscope and found abnormal output voltage during the control unit self-test. Further measurement of the internal sampling resistor in the ECU revealed a short to ground. Confirmed that the SRS control unit (ACU) internal circuit board had corrosion from moisture ingress (the vehicle previously had a water leak from a blocked sunroof drain tube). Replaced the airbag control unit, recoded the system, and completely cleared the fault. This case highlights that after ruling out wiring and airbag module faults, consider the control unit itself.
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]