AU
B163C1B

DTC B163C1B indicates the front passenger side airbag igniter circuit resistance exceeds the normal threshold (typically 2 — Atto 3

Safety System

DTC B163C1B indicates the front passenger side airbag igniter circuit resistance exceeds the normal threshold (typically 2.0–3.0 Ω).

The system triggers this fault upon detecting resistance > 6 Ω or an open circuit.

This fault falls under the SRS (Supplemental Restraint System) passive safety category, specifically indicating a high-resistance fault in the front passenger seat-mounted side airbag or curtain airbag electrical circuit.

High resistance indicates poor circuit contact, a broken wiring harness, an oxidized connector, or an open airbag igniter.

This condition may prevent proper airbag deployment during a collision, constituting a safety-related functional fault.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Loose or oxidized airbag wiring harness connector under the front passenger seat: Qin PRO series seats are electrically adjustable. Frequent forward and backward movement causes the yellow airbag connector under the seat (usually located on the inner side of the seat rail) to loosen, terminals to back out, or pins to oxidize, increasing contact resistance.
  • 2Internal open circuit in the clock spring (spiral cable): The clock spring under the steering wheel primarily connects the driver-side airbag, but some models route the passenger-side airbag signal through it. Fatigue fracture of the internal flat cable causes abnormal circuit resistance.
  • 3Airbag igniter internal open circuit: The internal igniter resistance wire in the front passenger side airbag module (integrated into the side of the seat backrest) broke due to aging, or poor welding in the production batch caused resistance drift.
  • 4Wiring harness wear/open circuit: Long-term chafing of the wiring harness against the seat frame edge or inside the B-pillar trim partially breaks the copper wire, creating a high-resistance state without a complete disconnection.
  • 5SRS control module (ACU) internal sampling circuit fault: A faulty internal A/D converter or voltage divider resistor causes a false high resistance reading, while the actual external circuit is normal.
What To Do
  • 1
    Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes to discharge residual charge in the system capacitors. Use a multimeter to confirm the SRS system voltage is 0V. Wear an anti-static wrist strap.
  • 2
    Read data stream: Use the BYD VDS2000/VDS3000 diagnostic tool to access the SRS system. Read the B163C1B freeze frame data. Confirm the current resistance value (typically 10Ω or higher, or displays 'open circuit') and confirm the fault frequency (current/history).
  • 3
    Visually inspect the seat wiring harness: Remove the front passenger seat (4 retaining bolts, 25Nm torque). Inspect the yellow dedicated connector (2-pin or 4-pin) under the seat. Check for looseness, water ingress, oxidation, or terminal back-out. Use a dedicated probe to test the connector contact pressure.
  • 4
    Resistance measurement: Use a dedicated fused airbag test lead (to prevent electrostatic deployment). Disconnect the airbag connector and measure the airbag inflator resistance (standard: 2.0 ± 0.3 Ω). If >5 Ω, replace the airbag module. Measure wiring harness continuity from the seat connector to the SRS control module; resistance must be <1 Ω.
  • 5
    Check the clock spring (if applicable): Remove the steering wheel and check continuity in the clock spring passenger-side circuit. If the circuit is open, replace the clock spring (align the centering marks during installation).
  • 6
    Repair and verification: Clean the oxidized connector using electrical contact cleaner. If necessary, replace the connector or repair the wiring harness (solder and heat-shrink tubing). Restore the connection and clear the fault code. Perform 3 ignition cycle self-checks to confirm the fault code does not return. Finally, perform an airbag system simulated deployment test using a dedicated tool in place of the airbag to verify circuit integrity.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Oxidised seat connector caused intermittent high resistance on Qin Pro DM

✓
A 2019 Qin Pro DM with 32,000 km had an intermittent SRS warning light on the instrument panel. The stored DTC was B163C1B (active). Inspection found green oxide inside the yellow connector under the front passenger seat, and insufficient pin contact pressure. The cause: the vehicle had been driven through water, allowing moisture to seep under the seat. The fix: cleaned the connector with WD-40 Precision Electrical Contact Cleaner, applied conductive grease, and adjusted the terminal spring tension. The fault cleared. A one-week follow-up confirmed no recurrence.
BYD DTC AI AnalysisFrom Chinese market (translated)

Open circuit in passenger-side airbag module internal igniter.

✓
2018 BYD Qin PRO (petrol). Replaced the passenger seat assembly after accident repairs. After installation, logged DTC B163C1B. Measured the new seat airbag resistance: open circuit. Disassembly revealed the airbag igniter pins fractured due to stress during transport. Replaced the seatback side airbag module (PN: K8A-5820400). Remeasured resistance: 2.1 Ω. Cleared the DTC, system normal. Do not drop or stack airbag modules.
BYD DTC AI AnalysisFrom Chinese market (translated)

Worn B-pillar wiring harness caused resistance drift.

✓
A Qin PRO DM with 58,000 km had the passenger side airbag warning light staying on constantly. Diagnosis found the wiring harness between the seat connector and SRS module had worn through its insulation at a corner of the B-pillar trim, the copper core partially broken with only 2-3 strands still connected. Resistance measured 8.5Ω (unstable). Stripped back the harness, cut out the damaged section, and soldered in 0.5mm² high-temperature silicone wire. Reinforced the harness routing to prevent contact with sharp edges. Fault resolved.
BYD DTC AI AnalysisFrom Chinese market (translated)

SRS control module false positive

✓
2019 Qin Pro, no accident history. SRS warning light illuminated suddenly, storing DTC B163C1B. Passenger airbag resistance: 2.0Ω (normal). Wiring harness continuity checked normal. Connectors showed no abnormalities. Suspected internal ACU fault. Upgraded SRS control module software from V1.2 to V1.4; fault persisted. Replaced SRS control module (part no. K8A-3636100), performed online configuration coding, and cleared the fault. Cause: aging of the internal sampling resistor in the control module.
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]