AU
B161B1A

DTC B161B1A indicates the airbag control module (SRS ECU) detects the Passenger Front Airbag ignition circuit resistance is below the calibrated threshold (typically below 1 — Atto 3

Safety System

DTC B161B1A indicates the airbag control module (SRS ECU) detects the Passenger Front Airbag ignition circuit resistance is below the calibrated threshold (typically below 1.0-1.5Ω; normal range is generally 2.0-5.0Ω).

Low resistance typically indicates a parallel short circuit path in the airbag circuit.

Potential causes include a wiring harness short to ground, bridged connector pins, or an internal short circuit in the airbag inflator.

The ECU classifies this as a "Low Resistance" fault.

This condition can prevent proper airbag deployment during a collision because the short circuit diverts the current.

In extreme cases, static electricity or electromagnetic interference can cause unintended deployment.

Consequently, the SRS system enters fail-safe mode, illuminates the airbag warning light, and disables the passenger front airbag.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Front passenger airbag wiring harness chafing causing a short to ground: Vibration chafes the harness insulation against the edges of the instrument panel frame or air-conditioning duct. The exposed copper core contacts the vehicle body metal, creating a parallel resistance.
  • 2Bent airbag connector pins or water ingress: Improper removal or installation causes pins in the airbag connector (usually yellow, located inside the centre console or behind the glovebox) to contact the housing, or poor sealing allows electrolyte corrosion to form a low-resistance path.
  • 3Clock spring internal short circuit: If the front passenger airbag features a steering wheel-mounted trigger mechanism (some models), an interlayer short circuit within the clock spring flat cable reduces circuit resistance.
  • 4SRS control module internal sampling circuit fault: A damaged internal ECU shunt resistor or A/D converter triggers a false low-resistance fault while the actual airbag circuit is normal.
  • 5Internal short circuit in the airbag inflator: Insulation failure between the igniter bridgewire and housing (manufacturing defect or moisture ingress) causing abnormally low resistance.
What To Do
  • 1
    Safety preparation: Switch off the ignition, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 2
    Fault confirmation: Connect the VDS diagnostic tool, read the freeze frame data (Fault Frame), record the vehicle status at the time of the fault, and confirm B161B1A is a current fault (Present), not a history fault.
  • 3
    Visual inspection: Remove the glove box or passenger-side lower instrument panel trim. Inspect the yellow airbag wiring harness for wear or crush marks. Verify the connector is fully locked and check for signs of water ingress or terminal oxidation.
  • 4
    Isolate the circuit: Disconnect the front passenger airbag connector (usually located in the centre of the dashboard or rear of the airbag). Measure the resistance on the wiring harness side (ECU side) using a multimeter. A normal reading shows infinity or extremely high resistance (>10kΩ). Low resistance indicates a short to ground in the wiring harness.
  • 5
    Component Test: If the wiring harness side is normal, connect a dedicated airbag load simulator (2.7Ω dummy resistor) to the ECU side. Clear the fault code. If the fault disappears, the SRS ECU is normal. Next, measure the airbag unit resistance. It should be between 2.0-5.0Ω. If it is below 1.5Ω, replace the airbag assembly.
  • 6
    Clock spring inspection: If equipped with a passenger-side clock spring, measure the internal slip ring resistance. Turn the steering wheel and verify the resistance remains stable. Replace the clock spring if intermittent low resistance occurs.
  • 7
    ECU verification: If the wiring harness, airbag, and clock spring are normal but the fault code persists, inspect the SRS ECU connector for backed-out pins. Replace the SRS control module if necessary.
  • 8
    Repair verification: After repairing the short circuit or replacing the faulty component, reconnect all connectors and the battery negative terminal. Use VDS to perform 'Airbag System Configuration Check' and 'Sensor Calibration'. Clear the fault code and perform a collision simulation test (activate test mode using the diagnostic tool; do not strike the vehicle directly). Verify B161B1A does not return and the warning lamp turns off.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin Pro DM dashboard wiring harness chafing causing intermittent low resistance

✓
A 2019 Qin Pro DM with 32,000 km intermittently displayed a 'Check Airbag' warning on the instrument cluster. VDS read B161B1A as an intermittent fault. Teardown inspection found the retaining clip for the passenger airbag wiring harness had come loose where it routes through the dashboard crossmember, allowing the harness to chafe against a sharp metal edge over time. The insulation wore through, exposing the copper core and creating a 0.8 ohm parallel resistance to ground. Re-wrapped the harness, fitted anti-chafe sleeving, and adjusted the routing to fix the fault.
BYD DTC AI AnalysisFrom Chinese market (translated)

Passenger airbag connector water ingress corrosion case

✓
2018 Qin Pro petrol variant. Airbag warning light stayed on constantly after the vehicle waded through water; DTC B161B1A currently present. Inspection found the passenger airbag connector (located to the right of the evaporator housing) had a deteriorated seal. Water entry during wading caused electrolytic corrosion between the pins, creating a low-resistance path. Cleaned the connector terminals, applied electrical contact cleaner, and replaced the seal and connector housing. Fault resolved. Recommend checking the vehicle's water wading depth history.
BYD DTC AI AnalysisFrom Chinese market (translated)

Internal short circuit in airbag assembly caused abnormal resistance

✓
After an accident, a 2019 Qin PRO DM had its passenger airbag replaced with an aftermarket unit. After installation, DTC B161B1A set. Resistance measured normal on the harness side, but the new airbag measured only 0.6Ω, confirming an internal bridge wire short in the aftermarket gas generator. Replacing with a genuine part restored resistance to 2.8Ω. Cleared the DTC and it did not return. Must use genuine or certified parts; non-OEM airbags may have resistance deviations.
BYD DTC AI AnalysisFrom Chinese market (translated)

SRS ECU sampling circuit false fault

✓
2018 Qin Pro repeatedly logged DTC B161B1A, yet the airbag circuit resistance always measured normal at 2.4 Ω. Capturing the ECU detection pulses with an oscilloscope revealed a drift in the ECU’s internal sampling circuit reference voltage, causing it to falsely read low resistance. Replacing the SRS control module and recoding it—a step that requires writing the VIN and configuration code—permanently eliminated the fault. This is a rare case of control module hardware failure.
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]