AU
B162C

DTC B162C indicates the driver side airbag ignition circuit resistance exceeds the normal upper limit set by the SRS control unit (typically >3 — Atto 3

Safety System

DTC B162C indicates the driver side airbag ignition circuit resistance exceeds the normal upper limit set by the SRS control unit (typically >3.5Ω; normal value 1.5-3.0Ω).

The SRS ECU continuously monitors the airbag inflator (gas generator) circuit resistance via its internal detection circuit.

Excessive resistance indicates poor contact, a partial open circuit, or inflator aging within the ignition circuit.

This condition may prevent the circuit current from reaching the ignition threshold (typically 1.5-2.0A required) during a collision.

This fault prevents the side airbag from deploying normally in a crash.

Repair this safety-critical fault immediately.

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Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Fatigue fracture or poor contact of the internal flat cable in the clock spring (spiral cable). This is the most common fault point for the steering wheel airbag, especially on vehicles with frequent steering wheel rotation.
  • 2Internal resistance of the driver seat side airbag module (gas generator) increased due to aging, or moisture in the internal igniter charge shifted the resistance value.
  • 3The SRS-specific yellow connector under the seat or at the B-pillar (usually with a shorting bar) is loose, oxidized, has water ingress, or has backed-out terminals, causing increased contact resistance.
  • 4Long-term mechanical movement at the seat slide rail or steering column partially breaks the copper strands in the airbag wiring harness (not completely severed, but effective cross-sectional area reduced).
  • 5Previous vehicle wading or high humidity causes micro-corrosion inside the wiring harness connector, forming an oxide layer that increases contact resistance.
What To Do
  • 1
    Safe power-down: Turn off the ignition switch, 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: Use the BYD ED400/ED600 diagnostic tool to read the live data stream, record the current resistance (normal: 1.5-3.0Ω; usually >3.5Ω or displays open circuit during a fault), and view freeze frame data to confirm vehicle status at the time of the fault.
  • 3
    Visual inspection: Check the clock spring connector under the steering wheel and the SRS connector under the seat for looseness, water ingress, corrosion, backed-out pins, or unreleased shorting bars.
  • 4
    Segmented measurement method: Disconnect the airbag module connector. Use a digital multimeter to measure the module resistance (should be 1.5-3.0Ω). Measure the wiring harness side resistance (clock spring to SRS ECU) (should be <1Ω). Turn the steering wheel and measure the clock spring continuity (should be <1Ω throughout the full range).
  • 5
    Replacement test: Connect a dedicated 2-3Ω airbag substitute resistor (or a known-good airbag module) to the wiring harness. Clear the fault code and check if it returns to isolate the fault to the wiring harness or the module.
  • 6
    Targeted repair: Based on measurement results, replace the clock spring (most common), repair the wiring harness (soldering + heat shrink tubing), clean the connector, or replace the airbag module.
  • 7
    System verification: Reconnect all components and the battery, clear the fault code, and perform the SRS system self-check (turn the ignition switch to ON and verify the airbag warning light turns off after 6 seconds). Road test the vehicle to confirm the fault does not recur.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Tang DM clock spring internal contact failure

✓
2021 Tang DM, 30,000 km. SRS warning light illuminated. Retrieved DTC B162C. Driver side airbag module resistance: 2.1Ω (normal). Measured from the harness side: clock spring resistance normal with steering wheel centred, but fluctuated above 5Ω when turning left or right. Disassembled the clock spring and found a fatigue fracture in the internal flat cable. Replaced the clock spring (possibly part number K9H-5823947). Fault cleared, resistance now stable at 2.0Ω.
BYD DTC AI AnalysisFrom Chinese market (translated)

Oxidised connector under seat — Yuan EV

✓
A 2019 Yuan EV showed B162C one month after water ingress repairs. Inspection found green corrosion inside the yellow SRS connector beneath the driver's seat (usually on the inner side of the seat rail). Pin contact resistance measured 2.8Ω (should be <0.5Ω). Cleaned the connector pins with electronic cleaner, applied conductive paste, reconnected and reinforced the waterproof seal. Cleared the fault code; it has not returned.
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin Pro airbag module high internal resistance

✓
2020 BYD Qin petrol, 4 years old, no collision history. B162C appeared suddenly. Disconnected the airbag module and measured resistance directly: 4.2 Ω, above the 3.0 Ω upper limit. Determined that aging or moisture ingress of the initiator inside the gas generator caused the high resistance. Replaced the driver-side side airbag module (seat backrest removal required; airbag mounting bolt torque typically 8–10 Nm). Cleared fault codes and performed system matching using a diagnostic tool, resolving the fault.
BYD DTC AI AnalysisFrom Chinese market (translated)

Song MAX wiring harness worn at seat slide rail

✓
2019 BYD Song MAX. The tall driver frequently adjusted the seat, causing intermittent DTC B162C. Inspection revealed the wiring harness retaining clip at the rear of the seat rail had detached, allowing the seat frame to pinch the harness. This damaged the insulation and partially fractured the internal copper wires (only a few strands remained connected), causing resistance to fluctuate between 2-10Ω. Cut out the damaged harness section, re-soldered the wires, applied heat-shrink tubing, adjusted the harness routing, and re-secured the clip. This permanently resolved the fault.
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]