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 8

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.

4
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Fatigue fracture or poor contact of the internal flat cable in the clock spring (spiral cable). This is the most common point of failure for the driver's airbag, especially in 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 caused a resistance shift.
  • 3The dedicated yellow SRS connector under the seat or at the B-pillar (usually fitted with a shorting bar) is loose, oxidized, water-damaged, or has backed-out pins, causing increased contact resistance.
  • 4Airbag wiring harness copper strands partially fractured at the seat slide rail or steering column due to long-term mechanical movement (not completely severed, but effective cross-sectional area reduced).
  • 5Previous vehicle wading or high-humidity environments caused 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 value (normal: 1.5-3.0Ω; typically >3.5Ω or open circuit during a fault). Check the freeze frame 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 an unreleased shorting bar.
  • 4
    Sectional measurement method: Disconnect the airbag module connector. Use a digital multimeter to measure the resistance of the module itself (1.5-3.0 Ω). Measure the wiring harness side resistance (clock spring to SRS ECU) (<1 Ω). Turn the steering wheel to measure clock spring continuity (<1 Ω 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 either 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. Perform the SRS self-check (turn the ignition switch to ON and observe if the airbag warning light turns off after 6 seconds). Perform a road test 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 8 Fault Codes
B1108For 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.B1109DTC B1109 indicates an open circuit in the communication line between the air conditioning system PM2.5 air quality sensor (dust concentration sensor) and the air conditioning control unit (AC ECU), or an open circuit within the sensor internal circuitry. Typically located in the air conditioning intake duct, this sensor monitors real-time PM2.5 particle concentration inside and outside the vehicle. It provides data to the automatic air conditioning system for intelligent switching between fresh air and recirculation modes and for controlling the air purification device. During an open circuit fault, the AC ECU cannot receive the air quality signal, triggering the system fail-safe mode. Symptoms typically include failure of the automatic recirculation function, abnormal air purification indicator light operation, or abnormal air quality data displayed on the air conditioning panel. Severe cases may compromise the cabin environment control strategy, but do not directly affect vehicle driving safety.B110913DTC B110913 indicates an open signal circuit for the PM2.5 rapid detector (in-cabin air quality sensor). This sensor typically mounts inside the air conditioning system intake duct. It monitors in-cabin PM2.5 concentration in real time and provides data to the automatic air conditioning system for intelligent control of the air purification function. The BYD diagnostic protocol uses sub-code '13' to specifically indicate an open signal circuit. Although this fault theoretically affects a comfort feature, BYD Qin series vehicles classify it as a Level 3 (severe) fault. This classification occurs because the air conditioning system interacts with the battery thermal management system (e.g., monitoring battery cooling intake air quality). The fault can disable the automatic air conditioning mode and prevent the air purification function from operating. In extreme cases, it affects the battery compartment intake air quality assessment, triggering the 'repair immediately' strategy.B110AThis DTC indicates interrupted CAN bus communication or abnormal data between the air conditioning control unit (ACU) and the PM2.5 air quality sensor. The PM2.5 sensor monitors particulate concentration inside and outside the vehicle and provides the basis for purification control in the automatic air conditioning system. The ACU triggers this fault if it fails to receive a valid CAN message from the sensor within the specified period (usually 100-500 ms), if message verification fails, or if the signal frame times out. Although this fault does not affect vehicle driving safety, it disables the automatic air purification function. The air conditioning system cannot automatically switch between recirculation and fresh air modes or activate the air purification mode based on air quality. A persistent fault may restrict the thermal management strategy.
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]