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B161A-00

Fault code B161A-00 indicates the front passenger frontal airbag ignition circuit resistance is 0 ohms — Seal U

Safety System

Fault code B161A-00 indicates the front passenger frontal airbag ignition circuit resistance is 0 ohms.

This condition signifies a short to ground in the airbag circuit or an internal short circuit within the airbag module.

Normal airbag system resistance is typically 2-3 ohms.

A 0-ohm resistance allows current to bypass the airbag inflator and flow directly from the positive terminal to ground.

Consequently, the Airbag Control Unit (ACU) determines the airbag risks unintended deployment or failure to deploy.

The system then illuminates the airbag warning lamp and disables the airbag.

Repair procedures for certain BYD models (such as the Qin, Tang, and Song series) may also log this fault code as a Left Front Impact Sensor communication fault or wiring short circuit.

Verify the exact definition using the specific model year and SRS software version.

Regardless of the definition, this constitutes a critical safety system fault that prevents the airbag system from protecting occupants during a collision.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Front passenger airbag igniter internal short circuit (damaged airbag assembly causing 0 resistance).
  • 2Airbag wiring harness short to body ground (insulation damage, harness pinching, or abrasion causing a short circuit between positive and negative wires)
  • 3Water ingress and oxidation in the airbag connector plug (common after car washing or wading, causing a short circuit between pins)
  • 4Internal short circuit in the clock spring (spiral cable) (if the front passenger airbag connects via the clock spring, the internal ribbon cable breaks and shorts to ground)
  • 5Left front crash sensor circuit short to ground or internal sensor short circuit (fault definition for sensor versions, due to damaged wiring insulation).
What To Do
  • 1
    Safety preparation: Turn off the ignition, disconnect the negative battery terminal, and wait at least 3 minutes to fully discharge the SRS system capacitors and prevent accidental airbag deployment.
  • 2
    Use the BYD dedicated diagnostic tool (VDS2000 or Launch X431) to read the detailed fault code and freeze frame data. Determine if the fault is continuous or intermittent, and record the vehicle status when the fault occurred.
  • 3
    Remove the front passenger airbag module and disconnect the airbag connector. Use a multimeter to measure the resistance between the two terminals of the airbag assembly (Normal: 2-3 Ω. If 0 Ω, replace the airbag assembly. Note: Some models require a dedicated shorting connector to prevent static electricity).
  • 4
    If the airbag unit is normal, measure the resistance to ground at both terminals of the airbag harness-side connector (expected: infinite; 0 Ω indicates a short to ground). Inspect along the underside of the instrument panel and the floor harness for damage, crushing, or contact with vehicle body metal.
  • 5
    Inspect the SRS system connectors (especially the airbag harness plugs behind the glove box and under the dashboard). Inspect the pins for oxidation, deformation, or signs of water ingress. Clean with electrical contact cleaner. Replace the plugs or repair the wiring harness if necessary.
  • 6
    For applicable models, check the crash sensor plug connection at the left front longitudinal beam. Inspect the clip for looseness or oxidation. Measure the sensor power supply (12V), ground, and CAN line voltages to verify normal readings.
  • 7
    Check the Airbag Control Unit (ACU) software version. If the fault occurred after an OTA upgrade, use the dedicated diagnostic tool to reflash the ACU software and perform sensor ID configuration learning.
  • 8
    After repair, reconnect all components, fully engage all connector locking tabs, connect the battery, and clear the fault code. Perform a crash simulation test (lightly tap the sensor or simulate short-circuit release) to verify the fault is resolved.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Airbag warning light suddenly came on while driving a BYD Tang DM

✓
Symptoms: Airbag warning light suddenly came on and stayed on while driving. No collision history, vehicle drove normally, but airbag system entered protection mode. Diagnosis: Used a Launch X431 scan tool. Pulled DTC B161A-00 (Left front impact sensor signal abnormal / open circuit). Live data showed no signal from the left front impact sensor; other sensors were normal. Inspected the engine bay and found oxidation traces on the left front impact sensor connector at the left front longitudinal beam. Connector clip was loose, causing poor contact. Repair: Cleaned the connector pins with electrical contact cleaner. Re-secured the connector and wrapped it with waterproof tape. Cleared fault codes and test-drove; fault resolved. Recommended adding a waterproof protective cover to prevent future oxidation.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin Pro residual fault after accident repair

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Symptom description: After a front-end collision, a repair shop replaced the front bumper, left headlight, and left impact sensor. Upon starting the vehicle, the airbag warning light stayed on continuously and the fault codes would not clear. Diagnostic process: The scan tool showed B161A-00 (Left impact sensor not configured/communication fault) and B1650-00 (Airbag system fault). Checking the newly fitted sensor revealed it was an aftermarket part with the wrong part number (genuine should be BYD-3636500-L). Further checks found the sensor installation torque was insufficient, causing poor earth contact between the sensor base and the body. Solution: Replaced the left impact sensor with a genuine BYD unit (Part No: BYD-3636500-L). Tightened the sensor to the specified torque (8-10 N·m) using a torque wrench, ensuring firm metal-to-metal contact with the body. Performed 'Collision Sensor Configuration Learning' (Sensor ID Registration) with the dedicated diagnostic tool. Cleared the fault codes and ran a crash simulation test (lightly tapping around the sensor to verify signal response). Fault resolved.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Song PLUS DM-i fault after water wading

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Symptom description: Drove through a flooded road during heavy rain (water depth approximately 30 cm). The next day when starting the vehicle, the airbag warning light remained on, with occasional beeping near the left A‑pillar. Diagnosis: Read fault code B161A‑00 (Left impact sensor circuit short to ground). Removed the left front wheel liner and inspected the longitudinal beam area, finding the impact sensor wiring harness damaged at the waterproof sleeve joint. Water ingress caused the harness to corrode and short‑circuit. Measured sensor resistance: normal value should be 2–3 kΩ, actual measurement was 0.5 Ω (short‑circuit condition). Resolution: Cut out the corroded section of wiring harness, re‑soldered the wires and sealed with heat‑shrink tubing. Replaced the sensor connector (pins had corroded). Re‑routed the harness at a raised position to avoid contact with the lowest point of the body, and wrapped it with waterproof insulation tape. Dried out the airbag control unit by parking the vehicle in a dry environment for 24 hours.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Han EV software compatibility issue

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Symptoms: The vehicle underwent a DiLink system OTA update at the dealership. The following day, the airbag warning light illuminated. No physical collision occurred and the vehicle has no modifications. Diagnostic Process: Read fault codes: B161A-00 (Left impact sensor communication timeout) and multiple network communication DTCs. Checked sensor power supply (12V normal), earth (normal), and CAN bus voltage (approximately 2.5V abnormal; normal should be 2.0-2.5V and 2.5-3.0V). Determined the airbag control unit software version was incompatible with the sensor firmware; an interrupted upgrade caused a communication protocol error. Solution: Disconnected the battery negative terminal for 10 minutes to reset the system (no effect). Accessed 'Airbag System → Special Functions → ECU Programming' using the VDS2000/BYD dedicated diagnostic tool. Flashed the airbag control unit with the latest software (version BGD-2023-V2.1 or above). Executed the 'Sensor Auto Search' function; the system automatically detected and configured the left sensor ID. Cleared the fault codes. Fault resolved.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD e5 taxi wiring degradation fault

✓
Symptoms: e5 taxi with 280,000 km; airbag warning light illuminates intermittently on bumpy roads, operates normally on flat surfaces; fault codes appear intermittently. Diagnosis: Read stored DTCs: B161A-00 (Left crash sensor signal intermittent interruption). Performed harness wiggle test: shaking the wiring between the left front rail and airbag ECU reproduced the fault. Stripped back the harness protective sleeve and found the internal CAN-H wire (orange-black) at a body sheet metal bend had fractured copper strands, with only a few wires remaining connected, causing high contact resistance (measured 15Ω, normal <1Ω). Resolution: Replaced the complete wiring harness assembly between the left front crash sensor and airbag ECU (Part No.: BYD-CG-3636-L). Installed rubber protective grommets at the harness-to-body fixing points to prevent direct friction. Applied conductive grease at the airbag ECU connector to enhance contact. Fault eliminated completely; no recurrence after one month of monitoring.
Original source ↗
Other Seal U 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]