AU
B1622-00

DTC B1622-00 indicates the driver side airbag squib circuit is shorted to the vehicle constant power supply (+B, battery voltage) — Atto 3

Safety System

DTC B1622-00 indicates the driver side airbag squib circuit is shorted to the vehicle constant power supply (+B, battery voltage).

The SRS (Supplemental Restraint System) ECU continuously monitors the airbag igniter circuit resistance and voltage.

When detecting an abnormally high voltage on the igniter wiring (approaching the 12V supply voltage), the ECU registers a short to power.

This fault is extremely dangerous and may cause: 1) accidental airbag deployment while driving, resulting in serious personal injury; 2) failure of the airbag to deploy during a collision due to the circuit fault; 3) the SRS entering fail-safe mode, disabling all airbag functions.

This is a hard fault (Hard DTC).

Once confirmed, the system triggers a severe warning and prohibits further vehicle operation.

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Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Under-seat wiring harness wear: Long-term forward and backward seat movement chafes the driver's seat side airbag wiring harness (typically routed near the seat rail), damaging the insulation and causing a short circuit to a power wire (such as the seat heater or power adjustment supply wire).
  • 2Airbag connector fault: Poor sealing of the yellow dedicated airbag connector (CPA connector) under the seat allows water ingress or corrosion, causing a short circuit between pins. Incomplete locking after repair causes terminal misalignment and contact with the power terminal.
  • 3Internal short circuit in the spiral cable (clock spring): Damaged insulation on the internal ribbon cable of the spiral cable beneath the steering wheel shorts the airbag igniter wire to other power supply circuits.
  • 4Improper modification or repair: Mistakenly connecting the power wire to the airbag circuit or damaging the wiring harness during drilling when installing aftermarket equipment (such as seat ventilation/heating or dash cams).
  • 5SRS ECU internal drive circuit fault: The internal ignition drive chip in the control unit breaks down, causing a false short-to-power fault (relatively uncommon; confirm after ruling out wiring faults).
What To Do
  • 1
    Safety preparation: Disconnect the battery negative terminal, wait at least 90 seconds (to fully discharge the SRS capacitor), and hang 'Do Not Operate' warning tags on the steering wheel and seat.
  • 2
    Initial visual inspection: Inspect the driver-side airbag module connector (located on the side or under the seat, with yellow markings) and the spiral cable connector for obvious burn marks, water ingress, or physical damage.
  • 3
    Circuit isolation: Disconnect the SRS ECU connector. Use a multimeter to measure the resistance between the driver side airbag ignition circuit terminal and power. Normal resistance is infinite. Continuity confirms a short circuit.
  • 4
    Section-by-section inspection: Follow the airbag wiring harness routing (from SRS ECU → floor wiring harness → under seat → airbag module), opening the corrugated conduit section by section to inspect. Check the seat slide rail friction areas and wiring harness retaining clips for wear and exposed copper.
  • 5
    Swap test (if applicable): If supported, verify the wiring has no short circuits. Temporarily swap the driver-side and front passenger-side airbag wiring harnesses and read the fault codes. If the fault code changes to B1623-00 (passenger side short circuit), diagnose an internal short circuit in the airbag module.
  • 6
    Repair and replacement: Repair the damaged wiring harness (use heat-shrink tubing or replace the entire harness section). Replace damaged connectors or the airbag module (replace the module if internally shorted; do not repair).
  • 7
    System verification: Connect the battery, use the BYD EDT or VDS diagnostic tool to clear the fault code, and perform the SRS system self-check. Confirm B1622-00 does not return and the airbag warning light turns off normally.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Seat rail wear caused a wiring harness short circuit on a Qin EV450.

✓
Following water ingress, the wiring harness beneath the seat corroded. Long-term seat adjustment chafed through the airbag harness insulation at the slide rail edge, bringing it into contact with the seat heater power wire. The instrument cluster airbag warning light stayed on. Retrieved fault code B1622-00. Inspection found water stains inside the yellow connector under the seat, and the harness worn through to bare copper at the slide rail retaining clip. Cleaned and dried the connector, replaced the damaged harness section, rerouted the harness away from the slide rail friction point, and resolved the fault.
BYD DTC AI AnalysisFrom Chinese market (translated)

Aftermarket seat ventilation retrofit caused short circuit on Qin 80

✓
The owner had made an unauthorised modification to the seat ventilation system. The installer mistakenly connected the fan power wire to the airbag circuit. The DTC appeared the day after the modification, and the airbag warning light came on. Diagnosis found additional power wires spliced into the driver-side airbag igniter terminals inside the harness connector. Resolution: Removed the unauthorised modification wiring, replaced the damaged OEM airbag connector (terminal bores were enlarged), and re-crimped the terminals using the OEM harness repair kit. Fault resolved.
BYD DTC AI AnalysisFrom Chinese market (translated)

Internal short circuit between layers of the clock spring

✓
After the accident repair, incorrect steering wheel centering during reassembly overstretched and fractured the internal ribbon cable of the spiral cable (clock spring). The fracture site shorted to the horn power circuit layer, resulting in intermittent DTC B1622-00 that increased in frequency when turning the steering wheel. Disassembly revealed burn marks on the clock spring's ribbon cable. Replaced the spiral cable with an OEM unit, reinstalled the steering wheel with correct centering, and calibrated the steering angle sensor. Fault no longer present.
BYD DTC AI AnalysisFrom Chinese market (translated)

Troubleshooting SRS ECU False Fault Reports

✓
Vehicle had no collision history or modification records. Intermittent B1622-00 DTC stored. Checked wiring harness: insulation intact; airbag module resistance normal (2.0–2.5 Ω). Suspected internal SRS ECU fault. Disconnected the airbag module and connected a dedicated airbag simulator (2 Ω resistor) at the ECU end; fault code still appeared intermittently. Repair: replaced SRS ECU control unit, recoded and matched system. Fault completely eliminated. Disassembled the original ECU and found micro-cracks in the ignition driver chip.
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]