AU
B1622-00

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

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
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Causes
Likely Causes — Seal U
  • 1Under-seat wiring harness wear: Friction from long-term forward and backward seat movement damages the insulation of the driver seat side airbag wiring harness (usually routed near the seat slide rail), causing a short circuit to power wires (such as seat heating or power adjustment supply wires).
  • 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; or failing to fully lock the connector after repair causes terminal misalignment and contact with the power terminal.
  • 3Internal short circuit in the spiral cable (clock spring): Damaged insulation on the ribbon cable inside the spiral cable beneath the steering wheel shorts the airbag igniter wire to other power supply circuits.
  • 4Improper modification or repair: When installing aftermarket equipment such as seat ventilation/heating or a dash cam, the technician mistakenly connected the power wire to the airbag circuit or damaged the wiring harness while drilling.
  • 5SRS ECU internal drive circuit fault: Control unit internal ignition drive chip breakdown causes a false short-to-power fault (relatively rare; confirm after ruling out wiring faults).
What To Do
  • 1
    Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds (to ensure the SRS capacitor fully discharges). 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, marked yellow) and the clock spring 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: Trace the airbag wiring harness path (from SRS ECU → floor wiring harness → under seat → airbag module). Open the corrugated conduit section by section to inspect. Inspect the seat slide rail contact area and wiring harness retaining clips for wear and exposed copper.
  • 5
    Swap test (if applicable): If supported by the vehicle model, confirm the wiring has no short circuits, then 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), the airbag module has an internal short circuit.
  • 6
    Repair and Replacement: Repair the damaged wiring harness (use heat shrink tubing or replace the entire harness section). Replace the damaged connector or airbag module (replace the module if it has an internal short circuit; 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. Verify B1622-00 does not return and the airbag warning lamp turns off.
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 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]