AU
B1622

DTC B1622 indicates the Supplemental Restraint System (SRS) control module detects an abnormally low-resistance connection (typically below 1 — Atto 3

Safety System

DTC B1622 indicates the Supplemental Restraint System (SRS) control module detects an abnormally low-resistance connection (typically below 1.0Ω) between the driver side airbag inflator circuit and battery positive (B+, 12V).

Normally, the airbag inflator circuit maintains a high-resistance state (open circuit or the 2-3Ω resistance of the inflator itself).

A short to power means the SRS module detects supply voltage instead of the expected high-resistance signal when checking circuit integrity.

This fault poses extreme safety risks.

During a collision, the SRS module may fail to trigger the inflator circuit, preventing airbag deployment.

Additionally, specific operating conditions (such as intermittent wiring contact or voltage fluctuations) can cause unintended airbag deployment, severely threatening driver safety.

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Cases Logged
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Causes
Likely Causes — Atto 3
  • 1Aged or damaged insulation on the internal flat ribbon cable in the clock spring (spiral cable) causes the airbag ignition wire (usually the yellow harness) to short to power wires inside the steering wheel (such as the horn or multifunction button power supply).
  • 2Friction from frequent fore-aft seat adjustment or door operation wears the insulation on the airbag wiring harness under the driver's seat or inside the A/B-pillar trim, causing it to contact the body power wiring harness.
  • 3Airbag connector terminals (usually under the seat or steering wheel) backed out or bent, or water ingress and corrosion inside the connector causing a short circuit between adjacent power terminals and airbag igniter terminals.
  • 4Non-professional modifications (such as installing seat ventilation/heating, steering wheel heating, or dashcam power taps) pierced or damaged the airbag wiring harness insulation during installation, causing a short circuit to a constant live circuit.
  • 5Internal fault in the SRS control module driver circuit (such as squib driver internal breakdown) causing the system to falsely detect an external short to power (relatively uncommon).
What To Do
  • 1
    Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds (to fully discharge the SRS capacitor). Hang an 'Airbag Under Repair' warning sign to prevent accidental deployment.
  • 2
    Fault freeze frame analysis: Use the BYD VDS diagnostic tool to read the DTC freeze frame. Record the vehicle speed, temperature, voltage, and other data at the time the fault occurred. Determine whether the fault is continuous or intermittent.
  • 3
    Visual and physical inspection: Inspect the clock spring connector under the steering wheel, the airbag connector under the driver's seat (on some models, the side airbag is inside the seat), and the wiring harness inside the B-pillar trim for damage, water stains, burn marks, or signs of modification.
  • 4
    Isolation diagnosis (clock spring): Disconnect the connector between the clock spring and the airbag. Install a special shorting piece (Dummy Load, 2Ω) in place of the airbag, and measure the circuit resistance to power. If the resistance remains low, the short circuit is located before the clock spring (wiring harness or ECU). If the resistance is normal, the clock spring or the airbag is faulty.
  • 5
    Harness continuity test: Disconnect the SRS ECU connector. Measure insulation resistance between the ignition wire (usually yellow) and vehicle power supply (B+) section by section, from the ECU to the airbag connector. Resistance must exceed 1 MΩ. Inspect harness bends under the seat rail and inside the sill trim.
  • 6
    Component replacement verification: For a suspected clock spring fault, replace it with a known good clock spring for testing. For a suspected SRS ECU fault, carefully check the igniter output waveform using an oscilloscope (perform only in a professional environment).
  • 7
    Repair and Verification: Locate and repair the short circuit (re-wrap with insulating tape, or replace the wiring harness or connector). Use a dedicated 2-3Ω resistor to simulate the airbag load, clear the fault code, and perform the SRS system self-check cycle (cycle IGN ON 3 times). Verify B1622 does not recur and the system has no communication faults.
  • 8
    Final reassembly and testing: Restore all connections, reinstall the airbag assembly, connect the battery, perform a final system self-check, and verify the airbag warning light turns off.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Tang DM: internal short in clock spring caused B1622.

✓
Vehicle: 2021 Tang DM. Symptom: SRS warning light on instrument cluster stays on. DTC retrieved: B1622 (driver side airbag short to power). Repair procedure: Disconnected the battery and removed the steering wheel to inspect the clock spring. Found obvious wear marks on the internal flat cable at the rotating disc. The insulation on the airbag igniter wire (yellow) and multi-function button backlight power wire (red) was damaged, and the wires stuck together. Replaced the clock spring (part number: EC-3636100) and tested using a 2.2Ω resistor to simulate the airbag. The DTC cleared and did not return. No recurrence during one-month follow-up after reassembly.
BYD DTC AI AnalysisFrom Chinese market (translated)

Seat wiring harness chafed through and shorted on BYD Song Pro

✓
Vehicle: 2019 BYD Song Pro. Symptoms: SRS warning light illuminated intermittently while driving. Scan tool showed stored DTC B1622. Investigation: Found the airbag wiring harness beneath the driver's seat (feeding the side airbag) had chafed against the seat slide rail mounting bracket. The harness insulation had worn through, allowing the internal copper wires to contact the positive supply wire of the seat heating module. Repair: Repaired the damaged harness by re-soldering the connections and insulating with heat shrink tubing. Repositioned the harness retaining clips and fitted anti-chafe sleeving. Verified the harness clears all metal edges and power wires throughout the full range of seat adjustment.
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin Plus airbag connector shorted after driving through water

✓
Vehicle Model: 2020 Qin Plus. Symptom: After water ingress repairs (water level reached the middle of the seats), the SRS warning light illuminated with DTC B1622. Repair: Removed the driver's side airbag and seat. Found mud and water residue inside the 2-pin airbag connector beneath the seat, with verdigris corrosion between terminals, causing a short circuit between the igniter terminal and the adjacent seat memory module power terminal (high-spec variant with memory seats). Cleaning: Thoroughly cleaned the connector using electronics-grade cleaner, blow-dried it, applied conductive protectant, and confirmed insulation resistance returned to normal. Inspected the wiring harness beneath the carpet for water ingress; found none, then reassembled.
BYD DTC AI AnalysisFrom Chinese market (translated)

Aftermarket modifications damaged the wiring harness on a BYD Yuan EV.

✓
Vehicle: 2019 Yuan EV. Symptom: SRS warning light illuminated with DTC B1622 after the owner installed an aftermarket steering wheel heating system. Diagnosis: Inspection found the installer bundled the heating harness and the airbag harness together with cable ties inside the steering wheel. A screw pierced the heating harness insulation, causing a short between the 12V positive supply and the airbag igniter circuit. Repair: Removed the non-genuine retrofit wiring. Repaired the airbag harness insulation by wrapping multiple layers of heat-resistant insulation tape. Restored factory wiring routing. Fault resolved. Advised the owner not to self-modify circuits involving the airbag system.
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]