AU
B1622

DTC B1622 indicates the Supplemental Restraint System (SRS) control module detects an abnormally low-resistance connection (typically below 1 — Atto 8

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 8
  • 1Aged or damaged insulation on the internal flat cable of 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).
  • 2The airbag wiring harness under the driver's seat or inside the A/B-pillar trim contacts the body power wiring harness due to insulation wear from frequent fore-and-aft seat adjustment or friction from opening and closing the door.
  • 3Airbag connector (usually located under the seat or steering wheel): Backed-out or bent terminal pins, or water ingress and corrosion inside the connector causing a short circuit between adjacent power supply terminals and airbag igniter terminals.
  • 4Non-professional vehicle modifications (e.g., installing seat ventilation/heating, steering wheel heating, or hardwiring a dash cam) pierced or damaged the airbag wiring harness insulation during installation, causing a short circuit to a constant power circuit.
  • 5Internal driver circuit fault in the SRS control module (such as squib driver internal breakdown), causing the module to falsely detect an external short to power. This condition is relatively uncommon.
What To Do
  • 1
    Safety preparation: Disconnect the negative battery terminal and wait at least 90 seconds (to ensure the SRS capacitor fully discharges). 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 from when the fault occurred to confirm whether the fault is continuous or intermittent.
  • 3
    Visual and physical inspection: Check 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. Measure the circuit resistance to the power supply. 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 itself is faulty.
  • 5
    Harness continuity test: Disconnect the SRS ECU connector. Measure the insulation resistance between the ignition wire (usually yellow) and vehicle power (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: If you suspect a clock spring fault, test by replacing it with a known-good clock spring. If you suspect an SRS ECU fault, carefully use an oscilloscope to check the igniter output waveform (perform only in a professional environment).
  • 7
    Repair and Verification: After locating and repairing 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). Confirm B1622 does not return and the system has no communication faults.
  • 8
    Final reassembly and testing: Reconnect all connections, reinstall the airbag assembly, reconnect the battery, perform a final system self-check, and verify the airbag warning light turns off normally.
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 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]