AU
B1612-00

DTC B1612-00 indicates the airbag control module (SRS ECU) detected an unintended electrical connection between the front passenger frontal airbag inflator circuit and the vehicle positive power supply (B+), constituting a short to power — Atto 8

Safety System

DTC B1612-00 indicates the airbag control module (SRS ECU) detected an unintended electrical connection between the front passenger frontal airbag inflator circuit and the vehicle positive power supply (B+), constituting a short to power.

In the airbag system dual-stage ignition architecture, the ECU monitors the inflator circuit voltage state through internal diagnostic resistors.

Normally, the circuit maintains high impedance to the power supply (open-circuit state).

The ECU logs a short to power when it detects circuit voltage abnormally close to battery voltage (typically >5V or a sustained high level) instead of the expected low-voltage state.

This is a hardwire circuit fault.

Potential risks include: 1) the airbag fails to deploy in a collision because supply voltage clamps the ignition circuit, preventing sufficient firing current; 2) unintended airbag deployment in extreme cases if the safety capacitor design interacts with the short to power.

Possible fault locations include the clock spring (spiral cable), instrument panel wiring harness, airbag module connector, or the internal SRS ECU driver circuit.

On some BYD models, this DTC logic also monitors the front passenger seat Occupant Classification System (OCS) power supply circuit for abnormalities.

Because the OCS sensor status directly determines whether the system permits front passenger airbag deployment, a short to power in the OCS signal circuit triggers the same DTC.

5
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Airbag wiring harness insulation wear causing a short circuit: Long-term vibration and friction against sharp metal edges damage the front passenger airbag wiring harness insulation where it passes through the dashboard crossmember, A-pillar trim panel, or floor channel. The exposed wire contacts a constant power circuit (such as the dashboard lighting circuit or cigarette lighter power supply), creating a short to power.
  • 2Connector water ingress and corrosion: An aged seal on the yellow airbag module connector (usually located behind the glove box or inside the center console) allows water entry. Following vehicle wading or an air conditioning condensate leak, electrolytic corrosion forms between the internal plug pins, creating a low-resistance path between the igniter pin and the adjacent power supply pin.
  • 3Clock spring internal interlayer short circuit: Long-term rotational fatigue damages the insulation of the flat ribbon cable inside the clock spring (spiral cable) below the steering wheel. Although this cable primarily connects the driver airbag, the front passenger airbag return circuit wiring also routes through this area on some models and may short circuit to internal power wires (such as the steering wheel heating or multifunction switch power supply).
  • 4SRS ECU internal drive circuit fault: Airbag control module internal ignition drive transistor (MOSFET) breakdown or filter capacitor short circuit causes abnormal voltage at the output terminal, triggering a false detection of an external short to power.
  • 5Incorrect wiring connection after accident repair: During collision repair, incorrectly connecting the front passenger airbag wiring harness to the dashboard constant power circuit, or shifting the connector pins via forced insertion, causes the ignition pin to contact the power supply pin.
What To Do
  • 1
    Safe power isolation and capacitor discharge: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds (some BYD models require 3 minutes) to fully discharge the SRS ECU backup capacitor and prevent accidental airbag deployment.
  • 2
    Initial visual inspection: Inspect the front passenger airbag module connector (yellow marking, usually located inside the glove box or behind the instrument panel), floor wiring harness grommet, and A-pillar wiring harness sleeve for obvious damage, burn marks, fluid intrusion, or terminal corrosion.
  • 3
    Static circuit parameter measurement: Reconnect the battery. Use a high-impedance digital multimeter to measure the airbag circuit voltage to the power supply (normally close to 0V). Measure the circuit resistance to ground and to the power supply (should be greater than 1MΩ).
  • 4
    Segmented isolation diagnosis: First, disconnect the SRS ECU connector and check the wiring harness side for a short to power. If the short disappears, the fault is inside the ECU. If the short persists, disconnect the front passenger airbag module connector to determine whether the fault is in the wiring harness or an internal short in the airbag module.
  • 5
    Harness repair and protection: If the wiring harness is damaged, cut out the damaged section and replace it with high-temperature silicone wire (usually 0.5-0.75mm², shielded twisted pair). Wrap harness sections crossing metal edges with abrasion-resistant corrugated conduit. Maintain a clearance of over 50mm from constant live circuits.
  • 6
    Component replacement and system verification: For an internal SRS ECU fault, replace the control module, write the vehicle VIN, and program the configuration code. For an internal short circuit in the airbag module, replace the airbag assembly. After repair, use a BYD VDS or Launch X431 diagnostic tool to clear the fault code, perform an "Airbag System Self-Diagnosis", and verify the ignition circuit resistance is within the normal 1.5-3.0Ω range.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin PLUS DM-i: Oxidised connector causing intermittent short to power

✓
Symptoms: After starting the vehicle, the SRS airbag warning light on the dashboard stays on constantly. The passenger seat displays "unoccupied" regardless of whether someone is sitting in it. The scan tool read DTC B1612-00 (right seat occupancy sensor circuit fault, related to airbag system monitoring). Diagnosis: Removed the passenger seat and inspected the OCS (Occupant Classification System) sensor harness connector underneath. Found obvious oxidation and green copper corrosion on the connector pins, causing abnormal contact resistance and generating parasitic voltage in humid conditions, which the ECU misinterpreted as a short to power. Measured the sensor resistance and found it within the normal range (approximately 50-200Ω varying with pressure). Solution: Cleaned the connector pins using electronic cleaner, applied conductive grease to prevent corrosion, and re-secured the harness connector (using cable ties to prevent movement). Cleared the fault codes and road tested; the warning light went out and the OCS system returned to normal occupancy detection.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Song Pro: Damaged sensor pressure pad caused signal wire short to power

✓
Symptoms: After about 40,000 km, the airbag warning light illuminated suddenly with a beep. DTC B1612-00 was stored and could not be cleared. When an adult sat in the front passenger seat, the instrument cluster still displayed the passenger airbag as "OFF" (disabled). Diagnosis: Read the live data stream with the BYD VDS2000 diagnostic tool. The passenger seat occupancy status always showed "unoccupied" regardless of actual occupancy. Removed and inspected the seat, finding the internal film pressure sensor (pressure pad) fractured at a fold point. The broken wiring at the fracture contacted the seat metal frame, creating a short to power. Solution: Replaced the entire front passenger seat cushion assembly (the sensor and cushion are an integrated unit, part number: HA2E-5813800). After replacement, performed the "seat occupancy sensor calibration" procedure using the diagnostic tool. Fault cleared after a drive cycle and self-check.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Tang DM: Failure to calibrate the OCS after accident repair caused the SRS to log a power short circuit fault.

✓
Symptoms: After front-end collision repairs, the airbag warning light stayed on with stored DTCs B1612-00 and B1650-00. The passenger airbag remained disabled and could not be enabled even with an occupant in the seat. Diagnosis: Checks revealed the passenger seat assembly had been replaced during accident repairs, but the new seat’s OCS (Occupant Classification System) sensor was not initialised and calibrated. The sensor output voltage fell outside the normal range (0.8V–4.2V), causing the system to register a circuit fault (short to power). Solution: Performed the “Occupant Classification System Calibration” procedure using BYD dedicated diagnostic equipment: recorded the baseline with the seat empty, then placed a standard weight (approximately 75 kg simulating an adult occupant) to complete calibration. The fault codes cleared automatically and the airbag system returned to normal operation.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Worn seat track wiring harness on BYD e5 450 causes intermittent short circuit.

✓
**Symptoms:** Vehicle used as a ride-hailing car. After about 120,000 km, the airbag warning light occasionally came on. The light flickered over speed bumps or rough roads, and sometimes went out automatically on smooth roads. DTC B1612-00 appeared intermittently. **Diagnosis:** Inspection found the wiring harness at the front passenger seat adjustment rails had insulation damage from long-term rubbing against the metal rail edges due to frequent seat adjustments. During vehicle vibration, internal conductors occasionally contacted the constant power line under the seat (seat heater power supply), causing an intermittent short to power. **Solution:** Replaced the damaged section of the harness (from the floor harness to the OCS sensor). Wrapped the harness in high-temperature resistant corrugated tubing where it routes through the rail area. Adjusted harness mounting points to prevent mechanical interference with the seat rails. Secured the harness to non-moving parts of the seat frame with cable ties. Cleared the fault code and repeatedly tested the seat adjustment function; the fault did not return.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Han EV SRS ECU internal driver circuit fault

✓
Symptoms: After sitting overnight, the next morning the SRS light stayed on. DTC B1612-00 (front passenger airbag short to power) could not be cleared. No accident history, and the wiring harness showed no visible damage. Diagnosis: Measured the front passenger airbag circuit resistance – normal (2.0-3.0 Ω). However, measuring voltage between the circuit and power showed an abnormal 12 V. Disconnected the airbag module and dashboard harness, leaving only the SRS ECU connected; the scan tool still reported a short to power. Disconnected the ECU connector and found continuity between the corresponding internal ECU pins and the power pins, indicating the ECU’s internal ignition driver transistor had shorted. Solution: Replaced the airbag control module (SRS ECU; part number depends on vehicle configuration). Programmed the VIN, coded the airbag system configuration, ran the self-test, and cleared the crash records. Fault resolved.
Original source ↗
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]