AU
B1612

DTC B1612 indicates the SRS (Supplemental Restraint System) detected an abnormally low-resistance connection between the front passenger frontal airbag igniter circuit and the vehicle power supply (B+), indicating a short to power — Seal U

Safety System

DTC B1612 indicates the SRS (Supplemental Restraint System) detected an abnormally low-resistance connection between the front passenger frontal airbag igniter circuit and the vehicle power supply (B+), indicating a short to power.

Under normal conditions, the airbag igniter circuit remains in a high-resistance state isolated from both power and ground (typically greater than 10kΩ).

The SRS ECU momentarily connects power through an internal switch only during airbag deployment.

A short to power means one or both sides of the igniter continuously connect to the 12V power supply.

This condition causes: (1) failure of the airbag to deploy during a collision (the ECU detects the circuit fault and inhibits triggering); (2) unintended airbag deployment in extreme cases due to abnormal current; (3) damage to the diagnostic driver circuit inside the SRS ECU.

This fault involves the connections between the front passenger airbag module, clock spring (spiral cable), floor wiring harness, and SRS ECU.

3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Damaged internal wire insulation in the clock spring (spiral cable) shorts the airbag ignition wire to the power wire or ignition signal wire.
  • 2The front passenger airbag wiring harness chafes inside the dashboard and shorts to body power wires (such as the instrument panel lighting circuit or cigarette lighter power supply).
  • 3Water ingress, oxidation, or metal debris in the airbag connector (usually located under the center console or on the airbag module), causing a short circuit between terminals.
  • 4Breakdown of the SRS ECU internal ignition drive transistor or a filter capacitor short circuit causes a false external short circuit diagnosis.
  • 5Improper servicing procedures, such as directly measuring airbag terminals with a multimeter set to resistance (use a dedicated diagnostic tool), causing external current to damage the squib or create a false short circuit.
What To Do
  • 1
    Safety preparation: Switch the vehicle OFF. Disconnect the low-voltage battery negative terminal and wait at least 90 seconds to completely discharge the SRS capacitor. Wear an anti-static wrist strap.
  • 2
    Visual inspection: Remove the passenger-side dashboard trim panel and inspect the airbag module, clock spring, and wiring harness connectors for burn marks, water ingress, or mechanical damage.
  • 3
    Circuit isolation: Disconnect the SRS ECU connector (usually under the centre console or near the gear selector) and the front passenger airbag connector. Use a multimeter to measure the resistance between the airbag harness-side terminal and the vehicle power supply (B+). Normal resistance is infinity.
  • 4
    Sectional diagnosis: If a short circuit exists, disconnect the clock spring. Separately measure continuity to power on the airbag module side (upper end of the clock spring) and the wiring harness side (lower end of the clock spring) to determine if the short circuit is in the airbag module, clock spring, or floor wiring harness.
  • 5
    Component test: Measure the front passenger airbag module resistance (through the clock spring or directly). Normal resistance is 2.0-3.0 Ω. If resistance is abnormal or continuity exists between the terminal and the housing, replace the airbag module.
  • 6
    Repair verification: After repairing the wiring harness or replacing the faulty component, reconnect all connectors and turn on the power. Use VDS or a dedicated diagnostic tool to clear the fault code. Perform the SRS system self-check to confirm B1612 does not return and the airbag warning light turns off.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD S7 rear wiper intermittent mode failure (B1612 related)

✓
SYMPTOMS Rear wiper inoperative. Instrument cluster intermittently displays wiper system fault. Customer reports rear wiper either does not move when switched on, or does not work in intermittent mode. DIAGNOSIS 1. Scanned vehicle systems with VDS diagnostic tool. Retrieved DTC B1612 from Body Control Module (BCM): rear wiper mode select switch circuit open. 2. Inspected wiper switch assembly. Measured resistance of rear wiper mode select switch — poor internal contact found. 3. Checked wiring harness between rear wiper switch and BCM. Inspected connectors CJB01 and GJB01; no visible wire breaks. 4. Measured switch signal line voltage. Voltage abnormal with switch in intermittent position (should be 5V pulse; actual 0V). REPAIR Replaced combination switch assembly (wiper switch). Cleared DTCs and road tested. Rear wiper operates correctly in all modes; DTC has not returned.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Song series rear wiper intermittent mode fault (DTC B1612)

✓
Symptoms: The owner of a BYD Song (petrol variant) reported the rear wiper only worked continuously; intermittent mode was inoperative. The instrument cluster occasionally illuminated a warning light. Diagnosis: 1. Scanned with VDS: stored DTC B1612 (rear wiper mode select switch circuit open). 2. Removed the combination switch below the steering wheel. Inspection revealed oxidation on the internal reed of the rear wiper mode switch, causing poor contact. 3. Measured continuity between switch pins 3 and 4: open circuit in the intermittent position (normally closed). 4. Inspected the wiring harness – no damage found. BCM supply voltage normal at 12V. Resolution: Cleaned the internal contacts of the combination switch and applied conductive grease. Fault was temporarily cleared after reassembly. Advised the owner to monitor during use; if the fault recurs, replace the combination switch assembly.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Tang DM rear wiper failure (B1612 related)

✓
Symptoms: All-New Tang DM. Rear wiper completely inoperative, front wiper normal. Instrument panel displays "Check wiper system". Diagnosis: 1. Scanned with VDS2000 diagnostic tool; Body Control Module reported fault code B1612. 2. Checked rear wiper motor power supply (pin B16-1); voltage normal at 12V. 3. Checked rear wiper switch signal line (pin B16-2); no signal input detected. 4. Further inspection found dry solder joint on rear wiper mode select switch inside combination switch. Solution: Replaced combination switch assembly; fault resolved. Teardown analysis of old part confirmed dry solder joint on internal PCB caused signal interruption.
Original source ↗
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]