AU
B179E00

This fault code indicates the Airbag Control Unit (ACU) detects an abnormal electrical series connection between an airbag ignition circuit (e — Seal 6 EV

Safety System

This fault code indicates the Airbag Control Unit (ACU) detects an abnormal electrical series connection between an airbag ignition circuit (e.g., driver/front passenger frontal airbag, side airbag, or curtain airbag) and another vehicle electrical circuit (e.g., another airbag circuit, seat belt pretensioner circuit, or sensor circuit).

Normally, each ignition circuit remains independent with a specific resistance (typically 2.0 ± 0.2 Ω).

When a series connection occurs, total circuit resistance increases abnormally (combining to exceed 4 Ω) or the control unit detects cross-circuit signal interference.

This prompts the ACU to flag compromised circuit integrity.

This fault can prevent airbag deployment during a collision (due to insufficient ignition energy) or cause unintended deployment, severely compromising occupant protection.

The B179E00 fault code on the Seal 6 EV indicates the airbag control unit has detected an abnormal electrical link between an airbag ignition circuit and another vehicle circuit. Severity is medium because it may affect correct airbag deployment. Common causes include crossed or shorted wiring in connectors, moisture or corrosion, or an internal ACU fault. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
3
Cases Logged
5
Causes
Likely Causes — Seal 6 EV
  • 1Short circuit or crossed wires between wiring harness connector terminals, especially where moisture, oxidation, or physical damage causes terminal bridging in connectors under the seat, in the steering wheel clock spring, or inside the B-pillar trim.
  • 2Airbag Control Unit (ACU) internal MOSFET drive circuit or detection circuit fault, causing signal crosstalk between different circuits and false detection of an external series connection.
  • 3Incorrect wiring connection during airbag or seat belt pretensioner replacement after accident repairs, cross-connecting pins from different ignition circuits and forming a series circuit.
  • 4After vehicle wading or deep interior cleaning, an aging connector sealing ring creates a conductive path between terminals, especially at the connection between the seat wiring harness and the floor wiring harness.
  • 5Wiring harness manufacturing defects or long-term wear damages the insulation, causing unintended connections between adjacent circuits, or using a non-genuine wiring harness during repairs results in mismatched pin assignments.
What To Do
  • 1
    Use a VDS2000 or VDCI diagnostic tool to read the complete DTCs and freeze frame data. Identify the specific airbag circuit involved (e.g., driver side stage 1/stage 2 airbag, side airbag) and the series-connected circuit. Record the environmental conditions (temperature, voltage) at the time of the fault.
  • 2
    Perform the airbag system power-down procedure: disconnect the 12V battery negative terminal and wait at least 3 minutes (5 minutes recommended) to ensure the system fully discharges. Inspect the airbag control module (ACU) connector and related airbag component connectors (focusing on the areas under the seats, under the steering wheel, B-pillar, and C-pillar) for signs of water ingress, green corrosion, or terminal deformation.
  • 3
    Use a digital multimeter to measure the resistance between the faulty circuit pins. Normal resistance is approximately 2.0 Ω (including approximately 0.5 Ω clock spring resistance). A resistance of approximately 4 Ω confirms the two circuits are in series. Measure the insulation resistance between the involved circuits; it must be greater than 1 MΩ. A lower resistance indicates a short circuit.
  • 4
    If a connector fault exists, clean the connector with electrical contact cleaner and apply conductive protectant. Replace the connector or wiring harness if necessary. If the wiring harness has an internal short circuit, use the circuit diagram to locate and repair the damaged point, or replace the entire wiring harness. If the ACU has an internal fault (abnormal resistance between ACU terminals), replace the airbag control unit and complete online coding, VIN writing, and crash sensor calibration.
  • 5
    After repair, clear the fault code. Perform a static test (turn the ignition switch ON and verify the SRS warning lamp turns off after self-check) and a dynamic test (use the diagnostic tool to perform an actuator test and verify the resistance value of each circuit is within the standard range). Finally, perform a road test to verify the repair.
Real-World Cases
BYD DTC AI Analysis

Seat wiring harness series fault in water-damaged vehicle

✓
A 2019 Qin PRO DM drove through floodwater after heavy rain in Guangdong, and the dashboard displayed 'Check SRS System'. The scan tool retrieved codes B179E00 and B179D00 (passenger airbag circuit malfunction). Disassembly revealed water in the wiring harness connectors beneath the front seats; green corrosion between the terminals had connected the driver side airbag circuit in series with the passenger side pretensioner circuit. Technicians thoroughly cleaned the seat wiring harness connectors, replaced the waterproof seals, blew out the harness interior with compressed air, confirmed normal insulation resistance, then cleared the fault codes. Check wiring harness sealing at other low-lying areas of the vehicle.
BYD DTC AI Analysis

Accident repair misconnected wiring harness, causing series connection

✓
A 2018 Qin PRO petrol sustained front-end impact damage. An independent workshop replaced the driver's airbag, clock spring and seatbelt pretensioners. After the repair, the airbag warning light stayed on. Scanning revealed DTC B179E00. Inspection showed the workshop had swapped the driver's seat pretensioner connector with the side airbag connector when reconnecting the yellow plugs beneath the seat. Both connectors share identical specifications but different pin definitions, causing ignition circuit 1 and ignition circuit 2 to connect in series. Repositioned the connectors according to the service manual wiring diagram (section SRS-10) and verified that each airbag component's 2-pin plug matched the corresponding colour markings on the harness. Fault resolved.
BYD DTC AI Analysis

Clock spring internal break caused series circuit

✓
A 2019 Qin PRO DM's airbag warning light illuminated suddenly while driving; no collision history. Diagnosis revealed DTC B179E00 accompanied by B176200 (driver airbag short-to-ground history code). Steering wheel removal revealed a fractured flat cable inside the clock spring (spiral cable). The broken wire intermittently contacted other metal components during steering rotation, creating an intermittent series connection between the driver-side stage 1 and stage 2 airbag circuits. Replaced the clock spring with a genuine part (part number HA2E-5820000), calibrated the steering wheel angle sensor, and performed the 'airbag system configuration' procedure using a diagnostic tool to ensure resistance matching of the new component.
Other Seal 6 EV 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.B1737DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Seal 6 EV →Seal 6 EV overview →
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.