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B1742

DTC B1742 indicates an abnormal short circuit between the left rear side airbag ignition loop (typically installed in the left rear seat backrest or C-pillar) and the vehicle power supply positive (B+) — Seal 6 EV

Safety System

DTC B1742 indicates an abnormal short circuit between the left rear side airbag ignition loop (typically installed in the left rear seat backrest or C-pillar) and the vehicle power supply positive (B+).

In the Supplemental Restraint System (SRS), the airbag module connects to the Airbag Control Unit (ACU) via two wires.

Normal wiring harness resistance measures approximately 2-3 ohms.

The diagnostic system triggers this fault code upon detecting a short to power in this circuit (voltage approaching 12V battery voltage instead of the normal low-voltage signal).

This fault is extremely dangerous.

The short circuit can cause unexpected airbag deployment while driving, severely injuring occupants.

Furthermore, the system enters protection mode and disables the airbag, preventing inflation during a collision and eliminating side-impact protection.

Additionally, the SRS illuminates the instrument cluster airbag warning light and may lock the entire airbag system, disabling all airbags.

The B1742 fault code on the Seal 6 EV indicates a high-severity short to battery power in the left rear side airbag ignition circuit. This can disable the SRS and may risk unintended airbag deployment or loss of side-impact protection. Common causes include damaged wiring under the seat or in the pillar, or water/corrosion in the connector. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
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Cases Logged
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Causes
Likely Causes — Seal 6 EV
  • 1Wiring harness insulation wear under the seat or inside the B-pillar/C-pillar: Frequent fore-and-aft seat adjustment or friction from passengers entering and exiting damages the airbag wiring harness insulation, causing the conductor to directly contact the metal body frame or power wiring.
  • 2Water ingress or corrosion in the under-seat connector: Spilled drinks, water seepage during car washes, or vehicle wading creates a conductive path between the airbag connector terminals or causes electrolytic corrosion, resulting in a short circuit between the pins.
  • 3Airbag module internal fault: Insulation failure of the igniter (squib) inside the airbag inflator causing a short circuit between the bridgewire and the housing, or an internal circuit board fault.
  • 4SRS control unit (ACU) internal drive circuit damage: The airbag drive transistor or related circuit inside the control unit shorted, causing the output terminal to continuously output a high level.
  • 5Harness damage caused by aftermarket modifications: mounting screws pierce the harness or metal edges pinch the harness when installing seat covers, seat heating pads, dash cam wiring, or audio upgrades.
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (some models require 3 minutes) to fully discharge the SRS backup power supply and prevent accidental airbag deployment during repair.
  • 2
    Fault confirmation and freeze frame retrieval: Use a dedicated diagnostic tool (such as BYD VDS2000/3000) to read the complete fault codes and freeze frame data. Record the vehicle status when the fault occurred (vehicle speed, temperature, etc.) and confirm if the fault is intermittent.
  • 3
    Visual and wiring harness inspection: Inspect the wiring harness in the left rear seat side airbag area (usually located on the left side of the seat backrest) for obvious damage, crushing, or burn marks. Inspect the yellow SRS connector under the seat for looseness, water ingress, or foreign objects.
  • 4
    Electrical measurement and isolation diagnosis: Disconnect the airbag module connector. Use a multimeter to measure the resistance/voltage from both harness-side connector terminals to body ground and to the 12V power supply to confirm whether the short circuit is on the harness side or the module side. Measure the resistance between the two airbag module terminals and between the terminals and the housing (Normal: greater than 1 MΩ to power/ground; 2-3 Ω between terminals).
  • 5
    Section-by-section troubleshooting: If the wiring harness has a short to power, sequentially disconnect the intermediate connectors from the ACU to the airbag module (usually located under the B-pillar or seat). Measure each section to pinpoint the short circuit.
  • 6
    Component replacement and repair: Based on diagnostic results, replace the damaged airbag module, repair the damaged wiring harness (use high-temperature wire of the same specification and double-insulate), or replace the SRS control unit. Never use standard electrical tape to wrap the SRS wiring harness.
  • 7
    System verification: Reconnect all connectors, connect the battery, use the diagnostic tool to clear the fault code, and perform the SRS system self-check; perform a dynamic test (simulate the full seat adjustment process) to confirm the fault does not recur; verify the instrument panel airbag warning light turns off after 6 seconds.
Real-World Cases
BYD DTC AI Analysis

Worn left rear seat wiring harness caused intermittent B1742 fault in Song MAX

✓
A 2019 Song MAX with 32,000 km showed an intermittent airbag warning light on the instrument panel. The scan tool retrieved DTC B1742 as an intermittent history code. The technician found the wiring harness retaining clip under the left rear seat rail had detached. The harness had chafed against the seat metal bracket, damaging the insulation and exposing the copper core. The exposed conductor intermittently touched the bracket; measurements showed low impedance between the bracket and battery positive, indicating an abnormal contact between the body harness and a power line elsewhere. Replaced the complete SRS harness assembly from the B-pillar to the seat (BYD part number: KBC-5823947). Rerouted the wiring and secured it using dedicated harness clips to prevent interference with seat moving parts. No recurrence after one month of follow-up.
BYD DTC AI Analysis

Tang DM seat modification caused airbag harness short to power

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A 2021 Tang DM owner reported the airbag warning light staying on with active fault code B1742. Aftermarket ventilated seats and leather seat covers had been fitted. The technician found the installer used excessively long self-tapping screws to secure the rear seat back cover panel, one of which pierced the left rear side airbag wiring harness. The screw contacted battery positive through the metal frame because the insulation on the aftermarket relay wiring was damaged. This shorted the airbag igniter circuit to positive via the screw. Repairs: Removed the offending screws. Replaced the pierced SRS harness section with BYD-certified high-temperature flame-retardant wire. Removed the aftermarket relay wiring and restored the original vehicle circuit. Replaced the left rear side airbag module, as the short may have damaged the internal igniter.
BYD DTC AI Analysis

SRS connector shorted from corrosion after Yuan EV wading

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A 2019 Yuan EV presented with the airbag warning light continuously illuminated after wading through deep floodwater. The diagnostic scan retrieved DTCs B1742 and B1740 (left front side airbag) along with multiple short-circuit fault codes. Inspection revealed the vehicle had driven through water deeper than the door sills, allowing water to penetrate the door seals and accumulate beneath the seats. The yellow 2-pin SRS connector located under the left rear seat showed obvious water staining and verdigris corrosion inside, causing short circuits between the terminals and between the terminals and the connector housing (the housing had established an abnormal connection to the power supply through the vehicle body). Repair procedure: Thoroughly dried the area beneath the seats, cleaned the connector using electronic cleaner, and replaced the corroded terminals (Part number: BYD-SRS-CONN-02). Applied protective wax inside the connector. Since the short circuit was brief, the airbag module tested undamaged. Retained the original module. Advised the owner to inspect the door drain holes for blockages.
BYD DTC AI Analysis

Qin Pro SRS control unit falsely reporting internal fault B1742

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A 2020 Qin Pro logged DTC B1742. Inspection found the left rear side airbag harness and connectors completely normal, with resistance to power exceeding 10 MΩ and airbag module resistance at 2.1 Ω (within specification). The fault code consistently returned after approximately 50 km of driving following each clear, with freeze frame data indicating the fault occurred while the vehicle was stationary. Further checks revealed the SRS control unit (ACU, located beneath the centre console) outputting abnormal voltage at the corresponding pin (continuous 12 V instead of the normal low-level scan signal). Diagnosed internal driver circuit breakdown within the ACU. Replaced the airbag control unit (part number: SC-3992847-B1), performed ACU coding and configuration using a diagnostic tool (entering the vehicle VIN and airbag configuration code), and carried out system calibration. This completely resolved the fault. This is a known quality issue affecting this batch of ACUs; check for any extended warranty coverage.
BYD DTC AI Analysis

Yuan Plus left rear side airbag module internal short circuit

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A 2022 Yuan Plus (DTC B1742 also applies to this platform) developed a constantly illuminated airbag warning light during normal use. Diagnosis confirmed B1742 as an active hard fault. After disconnecting the connector beneath the seat, the harness side measured no short to power. However, resistance between the two terminals of the airbag module (mounted inside the seat back) was 0.5 Ω (too low), and resistance to the module metal housing was 0 Ω (full continuity). Disassembly revealed the internal igniter bridge wire insulation had melted under high temperatures due to a manufacturing defect, causing a short to the housing. Repair: replace the left rear side airbag module assembly (part number YQ-5823947). Disconnect the battery and follow anti-static procedures during replacement. This case points to a supplier batch quality issue; check for any recalls or Technical Service Bulletins (TSBs).
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.