AU
B1742-00

DTC B1742-00 indicates the SRS (airbag) control module detects an abnormally low-resistance short circuit between the Left Rear Side Airbag squib circuit and the vehicle positive power supply (+B, typically 12V battery voltage) — Atto 8

Safety System

DTC B1742-00 indicates the SRS (airbag) control module detects an abnormally low-resistance short circuit between the Left Rear Side Airbag squib circuit and the vehicle positive power supply (+B, typically 12V battery voltage).

Under normal conditions, high resistance isolates the airbag squib circuit from both power and ground.

The SRS module internal capacitor releases current only at the moment of deployment.

A short to power causes: 1) airbag deployment failure (the power supply bypasses the trigger current); 2) a risk of unintended deployment (if short circuit resistance changes or voltage fluctuates); 3) the SRS system to enter fail-safe mode, disabling all airbag functions.

This fault is a continuous, non-intermittent hard short.

The B1742-00 fault code on the Atto 8 indicates a high-severity SRS airbag fault where the left rear side airbag squib circuit is shorted to battery power. This can stop airbags working, cause fail-safe mode, or create a risk of unintended deployment. Common causes include damaged rear seat wiring or water-corroded airbag connectors. Do not drive unnecessarily; visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from 5 recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Mechanical wear of the rear seat wiring harness: Long-term friction between the left rear seat fore-and-aft slide rail adjustment mechanism and the floor wiring harness damages the yellow airbag wire insulation. The exposed copper core contacts and short-circuits to body power wires (e.g., seat heating power wire, 12V permanent live wire).
  • 2Connector water ingress causing electrolytic corrosion: Water ingress in the rear footwell from wading, high-pressure washing, or a blocked air conditioning drain hose causes water to seep under the seat. Water accumulates between the pins of the airbag wiring harness connector (typically located under the seat or below the C-pillar). This creates an electrolytic conductive path, causing a short circuit between the power and signal terminals.
  • 3Modification damage: Clips, screws, or other fasteners used to install aftermarket full-cover seat covers, leather seats, or rear seat heating pads directly pierce or crush the airbag wiring harness, causing the internal wires to short to the power wire.
  • 4Harness securing failure: Original wiring harness retaining clips age and break, causing the harness to sag and contact the seat metal slide rail, bracket, or sharp body edge. Vibration damages the insulation, allowing the harness to contact a live component.
  • 5SRS control module internal fault: Power transistor (IGBT) breakdown in the internal ignition drive circuit or a stuck relay causes the circuit terminal to continuously output battery voltage, resulting in a false external short circuit detection.
What To Do
  • 1
    Safe power-off and discharge: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds (3 minutes on some models) to fully discharge the SRS control module internal backup capacitor and prevent accidental airbag deployment.
  • 2
    Removal and visual inspection: Remove the left rear seat assembly (cushion and backrest) and the lower C-pillar trim panel to expose the left rear side airbag module (usually located on the side of the seat backrest or inside the C-pillar trim panel) and wiring harness connector. Inspect the wiring harness insulation for damage, scorch marks, or punctures. Check the connector for water ingress, oxidation, or deformed pins.
  • 3
    Circuit isolation measurement: Disconnect the SRS control module main harness connector. Using a multimeter set to resistance, measure the resistance between the left rear side airbag circuit pin and power (+B). Normal resistance is infinity (OL). If the resistance is less than 1Ω, this confirms a short to power. Next, disconnect the airbag assembly connector. Measure the harness side and the airbag side separately to isolate the short circuit to either the harness or the airbag assembly.
  • 4
    Repair or replace the wiring harness: If the harness is damaged, repair it using layered insulation (inner layer: waterproof tape, outer layer: heat-shrink tubing) and maintain at least 50 mm clearance from adjacent power wires. If the harness runs along the seat slide rail path, reroute it and install abrasion-resistant corrugated conduit or fabric tape. If the airbag itself has an internal short circuit (very rare; resistance is 0 Ω and the harness is normal), replace the airbag module.
  • 5
    Connector treatment and sealing: If water enters the connector, thoroughly clean the pins with precision electrical contact cleaner (not a general-purpose cleaner), blow dry with compressed air, apply conductive grease, and reconnect. Check the connector waterproof sealing ring and replace if necessary. Secure the connector in a high position with cable ties to prevent future water ingress.
  • 6
    System reset and verification: Restore all connections, reinstall the seat, and reconnect the battery. Use the BYD dedicated diagnostic tool (VDS2000 or Launch X-431) to clear the fault code. Perform the 'SRS system self-check' or 'ignition circuit resistance learning', and confirm DTC B1742-00 does not return. Conduct a road test, simulate seat adjustments and bumpy road conditions, and verify the fault is resolved.
Real-World Cases
BYD DTC AI Analysis

BYD Qin EV - Rear seat runner chafed through wiring harness

✓
The airbag warning light would illuminate intermittently while driving, and always after rear passengers adjusted their seat position. Technicians removed the left rear seat and found interference between the seat runner and the airbag wiring harness mounting point. Repeated forward and rearward adjustment had chafed through the insulation of the yellow airbag wire, and the exposed copper contacted the 12V power supply wire for the seat heating module, causing a short to power. Stripping back the harness revealed three wear points, one of which had fused to the red wire.
Original source ↗
BYD DTC AI Analysis

BYD Qin EV450 - Rear connector corroded due to water wading

✓
After driving through standing water (depth up to the lower door sill), the airbag warning light on the instrument panel remained on. The scan tool retrieved code B1742-00. Inspection found obvious mud and water traces inside the white 2-pin airbag connector under the left rear seat. Electrolytic corrosion between the pins formed green oxide, reducing resistance between the power and signal pins to 0.5Ω and causing a short to power.
Original source ↗
BYD DTC AI Analysis

BYD Qin 100 - Aftermarket seat cover damaged wiring harness

✓
After the owner fitted full-surround genuine leather seat covers, the airbag warning light immediately came on and stayed on. Inspection found that metal staples securing the covers had pierced the left rear side airbag wiring harness sheath, causing a short between the airbag igniter wire (yellow) and the seat heater power wire (red). A multimeter reading showed 0Ω resistance to the power supply terminal. After removing the staples and repairing the harness, the fault cleared.
Original source ↗
BYD DTC AI Analysis

BYD Qin 80 - Connector locking tab broke, causing the plug to come loose and short out.

✓
The vehicle operated as a ride-share car. Rear passengers frequently kicked the left rear C-pillar area. Inspection found the left rear side airbag connector locking tab fractured, so the connector did not fully latch. On bumpy roads the connector shifted, the pins contacted the adjacent 12V constant power terminal and caused an intermittent short to power. Replaced the connector and re-secured the wiring harness routing. Problem resolved.
Original source ↗
BYD DTC AI Analysis

BYD Qin EV300 - Wiring harness retaining clip aged and detached.

✓
The vehicle is 5 years old. The factory wiring harness retaining clip under the left rear seat had aged and snapped, allowing the harness to sag and contact the seat rail. An aftermarket rear seat heater was installed later; its 12V power cable insulation had worn through and bonded to the OEM airbag harness, causing fault B1742-00. Repair involved reorganising both harnesses, replacing the clip, and separating the high- and low-voltage circuits.
Original source ↗
Other Atto 8 Fault Codes
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.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.