AU
B1735

DTC B1735 indicates the airbag control unit (SRS ECU) detects a communication loss or abnormal circuit resistance in the second-row right side airbag module (typically located in the side of the second-row right seat or inside the C-pillar/door trim panel) — Atto 3

Safety System

DTC B1735 indicates the airbag control unit (SRS ECU) detects a communication loss or abnormal circuit resistance in the second-row right side airbag module (typically located in the side of the second-row right seat or inside the C-pillar/door trim panel).

Specifically, the inflator circuit of this airbag assembly is open (infinite resistance), or the communication line between the module and the SRS ECU is open.

This is an active safety system fault.

During a side collision, this airbag may fail to deploy, leaving the second-row right occupant without side impact protection.

Disconnected physical connections, damaged wiring harnesses, an open inflator inside the airbag module, or poor terminal contact at the SRS ECU typically cause this fault.

Use the dedicated diagnostic tool (VDS2000/VDS3000) and the wiring diagram to pinpoint the fault.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Yellow dedicated wiring harness connector under the seat or at the B-pillar is loose or disconnected, or the locking tab is not fully engaged (commonly results from frequent fore-and-aft adjustment of the second-row seat or passenger kicks).
  • 2Right middle-row side airbag module internal igniter open circuit or module communication circuit fault (damaged airbag assembly)
  • 3The wiring harness between the airbag module and the SRS ECU is worn or broken, or the seat rail pinched or sheared the harness over time, breaking the copper wire.
  • 4Vehicle water ingress or improper interior cleaning causes connector terminal oxidation and corrosion, creating excessive contact resistance (>3Ω) that the system identifies as an open circuit.
  • 5Airbag wiring harness incorrectly reconnected after recent seat removal and installation, interior trim modification, or accident repair, or connector not fully locked (no audible 'click').
What To Do
  • 1
    Safety preparation: Switch the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds (to fully discharge the SRS backup power capacitor). Never use a standard multimeter to directly measure the airbag inflator resistance, as this may trigger accidental deployment.
  • 2
    Visual inspection: Remove the second-row right seat side trim panel or the lower C-pillar trim panel. Verify the airbag module's yellow dedicated connector (usually equipped with a double-locking mechanism) is fully inserted. Confirm the locking tab (CPA) is in the locked position, with no looseness or terminal back-out.
  • 3
    Wiring harness physical inspection: Inspect along the wiring harness route from the airbag module to the SRS ECU. Check the protective corrugated conduit near the seat rail and B-pillar hinge area for damage. Inspect for signs of the seat track crushing or shearing the harness.
  • 4
    Resistance and continuity test: Use a dedicated airbag system diagnostic tool (or a multimeter with a low-current test function) to measure the right middle-row side airbag circuit resistance at the SRS ECU connector. The standard value is typically 2.0-3.0 ohms. Infinite (∞) resistance indicates an open circuit in the wiring or module; resistance <1 ohm indicates a possible short circuit. Measure the wiring harness insulation to ground and power supply; the value must be >1 MΩ.
  • 5
    Sectional isolation diagnosis: Disconnect the airbag module connector and use a jumper wire to short the two terminals on the ECU-side wiring harness. If the fault code changes to 'resistance too low', the wiring harness is normal and the fault is in the airbag module itself. If the system still reports 'not connected', the fault is in the wiring harness or the ECU.
  • 6
    Component Replacement and Verification: If the airbag module is faulty, replace the right second-row side airbag assembly. If the wiring harness is faulty, repair or replace the wiring harness. After repair, reconnect the battery. Use the VDS diagnostic tool to clear the fault code. Perform 'SRS system self-check' and 'crash sensor calibration' (if required). Confirm DTC B1735 does not return and the airbag warning light turns off.
Real-World Cases
BYD DTC AI Analysis

2019 Song MAX reports B1735 fault after frequent seat adjustments

✓
The owner of a Song MAX with 30,000 km reported the airbag warning light on the instrument panel was constantly on. VDS retrieved DTC B1735 (right middle-row side airbag not connected). Inspection found the right-hand second-row seat adjusted to the foremost position. The yellow airbag connector lock tab under the seat had detached, and the plug was loose by about 5 mm. The owner frequently moved the seat for child pick-ups; the rail movement pulled on the wiring harness. Reconnected the connector firmly, reinstalled the lock tab, and secured the wiring harness with cable ties to keep it clear of the seat rail. Resolved the fault.
BYD DTC AI Analysis

2021 Tang DM airbag warning light on after accident repair

✓
Minor scrape on right rear side. After a third-party repair shop replaced the right rear door and C-pillar trim panel, the dashboard displayed an airbag fault. The diagnostic scanner showed code B1735. Inspection found the technician had trapped the right second-row side airbag wiring harness connector beneath the trim panel clip during installation, leaving the connector partially disconnected and the pins bent. Straightened the pins and rerouted the wiring to ensure the connector fully locked. Fault resolved.
BYD DTC AI Analysis

2019 BYD Yuan EV: Airbag system warning after wading through water

✓
After the vehicle was driven through heavy rain and floodwater (water level up to the middle of the doors), the instrument cluster displayed an airbag fault. Retrieved fault codes included B1735. Removed the second-row right-side seat and carpet, and found clear water stains and copper oxidation inside the airbag wiring harness connector. The cause: deteriorated door seals allowed rainwater to enter and pool at the lowest point of the harness under the seat. Cleaned the oxidised terminals, applied a special conductive anti-corrosion compound, replaced the door seals, and dried the harness. Fault resolved.
BYD DTC AI Analysis

2020 Qin Pro airbag module internal open circuit

✓
No accident history. Airbag warning light came on intermittently, especially during cold starts. DTC B1735 appeared intermittently. Checked harness connections: normal; measured harness continuity: good. Suspected a cold solder joint or poor connection in the igniter or flexible circuit board inside the airbag module. After disconnecting the battery and allowing sufficient time, substituted a known-good airbag module for testing; fault did not reappear. Replaced the right middle row side airbag assembly (part number must match vehicle configuration). Fault completely resolved.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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.