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) — Seal U

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.

The B1735 fault code on the Seal U indicates a medium-severity fault with the second-row right side airbag circuit, where the SRS ECU detects an open circuit or communication loss. Common causes include a loose yellow airbag connector under the seat or near the B-pillar, or a damaged airbag module/igniter. Visit an authorised dealer for diagnosis and repair using the correct scan tool. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Yellow dedicated wiring harness connector under the seat or at the B-pillar is loose, disconnected, or the locking tab is not fully engaged (commonly caused by frequent fore/aft adjustment of the second-row seat or passenger kicks).
  • 2Open circuit in right middle-row side airbag module internal igniter or module communication circuit fault (airbag assembly damaged)
  • 3The wiring harness connecting the airbag module to the SRS ECU is worn or broken, or the seat rail crushed or sheared the harness over a long period, breaking the copper wires.
  • 4Water ingress or improper interior cleaning causes connector terminal oxidation and corrosion, resulting in excessive contact resistance (>3Ω) that registers as an open circuit.
  • 5Airbag wiring harness incorrectly reconnected after recent seat removal/installation, interior trim modification, or accident repair, or connector not locked in place (no audible 'click').
What To Do
  • 1
    Safety preparation: Switch the vehicle to 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 lower C-pillar trim panel. Verify the dedicated yellow airbag module 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 the wiring harness along its 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. Look for crush or shear marks caused by the seat track.
  • 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 usually 2.0-3.0 ohms. If the resistance is infinite (∞), this indicates an open circuit in the wiring or module; if the resistance is <1 ohm, a short circuit may exist. Also measure the wiring harness insulation resistance to ground and to power supply; it must be >1MΩ.
  • 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 fault code 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 the 'SRS system self-check' and 'crash sensor calibration' (if required). Verify 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 Seal U Fault Codes
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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173712DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Common problems reported for Seal U →Seal U 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.