AU
B1751

DTC B1751 indicates the SRS (Supplemental Restraint System) control module detects a short to ground in the right rear side airbag deployment circuit — Seal U

Safety System

DTC B1751 indicates the SRS (Supplemental Restraint System) control module detects a short to ground in the right rear side airbag deployment circuit.

Specifically, an abnormally low resistance path (typically less than 1 ohm) exists between the vehicle body ground and the igniter wiring for the right rear side curtain airbag (C-pillar side curtain airbag) or the right rear seat side airbag.

The standard igniter resistance is 2.0 ± 0.3 ohms.

When the ECU detects a circuit short to ground, it immediately sets this DTC and cuts off the airbag deployment circuit to prevent accidental deployment while driving or failure to deploy during a collision.

This safety-critical fault causes the airbag warning light to remain illuminated and may fail to protect the right rear passenger during a crash.

The B1751 fault code on the Seal U indicates a high-severity SRS fault where the control module detects a short to ground in the right rear side airbag deployment circuit. This can be caused by a damaged airbag igniter or chafed wiring in the sill trim or C-pillar area. The airbag warning light may stay on and rear passenger protection may be reduced. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1A short circuit or damage in the internal igniter of the right rear side curtain airbag (C-pillar curtain airbag) module causes an abnormal drop in resistance.
  • 2The wiring harness from the SRS ECU to the right rear airbag chafes in the sill trim panel or C-pillar area, damaging the insulation and shorting to the vehicle body metal.
  • 3Failed seal on the right rear seat airbag connector (if equipped with a seat side airbag) allows water ingress or moisture, causing a short circuit between terminals or a short to ground.
  • 4Aging rear door weatherstrip allows rainwater to seep in and corrode the airbag wiring harness connectors inside the B-pillar/C-pillar.
  • 5After accident repairs, an incompletely locked airbag connector or improperly secured wiring harness rubs against metal body parts during driving, causing a short circuit.
What To Do
  • 1
    Connect the BYD dedicated diagnostic tool (VDS or ED400), enter the SRS system, and read the data stream. Verify the right rear side airbag resistance reads 0 ohms or close to 0 ohms, and confirm the fault is currently present.
  • 2
    Disconnect the 12V battery negative terminal and wait at least 3 minutes for the SRS capacitor to fully discharge to ensure safe operation.
  • 3
    Remove the right rear C-pillar trim panel (rear quarter window trim panel), locate the yellow connector for the right rear side curtain airbag, and check the connector for signs of water ingress, corrosion, or terminal deformation.
  • 4
    Disconnect the airbag module connector and use a multimeter to measure the resistance on the airbag module side. Normal resistance is 2-3 ohms. If the reading indicates a short circuit (0 ohms), replace the right rear curtain airbag assembly.
  • 5
    If the airbag module is normal, measure the resistance to ground on the wiring harness side. The reading should be infinity (open circuit). Continuity indicates a wiring harness short to ground. Inspect along the circuit for wear inside the door sill wiring harness sleeve.
  • 6
    Check the connector under the right rear seat (if equipped with a side airbag). Specifically inspect the wiring harness near the seat slide rail for wear caused by frequent seat movement.
  • 7
    Repair the damaged wiring harness section (use heat-shrink tubing or replace the wiring harness) or replace the faulty airbag module. Reconnect all connectors and verify the yellow connector locks fully into place.
  • 8
    Reconnect the battery, clear the fault code using the diagnostic tool, and perform an SRS system self-check. Confirm B1751 does not recur and the airbag warning light is off.
Real-World Cases
BYD DTC AI Analysis

BYD Song MAX B1751 fault after wading

✓
A 2019 BYD Song MAX had the airbag warning light on the dashboard after driving through deep water in a heavy rainstorm. The diagnostic tool retrieved DTC B1751 (Right rear seat side airbag short to ground). Inspection found the right rear door frame seal had aged, letting rainwater leak into the C‑pillar and corrode the side curtain airbag connector terminals. Removing the C‑pillar trim revealed water staining and verdigris inside the yellow connector. Technicians cleaned the terminals with electronic cleaner, applied conductive protectant, replaced the seal, and resolved the fault.
BYD DTC AI Analysis

BYD Tang door sill wiring harness chafed, causing intermittent short circuit

✓
2021 BYD Tang owner reported the airbag warning light occasionally illuminating, particularly on rough roads. Diagnosis revealed an intermittent B1751 fault. Removed the right rear sill trim panel and found the side curtain airbag wiring harness had chafed at the fixing clip due to prolonged vibration, with insulation damage causing an intermittent short to earth. Re-wrapped the harness, adjusted the fixing position to avoid contact with sharp edges, and replaced the damaged harness section, completely resolving the fault.
BYD DTC AI Analysis

BYD Yuan EV: Fault left after seat removal and refitting

✓
2019 BYD Yuan EV: Airbag warning light remained on after replacing the right rear seat cover. Read fault code B1751. Inspection found that the technician had not paid attention to the airbag harness routing during seat removal and installation, causing the side airbag connector to be pinched against the seat frame. The connector housing cracked, allowing the terminals to contact the metal seat frame and create a short to ground. Replaced the damaged airbag connector and wiring harness, routed the wiring correctly, and resolved the fault.
BYD DTC AI Analysis

BYD Qin petrol variant: Airbag fault after accident repair

✓
2020 BYD Qin petrol variant. After repairing a minor collision to the right rear, the airbag light stayed on. Retrieved fault code B1751. Inspection found an internal short circuit in the right rear curtain airbag trigger caused by the accident, with no external damage visible. Measured the curtain airbag resistance at 0.2 ohms (normal 2 ohms), indicating internal damage. Replaced the right rear curtain airbag module, then configured and calibrated it using a diagnostic tool. System returned to normal.
BYD DTC AI Analysis

BYD Song MAX ageing connector corrosion fault

✓
A 2019 Song MAX with 80,000 km displayed DTC B1751. Inspection found the airbag connector inside the right rear C-pillar had deteriorated from prolonged heat exposure, leaving the plastic housing brittle and the connector seal compromised. Terminal oxidation produced verdigris, causing a short to ground. Cleaning the terminals was ineffective — the oxidation had penetrated too deeply. Replaced the entire airbag harness connector and terminals. Fault 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.