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 — Atto 8

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.

5
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Right rear side curtain airbag (C-pillar curtain airbag) module internal igniter is shorted or damaged, causing abnormally low 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 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, corroding the airbag wiring harness connectors inside the B-pillar/C-pillar.
  • 5Airbag connector not fully locked or wiring harness improperly secured after accident repairs, causing rubbing against metal body parts during driving and resulting in 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 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 inspect 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 shows a short circuit (0 ohms), replace the right rear side curtain airbag assembly.
  • 5
    If the airbag module is normal, measure the resistance to ground on the wiring harness side. It should display infinity (open circuit). Continuity indicates a short to ground in the wiring harness. Inspect along the circuit for wear inside the sill wiring harness sleeve.
  • 6
    Check the connector under the right rear seat (if equipped with a side airbag). 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 plugs and ensure the yellow plug locks fully into place.
  • 8
    Reconnect the battery, use the diagnostic tool to clear the fault code, and perform an SRS system self-check. Confirm B1751 does not return and the airbag warning light turns 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 Atto 8 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.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.
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.