AU
B1751-00

B1751-00 is a Supplemental Restraint System (SRS) hard fault code indicating a short circuit to body ground (GND) in the right rear seat side airbag squib circuit (typically integrated into the seat backrest or C-pillar trim) — Atto 8

Safety System

B1751-00 is a Supplemental Restraint System (SRS) hard fault code indicating a short circuit to body ground (GND) in the right rear seat side airbag squib circuit (typically integrated into the seat backrest or C-pillar trim).

The SRS ECU internal detection circuit continuously monitors the airbag squib circuit resistance (normal range: 2.0-3.0 Ω; 1.6-2.1 Ω on some models).

The ECU registers a short to ground when it detects circuit resistance to ground below 1.0 Ω (near 0 Ω).

This fault causes the following: 1) The affected airbag fails to deploy during a collision, losing its protective function. 2) The SRS enters fail-safe mode, which may restrict seat belt pretensioner operation. 3) The instrument panel airbag warning light remains illuminated, indicating a critical safety hazard.

This is a level 3 severe fault requiring immediate repair.

3
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Mechanical wear of the under-seat wiring harness: Frequent right rear seat movement or folding causes long-term friction between the seat frame and the wiring harness sleeve. Damaged insulation allows the wire to directly contact the metal vehicle body frame, creating a short to ground (most common cause, approx. 60% of cases).
  • 2Airbag module internal short circuit: The bridge wire inside the airbag inflator shorts to the housing. Airbag module aging, moisture ingress (water entering through open windows), or improper previous repairs usually cause this fault (approximately 25% of cases).
  • 3Connector corrosion or water ingress: Poor sealing of the wiring harness connector under the right rear seat (usually designated KJ10 or similar) allows water entry after vehicle washing or wading, causing a short circuit between terminals or to ground (approximately 10% of cases).
  • 4Improperly secured wiring harness: After accident repairs or interior trim removal and installation, failing to properly secure the wiring harness in the retaining clips allows the seat slide rail to pinch or chafe the harness, causing a short to ground.
  • 5Internal SRS ECU fault: Damaged internal detection circuit or driver chip falsely reports a short circuit fault (very rare; rule out other possible causes before confirming).
What To Do
  • 1
    Safety preparation: Turn the vehicle power mode to OFF, disconnect the negative battery cable, and wait at least 90 seconds to fully discharge the SRS backup power supply and prevent accidental airbag deployment during repair.
  • 2
    Fault confirmation: Connect a genuine BYD diagnostic tool (such as VDS or ED400). Read the fault codes to confirm B1751-00 is present. Record the freeze frame data (ambient temperature and voltage). Attempt to clear the fault code, cycle the power, and observe if the fault returns.
  • 3
    Visual inspection: Remove the right rear seat (typically requires loosening the seat retaining bolts and sliding backward). Inspect the yellow SRS wiring harness and connector (KJ10) under the seat for obvious wear, damaged insulation, signs of water ingress, or an unlocked connector.
  • 4
    Circuit isolation test: Disconnect the right rear seat side airbag connector. Use a multimeter to measure the resistance between the harness-side terminals (B/Y black/yellow wire and Y/L yellow/green wire) and body ground. The normal value is greater than 1 MΩ (infinite). A lower resistance confirms a harness short to ground.
  • 5
    Voltage check: Keep the connector disconnected, set the power mode to ON, and measure the voltage between the wiring harness side terminal and ground. The voltage should be less than 1V. If voltage exists, suspect an internal ECU fault or a short circuit to another power supply wire.
  • 6
    Airbag module test: If wiring harness measurements are normal, connect a dedicated 2.0-3.0Ω resistor (or a known-good airbag simulator) across the wiring harness connector and restore power. If the fault code clears and the SRS light turns off, the airbag module has an internal short circuit. Replace the airbag module.
  • 7
    Fault repair: If the wiring harness is damaged, wrap the damaged area with insulating tape, install corrugated conduit for protection, and re-secure the wiring harness away from the seat slide rail. If the connector has water ingress, clean it with electrical contact cleaner and blow dry. Replace the connector if necessary. If the airbag module is faulty, replace it with a genuine airbag module (verify the part number matches).
  • 8
    System reset: After completing the repair, reconnect all connectors and confirm they lock. Install the seat. Connect the battery. Use the diagnostic tool to clear the fault code. Perform an SRS system self-check (typically, wait 10-20 seconds after power-on to observe if the SRS warning light turns off). Finally, perform a road test to verify the repair.
Real-World Cases
BYD DTC AI Analysis

Wiring harness chafing caused a short to ground.

✓
Symptoms: BYD Qin EV450 SRS warning light stays on. Scan tool reads DTC B1751-00. Diagnosis: Removed the right rear seat. Found the wiring harness protective sleeve beneath the seat rail damaged. Yellow-green wire insulation worn through, contacting the seat frame and causing a short to earth. Measured resistance to earth: 0.3Ω. Resolution: Taped the damaged section with electrical insulating tape. Fitted flame-retardant corrugated tubing. Rerouted the harness and secured it with cable ties to the seat base mounting slots, keeping clear of moving parts. Cleared the DTC. SRS light went out and function restored.
Original source ↗
BYD DTC AI Analysis

Internal short circuit in the airbag module

✓
Symptoms: After the vehicle drove through water (water entered because the right rear window was not fully closed), the SRS warning light illuminated, showing DTC B1751-00. Diagnosis: Disconnected the rear seat airbag connector and measured harness resistance to earth at >10MΩ (normal) and voltage to earth at 0V (normal), ruling out a harness fault. Bridged the circuit with a 2.5Ω resistor and the fault disappeared. Fitted the faulty airbag module to a known-good vehicle and the fault recurred, confirming an internal igniter short to earth within the airbag module. Resolution: Replaced the right rear side airbag module (part number must match the VIN). After fitting, performed system configuration and self-test. Fault resolved.
Original source ↗
BYD DTC AI Analysis

Poor connector contact causing intermittent short circuit.

✓
Symptoms: SRS warning light illuminates intermittently, mainly on rough roads. Scan tool detected intermittent fault code B1751-00. Diagnosis: Inspection of the connector under the right rear seat found the locking tab not fully engaged, the connector loose, and minor oxidation on the internal terminals. On bumpy roads, vibration caused the terminals to contact the body, producing a momentary short circuit. Resolution: Cleaned the connector terminals with electrical contact cleaner and applied a small amount of conductive grease. Reconnected the connector firmly and made sure the locking tab engaged fully. Secured the connector with cable ties to prevent loosening. Completed a 20 km road test with no fault recurrence.
Original source ↗
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.