AU
B1761

DTC B1761 indicates the Left Front Side Curtain Airbag ignition drive circuit shorted to the vehicle power supply positive (B+) — Seal U

Safety System

DTC B1761 indicates the Left Front Side Curtain Airbag ignition drive circuit shorted to the vehicle power supply positive (B+).

In the SRS system, normal airbag igniter resistance is approximately 2.0-3.0Ω.

The control module determines circuit condition by monitoring voltage and resistance.

If wiring harness insulation damage, misaligned connector terminals, or an internal airbag module fault causes the ignition circuit to contact a power wire, the control module detects an abnormally high voltage (near battery voltage).

The module immediately sets DTC B1761 and enters fail-safe mode.

This disables the Left Front Side Curtain Airbag and potentially related airbag functions, preventing deployment during a side impact and creating a severe safety hazard.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Harness insulation damage: Chafing, crushing, or rodent damage at the A-pillar, roof side rail, or B-pillar damages the left front side curtain airbag harness insulation, causing a short circuit to the body power supply wire.
  • 2Connector fault: Water ingress, corrosion, or detached terminals at the airbag connector below the A-pillar (usually marked DAB or SAB), shorting the ignition circuit terminal to the power supply terminal.
  • 3Airbag module internal short circuit: Insulation failure of the side curtain airbag inflator igniter causes a short circuit between the terminals or to power.
  • 4Improper accident repair: After a collision or water ingress, improperly secured wiring harnesses or missing clips during repair cause the harness to rub against sharp metal edges and sustain damage.
  • 5SRS control module internal fault: An internal drive circuit component failed, causing a continuous high-level output and a false external short circuit detection.
What To Do
  • 1
    Safety Preparation: Park the vehicle on a level surface, turn off all electrical equipment, disconnect the battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 2
    Fault Confirmation: Use VDS2000 or a dedicated BYD diagnostic tool to read fault codes. Confirm B1761 is a current fault (Active). Record freeze frame data. Check for accompanying fault codes (e.g., B1762, U0151).
  • 3
    Visual inspection: Check the routing of the left front side curtain airbag wiring harness at the A-pillar trim, front roof section, and B-pillar. Look for harness damage, crushing, or scorch marks. Specifically inspect connector D111 (Song MAX) or D10 (Qin series) for water ingress, corrosion, or terminal back-out.
  • 4
    Circuit measurement: Disconnect the SRS control module and left front side curtain airbag module connectors. Use a multimeter to measure the insulation resistance between the ignition circuit and the power supply. Normal resistance is greater than 10MΩ. Continuity or low resistance confirms a short circuit.
  • 5
    Section-by-section diagnosis: Use the section isolation method. Disconnect the main wiring harness intermediate connector. Measure the control module side and airbag side circuits separately to determine which section contains the short circuit. Common short-circuit points are located near the A-pillar hinge (at the connection between the door wiring harness and body wiring harness).
  • 6
    Repair or replace: If the wiring harness is damaged, repair it with heat-shrink tubing or waterproof tape and re-secure the harness to prevent interference; if the connector is damaged, replace the connector; if testing confirms an internal short circuit in the airbag module, replace the left front side curtain airbag assembly.
  • 7
    System verification: Restore all connections, connect the battery, turn the ignition switch ON, clear the fault code using the diagnostic tool, perform the SRS system self-test (Active Test), confirm B1761 does not return, and verify the instrument panel airbag warning light turns off.
  • 8
    Road test verification: Perform a road test simulating bumpy road conditions. Check if the fault code returns to confirm the repair is complete.
Real-World Cases
BYD DTC AI Analysis

Song MAX B1761 Fault After Water Wading — A-Pillar Connector Water Ingress Corrosion

✓
A 2019 Song MAX developed a constant airbag warning light after driving through heavy flood water. Scanning revealed DTC B1761. Inspection showed the water level had exceeded the door sills. Removing the A-pillar trim revealed significant water ingress and verdigris inside the left front side curtain airbag connector D111. The technician cleaned the connector terminals, applied conductive grease, and verified normal insulation resistance. They replaced the waterproof seal, re-secured the wiring harness, and cleared the fault. The connector seal had aged and failed during wading, causing a short circuit between terminals.
BYD DTC AI Analysis

Intermittent B1761 fault following Qin Pro accident repair — crushed wiring harness

✓
2020 Qin Pro intermittently set DTC B1761 after side impact collision repairs. Inspection found accident repairs had pinched the left front side curtain airbag wiring harness at the B-pillar trim clip, damaging the insulation and exposing copper wires. Harness movement while driving occasionally contacted body power lines, causing a short. Rerouted the harness to avoid the interference point, wrapped it with fleece tape, secured it, and replaced the damaged section. Fault completely resolved.
BYD DTC AI Analysis

Song Plus B1761 after panoramic sunroof modification — wiring harness pierced by screw

✓
A Song PLUS DM-i showed an airbag warning light after a third-party panoramic sunroof install, with the scanner reading B1761. Inspection revealed that during the modification, the installer missed the wiring clearance when tightening roof crossbeam screws, and a screw pierced the left front side curtain airbag harness, shorting the power wire to the igniter wire. The short was inside the roof rail, so the shop removed the headliner to repair the harness. They replaced the damaged section and adjusted the screw length, clearing the fault. When modifying, strictly follow the body wiring layout diagram.
BYD DTC AI Analysis

Long-term vibration caused B1761 in Qin EV — wiring harness chafing, short to power

✓
A 2020 Qin EV with 120,000 km set a B1761 DTC. Inspection revealed the left front side curtain airbag harness at the A-pillar hinge had suffered insulation damage from vibration due to repeated door opening and closing, with the wiring rubbing against sharp sheet metal edges. Internal conductors contacted both the A-pillar reinforcement beam (ground) and the adjacent interior light power wire simultaneously, creating a short to power. Repaired the damaged harness, fitted rubber protective sleeving and harness retaining clips, and eliminated the vibration source to resolve the fault.
Other Seal U 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.