AU
B1764

DTC B1764 indicates the Right Front Side Curtain Airbag igniter circuit resistance falls below the SRS control unit (ACU) threshold (typically <1 — Seal U

Safety System

DTC B1764 indicates the Right Front Side Curtain Airbag igniter circuit resistance falls below the SRS control unit (ACU) threshold (typically <1.0Ω or below 70% of the nominal 2.0Ω).

This fault suggests an internal inter-turn short circuit in the airbag squib, or a short to ground or power in the wiring harness or connector, causing an abnormal drop in total circuit resistance.

This critical safety fault causes the SRS system to detect a short-circuit risk in the airbag circuit, potentially triggering unintended deployment or failure during a collision.

Consequently, the system illuminates the airbag warning light and disables the airbag's deployment function, severely compromising side-impact protection.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Airbag igniter internal short circuit: Moisture, aging, or manufacturing defects in the gas generator bridgewire or ignition charge reduce internal resistance.
  • 2Harness short to ground: Worn airbag harness insulation in the A-pillar, B-pillar, or roof side rail contacts the vehicle body metal, causing a short circuit.
  • 3Connector fault: Water ingress, oxidation, bent pins, or foreign objects in the airbag connector (usually located below the A-pillar or in the roof) cause abnormal continuity.
  • 4SRS control unit internal fault: A damaged A/D conversion circuit or detection circuit inside the ACU causes a false low resistance reading.
  • 5Improper repair: During accident repairs or interior modifications, tools pierced the wiring harness, metal edges pinched the harness, or missing retaining clips caused wear and a short circuit.
What To Do
  • 1
    Safety preparation: Shift the vehicle into P, apply the parking brake, turn off the ignition, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor.
  • 2
    Fault confirmation: Connect the VDS diagnostic tool. Read the DTCs to confirm B1764 is a current fault (Active). Record the freeze frame data. Check for accompanying fault codes such as B1763 (resistance is 0) or B1765 (resistance too high).
  • 3
    Visual inspection: Check the right front curtain airbag area (A-pillar trim, headliner, B-pillar) for signs of impact, water stains, mold odor, or unauthorized modifications.
  • 4
    Disconnect the airbag: Remove the right front A-pillar trim, locate the yellow SRS connector, disconnect the right front side curtain airbag connector, and check the terminals for corrosion, burning, water ingress, or push-out.
  • 5
    Measure airbag assembly resistance: Use a digital multimeter (low-resistance setting, <1 Ω accuracy) to measure the resistance between the two terminals of the airbag-side igniter. Normal resistance is 1.5–3.0 Ω. A reading <1.0 Ω indicates an internal short circuit in the airbag assembly. Replace the airbag assembly.
  • 6
    Measure wiring harness insulation: Measure the resistance from both terminals of the harness-side connector to body ground. The resistance must be infinite (>1MΩ). A low resistance indicates a short to ground in the wiring harness. Locate the damaged point.
  • 7
    Harness continuity and short circuit check: Measure harness continuity between the SRS ECU and the airbag connector, and check the harness for a short circuit to the power supply (+B).
  • 8
    Component replacement and repair: Based on measurement results, replace the right front side curtain airbag assembly (if resistance is abnormal) or repair/replace the wiring harness (if insulation is damaged). Replace the SRS control unit if necessary.
  • 9
    System reset and calibration: Reconnect all connectors, reinstall the battery, and clear fault codes. On some models, perform SRS system self-learning or calibration.
  • 10
    Final verification: Perform a static test (ignition switch ON, verify the warning light turns off) and a road test to confirm B1764 does not return and the system operates normally.
Real-World Cases
BYD DTC AI Analysis

Song MAX A-pillar wiring harness chafing caused airbag circuit short

✓
After accident repairs, a 2019 Song MAX had the SRS warning light on constantly. VDS read current DTC B1764. Removing the right front A-pillar trim revealed the airbag wiring harness retaining clip missing from the crash repair. The harness had rubbed against the door hinge during door operation, wearing through the insulation and shorting the copper core to ground. Repaired the harness, secured it properly, and wrapped it in abrasion-resistant sleeving. Resistance measurements returned to normal; cleared the DTC and resolved the issue.
BYD DTC AI Analysis

Qin Pro sunroof leak caused airbag connector corrosion and short circuit

✓
A 2020 Qin Pro owner reported the airbag warning light came on after a car wash. The diagnostic tool showed active fault code B1764. Inspection of the right front side curtain airbag connector (located below the A-pillar) found water inside with oxidized, blackened pins. Resistance measured only 0.6Ω. Traced to a detached right front sunroof drain hose connector, allowing water to run down the A-pillar. Cleaned the connector oxides, blew it dry, applied conductive protective agent, and repaired the drain hose. Fault cleared.
BYD DTC AI Analysis

Song MAX aftermarket dash cam installation triggered airbag fault

✓
While self-installing a dashcam, the owner forced the power cable behind the right-front A-pillar trim, crushing and piercing the factory SRS harness insulation. This shorted the right-front side curtain airbag circuit to ground, measuring 0.8Ω resistance and setting DTC B1764. Removing the A-pillar trim revealed a flattened harness with cut marks. Repaired the damaged section, restored the original harness routing, and properly secured the aftermarket cable to return the system to normal.
BYD DTC AI Analysis

Qin Fuel SRS control unit false positive B1764

✓
A 2020 Qin petrol with no accident history had an intermittent SRS warning light. VDS read code B1764 (intermittent historical fault). Multiple measurements of right front side curtain airbag resistance showed normal readings (2.1Ω). No shorts or opens in the wiring harness; wiggling the harness did not reproduce the fault. Replaced the SRS control unit (ACU) and performed coding/matching. The fault did not return. Determined this was a false trigger caused by an intermittent fault in the control unit's internal sampling circuit.
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.