AU
B1766

DTC B1766 indicates the SRS (Supplemental Restraint System) control unit cannot identify or establish communication with the Right Front Curtain Shield Airbag — Seal 6 EV

Safety System

DTC B1766 indicates the SRS (Supplemental Restraint System) control unit cannot identify or establish communication with the Right Front Curtain Shield Airbag.

This fault constitutes an "airbag not present" condition; the ECU detects no load signal from the airbag module during the system self-check.

This typically indicates an open airbag circuit (infinite resistance).

Potential causes include a disconnected airbag connector, broken wiring harness, internal open circuit in the airbag module, or poor contact at the ECU terminal.

This safety-critical fault prevents the right front curtain airbag from deploying during a collision, severely compromising side-impact protection.

The B1766 fault code on the Seal 6 EV indicates the SRS control unit cannot detect or communicate with the right front curtain airbag, creating an “airbag not present” condition. Severity is medium, as the airbag may not deploy in a side impact. Common causes include a loose airbag connector or an open/damaged wiring harness near the A-pillar or roof rail. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Seal 6 EV
  • 1Right front side curtain airbag module connector loose, disconnected, or making poor contact (common if not fully seated after A-pillar trim removal and installation)
  • 2Airbag wiring harness open circuit or wear (especially at the A-pillar and roof side rail routing, where vibration or removal and installation causes copper core breakage)
  • 3Airbag module internal open circuit (airbag igniter open circuit or module internal circuit fault)
  • 4Internal fault or software error in the SRS control unit (ACU) causing a false 'airbag not present' warning.
  • 5Airbag deployed in a collision and not replaced, or the used replacement airbag module is faulty.
What To Do
  • 1
    Step 1: Safety preparation - Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS system and prevent accidental airbag deployment.
  • 2
    Step 2: Visual inspection - Remove the right front A-pillar trim panel and right roof trim panel. Verify the curtain airbag module connector is fully seated, and inspect the wiring harness for damage, pinching, or water stains.
  • 3
    Step 3: Resistance measurement - Disconnect the airbag connector. Measure the airbag inflator resistance using a dedicated SRS resistance tester (a multimeter may trigger a fault). Normal resistance is 1.5-3.0 Ω. A reading of ∞ indicates an internal open circuit in the airbag.
  • 4
    Step 4: Wiring harness continuity test - Measure wiring harness continuity between the airbag connector and the SRS ECU. Focus on the A-pillar hinge area and roof harness mounting points. Repair any broken wires.
  • 5
    Step 5: Connector inspection - Check the connector terminals for oxidation, backed-out pins, or deformation. Clean or replace the connector.
  • 6
    Step 6: Replacement verification - If the wiring harness is normal, install a known-good right front curtain airbag module to verify (ensure the part number matches).
  • 7
    Step 7: System reset - Reconnect the battery, use the BYD dedicated diagnostic tool to clear the fault code, perform SRS system configuration coding (if replacing the airbag or ECU), and perform a system self-check to confirm B1766 no longer appears.
Real-World Cases
BYD DTC AI Analysis

Song MAX: Loose right front curtain airbag connector causes B1766

✓
A 2019 Song MAX came in with the airbag warning light on. Scanning with VDS2000 showed code B1766 (Right Front Side Curtain Airbag Not Present). Removed the right front A-pillar trim and found the curtain airbag connector had approximately 2mm of gap and wasn't fully seated—likely from previous A-pillar work. Reconnected the connector firmly, confirmed the locking tab engaged, cleared the fault code, and the SRS light went out. Fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD S6 SRS wiring harness chafing, open circuit (similar to B1766)

✓
The instrument cluster displayed an airbag warning. The scan tool retrieved side airbag-related DTCs. Inspection found the vehicle had been in a side scrape accident that damaged the wiring harness inside the right front A-pillar. Removing the A-pillar trim revealed damaged airbag harness insulation with the copper conductor fractured, causing an open circuit. Repair: Cut out the damaged section, soldered in specialist high-temperature wire (0.5mm² or larger), wrapped the insulation properly, and rerouted the harness to avoid contact with metal edges. Fault resolved.
Original source ↗
BYD DTC AI Analysis

General Motors Curtain Airbag Module Internal Open Circuit Fault Diagnosis

✓
Symptom: Airbag warning light on. Diagnostic scan showed the right front side curtain airbag was missing or had abnormal resistance. Diagnostic process: Disconnected the airbag connector and measured resistance across the airbag terminals. Found infinite resistance (normal is approximately 2Ω), indicating an open circuit in the airbag module internal igniter. Checked continuity of the wiring harness from the airbag to the SRS ECU; it was normal. Connectors showed no abnormalities. Solution: Replaced the right front side curtain airbag module with a new unit (along with the airbag label and SRS ECU configuration update). Cleared the fault codes; the system returned to normal.
Original source ↗
Other Seal 6 EV 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.B1737DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Seal 6 EV →Seal 6 EV 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.