AU
B1775-00

This DTC indicates an abnormally low-resistance connection (typically <1 kΩ) between the right rear seat belt pretensioner squib circuit and vehicle chassis ground (GND) — Atto 3

Safety System

This DTC indicates an abnormally low-resistance connection (typically <1 kΩ) between the right rear seat belt pretensioner squib circuit and vehicle chassis ground (GND).

As a pyrotechnic safety device, the pretensioner relies on the SRS ECU to supply a high-current pulse during a collision.

A short to ground causes: 1) abnormal circuit resistance, leading the ECU to register a device fault; 2) potential inadvertent deployment if the short-circuit current reaches the ignition threshold; 3) the SRS system to enter fail-safe mode, disabling the right rear pretensioner and associated seat belt reminder function.

This is a hard fault in the passive safety system that directly affects the integrity of the occupant restraint system.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Wiring harness abrasion below the right B-pillar: The pretensioner wiring harness routes through the B-pillar trim to the floor. Prolonged fore-and-aft seat adjustment or passenger foot movement wears the insulation, causing a short circuit to the metal body.
  • 2Connector water ingress and oxidation: Water accumulation on the rear floor (e.g., blocked sunroof drain or A/C condensate leak) corrodes the pretensioner connector pins (typically located under the seat or at the base of the B-pillar), creating a short-to-ground path.
  • 3Pretensioner unit internal fault: Igniter (squib) internal bridge wire insulation fails, or moisture makes the pyrotechnic charge conductive, causing continuity between the terminal and the housing.
  • 4Post-accident repair issues: During vehicle collision repair, when repairing B-pillar sheet metal or rerouting the wiring harness, missing retaining clips cause the harness to contact sharp edges, or tools damage the wiring harness during pretensioner removal and installation.
  • 5Manufacturing defect: Wiring harness insulation batch quality issue causing premature aging and cracking at bend points (such as near the seat hinge).
What To Do
  • 1
    Safe power-down: Turn the power switch to OFF, disconnect the battery negative terminal and wait at least 90 seconds (to fully discharge the SRS capacitor). Wear an anti-static wrist strap.
  • 2
    DTC freeze frame analysis: Connect the VDS or a dedicated diagnostic tool and record the vehicle status (temperature, voltage, mileage) when the DTC occurred to determine if the fault is intermittent.
  • 3
    Visual inspection: Remove the right rear B-pillar lower trim panel and seat side trim panel. Inspect the pretensioner connector (black/yellow marking) for looseness, signs of water ingress, or discolored pins. Check the wiring harness at the floor retaining strip for wear exposing copper.
  • 4
    Harness-to-ground insulation test: Disconnect the pretensioner connector. Use a multimeter to measure the resistance between the harness side (ECU side) and body ground. Normal resistance is >1MΩ. Measure the voltage to ground. Voltage must be <1V (to rule out an internal ECU short circuit).
  • 5
    Pretensioner unit test: Measure the resistance between the pretensioner terminals (normal: 2.0-4.0 Ω). Measure the resistance between either terminal and the pretensioner metal housing (should be infinite).
  • 6
    Wiring harness repair: If the wiring harness is damaged, repair it using heat-shrink tubing or electrical tape. Install corrugated conduit for protection. Maintain a clearance of more than 20 mm from the seat slide rail and body panels. Secure the harness with OEM cable ties.
  • 7
    Component replacement: If the pretensioner has an internal short circuit, replace the right rear seat belt pretensioner assembly (replace the seat belt assembly simultaneously, as the pretensioner usually integrates into the retractor or base).
  • 8
    System verification: Restore connections, reinstall the trim panel, and connect the battery. Turn the ignition switch ON and confirm the SRS warning lamp turns off after the self-check. Use the diagnostic tool to perform the 'Airbag System Configuration Test' or 'Crash Output Test' (static test mode), clear the fault code, and perform a road test to verify.
Real-World Cases
BYD DTC AI Analysis

Wiring harness worn by right rear seat rail causing intermittent short circuit

✓
2017 BYD Qin EV300, 80,000 km. Intermittent SRS warning light. Scanner read B1775-00; freeze frame showed rough-road trigger. Inspection revealed the right rear seat rail mounting bolt interfering with the pretensioner wiring harness. Prolonged friction had worn through the insulation, exposing copper wire that contacted the seat frame. Repaired the harness, rerouted the wiring, and installed abrasion-resistant sleeving. Fault resolved.
BYD DTC AI Analysis

Sunroof drain tube detached; water entered and corroded the pretensioner connector.

✓
After driving through water, the SRS warning light stayed on. Retrieved DTC B1775-00. Inspection found the right rear sunroof drain hose connector had detached, letting water run down the A-pillar into the base of the B-pillar. The pretensioner connector pins (located at the floor harness junction) showed severe oxidation and measured only 200 Ω to ground. Cleaned the connector, applied conductive paste, replaced the drain hose connector, and waterproofed the wiring harness. Fault resolved.
BYD DTC AI Analysis

Internal short circuit in pretensioner after accident repair

✓
A BYD Qin 100 repaired following a collision with prior right rear impact. After repairs, DTC B1775-00 was retrieved. Continuity between the pretensioner terminal and housing measured 0.5Ω, indicating the pretensioner internal igniter insulation had been damaged by impact. Replaced the right rear seatbelt pretensioner assembly (including retractor). SRS configuration coding restored normal system operation.
BYD DTC AI Analysis

B-pillar trim improperly installed, crushing wiring harness insulation

✓
The SRS warning light came on the day after window tinting. Customer stated the B-pillar trim was removed during tinting. Inspection found the lower clip on the right rear B-pillar trim misaligned; the panel’s sharp edge crushed the seatbelt pretensioner harness insulation, causing a short to ground. Rerouted and secured the harness, wrapped it with fleece tape to prevent chafing, replaced the damaged clip. Fault cleared.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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.