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) — Seal 6 EV

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 — Seal 6 EV
  • 1Wiring harness chafing below the right B-pillar: The pretensioner wiring harness routes through the B-pillar trim to the floor. Repeated 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 tube or leaking air conditioning condensate) corrodes the pins of the pretensioner connector (usually located under the seat or at the base of the B-pillar), forming a short-to-ground path.
  • 3Internal fault in the pretensioner unit: Igniter (squib) internal bridge wire insulation fails, or moisture makes the pyrotechnic charge conductive, causing continuity between the terminals and the housing.
  • 4Post-accident repair damage: During 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 scratch the harness during pretensioner removal and installation.
  • 5Manufacturing defect: Wiring harness insulation batch quality issue causes 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 ensure the SRS capacitor fully discharges). Wear an anti-static wrist strap.
  • 2
    DTC freeze frame analysis: Connect the VDS or a dedicated diagnostic tool, record the vehicle status (temperature, voltage, mileage) when the DTC occurred, and confirm 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, water ingress, or discolored pins. Inspect the wiring harness at the floor trim strip for wear or exposed copper.
  • 4
    Harness-to-ground insulation test: Disconnect the pretensioner connector. Use a multimeter to measure resistance between the harness side (ECU side) and body ground. Normal resistance is >1MΩ. Measure 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 insulating tape. Add corrugated conduit for protection. Maintain a clearance of more than 20 mm from the seat slide rail and body sheet metal. Secure the harness with genuine 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, connect the battery, and turn the ignition switch ON. Confirm the SRS warning lamp turns off after the self-check. Use a diagnostic tool to perform the 'Airbag System Configuration Test' or 'Crash Output Test' (static test mode), clear the fault codes, 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 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.