AU
B1775

DTC B1775 indicates the SRS (Supplemental Restraint System) detects a short to ground in the right rear seat belt pretensioner circuit — Seal 6 EV

Safety System

DTC B1775 indicates the SRS (Supplemental Restraint System) detects a short to ground in the right rear seat belt pretensioner circuit.

The seat belt pretensioner is a pyrotechnic actuator containing an explosive device and a resistance wire.

Normal resistance is approximately 2-3 Ω.

When the SRS control module detects circuit resistance below the threshold (typically <1 Ω) or an abnormal voltage drop to ground, it identifies a short to ground.

This safety-critical fault causes: 1) the SRS to enter degraded mode, disabling right rear side impact protection; 2) continuous illumination of the airbag warning light; 3) a risk of unintended pretensioner deployment in extreme cases.

The pretensioner wiring harness routes through the right rear door sill trim and C-pillar, exposing it to seat movement, liquid ingress, or mechanical damage.

The B1775 fault code on the Seal 6 EV indicates a high-severity SRS fault caused by a short to ground in the right rear seat belt pretensioner circuit. This can disable part of the rear side impact protection and keep the airbag warning light on. Common causes include chafed wiring under the rear seat or a loose C-pillar harness clip. 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
  • 1Long-term chafing of the wiring harness under the right rear seat: During fore/aft seat adjustment or folding, the pretensioner wiring harness wears against the seat frame or floor, damaging the insulation and shorting to body ground.
  • 2C-pillar interior trim panel wiring harness clip failure: A loose or missing C-pillar trim panel retaining clip allows the wiring harness to contact the metal body during driving, causing an intermittent or continuous short to ground.
  • 3Pretensioner connector water ingress: Rainwater enters through an aging right rear door seal or open window, forming an electrolyte at the pretensioner connector (usually located under the seat or at the base of the C-pillar) and causing a short circuit between pins or to ground.
  • 4Modification or repair damage: When installing seat covers, floor sound insulation, or rear entertainment systems, retaining screws pierce the pretensioner wiring harness, or the seat track crushes an improperly secured harness.
  • 5Pretensioner internal short circuit: Resistance wire insulation inside the pretensioner body fails due to high temperatures or aging, causing an internal short to the metal housing (rare; typically shows abnormally low resistance).
What To Do
  • 1
    Safe power-down and wait: Disconnect the low-voltage battery negative terminal. Wait at least 90 seconds for the SRS capacitor to discharge fully to prevent pretensioner deployment during diagnosis.
  • 2
    Freeze frame data analysis: Use the VDS2000 diagnostic tool to read freeze frame data at the time of the fault, including vehicle speed, crash signal, and voltage, to confirm if the fault is intermittent.
  • 3
    Physical and visual inspection: Remove the right rear sill trim panel and lower C-pillar trim panel. Inspect the pretensioner wiring harness (usually in yellow sleeving) for wear, cuts, or burn marks. Focus on the area below the seat mounting points and the C-pillar transition area.
  • 4
    Pretensioner resistance measurement: Disconnect the pretensioner connector (install the short-circuit protection plug) and use a digital multimeter to measure the pretensioner body resistance. The normal value is 2.0-3.0 Ω. If the resistance is <1 Ω, replace the pretensioner assembly.
  • 5
    Wiring harness insulation check: With the pretensioner connector disconnected, measure the resistance from the harness side to ground. Resistance must be >1MΩ. Measure continuity between both ends of the harness (SRS ECU side and pretensioner side) and verify no short to ground.
  • 6
    Short circuit location: If the wiring harness is shorted, use the sectional isolation method (cut the wire or disconnect the intermediate connector at the midpoint) to locate the exact short circuit position. Repair the wiring harness (use solder and heat-shrink tubing; do not simply twist wires together).
  • 7
    Component Replacement: If the pretensioner is internally shorted, replace the right rear seat belt assembly (the pretensioner is usually integrated with the seat belt retractor). After replacement, re-mark the wiring harness routing and secure it firmly.
  • 8
    System Reset and Verification: Reconnect all connectors and restore power. Use the diagnostic tool to clear the fault code. Perform the 'SRS system self-check' and 'crash sensor test' (software simulation, does not trigger pyrotechnic devices). Verify B1775 does not return and the warning light is off.
Real-World Cases
BYD DTC AI Analysis

Worn right rear seat wiring harness caused intermittent B1775 fault on Song MAX

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Vehicle: 2020 Song MAX, 38,000 km. Symptoms: Intermittent airbag warning light, worse on rough roads. VDS logged historic fault B1775. Diagnosis: Removed right rear seat. Found seatbelt pretensioner harness chafed by seat slide rail bracket edge at full forward position; copper core exposed and contacting body. Repair: Cut damaged section (approx. 15 cm). Extended with high-temperature solder. Double-layer heat shrink insulation. Rerouted harness and added rubber sleeve. Repositioned cable clips to clear moving parts. No recurrence after 3 months.
BYD DTC AI Analysis

Tang DM right rear pretensioner connector corroded and short-circuited after water ingress

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Vehicle: 2021 Tang DM, wading depth approximately 40 cm. Symptoms: Airbag warning light remained on the day after wading; VDS reported active fault B1775. Diagnosis: Found muddy water inside the right rear C-pillar lower pretensioner connector. Measured 0.8 Ω between pin 3 (ground side) and pin 1 (signal line), and 0.3 Ω from pin 1 to ground. Repair: Cleaned the connector thoroughly with electronic cleaner; insulation measured >10 MΩ after drying. Applied conductive grease and wrapped with waterproof tape. Checked and cleared blocked door seal drain holes. Cleared fault codes; system returned to normal.
BYD DTC AI Analysis

Aftermarket heated seat installation on Yuan EV damaged pretensioner wiring harness

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Vehicle: 2019 Yuan EV, aftermarket rear seat heating retrofit. Symptoms: One week post-modification, B1775 code appeared and would not clear. Diagnosis: Mounting screws for the heating pad pierced the yellow sleeve of the right rear pretensioner harness, shorting both positive and negative wires to the screw (vehicle ground). Pretensioner resistance measured 0.5Ω (possible internal damage). Repair: Replaced right rear seatbelt assembly (includes pretensioner). Rerouted harness clear of seat mounting points, secured with dedicated cable clamps, and added an insulating sleeve to the pretensioner connector. Recommendation: Advised owner to carry out seat-related modifications at a 4S dealership.
BYD DTC AI Analysis

Qin Pro: Wiring harness clip at right rear C-pillar detached, causing intermittent short circuit.

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Vehicle: 2020 Qin petrol variant, 52,000 km. Symptoms: Airbag warning light illuminates after rain or washing, clears in dry weather. Diagnosis: Removed C-pillar trim panel. Found pretensioner harness retainer clip broken; harness drooped against C-pillar metal reinforcement plate. Long-term micro-vibration wore through insulation. Ground resistance measured 200 Ω wet, >10 MΩ dry. Repair: Replaced C-pillar harness retainer clip. Wrapped worn harness section with fleece tape. Applied 3M insulating tape to C-pillar metal edges. Maintained harness-to-body metal clearance >20 mm. Verified insulation with spray test.
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.