AU
B1772-00

DTC B1772-00 indicates the airbag control unit (SRS ECU) detects the right rear seatbelt pretensioner circuit resistance exceeds the calibrated range (normal range: 1 — Seal 6 EV

Safety System

DTC B1772-00 indicates the airbag control unit (SRS ECU) detects the right rear seatbelt pretensioner circuit resistance exceeds the calibrated range (normal range: 1.8–3.0Ω; high resistance typically indicates >5Ω or infinite).

As a key passive safety system actuator, the pretensioner features a pyrotechnic design, using propellant gas to instantly tighten the seatbelt during a collision.

High resistance indicates a high-impedance connection or open circuit.

Causes include poor connector contact, a damaged wiring harness, or an open gas generator coil inside the pretensioner.

This fault continuously illuminates the SRS warning light and can trigger a degraded system mode.

During a collision, the pretensioner may fail to deploy, and the SRS ECU may suspend the right rear side airbag deployment logic, significantly reducing crash protection for the right rear passenger.

The B1772-00 fault code on the Seal 6 EV indicates high resistance or an open circuit in the right rear seatbelt pretensioner circuit. Severity is medium because the SRS warning light may stay on and the pretensioner may not work in a crash. Common causes include a loose or corroded pretensioner connector or damaged wiring near the seat track. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
3
Cases Logged
5
Causes
Likely Causes — Seal 6 EV
  • 1Loose connection, backed-out terminals, or oxidized pins at the right rear seat belt pretensioner yellow waterproof connector (usually located under the seat or inside the C-pillar trim panel) cause increased contact resistance.
  • 2During fore-and-aft seat adjustment, the seat track pinches or abrades the pretensioner wiring harness, causing a hidden break in the copper core (insulation intact but internal open circuit) or high resistance.
  • 3The pretensioner internal gas generator (squib) heating wire is aged, broken, or open, resulting in infinite resistance.
  • 4Poor contact, corrosion, or water ingress in the wiring harness or connectors between the SRS ECU and the pretensioner (especially common after driving through water or interior cleaning).
  • 5SRS ECU internal monitoring circuit fault or software calibration error (less common; consider only after ruling out wiring issues)
What To Do
  • 1
    Use BYD VDS or a dedicated diagnostic tool to access the SRS system, read the fault codes to confirm B1772-00 is a current active fault, and record the freeze frame data (e.g., vehicle speed and timestamp at the time of occurrence).
  • 2
    Perform safety procedure: Turn off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 3
    Remove the right rear seat or C-pillar trim panel. Visually check that the yellow pretensioner connector (with shorting spring tab) is fully locked. Inspect the terminals for oxidation or deformation. If necessary, clean with electrical contact cleaner and apply conductive grease.
  • 4
    Disconnect the pretensioner connector and use a multimeter to measure the resistance of the pretensioner unit (standard value: 1.8–3.0 Ω). If the resistance is >5 Ω or infinite, replace the right rear seat belt pretensioner assembly (Note: the pretensioner is a single-use component; do not dismantle it for testing).
  • 5
    If pretensioner unit resistance is normal, measure wiring harness continuity from the SRS ECU (usually located under the centre console or inside the centre armrest box) to the pretensioner connector. Resistance must be <1Ω. Check for shorts to ground and power.
  • 6
    Check the wiring harness routing within the seat rail movement range and confirm ≥15cm of slack. Use cable ties to secure the wiring harness to the seat frame instead of the slide rail to prevent repeat pinching.
  • 7
    After repair, reconnect all connectors, install the battery, turn the ignition switch to the ON position, use the diagnostic tool to clear the fault codes, and perform 'SRS System Self-test' or 'Write Configuration'.
  • 8
    Perform a road test or simulation test (such as lightly tapping the seat to simulate vibration) to verify the fault code does not return and the instrument cluster SRS warning light is off.
Real-World Cases
BYD DTC AI Analysis

BYD Song Pro DM-i: Seat wiring harness poor contact

✓
Symptoms: SRS warning light stays on. Scan tool shows DTC B1772-00 (Driver seat occupancy status uncertain). Returns after clearing. Diagnosis: Found the Occupant Detection System (ODS) connector (left side of seat rail) had a broken locking tab causing poor contact. Resistance fluctuated between open circuit and 800 Ω (normal: 380–420 Ω). Solution: Replaced the wiring harness connector, re-crimped terminals and secured the harness. Performed Seat Calibration. Fault cleared.
BYD DTC AI Analysis

BYD Qin Plus EV seat pressure sensor internal leak

✓
Symptoms: Airbag warning light occasionally flickers when driving on rough roads; stored DTCs B1772-00 and B1650-00. Diagnosis: Live data showed the Occupant Detection signal jumping erratically between 0% and 100%. Removed the seat and found the pressure-sensing bladder (Bladder) cracked at the edge with internal silicone medium leaking; output voltage dropped to 0.8V (normal 2.5V). Resolution: Replaced the driver's seat cushion assembly (including occupant sensor) and performed the seat calibration procedure to learn the pressure baseline.
BYD DTC AI Analysis

BYD Tang DM wiring harness damaged after accident repair

✓
Symptom: After left front collision repairs, the airbag warning light stays on constantly and DTC B1772-00 will not clear. Diagnosis: During accident repair, seat removal pinched the yellow SRS harness against the seat rails. Damaged insulation caused an intermittent short between the signal wire and ground. Repair: Cut out the damaged section and spliced in high-temperature flame-retardant flying leads. Insulated with double-layer heat-shrink tubing. Rerouted the harness with 20cm slack. Cleared the fault codes; self-test passed.
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.