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 — Qin Plus

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 Qin Plus indicates high resistance or an open circuit in the right rear seatbelt pretensioner circuit. This is a medium-severity SRS fault because the pretensioner may not deploy in a crash, reducing rear passenger protection. Common causes include a loose or corroded yellow pretensioner connector or damaged wiring near the seat rail. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
3
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 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), causing increased contact resistance.
  • 2During fore-and-aft adjustment, the seat slide rail pinches or chafes the pretensioner wiring harness, causing a concealed 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, causing infinite resistance.
  • 4Poor connection, 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 the BYD VDS or a dedicated diagnostic tool to access the SRS system. Read the fault code to confirm B1772-00 is an active fault. Record the freeze frame data (such as vehicle speed and timestamp at the time of occurrence).
  • 2
    Perform the safety procedure: Turn off the ignition switch, 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 inspect the yellow pretensioner connector (with shorting spring tab) to verify it is fully locked. Inspect the pins 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 body (standard value: 1.8–3.0Ω). If the resistance is >5Ω 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 the pretensioner unit resistance is normal, measure harness continuity from the SRS ECU (usually located under the center console or inside the center armrest box) to the pretensioner connector. Continuity should be <1Ω. Also 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 repeated pinching.
  • 7
    After repair, reconnect all connectors, install the battery, and turn the ignition switch to ON. Use the diagnostic tool to clear the fault code and perform the 'SRS system self-check' or 'Write Configuration'.
  • 8
    Perform a road test or simulation test (such as lightly tapping the seat to simulate vibration) to confirm the fault code does not return and the instrument cluster SRS warning light turns 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 Qin Plus 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.B110913DTC B110913 indicates an open signal circuit for the PM2.5 rapid detector (in-cabin air quality sensor). This sensor typically mounts inside the air conditioning system intake duct. It monitors in-cabin PM2.5 concentration in real time and provides data to the automatic air conditioning system for intelligent control of the air purification function. The BYD diagnostic protocol uses sub-code '13' to specifically indicate an open signal circuit. Although this fault theoretically affects a comfort feature, BYD Qin series vehicles classify it as a Level 3 (severe) fault. This classification occurs because the air conditioning system interacts with the battery thermal management system (e.g., monitoring battery cooling intake air quality). The fault can disable the automatic air conditioning mode and prevent the air purification function from operating. In extreme cases, it affects the battery compartment intake air quality assessment, triggering the 'repair immediately' strategy.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.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 Qin Plus →Qin Plus 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.