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 U

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 U indicates high resistance or an open circuit in the right rear seatbelt pretensioner circuit. Severity is medium because the SRS warning light stays on and the pretensioner may not work in a crash. Common causes include a loose or corroded yellow connector, backed-out pins, 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 — Seal U
  • 1Loose yellow waterproof connector for the right rear seat belt pretensioner (usually located under the seat or inside the C-pillar trim), backed-out pins, or oxidized pins, causing increased contact resistance.
  • 2The seat rail pinches or abrades the pretensioner wiring harness during fore-and-aft adjustment, causing a hidden break in the copper core (insulation intact but internal open circuit) or high resistance.
  • 3Pretensioner 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 connector 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 codes to confirm B1772-00 is a currently active fault, and record the freeze frame data (such as 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 verify the yellow pretensioner connector (with shorting spring tab) is fully locked. Inspect the terminals for oxidation or deformation. If necessary, clean them with electrical contact cleaner and apply conductive grease.
  • 4
    Disconnect the pretensioner connector and measure the pretensioner body resistance using a multimeter (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 the pretensioner unit resistance is normal, measure wiring harness continuity between the SRS ECU (usually located under the center console or inside the center armrest box) and the pretensioner connector. Resistance should 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, not the slide rail, to prevent repeat 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 (e.g., 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 Seal U Fault Codes
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.B110AThis DTC indicates interrupted CAN bus communication or abnormal data between the air conditioning control unit (ACU) and the PM2.5 air quality sensor. The PM2.5 sensor monitors particulate concentration inside and outside the vehicle and provides the basis for purification control in the automatic air conditioning system. The ACU triggers this fault if it fails to receive a valid CAN message from the sensor within the specified period (usually 100-500 ms), if message verification fails, or if the signal frame times out. Although this fault does not affect vehicle driving safety, it disables the automatic air purification function. The air conditioning system cannot automatically switch between recirculation and fresh air modes or activate the air purification mode based on air quality. A persistent fault may restrict the thermal management strategy.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.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.B173712DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Common problems reported for Seal U →Seal U 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.