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 U

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.

The B1775-00 fault code on the Seal U indicates a high-severity short to ground in the right rear seat belt pretensioner circuit. This can disable part of the SRS safety system and may affect restraint performance in a crash. Common causes include worn wiring near the right B-pillar or water-damaged, corroded connectors under the seat. The recommended fix is inspection and repair by an authorised dealer. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Wiring harness wear below the right B-pillar: The pretensioner wiring harness routes through the B-pillar trim to the floor. Long-term 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., from a blocked sunroof drain tube or leaking air conditioning condensate) corrodes the pretensioner connector pins (usually located under the seat or at the base of the B-pillar), creating a short-to-ground path.
  • 3Internal fault in the pretensioner body: Igniter (squib) internal bridge wire insulation failure or moisture-induced conductivity in the pyrotechnic charge creates continuity between the terminal and the housing.
  • 4Accident repair after-effects: During vehicle collision repair, B-pillar sheet metal repair, or wiring harness rerouting, missing harness retaining clips cause the harness to contact sharp edges, or tools scratch the wiring 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 negative battery terminal, wait at least 90 seconds (to fully discharge the SRS capacitor), and wear an anti-static wrist strap.
  • 2
    Fault code freeze frame analysis: Connect the VDS or a dedicated diagnostic tool. Record the vehicle status (temperature, voltage, mileage) at the time the fault code occurred to confirm whether it is an intermittent fault.
  • 3
    Visual inspection: Remove the right rear lower B-pillar trim panel and seat side trim panel. Check the pretensioner connector (black/yellow marking) for looseness, signs of water ingress, or discoloured pins. Inspect the wiring harness at the floor trim strip for wear exposing copper.
  • 4
    Harness-to-ground insulation test: Disconnect the pretensioner connector and use a multimeter to measure the resistance between the harness side (ECU side) and body ground. Resistance should be >1MΩ. Measure the voltage to ground. Voltage should 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 positive terminal and the pretensioner metal housing (should be infinite).
  • 6
    Wiring harness repair: If the wiring harness is damaged, repair it with heat-shrink tubing or insulating tape. Install corrugated conduit for protection. Maintain a clearance of more than 20mm from the seat slide rail and body panels. Secure the harness using OEM cable ties.
  • 7
    Component replacement: If the pretensioner shorts internally, replace the right rear seat belt pretensioner assembly (replace the seat belt assembly simultaneously, as the pretensioner typically integrates into the retractor or base).
  • 8
    System verification: Reconnect connectors, reinstall trim panels, and connect the battery. Turn the ignition switch ON and confirm the SRS warning lamp turns off after self-check. Use a diagnostic tool to perform the 'Airbag System Configuration Test' or 'Crash Output Test' (static test mode), clear fault codes, and perform a road test to verify the repair.
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 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.