AU
B1770-00

DTC B1770-00 indicates the SRS (airbag) control module detects the right rear seat belt pretensioner circuit resistance is 0 Ω or close to 0 Ω — Seal U

Safety System

DTC B1770-00 indicates the SRS (airbag) control module detects the right rear seat belt pretensioner circuit resistance is 0 Ω or close to 0 Ω.

Normally, the seat belt pretensioner acts as a pyrotechnic actuator with a standard squib resistance between 2.0-5.0 ohms.

A resistance of 0 indicates a hard short in the circuit.

Possible causes include an internal short in the pretensioner squib, a wiring harness short to body ground or power, or an internal short in the connector.

This fault causes the SRS system to determine the pretensioner has failed.

During a collision, the right rear seat belt pretensioner will not deploy, severely compromising the occupant restraint system's effectiveness.

The fault also illuminates the instrument cluster airbag warning lamp and may inhibit the entire airbag system.

The B1770-00 fault code on the Seal U indicates the SRS control module has detected a short circuit in the right rear seat belt pretensioner, with resistance at or near 0 Ω. Severity is medium, as the pretensioner may not work in a crash and the airbag warning light may stay on. Common causes include a shorted pretensioner igniter or damaged wiring. 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 U
  • 1Right rear seat belt pretensioner internal igniter short circuit: Aging, moisture ingress, or manufacturing defects cause insulation failure between the two terminals of the pretensioner's internal squib, resulting in a short circuit.
  • 2Wiring harness short to ground or power: Long-term bending, wear, or crushing from an accident damages the wire insulation near the B-pillar, causing a short to the vehicle body metal or a power wire.
  • 3Connector fault: Water ingress, corrosion, bent pins, or foreign material in the right rear seat belt pretensioner connector (usually located below the B-pillar or under the seat), causing a short circuit between terminals.
  • 4SRS ECU internal detection circuit fault: Airbag control module internal monitoring circuit malfunctions and falsely reports a short circuit fault (relatively uncommon).
  • 5Improper repair operations: During recent removal and installation of the B-pillar, rear door, or seat, a screw pinched the wiring harness, retaining clips were damaged, or a tool accidentally cut the harness insulation.
What To Do
  • 1
    Safety preparation: Set the vehicle to OFF, disconnect the 12V low-voltage battery negative terminal, and wait at least 90 seconds (2 minutes for some models) to fully discharge the SRS capacitor and prevent accidental deployment.
  • 2
    Locate the component: Remove the right rear B-pillar lower trim panel. Find the right rear seat belt pretensioner and its yellow dedicated connector (which usually has a short-circuit protection tab).
  • 3
    Initial inspection: Visually inspect the connectors and wiring harness for obvious damage, water ingress, burn marks, or corrosion. Verify the connectors are fully seated.
  • 4
    Resistance measurement: Disconnect the pretensioner connector. Use a digital multimeter to measure the resistance across both terminals of the pretensioner body (do not set to continuity/buzzer mode to avoid triggering current). The normal value is 2.0-5.0 Ω. A reading of 0-0.5 Ω confirms an internal short circuit in the pretensioner.
  • 5
    Harness insulation check: With the connector disconnected, measure the resistance from the harness-side terminal to body ground and to the 12V power supply. Both readings must be infinite (OL). Continuity indicates a short circuit. Troubleshoot and repair the harness.
  • 6
    Cross-check: If the pretensioner itself measures normal, test with a known-good pretensioner, or measure the adjacent seat pretensioner resistance for comparison.
  • 7
    Fault repair: If a pretensioner short circuit is confirmed, replace the right rear seat belt assembly (the pretensioner is usually not supplied separately). If the wiring harness has a short circuit, repair or replace the wiring harness. Route the harness correctly, secure it firmly, and prevent interference.
  • 8
    System reset: Reconnect all connectors (listen for a click). Connect the battery. Clear the fault code using the BYD dedicated diagnostic tool (VDS). Perform an SRS system self-check. Verify B1770-00 does not return and the airbag warning light turns off.
Real-World Cases
BYD DTC AI Analysis

Water entered the B-pillar after fording, causing the connector to short-circuit.

✓
A 2017 Qin EV300 showed a constant airbag warning light after driving through floodwater during heavy rain. Retrieved DTC B1770-00. Removed the trim below the right rear B-pillar and found the pretensioner connector contained obvious water traces and green copper corrosion. Conductive debris shorted the terminals. Cleaned the terminals with alcohol, blew them dry, applied electrical contact protectant, and reinstalled the connector. Fault resolved. Check door seals and drain holes to prevent further water ingress.
BYD DTC AI Analysis

Pretensioner internal squib shorted from aging

✓
A 2018 BYD Qin EV450 with 60,000 km and no accident history suddenly displayed the airbag warning light. The scan tool showed B1770-00. After disconnecting the right rear pretensioner connector, direct measurement of the pretensioner read 0.3Ω (normal 2-5Ω), confirming an internal squib short. Replaced the right rear seatbelt assembly (including pretensioner), cleared the fault code, and the system self-test passed. Moisture in the pyrotechnic charge or insulation degradation after long-term use caused the failure.
BYD DTC AI Analysis

Wiring harness pinched and shorted after accident repair

✓
A 2017 Qin 100 underwent bodywork and paint on the right rear door. Three days after delivery, B1770-00 set. Inspection found the B-pillar interior trim panel mounting screw pinched the pretensioner harness during installation, damaging the insulation. The wires contacted the body metal, causing a short to ground. Rerouted the harness to avoid the screw mounting points, repaired the damage with insulation tape and heat-shrink tubing, and resolved the fault. Protect wiring harnesses during any B-pillar repair work.
BYD DTC AI Analysis

Connector short-circuit protection tab failed, causing false trouble code.

✓
A Qin EV300 set DTC B1770-00 after the right rear seat was removed and reinstalled. The pretensioner connector’s internal shorting bar had mechanically deformed and failed to spring open while disconnected, keeping the circuit shorted even when plugged in. A new pretensioner connector (with wiring harness plug) restored normal resistance and cleared the fault. Handle connectors carefully during removal and installation to avoid damaging the internal short-circuit protection.
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.