AU
B1770

This DTC indicates the SRS control module detects an abnormal 0 Ω resistance in the right rear seat belt pretensioner circuit — Seal U

Safety System

This DTC indicates the SRS control module detects an abnormal 0 Ω resistance in the right rear seat belt pretensioner circuit.

As a pyrotechnic device, normal pretensioner resistance ranges from 1.5 to 3.0 Ω.

A 0 Ω reading typically indicates a short circuit.

Possible causes include damaged wiring harness insulation shorting the positive and negative terminals, an internal connector short, a shorted internal resistance wire within the pretensioner body, or an SRS ECU internal drive circuit fault.

This fault prevents the pretensioner from deploying during a collision.

The SRS system may also disable airbag functions in the affected area, posing a severe safety hazard.

The B1770 fault code on the Seal U indicates a short circuit in the right rear seat belt pretensioner circuit, with the SRS module reading abnormal 0 Ω resistance. Severity is medium because the pretensioner may not deploy in a crash and related airbag functions may be disabled. Common causes include damaged wiring insulation or water/corrosion in the pretensioner connector. 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
  • 1Wiring harness wear and short circuit: Long-term bending and friction damage the wiring harness insulation inside the right rear B-pillar or sill panel, shorting the positive and negative wires.
  • 2Connector water ingress and corrosion: Poor sealing at the right rear seat belt pretensioner connector (usually located under the seat or at the base of the B-pillar) allows water ingress, causing a short circuit between pins.
  • 3Pretensioner unit fault: internal resistance wire short circuit (rare but possible; usually results from a manufacturing defect or overcurrent)
  • 4Improper repair work: A pinched wiring harness or screw puncture during previous seat removal or interior trim panel removal/installation caused a short circuit.
  • 5SRS ECU internal fault: Short circuit in the control module internal drive circuit falsely reports pretensioner resistance as 0 Ω (rule out via cross-validation).
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds for the SRS capacitor to discharge completely to prevent accidental airbag deployment.
  • 2
    Visual inspection: Check the right rear seat belt pretensioner connector (located at the base of the B-pillar or on the outboard side of the seat) for water ingress, corrosion, deformed pins, or foreign objects.
  • 3
    Wiring harness inspection: Inspect the wiring harness along the B-pillar trim panel and door sill trim panel for wear, pinching, or damaged insulation. Focus on the wiring harness near the seat slide rail.
  • 4
    Resistance measurement: Disconnect the pretensioner connector. Use a multimeter to measure the pretensioner body resistance (should be 1.5-3.0 Ω). Measure the harness-side resistance to ground (should be infinite).
  • 5
    Short circuit location: If testing confirms a wiring short circuit, inspect the wiring harness in sections. If necessary, open the corrugated conduit to find the short circuit point, and repair the insulation or replace the wiring harness.
  • 6
    Component replacement: If the pretensioner unit has a short circuit, replace the right rear seat belt assembly (including the pretensioner). Do not repair the pyrotechnic device separately.
  • 7
    Verification test: Restore connections, clear the fault code, perform an SRS system self-check, confirm B1770 does not return, and verify related functions operate normally.
Real-World Cases
BYD DTC AI Analysis

Tang DM right rear sill wiring harness worn through and shorted

✓
A 2021 Tang DM presented with DTC B1770. The technician removed the right rear sill trim and found the pretensioner wiring harness had chafed against the seat rail mounting bracket, wearing through the insulation and exposing the copper wires, which shorted. Repair: Wrapped the damaged area with insulation tape, rerouted the harness and added a protective sleeve. Fault resolved.
BYD DTC AI Analysis

Connector corrosion on Song MAX after water ingress

✓
A 2019 Song MAX logged DTC B1770 after wading through heavy floodwater. Found water in the right rear B-pillar base pretensioner connector; pins had oxidized and blackened, causing a short. Cleaned and dried the connector, but resistance remained below spec. Replaced the wiring harness connector and seal — fault resolved.
BYD DTC AI Analysis

Wiring harness pinched after seat removal on BYD Yuan EV

✓
A 2019 BYD Yuan EV developed this fault after seat cover replacement. The owner confirmed prior seat removal and reinstallation. Inspection found seat mounting bolts had crushed the pretensioner harness, causing a short. Repair: Replaced the damaged harness section, rerouted wiring to specification, and secured the harness clear of pinch points.
BYD DTC AI Analysis

Qin Pro pretensioner internal short circuit

✓
A 2020 BYD Qin Pro petrol variant logged DTC B1770. Disconnected the pretensioner connector and measured infinite resistance on the harness side (normal), but 0.2Ω across the pretensioner itself (near short). Replaced the right rear seatbelt assembly (includes pretensioner). Cleared the code—no recurrence.
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.