AU
B1797-00

This DTC indicates the front passenger seat belt pretensioner (second-stage deployment circuit) resistance is 0 Ω, indicating a short circuit — Seal U

Safety System

This DTC indicates the front passenger seat belt pretensioner (second-stage deployment circuit) resistance is 0 Ω, indicating a short circuit.

In the BYD SRS (Supplemental Restraint System) architecture, the dual-stage pretensioner deploys in stages based on collision severity: the first stage provides light tightening, and the second stage provides strong tightening to secure the occupant.

A 0 Ω resistance usually indicates an internal short circuit in the pretensioner generator winding, a wiring harness short to ground, or a short between connector terminals.

Upon detecting this fault, the SRS ECU enters fail-safe mode and disables the pretensioner circuit.

This may cause the second-stage protection to fail during a collision or create a risk of unintended deployment; therefore, the system illuminates the airbag warning lamp.

The B1797-00 fault code on the Seal U indicates a short circuit in the front passenger seat belt pretensioner second-stage deployment circuit, with resistance reading 0 Ω. Severity is medium because the SRS may disable this pretensioner stage and turn on the airbag warning lamp, reducing crash protection. Common causes include an internal pretensioner generator short or damaged seat wiring near the seat track. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Pretensioner generator internal short circuit: A broken bridge wire inside the pyrotechnic generator or damp propellant causes the resistance between the two terminals to drop to 0.
  • 2Seat wiring harness wear and short circuit: During front passenger seat fore/aft adjustment, continuous friction between the pretensioner wiring harness and the seat track or frame damages the insulation, causing a short to ground.
  • 3Connector water ingress and corrosion: Water entering the pretensioner connector (usually located under the seat) during vehicle wading or interior cleaning causes a short circuit between the terminals.
  • 4Improper modification or repair: Fixing screws piercing the wiring harness or incorrect terminal crimping when installing seat covers or modifying seat heating or power adjustment.
  • 5SRS ECU internal fault: A damaged ECU internal sampling resistor or detection circuit causes a false 0 Ω reading (the actual circuit is normal).
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal. Wait at least 90 seconds to ensure the SRS capacitor discharges completely to prevent accidental airbag deployment.
  • 2
    Visual inspection: Remove the front passenger seat (keep the wiring harness connected). Check the pretensioner connector under the seat (usually yellow) for looseness, water ingress, or obvious burn marks.
  • 3
    Measure with the ECU side disconnected: Locate the SRS ECU (usually under the center console or behind the armrest box). Disconnect the front passenger pretensioner connector and measure the resistance to ground on the wiring harness side. The resistance must exceed 10 kΩ; otherwise, the wiring harness has a short to ground.
  • 4
    Pretensioner unit measurement: Disconnect the inflator connector. Use a dedicated low-impedance multimeter to measure the resistance between the two terminals of the pretensioner plug. Normal resistance is 2.0-5.0 Ω. If the resistance is 0 Ω, replace the pretensioner assembly.
  • 5
    Wiring harness continuity check: If Step 3 reveals a short circuit, inspect along the seat wiring harness sleeve to the floor wiring harness, focusing on seat slide rail interference points. Repair any damaged insulation and reroute the harness.
  • 6
    Replacement verification: After replacing the suspected faulty pretensioner or repairing the wiring harness, reconnect all components and the battery. Use the diagnostic tool to clear the fault code, then perform the 'ignition cycle test' and 'pretensioner resistance value reading' to verify the repair.
  • 7
    System simulation test: On some models, perform SRS system self-learning or write the configuration so the ECU recognizes the new component parameters.
Real-World Cases
BYD DTC AI Analysis

Worn seat rails shorted the wiring harness

✓
Vehicle: Qin EV300 2018. Customer reported the airbag warning light on. Scan tool retrieved DTC B1797-00. Inspection found the passenger seat base harness chafed against the metal bracket when the seat was in the full forward position, wearing through the insulation and causing a short to ground. Repaired the damaged harness (3 wires, including 1 pretensioner signal wire), re-secured the harness routing, added corrugated tubing protection, and repositioned the cable clips to avoid contact with moving parts. Fault resolved.
BYD DTC AI Analysis

Connector corrosion and short circuit after water ingress

✓
Vehicle: Qin 100 2017. After driving through water, the passenger carpet was wet and the airbag light came on. Disassembly revealed water in the pretensioner connector under the passenger seat. Copper terminals had oxidized, producing green corrosion that shorted adjacent terminals. Repair: Cleaned the connector terminals with electronic cleaner and a specialty brush, dried the wiring harness, applied conductive grease, and replaced the connector seal. Pretensioner resistance measured normal at 2.3Ω. Cleared fault codes; no recurrence.
BYD DTC AI Analysis

Pretensioner generator internal short circuit

✓
Vehicle: Qin EV450 2018. Replaced the passenger side seat belt assembly after collision repairs. Post-installation DTC B1797-00 set. Measured the new seat belt pretensioner resistance at 0.2Ω (near short). Disassembling the old part revealed the new unit was aftermarket with an internal bridge wire design defect. Solution: Installed a genuine passenger side seat belt assembly (including pretensioner). Resistance: 2.8Ω. Fault code cleared after installation; SRS self-diagnostic passed.
BYD DTC AI Analysis

Aftermarket seat heater installation caused short circuit

✓
Model: Qin 80 2017. One week after the customer installed an aftermarket passenger seat heating pad, the airbag warning light came on. Inspection found incorrect splicing during the power tap; damaged insulation on the heating pad power wire had shorted to the pretensioner harness. Fix: Removed the unauthorized modification, restored the factory harness insulation with heat-shrink tubing, and remeasured pretensioner circuit resistance and insulation to ground. Advised the customer that SRS system wiring prohibits unauthorized modification.
BYD DTC AI Analysis

SRS ECU detection circuit false positive

✓
Model: Qin EV300 2017. Measured pretensioner and harness resistance multiple times; readings were normal (2.5Ω, good insulation to ground), but the DTC kept returning. Diagnosis: SRS ECU internal sampling circuit fault causing false 0Ω detection. Fix: Replaced the SRS control unit (programmed to match vehicle VIN and configuration codes). After replacement, the DTC has not returned and system function is normal.
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.