AU
B1797-00

This DTC indicates the front passenger seat belt pretensioner (second-stage deployment circuit) resistance is 0 Ω, indicating a short circuit — Atto 3

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.

5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Pretensioner generator internal short circuit: A broken internal bridge wire in the pyrotechnic generator or damp charge 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, long-term 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 terminals.
  • 4Improper modification or repair: Fixing screws piercing the wiring harness or incorrect terminal crimping when installing seat covers or modifying the seat heating or power adjustment systems.
  • 5SRS ECU internal fault: A damaged ECU internal sampling resistor or detection circuit causes a false 0 Ω reading (actual circuit is normal).
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 2
    Visual inspection: Remove the front passenger seat (leave the wiring harness connected) and inspect the pretensioner connector under the seat (usually yellow) for looseness, water ingress, or obvious burning marks.
  • 3
    Disconnect the ECU side and measure: Locate the SRS ECU (usually under the centre 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 be greater than 10kΩ; otherwise, the wiring harness has a short to ground.
  • 4
    Pretensioner unit measurement: Disconnect the inflator connector. Use a special low-impedance multimeter to measure the resistance between the two terminals of the pretensioner plug. Standard 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. Focus on interference points at the seat slide rail. Repair any damaged insulation and reroute the wiring harness.
  • 6
    Replacement verification: After replacing the suspected faulty pretensioner or repairing the wiring harness, reconnect all components, reconnect the battery, clear the fault code using the diagnostic tool, and perform the 'ignition cycle test' and 'pretensioner resistance reading' verification.
  • 7
    System simulation test: On some models, perform SRS system self-learning or write configuration data 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 Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For the BYD Song MAX (2017–2019), DTC B1108 indicates a short circuit in the PM2.5 air quality detection module (dust sensor) or its wiring harness. The sensor uses laser scattering to detect in-cabin and outside PM2.5 concentrations and transmits data to the HVAC ECU via the LIN bus or an analog signal. Short circuit conditions include: 1) Sensor power supply wire (+5V/+12V) shorted to ground 2) Signal wire shorted to power or ground 3) Short circuit in the sensor's internal photoelectric detection circuit This fault prevents the automatic climate control from switching between fresh air and recirculation based on air quality. The system enters fail-safe mode (typically forced recirculation). Severe short-circuit current can destroy the HVAC ECU sampling circuit. The system classifies this as a Level 3 severe fault and restricts vehicle operation to prevent electrical fires or controller damage. For other BYD models (such as the Qin EV, E5, and Song DM), B1108 indicates a driver-side sunload sensor fault, reflecting differences in DTC definitions across models.B110811This DTC indicates a short circuit in the air conditioning system PM2.5 air quality sensor (rapid detector). Specifically, abnormal continuity exists between the sensor power supply circuit or signal output circuit and body ground or battery positive. This causes the control module (ACU/air conditioning controller) to detect abnormal current or a voltage signal outside the valid range (typically 0V or supply voltage). The PM2.5 sensor monitors internal and external particulate concentrations, providing the data the automatic air conditioning system uses to switch between fresh air and recirculation modes. A short circuit disables the air quality monitoring function. This fault may force the air conditioning system into recirculation protection mode and trigger related thermal management system faults, as the air conditioning system acts as a key actuator in vehicle thermal management. In severe cases, the short circuit current can damage the internal sampling circuit of the air conditioning controller or overheat the wiring harness.
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.