AU
B1797

DTC B1797 indicates the SRS (airbag) control module detects a 0-ohm circuit resistance in the front passenger second-stage seat belt pretensioner (typically the igniter/squib) — Atto 3

Safety System

DTC B1797 indicates the SRS (airbag) control module detects a 0-ohm circuit resistance in the front passenger second-stage seat belt pretensioner (typically the igniter/squib).

Normal seat belt pretensioner resistance is 1.5-3.0 ohms.

A 0-ohm resistance indicates a short circuit (short to ground or internal short) within the pretensioner or its wiring.

This fault forces the SRS into degraded protection mode.

The front passenger airbag may fail to deploy, severely compromising crash safety.

The second-stage pretensioner works with the airbag to rapidly retract the seat belt during a collision, limiting forward occupant movement.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Pretensioner igniter internal short circuit: Moisture ingress or aging of the pyrotechnic charge inside the seat belt pretensioner causes a short circuit between the terminals, reducing resistance to 0 ohms.
  • 2Harness damaged and shorted to ground: Frequent door opening and closing wears the insulation on the seat belt pretensioner harness near the B-pillar, shorting it to the vehicle body metal.
  • 3Connector water ingress and corrosion: Water enters the pretensioner connector if the front passenger floor floods during water wading or a car wash, causing a short circuit between pins.
  • 4Improper repair procedure: During previous airbag system repairs, directly measuring the pretensioner circuit with a multimeter resistance setting damaged the pretensioner (use dedicated diagnostic equipment).
  • 5SRS module monitoring abnormality: Airbag control module internal monitoring circuit fault, falsely reporting a pretensioner short circuit (confirm via swap test).
What To Do
  • 1
    Safe power-down: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental deployment.
  • 2
    Inspection location: Remove the front passenger-side B-pillar trim panel and locate the second-stage seat belt pretensioner connector (usually a yellow connector located below the seat belt retractor or in the middle of the B-pillar).
  • 3
    Visual inspection: Check the pretensioner wiring harness for damage or crush marks, and the connector for water ingress, corrosion, or bent pins.
  • 4
    Resistance measurement: Disconnect the pretensioner connector and use a digital multimeter to measure the resistance directly between the two pretensioner terminals (normal: 1.5-3.0 Ω; 0 Ω indicates an internal short circuit, replace the pretensioner).
  • 5
    Harness continuity test: Measure the resistance to ground and the voltage to the power supply at the harness-side connector to check for a short circuit or short to ground in the harness.
  • 6
    Component replacement: If testing confirms an internal short circuit in the pretensioner, replace the front passenger seat belt assembly (the pretensioner is not serviced separately); if the wiring harness is faulty, repair or replace the harness.
  • 7
    System verification: Reconnect all connectors, restore power, use VDS or a dedicated diagnostic tool to clear the fault code, perform an SRS system self-test, and verify with a road test.
Real-World Cases
BYD DTC AI Analysis

BYD Tang DM B1797 Fault Code After Water Fording

✓
2021 BYD Tang DM drove through approximately 40 cm of floodwater during a heavy rainstorm, triggering the airbag warning light. Scanner read DTC B1797 (passenger side second stage pretensioner resistance 0). Found water in the SRS harness connector beneath the passenger seat; oxidized pins caused a short. Cleaned the connector, dried it with compressed air, sprayed electronic cleaner, applied conductive grease, and reconnected. Fault cleared. Check the door seals and floor drain holes.
BYD DTC AI Analysis

BYD Song MAX pretensioner short circuit after accident repair

✓
A 2019 Song MAX was in a collision that deployed the passenger side airbag. After an external shop replaced the seatbelt assembly, the warning light came on. Scanned DTC B1797. Inspection found the new passenger seatbelt pretensioner connector not fully seated, and the non-genuine part had abnormal internal resistance (measured 0.2Ω). Replaced with a genuine passenger seatbelt assembly; resistance measured 2.1Ω (normal). Cleared the DTC and the system returned to normal.
BYD DTC AI Analysis

Worn wiring harness causes intermittent short circuit in BYD Yuan EV

✓
2019 BYD Yuan EV intermittent airbag warning light, sometimes after driving over speed bumps. Scan tool retrieved historical fault code B1797. Inspection of the passenger side B-pillar wiring found the seatbelt pretensioner harness rubbing against the B-pillar metal frame, damaging the insulation and causing an intermittent short to ground. Repair: Wrapped the damaged section with insulation tape, rerouted the harness and added a protective sleeve, then secured it to prevent contact with the body. Fault eliminated.
BYD DTC AI Analysis

Seat modification triggers pretensioner fault in Qin Pro

✓
2020 Qin Pro owner installed a DIY front passenger seat heater. While routing the wiring, the heater power wire pierced the SRS harness, shorting the pretensioner circuit to chassis and triggering DTC B1797. Inspection found obvious puncture damage in the under-seat harness with damaged insulation on the pretensioner lines. Repaired the SRS harness using soldered joints and heat-shrink tubing, separated the heater wiring from the SRS harness, and cleared the fault. Never mix SRS wiring with non-safety system circuits.
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.