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 8

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.

The B1797 fault code on the Atto 8 indicates a short circuit in the front passenger second-stage seat belt pretensioner, with resistance reading 0 ohms instead of the normal 1.5–3.0 ohms. Severity is medium because SRS protection may be reduced and the airbag or pretensioner may not work correctly in a crash. Common causes include an internally shorted pretensioner or damaged wiring near the B-pillar. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
4
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Pretensioner igniter internal short circuit: Moisture ingress or aging of the pyrotechnic charge inside the seat belt pretensioner causes a short circuit between the two terminals, reducing resistance to 0 ohms.
  • 2Harness damaged and shorted to ground: Frequent door opening and closing wears through the seat belt pretensioner harness insulation near the B-pillar, causing a short to the vehicle body metal.
  • 3Connector water ingress and corrosion: Water enters the pretensioner connector during car washing or front passenger-side floor flooding, causing a short circuit between pins.
  • 4Improper repair procedures: During previous airbag system repairs, directly measuring the pretensioner circuit with a multimeter resistance setting (dedicated diagnostic equipment should be used) damaged the pretensioner.
  • 5Abnormal SRS module monitoring: Airbag control module internal monitoring circuit fault falsely reports 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
    Location and inspection: Remove the front passenger-side B-pillar trim and locate the second-stage seat belt pretensioner connector (usually a yellow connector 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 check 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 voltage to power supply at the harness-side connector to check for a short circuit or short to ground.
  • 6
    Component replacement: If diagnostics confirm an internal short circuit in the pretensioner, replace the front passenger-side seat belt assembly (do not replace the pretensioner separately); if the wiring harness is faulty, repair or replace the wiring 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-check, 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 8 Fault Codes
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.B1109DTC B1109 indicates an open circuit in the communication line between the air conditioning system PM2.5 air quality sensor (dust concentration sensor) and the air conditioning control unit (AC ECU), or an open circuit within the sensor internal circuitry. Typically located in the air conditioning intake duct, this sensor monitors real-time PM2.5 particle concentration inside and outside the vehicle. It provides data to the automatic air conditioning system for intelligent switching between fresh air and recirculation modes and for controlling the air purification device. During an open circuit fault, the AC ECU cannot receive the air quality signal, triggering the system fail-safe mode. Symptoms typically include failure of the automatic recirculation function, abnormal air purification indicator light operation, or abnormal air quality data displayed on the air conditioning panel. Severe cases may compromise the cabin environment control strategy, but do not directly affect vehicle driving safety.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.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.