AU
B17731B

This DTC indicates the SRS (Supplemental Restraint System) control module detects a missing signal or communication interruption from the right rear seat belt pretensioner during self-check or real-time monitoring — Atto 8

Safety System

This DTC indicates the SRS (Supplemental Restraint System) control module detects a missing signal or communication interruption from the right rear seat belt pretensioner during self-check or real-time monitoring.

Specifically, the control module cannot identify the pretensioner’s electronic identification (resistance signature code or LIN/CAN node ID) or detects an open circuit, short to ground, or short to power.

This prevents the seat belt at this position from tightening automatically during a frontal collision, increasing passenger forward displacement and significantly reducing restraint system effectiveness.

The SRS system also illuminates the airbag fault warning lamp and may disable the related collision trigger logic.

This is a critical fault affecting passive safety.

The B17731B fault code on the Atto 8 indicates a medium-severity SRS fault where the control module cannot detect or communicate with the right rear seat belt pretensioner. Common causes include a loose, corroded, or damaged connector under the seat/B-pillar, or an internal open circuit in the pretensioner. Visit an authorised dealer for diagnosis and repair, as this affects crash restraint performance. Typical repair cost data is available from recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Right rear seat belt pretensioner connector (located below the B-pillar or under the seat) loose, terminals backed out, or oxidized/corroded, causing excessive contact resistance or signal interruption.
  • 2Open circuit in the pretensioner body internal squib or resistance drift beyond the calibrated range (normal: 2.0-5.0 Ω), failing the SRS module safety check.
  • 3Long-term wear or pinching at the sill trim panel bend breaks the floor or B-pillar wiring harness, causing an open circuit between the pretensioner and the SRS module.
  • 4Incorrect vehicle software configuration parameters (e.g., programming the SRS module with a high-spec version on a low-spec vehicle lacking this pretensioner, or a hardware configuration mismatch after installing used parts).
  • 5Rear water ingress or liquid spillage causes an internal short circuit and corrosion in the pretensioner connector, or poor sealing below the B-pillar allows water into the wiring harness connector.
What To Do
  • 1
    Safety preparation: Turn off the ignition, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to allow the SRS capacitor to discharge fully. Wear an anti-static wrist strap. Never use a standard multimeter resistance setting to directly measure a pretensioner connected to the control module.
  • 2
    Visual inspection: Remove the right rear door sill trim panel and lower B-pillar trim panel. Check the pretensioner connector for looseness, water ingress, or deformed pins. Disconnect and reconnect the connector, and apply conductive grease to ensure good contact.
  • 3
    Circuit continuity test: Disconnect the SRS control module and pretensioner connectors. Use a multimeter to check wiring harness continuity between them. Inspect the harness insulation for damage, especially at the door sill bend. Repair any open or short circuits.
  • 4
    Resistance measurement: Use a dedicated SRS resistance meter (or a multimeter on the low-resistance setting) to measure the pretensioner body resistance directly. The standard value is 2.0-5.0Ω. Infinity indicates an open circuit; replace the pretensioner. 0Ω indicates a short circuit; check the wiring harness.
  • 5
    Configuration verification: Connect the VDS2000 or Launch X431 diagnostic tool, enter the SRS system to read the vehicle configuration code (VCU configuration or SRS configuration), and compare it against the actual hardware equipped. Rewrite the configuration parameters or update the SRS software if necessary.
  • 6
    Component replacement: If confirming the pretensioner is faulty, replace it with the same model pretensioner assembly (record the old part resistance value for reference). Perform configuration calibration after replacement.
  • 7
    System reset and verification: After repair, reconnect the battery, clear the fault codes, and perform the SRS system self-test cycle (Ignition ON-OFF three times). Verify the fault code does not return and the airbag warning light turns off. Read the live data stream with a diagnostic tool to confirm the channel resistance value is within the normal range.
Real-World Cases
BYD DTC AI Analysis

Worn right rear door sill wiring harness causing intermittent fault codes

✓
A 2019 BYD Qin EV developed an intermittent airbag warning light. Scanning revealed DTC B17731B. Inspection found the right rear door frame seal had deteriorated and the sill trim panel clips were loose, allowing the wiring harness to chafe through at the sill bend. The copper conductors had partially fractured, causing intermittent contact. Re-wrapped the wiring harness, secured the routing to avoid interference with the trim panel, and replaced the sill clips. Fault resolved.
BYD DTC AI Analysis

Loose connector caused signal interruption

✓
2020 E3. Rear passengers reported a seat belt malfunction. Scan tool showed B17731B. Disassembly found the right rear seat belt pretensioner connector wasn't fully locked—the terminal had backed out approximately 2mm, likely from a previous carpet repair that didn't fully seat it. Reinserted the connector, confirmed the locking tab engaged, cleared the fault code, and ran multiple bump tests with no recurrence.
BYD DTC AI Analysis

Software configuration error triggered false alarms

✓
A 2019 E2 persistently stored DTC B17731B after collision repairs. Inspection revealed this base model lacked a right rear seatbelt pretensioner from the factory, but the shop had replaced the SRS control module with a high-spec unit. The module set a fault during self-check when it could not detect the hardware. We used VDS2000 to access the SRS system and changed the vehicle configuration to "no right rear pretensioner". The fault code cleared and the system returned to normal.
BYD DTC AI Analysis

Internal open circuit in pretensioner

✓
A 2019 Qin EV. Airbag warning light stayed on after the vehicle waded through water. Inspection found the right rear carpet wet; the pre-tensioner connector contained water and green copper corrosion. Cleaning the connector didn't clear the fault. Resistance measured infinite (open circuit), indicating the internal igniter had corroded open. Replaced the right rear seatbelt assembly (including pre-tensioner) and dried/treated the wiring harness for corrosion. Fault resolved.
BYD DTC AI Analysis

Aftermarket seat covers pinched the connector.

✓
A 2020 E3 triggered DTC B17731B after the owner fitted full-surround seat covers. Inspection found the seat cover retaining clips were excessively thick and crushed the right rear seat pretensioner harness connector during installation, fracturing the connector housing and bending the pins, creating a short. Straightened the pins, replaced the connector housing, and repositioned the seat covers to avoid the wiring harness. Fault cleared.
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.