AU
B168800

DTC B168800 indicates the SRS (Supplemental Restraint System) control unit detects invalid configuration parameters in circuit 4 (typically the driver-side seat belt pretensioner circuit) — Atto 3

Safety System

DTC B168800 indicates the SRS (Supplemental Restraint System) control unit detects invalid configuration parameters in circuit 4 (typically the driver-side seat belt pretensioner circuit).

Specifically, the control unit detects the circuit resistance falls outside the standard range (normally 2-3 ohms), or the identified hardware configuration does not match the software calibration.

This constitutes a hard fault in the passive safety system.

During a collision, the corresponding restraint device (seat belt pretensioner or airbag) may fail to deploy, severely compromising occupant protection.

Upon fault detection, the SRS control unit illuminates the instrument cluster airbag warning light and may disable the entire airbag system.

The B168800 fault code on the Atto 3 indicates an invalid configuration in the SRS (airbag) system, specifically the driver-side seat belt pretensioner circuit showing incorrect resistance or hardware mismatch (medium severity). Common causes include a faulty pretensioner or loose/oxidised wiring connectors under the seat. You should visit an authorised dealer for repair. Typical repair cost data is available based on 5 recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Driver side seat belt pretensioner internal open circuit or resistance drift (pretensioner deployed or internal coil damaged)
  • 2Loose or oxidized pretensioner wiring harness connector under the seat, or backed-out terminals, causing excessive contact resistance.
  • 3Prolonged chafing of the wiring harness near the seat slide rail causes insulation damage, broken wires, or intermittent short circuits.
  • 4SRS control unit internal fault or software calibration error causing abnormal Circuit 4 identification.
  • 5Deployed pretensioner not replaced after accident repairs, or replacement part number does not match vehicle configuration.
What To Do
  • 1
    Use the BYD VDS2000/VDS3000 dedicated diagnostic tool to read all fault codes, record freeze frame data, and check for accompanying communication fault codes such as U0151.
  • 2
    Inspect the driver-side seat belt pretensioner for obvious signs of deployment (tightened webbing, cracked housing). Measure the pretensioner resistance (standard value: 2.0-3.0 Ω). Replace the assembly if the resistance is out of range.
  • 3
    Remove the driver's seat and inspect the yellow pretensioner connector under the seat (usually located on the inner side of the seat rail). Verify the connector is fully locked. Clean terminal oxidation with electrical contact cleaner and check for backed-out terminals.
  • 4
    Inspect the entire length of the pretensioner wiring harness down the B-pillar. Pay special attention to interference points at the seat slide rail and detached harness retaining clips. Repair damaged wires, re-wrap the harness, and protect it with abrasion-resistant sleeving.
  • 5
    Measure wiring harness continuity between the pretensioner and the SRS control unit (usually located under the centre console or inside the centre armrest box) to verify there is no open circuit or short to ground/power.
  • 6
    If the pretensioner has deployed or resistance is infinite, replace the driver-side seat belt assembly (including the pretensioner) and verify the new part number matches the vehicle configuration.
  • 7
    Reconnect all connectors, secure the wiring harness with cable ties to maintain a clearance of more than 20 mm from the seat slide rail, and reinstall the seat.
  • 8
    Clear the fault code, perform the 'SRS System Calibration' or 'Restraint System Configuration' function (enter the vehicle VIN or select the correct vehicle model configuration), and run the self-check procedure to confirm B168800 does not reappear.
  • 9
    Perform a simulated crash test (using the diagnostic tool 'Airbag Test' function without triggering actual ignition). Confirm the Circuit 4 status displays 'Normal' and the instrument panel warning light turns off.
Real-World Cases
BYD DTC AI Analysis

Qin Pro DM seat rail chafed wiring harness, causing open circuit in circuit 4

✓
Symptom: Airbag warning light stays on. Retrieved DTC B168800 (Loop 4 Invalid Configuration). Diagnosis: Measured driver-side pretensioner resistance — open circuit (infinite). Removed seat and found pretensioner harness had been chafing against seat rail over time; insulation worn through, three wires completely severed. Fix: Replaced pretensioner wiring harness assembly, rerouted harness to clear seat rail travel path, fitted dedicated protective sleeve. Fault cleared.
Original source ↗
BYD DTC AI Analysis

Qin Pro petrol – Loose connector causing intermittent fault

✓
Symptoms: Intermittent 'Check SRS System' warning after engine start. DTC B168800 set intermittently. Diagnosis: The pretensioner connector under the seat was not fully seated. Internal terminals showed slight oxidation. Contact resistance fluctuated when the vehicle was shaken. Resolution: Repaired the backed-out terminal pins using a specialised tool, applied conductive paste to improve contact, and reassembled. Repeated testing confirmed the fault did not return.
Original source ↗
BYD DTC AI Analysis

Pretensioner not replaced after accident repair, causing invalid configuration

✓
After the front-end collision repair, the airbag light stayed on and DTC B168800 was stored. The driver-side pretensioner had deployed in the accident (the belt webbing was visibly retracted), but the independent shop that did the repair only cleared the codes without replacing the pretensioner. The pretensioner circuit measured open. I replaced the driver-side seatbelt assembly (including pretensioner), recalibrated the SRS configuration with VDS, cleared the fault codes, and everything returned to normal.
Original source ↗
BYD DTC AI Analysis

Qin PRO DM terminal backed out causing poor contact

✓
Symptoms: The airbag warning light occasionally flickered while driving and cleared after stopping and restarting. Diagnostic process: Performed a harness wiggle test to simulate the fault. The issue reappeared when wiggling the wiring harness under the seat. Removed the connector plug and found the pins inside the pre-tensioner connector had backed out, causing intermittent communication loss with the control unit. Solution: Used a dedicated terminal repair tool to adjust the pin positions so the protrusion height met specifications. Applied conductive paste and reconnected. Fault resolved.
Original source ↗
BYD DTC AI Analysis

Frequent seat adjustments in commercial vehicles caused wiring harness aging.

✓
Symptoms: After 80,000 km, a ride-hailing vehicle's dashboard intermittently displayed an airbag fault, logging DTC B168800. Diagnosis: Given the vehicle's heavy use and frequent seat adjustments, we inspected the wiring harness beneath the seat. We found the pre-tensioner harness severely worn at the seat rail, with insulation damaged on multiple wires and exposed copper causing intermittent shorts. Solution: Replaced the pre-tensioner wiring harness, added three securing points to prevent movement, and fitted corrugated tubing for full protection. This completely resolved the fault.
Original source ↗
Other Atto 3 Fault Codes
P0AA6Hybrid Battery Voltage System Isolation FaultB1108For 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.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.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.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.
Common problems reported for Atto 3 →Atto 3 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.