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) — Seal U

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.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Driver side seat belt pretensioner internal open circuit or resistance drift (pretensioner deployed or internal coil damaged)
  • 2Loose, oxidized, or backed-out terminals in the under-seat pretensioner wiring harness connector cause excessive contact resistance.
  • 3Long-term chafing of the wiring harness near the seat slide rail causes insulation damage, broken wires, or intermittent short circuits.
  • 4Internal SRS control unit fault or incorrect software calibration causing abnormal identification of circuit 4.
  • 5Deployed pretensioner not replaced after accident repair, or replacement part model does not match vehicle configuration.
What To Do
  • 1
    Use BYD dedicated diagnostic tool VDS2000/VDS3000 to read complete fault codes, record freeze frame data, and check for accompanying communication fault codes such as U0151.
  • 2
    Visually 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 value is out of range.
  • 3
    Remove the driver's seat and check 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, focusing on seat slide rail interference points and detached harness retaining clips. Repair any damaged wires, rewrap the harness, and protect it with abrasion-resistant sleeving.
  • 5
    Measure wiring harness continuity from the pretensioner to the SRS control unit (usually located under the centre console or inside the centre armrest) and verify no open circuits or shorts to ground or power.
  • 6
    If the pretensioner has deployed or resistance is infinite, replace the driver-side seat belt assembly (including the pretensioner). Ensure the new part number matches the vehicle configuration.
  • 7
    Reconnect all connectors. Secure the wiring harness with cable ties to maintain a clearance of at least 20 mm from the seat slide rail. Reinstall the seat.
  • 8
    Clear the fault code, perform the 'SRS System Calibration' or 'Restraint System Configuration' function (input the vehicle VIN or select the correct vehicle model configuration), and run the self-check procedure to confirm B168800 no longer appears.
  • 9
    Perform a simulated crash test (using the diagnostic tool 'Airbag Test' function without triggering actual ignition). Verify Circuit 4 status displays 'Normal' and the instrument 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 Seal U Fault Codes
B1108For 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.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.B110913DTC B110913 indicates an open signal circuit for the PM2.5 rapid detector (in-cabin air quality sensor). This sensor typically mounts inside the air conditioning system intake duct. It monitors in-cabin PM2.5 concentration in real time and provides data to the automatic air conditioning system for intelligent control of the air purification function. The BYD diagnostic protocol uses sub-code '13' to specifically indicate an open signal circuit. Although this fault theoretically affects a comfort feature, BYD Qin series vehicles classify it as a Level 3 (severe) fault. This classification occurs because the air conditioning system interacts with the battery thermal management system (e.g., monitoring battery cooling intake air quality). The fault can disable the automatic air conditioning mode and prevent the air purification function from operating. In extreme cases, it affects the battery compartment intake air quality assessment, triggering the 'repair immediately' strategy.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.
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.