AU
B168C00

DTC B168C00 indicates the airbag control unit (SRS ECU) detects an invalid or missing configuration parameter for Trigger Circuit 8 (Loop 8) — Atto 8

Safety System

DTC B168C00 indicates the airbag control unit (SRS ECU) detects an invalid or missing configuration parameter for Trigger Circuit 8 (Loop 8).

In the BYD Qin PRO SRS architecture, Loop 8 typically corresponds to the driver-side airbag ignition circuit or the front passenger-side pretensioner circuit.

This is a Configuration Fault, not a hardware short or open circuit.

The ECU recognizes the loop hardware, but the internally stored configuration data (such as resistance thresholds, ignition characteristic curves, and installation position coding) mismatches the actual vehicle, or the ECU programming table does not activate the loop.

This fault disables the safety function of the affected loop, but typically does not affect the protective functions of other correctly configured loops.

4
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Failure to perform online programming or configuration writing after replacing the airbag control module (SRS ECU) results in the new module lacking vehicle-specific circuit configuration data.
  • 2After accident repairs, the technician replaced airbag assemblies (such as the driver airbag or pretensioner) but did not use a diagnostic tool to update the SRS ECU configuration or perform coding.
  • 3SRS ECU internal memory data corruption or checksum error. Attempting system startup with low battery voltage (<9V) or an ECU hardware fault can cause configuration area data loss.
  • 4Poor contact or oxidation in the wiring harness connector prevents the ECU from correctly reading the circuit 8 identification resistor (ID Resistor) during self-check, causing a false configuration error.
  • 5Installed non-genuine parts (such as salvaged parts or aftermarket airbags) have resistance characteristics or configuration codes that do not match the original ECU.
What To Do
  • 1
    Connect the BYD dedicated diagnostic tool (ED400/ED300). Enter the SRS system to read the complete fault codes and freeze frame data. Confirm the specific physical location (driver airbag/passenger airbag/pretensioner) and configuration status of Circuit 8.
  • 2
    Visually inspect the Circuit 8 wiring harness connector (usually located on the steering column below the steering wheel or under the center console). Check the terminals for oxidation or backed-out pins. Measure the circuit resistance (normal resistance is 2.0-3.0 Ω, including igniter and wiring harness resistance).
  • 3
    Use the diagnostic tool to execute the 'SRS System Configuration' or 'Online Programming' function. Rewrite the ECU configuration data using the vehicle VIN and configuration code (usually located on the B-pillar or inside the glovebox) to correctly activate circuit 8 and match the vehicle configuration.
  • 4
    If the fault remains after programming, perform the 'SRS ECU Reset' or 'Initialization' function (some models require simultaneously shorting specific diagnostic connector terminals to enter factory mode), then reconfigure.
  • 5
    Clear the fault code, turn the ignition switch from OFF to ON, and wait for the SRS self-check to complete (about 6 seconds). Confirm the fault code does not reappear. Finally, perform a vehicle collision simulation test (use the diagnostic tool to execute the 'Collision Output Test' function to verify it correctly triggers circuit 8).
Real-World Cases
BYD DTC AI Analysis

Replaced the SRS ECU on the accident vehicle without programming, triggering a Circuit 8 warning.

✓
After an accident, I replaced the SRS control module on my 2018 Qin Pro DM with a new unit. Once installed, the instrument cluster displayed 'airbag fault'. I read the fault code and got DTC B168C00. I checked and found the new ECU was blank — it had no vehicle configuration parameters. I performed online programming using the BYD diagnostic tool, entering the vehicle VIN and configuration code (driver airbag + passenger airbag + dual side pretensioners). After programming completed, the DTC cleared automatically, the SRS warning light went out, and the system returned to normal.
BYD DTC AI Analysis

Flat battery caused loss of SRS configuration data

✓
Owner reported the vehicle failed to start after sitting for a week. After a jump-start, the airbag warning light stayed on. The scanner retrieved DTC B168C00 and multiple circuit configuration errors. Measured battery voltage at only 8.5V. Analysis indicated the flat battery caused SRS ECU memory corruption. Replaced the battery and confirmed stable voltage, then used the scanner to reconfigure the SRS system. Cleared the fault codes and cycled the ignition switch repeatedly to test. The fault did not return.
BYD DTC AI Analysis

Oxidised steering wheel wiring harness connector caused misdiagnosis

✓
A 2019 BYD Qin Pro (petrol) developed an intermittent SRS warning light in humid conditions, storing DTC B168C00 (intermittent). Inspection of the driver-side airbag wiring harness connector (below the clock spring) revealed slightly oxidised terminals. After cleaning the terminals and applying conductive grease, the diagnostic tool's data stream showed the identification resistance of circuit 8 stabilised from abnormal fluctuation to 2.4 Ω. Cleared the DTC and monitored for one week—the fault did not return.
BYD DTC AI Analysis

Incorrectly fitted aftermarket airbag without configuration code

✓
Vehicle had the driver's side airbag replaced at a non-authorised repair shop with an aftermarket part. After installation, the vehicle logged DTC B168C00. The replacement airbag lacked the BYD factory identification resistor and configuration chip. Replaced it with a genuine airbag, then used the scan tool to run the 'Component Replacement' function and entered the new airbag's serial number to complete matching and configuration. Fault resolved. Must use components with factory configuration data, otherwise the ECU will not recognise the circuit as valid.
Other Atto 8 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.