AU
B168D00

DTC B168D00 indicates the Airbag Control Unit (ACU) detects invalid configuration data for Ignition Loop 9 — Qin Plus

Safety System

DTC B168D00 indicates the Airbag Control Unit (ACU) detects invalid configuration data for Ignition Loop 9.

In the BYD Qin PRO SRS system, Loop 9 typically corresponds to the front passenger knee airbag or rear seat side airbag circuit, depending on the vehicle configuration level. "Invalid configuration" means the "configuration present flag", "rated resistance parameter", or "capacity type" in the ACU EEPROM data does not match the installed hardware.

This condition also occurs if the ACU detects a load on a circuit marked "not installed", or detects an open circuit on a loop marked "installed".

This fault causes the ACU to enter degraded mode.

During a collision, the ACU may fail to deploy the airbag on this circuit, or it may trigger a fail-safe strategy that restricts overall SRS functionality.

The B168D00 fault code on the Qin Plus indicates invalid configuration data for Ignition Loop 9, which controls the front passenger knee or rear side airbag. This medium severity issue occurs when the airbag control unit detects mismatched hardware settings, typically after replacing the ACU or airbag without proper programming, or due to data corruption following a collision. Visit an authorised dealer for configuration and repair. Typical repair cost data is available from 3 recorded cases.
3
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Failure to write configuration data, or writing incorrect data, after replacing the Airbag Control Unit (ACU) (e.g., installing a used ACU with a stored configuration that does not match the original vehicle configuration).
  • 2Corrupted ACU internal data following a vehicle collision, or failure to update configuration parameters after replacing the airbag assembly (e.g., installing a high-spec airbag in a low-spec vehicle without reconfiguring).
  • 3Poor contact, short circuit, or abnormal resistance in the Circuit 9 wiring harness connector causes the ACU to falsely detect a configuration error (actual hardware does not match configuration).
  • 4ACU software version defect or programming error causing configuration data verification failure.
  • 512V battery depletion or improper operation during power disconnection maintenance causes loss or corruption of configuration data in the ACU non-volatile memory.
What To Do
  • 1
    Connect the VDS2000 or BYD dedicated diagnostic tool to the vehicle, read all fault codes, confirm B168D00 is a current fault (Active), and record the freeze frame data.
  • 2
    Confirm exact vehicle configuration: Check the vehicle VIN and configuration sheet to verify whether the specific component for Circuit 9 (knee airbag/rear side airbag) is actually installed on this vehicle.
  • 3
    Check the ACU software version. If a newer version is available, update the software to eliminate false alarms caused by software defects.
  • 4
    Enter the SRS system 'Special Functions' menu and execute the 'ECU Configuration' or 'Write Configuration Data' function. Reconfigure circuit 9 status (enabled/disabled) and parameters based on actual vehicle equipment.
  • 5
    If configuration fails or the fault persists after configuration, disconnect the battery negative terminal. Check the wiring harness connector for circuit 9 (usually located under the passenger dashboard or seat). Measure the circuit resistance (standard value is usually 1.8-2.5Ω) to rule out a short or open circuit in the wiring.
  • 6
    If the wiring harness is normal but configuration fails, replace the ACU with a new unit (verify the part number matches the vehicle configuration). Perform online configuration, coding, and security verification code (PIN) entry.
  • 7
    Reconnect the battery, clear the fault code, and perform the SRS system self-check (turn the ignition switch to the ON position and wait approximately 10 seconds for the self-check to complete).
  • 8
    Use the diagnostic tool to perform the 'Collision Output Test' (Simulation Test) to verify circuit 9 status. After confirming no fault codes are present, perform a road test on a bumpy road to verify the fault does not recur.
Real-World Cases
BYD DTC AI Analysis

Qin Pro DM ACU not reconfigured after accident repair

✓
A 2019 BYD Qin PRO DM had its airbag control unit replaced with a used unit from the same model at a non-authorised workshop after a front-end collision. The airbag warning light came on, and a scan revealed DTC B168D00. The used ACU came from a base-model car without a passenger knee airbag, while this vehicle is a high-spec variant with one. We ordered a new ACU with the correct high-spec part number. After fitting it, we ran the ‘ACU Replacement’ procedure on the diagnostic tool and programmed the configuration to enable circuit 9. The fault cleared.
BYD DTC AI Analysis

Configuration data lost after software upgrade

✓
A 2018 Qin PRO petrol variant developed an airbag warning light on the instrument cluster after an SRS system software upgrade at the dealership. The diagnostic tool retrieved DTC B168D00. Investigation revealed unstable battery voltage during the upgrade caused the configuration data write to fail. Repair: Checked circuit 9 harness and airbag connector – both normal. Used the diagnostic tool to enter 'System Configuration' and manually changed circuit 9 status from 'Disabled' to 'Enabled' (as the vehicle is actually fitted with a knee airbag). Wrote the configuration, cleared the DTC, and the system returned to normal.
BYD DTC AI Analysis

Loose wiring connection caused misdiagnosis as configuration error.

✓
A 2019 Qin Pro DM had an intermittent airbag warning light while driving. Retrieved DTC B168D00 (intermittent). Inspection found the passenger knee airbag connector (behind the glovebox) had a loose connection due to an assembly fault, causing the ACU to detect intermittent circuit resistance (open circuit state), conflicting with the stored 'installed' configuration. Repair: re-secured the wiring harness, cleaned and tightened the connector terminals. Measured circuit resistance stable at 2.1Ω. Cleared the fault code and monitored for one week with no recurrence.
Other Qin Plus 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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.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.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Qin Plus →Qin Plus 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.