AU
B168700

DTC B168700 indicates the Airbag Control Module (SRS ECU) detects that the configuration parameters for Ignition Circuit 3 (typically the left front seat belt pretensioner or left side airbag deployment circuit) do not match the actual vehicle configuration — Seal U

Safety System

DTC B168700 indicates the Airbag Control Module (SRS ECU) detects that the configuration parameters for Ignition Circuit 3 (typically the left front seat belt pretensioner or left side airbag deployment circuit) do not match the actual vehicle configuration.

Specifically, the airbag type, resistance range, or circuit topology data stored in the control module does not match the installed hardware, preventing the system from validating the circuit.

This fault prevents the safety device corresponding to Circuit 3 from deploying during a collision, creating a severe safety hazard that requires immediate repair.

Common causes include failing to complete online programming after replacing the SRS control module, installing non-genuine parts with different resistance characteristics, or modifying or damaging the wiring harness, which alters the circuit's electrical properties.

3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Failure to perform vehicle configuration (coding) after replacing the SRS control module, or incorrect programming data, prevents the control module from identifying the hardware parameters of circuit 3.
  • 2The seat belt pretensioner or side airbag assembly model for Circuit 3 does not match the vehicle configuration (e.g., installing a part from a different model year or trim level results in a resistance value outside the 1.5-3.5Ω standard range).
  • 3Poor contact at the under-seat SRS wiring harness connector (usually beside the front left seat rail), oxidized or corroded pins, or worn harness insulation causes intermittent short or open circuits, which the control module incorrectly identifies as a configuration fault.
  • 4Vehicle wading or high-humidity environments cause water ingress in the under-seat connector, altering circuit resistance characteristics; or a previous minor collision caused a faulty pretensioner internal triggering mechanism.
  • 5Improper handling during seat modification (such as installing sports seats or adding seat heating/ventilation) damaged the pretensioner wiring harness, or installing a non-genuine seat caused abnormal communication between the OCS (occupant classification system) and the SRS.
What To Do
  • 1
    Connect the VDS2000/VDS diagnostic tool. Read the complete fault codes and freeze frame data. Confirm whether 'Circuit 3' specifically refers to the left front seat belt pretensioner or the left side airbag. Record the environmental data from when the fault occurred.
  • 2
    Run the SRS control module 'Vehicle Configuration' function. Verify the system correctly wrote the VIN, vehicle model code, and airbag configuration code. If you just replaced the control module, perform Online Coding to match the actual vehicle hardware configuration.
  • 3
    Disconnect the battery negative terminal and wait at least 3 minutes for the SRS capacitor to discharge. Remove the left front seat (or inspect the B-pillar trim). Check the yellow SRS connector for circuit 3 for looseness, water ingress, or corrosion. Clean the connector with electrical contact cleaner and verify the locking tab is intact.
  • 4
    Use a multimeter to measure the resistance across circuit 3 (use the dedicated jumper or ensure the system is powered off). The standard value is 2.0-3.0 Ω. If the resistance is abnormal, disconnect the pretensioner/airbag connector and measure the component resistance separately. If the component is normal, check the wiring harness for continuity and shorts to ground/power.
  • 5
    Check the seat slide rails, frame, and pretensioner retaining bolts for signs of removal, installation, or collision deformation. Verify the pretensioner model label matches the part number in the repair manual. If the pretensioner was replaced, verify the part number matches the vehicle configuration.
  • 6
    After repairing the wiring harness or replacing the faulty component, reconnect all connectors and restore battery power. Use the diagnostic tool to clear the fault code and execute the 'SRS System Self-learning' or 'Configuration Verification' procedure. Finally, perform a simulated crash test or road test to verify the fault is resolved.
Real-World Cases
BYD DTC AI Analysis

Qin PRO DM reported B168700: Circuit 3 invalid configuration after seat replacement.

✓
After replacing the driver seat assembly on a 2019 Qin Pro DM, the airbag warning light stayed on constantly. VDS read DTC B168700. Inspection found the replacement seat came from a base trim; its seat belt pretensioner resistance (4.2Ω) did not match the resistance range (2.0-3.0Ω) expected by the SRS control module for this high-trim vehicle. Resolution: Replaced the driver seat assembly with a unit matching the original part number, performed the 'Seat Configuration Learning' procedure using VDS, and cleared the fault codes. The system returned to normal.
Original source ↗
BYD DTC AI Analysis

Wiring harness chafing under the Qin Pro seat caused an intermittent fault in Circuit 3.

✓
The owner reported the airbag warning light intermittently illuminated on their 2018 BYD Qin Pro (petrol), particularly after adjusting the seat position. Diagnosis revealed DTC B168700 stored as a history code. We removed and inspected the front left seat. The seat rails interfered with the SRS wiring harness beneath when sliding fore and aft, abrading the insulation and partially exposing the copper wires, causing an intermittent short. We replaced the entire yellow SRS harness, rerouted the wiring, fitted anti-chafe sleeving, and secured it with cable ties to eliminate contact with the rails. Fault resolved.
Original source ↗
BYD DTC AI Analysis

SRS connector corrosion after vehicle water wading triggers B168700

✓
A 2019 Qin Pro DM had cabin water ingress from a blocked sunroof drain. After repairs, the airbag warning light came on with DTC B168700 (Loop 3 Invalid Configuration). Inspection found water inside the SRS connector under the left front seat; the pins had green copper corrosion, increasing loop resistance and making it unstable. Fix: thoroughly cleaned the connector pins with precision instrument cleaner and fine sandpaper, applied conductive anti-corrosion compound, and replaced the connector seal. After confirming loop resistance normal, cleared the codes and performed a humidity adaptation test. The fault did not return.
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.