VEHICLE STABILITY CONTROL SYSTEM (for Vacuum Brake Booster), Diagnostic DTC:C1426

DTC Code DTC Name
C1426 Stop Light Switch OFF Stuck Malfunction

DESCRIPTION

The skid control ECU (brake actuator assembly) inputs stop light switch signals and brake operation condition.

The skid control ECU (brake actuator assembly) has an open detection circuit, which stores this DTC when detecting an open in the stop light input line or the ground line of the stop light circuit with the stop light switch off (brake pedal not depressed).

DTC Code DTC Detection Condition Trouble Area
C1426 When the brake pedal load sensing switch is on, the master cylinder pressure is 2 MPa or higher and the deceleration calculated from the vehicle speed is 0.2 G or more, the stop light switch is off for 2 seconds or more.
  • STOP fuse

  • Stop light switch assembly

  • Stop light switch circuit

  • Skid control ECU (Brake actuator assembly)

  • Brake pedal load sensing switch (Brake with switch pedal sub-assembly)

WIRING DIAGRAM

Refer to DTC C1425 Click here.

INSPECTION PROCEDURE

Note


  • When replacing the skid control ECU (brake actuator assembly), perform calibration Click here.

  • Inspect the fuses for circuits related to this system before performing the following inspection procedure.

PROCEDURE


  1. CHECK STOP LIGHT OPERATION


    1. Check that the stop lights come on when the brake pedal is depressed, and go off when the brake pedal is released.

      OK
      Condition Illumination Condition
      Brake pedal depressed On
      Brake pedal released Off

    NG
    OK
  2. READ VALUE USING INTELLIGENT TESTER (STOP LIGHT SW/BRAKE PEDAL LOAD SENSING SW)


    1. Turn the ignition switch off

    2. Connect the intelligent tester to the DLC3.

    3. Turn the ignition switch to ON.

    4. Turn the intelligent tester on.

    5. Enter the following menus: Chassis / ABS/VSC/TRC / Data List.

      ABS/VSC/TRC
      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      Stop Light SW Stop light switch/ ON or OFF

      ON: Brake pedal depressed

      OFF: Brake pedal released

      -
      Brake Pedal Load Sensing SW Brake pedal load sensing switch/ ON or OFF

      ON: Brake pedal depressed beyond specified point

      OFF: Brake pedal not depressed beyond specified point

      -
    6. Check that the stop light switch display and brake pedal load sensing switch display observed on the intelligent tester change according to the brake pedal operation.

      OK
      The intelligent tester displays ON or OFF according to brake pedal operation.
    7. Slowly depress the brake pedal and check when the stop light switch and brake pedal load sensing switch are turned on.

      OK
      The stop light switch turns on first, and then the brake pedal load sensing switch turns on.
      Result
      Result Proceed to
      OK A
      NG (Turning on of stop light switch is not confirmed) B
      NG (Brake pedal load sensing switch turns on first) C

    B
    C
    A
  3. RECONFIRM DTC


    1. Turn the ignition switch off.

    2. Clear the DTCs Click here.

    3. Start the engine.

    4. Depress the brake pedal several times to test the stop light circuit.

    5. Check if the same DTC is output Click here.

      Result
      Result Proceed to
      DTC C1426 is not output A
      DTC C1426 is output B

    B
    A
  4. CHECK TERMINAL VOLTAGE AND RESISTANCE (STOP LIGHT SWITCH ASSEMBLY POWER SOURCE TERMINAL)


    1. Make sure that there is no looseness in the locking part and connecting part of the connectors.

    2. Disconnect the A85 stop light switch assembly connector.

    3. A01DUWFE09
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Switch Assembly)

      Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      A85-1(B) - Body ground Always 11 to 14 V
    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      A85-3 (GND) - Body ground Always Below 1 Ω

    NG
    OK
  5. CHECK TERMINAL VOLTAGE (STP)


    1. Make sure that there is no looseness at the locking parts and connecting parts of the connectors.

    2. Disconnect the A6 skid control ECU (brake actuator assembly) connector.

    3. A01DMHLE14
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Skid Control ECU [Brake Actuator Assembly])

      Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      A6-2 (STP) - Body ground Brake pedal depressed 8 to 14 V
      Brake pedal released Below 1.5 V

    NG
    OK
  6. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY- BRAKE ACTUATOR ASSEMBLY)


    1. Disconnect the A85 stop light switch assembly connector.

    2. Disconnect the A6 skid control ECU (brake actuator assembly) connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      A85-2 (L) - A6-2 (STP) Always Below 1 Ω
      A85-2 (L) or A6-2 (STP) - Body ground Always 10 kΩ or higher

    NG
    OK
  7. ADJUST BRAKE PEDAL AND STOP LIGHT SWITCH ASSEMBLY INSTALLATION


    1. Adjust the brake pedal height and stop light switch assembly installation Click here.


    NEXT
  8. RECONFIRM DTC


    1. Clear the DTCs Click here.

    2. Start the engine.

    3. Depress the brake pedal several times to test the stop light circuit.

    4. Check if the same DTC is output Click here.

      Result
      Result Proceed to
      DTC C1426 is not output A
      DTC C1426 is output B

    B
    A