PRE-CRASH SAFETY SYSTEM, Diagnostic DTC:C1A4B

DTC Code DTC Name
C1A4B Stop Light Relay Circuit

DESCRIPTION

The skid control ECU outputs a stop light operation signal to the stop light control ECU. When the skid control ECU detects a malfunction in the stop light circuit, the driving support ECU outputs DTC C1A4B.

DTC Code DTC Detection Condition Trouble Area
C1A4B

  • For the pre-crash safety system:


    • The engine switch is on (IG).


  • For the radar cruise control system:


    • The vehicle is being driven at 50 km/h (31 mph) or more and the ACC main switch is ON.

When the skid control ECU detects a malfunction* in the stop light control ECU circuit, the skid control ECU sends a malfunction warning signal via CAN to the driving support ECU and a DTC is output.

*: Condition for skid control ECU malfunction warning signal output. When the voltage at the IG1 terminal is between 11 and 14 V and the stop light illumination output (STP0) is ON, there is no input signal to the STP2 terminal for 5 seconds or more, or when the input signals to terminals STP and STP2 are different for 5 seconds or more when the voltage at the IG1 terminal is between 11 and 14 V and the stop light illumination output (STP0) is OFF.

  • Lighting system

  • Harness or connector

  • Stop light control ECU

  • Driving support ECU

WIRING DIAGRAM

A00XE8QE01

INSPECTION PROCEDURE

Note


  • When replacing the master cylinder solenoid, perform calibration Click here.

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

  • When replacing the driving support ECU, always replace it with a new one and be sure to perform initialization Click here. If an ECU which was installed to another vehicle is used, the information stored in the ECU will not match the information from the vehicle, and as a result, a DTC may be stored.

Tech Tips


  • When DTC C1425 is output together with DTC C1380, inspect and repair the trouble areas indicated by DTC C1425 first Click here.

  • This circuit uses CAN communication. Therefore, if there are any malfunctions in the communication circuit, one or more DTCs in the CAN communication system are output.

PROCEDURE


  1. CHECK FOR DTC (VEHICLE STABILITY CONTROL SYSTEM)


    1. Check for DTCs Click here.

      OK
      Vehicle stability control system DTCs are not output.

    NG

    GO TO VEHICLE STABILITY CONTROL SYSTEM Click here

    OK

  2. 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

    CHECK TERMINAL VOLTAGE AND RESISTANCE (+B, GND) Click here

    OK

  3. READ VALUE USING INTELLIGENT TESTER (STOP LIGHT 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

      		 -

    6. Check that the stop light switch condition observed on the intelligent tester changes according to brake pedal operation.

      OK
      The intelligent tester displays ON or OFF according to brake pedal operation.

    NG

    CHECK TERMINAL VOLTAGE (STP) Click here

    OK

  4. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (STOP LIGHT RELAY)


    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 / Active Test.

      ABS/VSC/TRC
      Tester Display Test Part Control Range Diagnostic Note
      Stop Light Relay Stop light control ECU ECU ON/OFF Observe the stop lights (do not come on for 2 to 5 seconds).

    6. While performing the Active Test, check the illumination condition of the stop lights and "Stop Light Relay Output" in the Data List.

      ABS/VSC/TRC
      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      Stop Light Relay Output Stop light control ECU output/ ON or OFF

      ON: Stop light control ECU on (Stop lights on)

      OFF: Stop light control ECU off (Stop lights off)

      		 -
      Result
      Result Proceed to
      When Active Test performed, Data List item changes between ON and OFF and stop lights turn on and off A
      When Active Test performed, Data List item changes between ON and OFF, but stop lights do not turn on B

    B

    CHECK HARNESS AND CONNECTOR (SKID CONTROL ECU - STOP LIGHT CONTROL ECU) Click here

    A

  5. CHECK TERMINAL VOLTAGE (STP2)


    1. Disconnect the A7 skid control ECU connector.

    2. A00XIJVE30
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Skid Control ECU)

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A7-45 (STP2) - Body ground Brake pedal depressed 8 to 14 V
      Brake pedal released Below 1.5 V

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  6. RECONFIRM DTC


    1. Clear the DTCs Click here.

    2. Start the engine.

    3. Perform a road test.

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

      Result
      Result Proceed to
      DTC is not output A
      DTC is output (for LHD) B
      DTC is output (for RHD) C

    B

    REPLACE MASTER CYLINDER SOLENOID Click here

    C

    REPLACE MASTER CYLINDER SOLENOID Click here

    A

    USE SIMULATION METHOD TO CHECK Click here

  7. CHECK TERMINAL VOLTAGE AND RESISTANCE (+B, GND)


    1. Disconnect the A54 stop light control ECU connector.

    2. A00XFPEE04
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Control ECU)

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A54-6 (+B) - Body ground Always 11 to 14 V

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A54-8 (GND) - Body ground Always Below 1 Ω

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  8. CHECK TERMINAL VOLTAGE (STP)


    1. Disconnect the A54 stop light control ECU connector.

    2. A00XFPEE05
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Control ECU)

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A54-5 (STP) - Body ground Brake pedal depressed 8 to 14 V
      Brake pedal released Below 1.5 V

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  9. CHECK HARNESS AND CONNECTOR (STOP LIGHT CONTROL ECU - SKID CONTROL ECU)


    1. Disconnect the A54 stop light control ECU connector.

    2. Disconnect the A7 skid control ECU connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A54-1 (OUT) - A7-45 (STP2) Always Below 1 Ω
      A54-1 (OUT) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

    REPLACE STOP LIGHT CONTROL ECU Click here

  10. CHECK TERMINAL VOLTAGE (STP)


    1. Disconnect the A7 skid control ECU connector.

    2. A00XIJVE31
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Skid Control ECU)

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A7-7 (STP) - Body ground Brake pedal depressed 8 to 14 V
      Brake pedal released Below 1.5 V
      Result
      Result Proceed to
      NG A
      OK (for LHD) B
      OK (for RHD) C

    B

    REPLACE MASTER CYLINDER SOLENOID Click here

    C

    REPLACE MASTER CYLINDER SOLENOID Click here

    A

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  11. CHECK HARNESS AND CONNECTOR (SKID CONTROL ECU - STOP LIGHT CONTROL ECU)


    1. Disconnect the A7 skid control ECU connector.

    2. Disconnect the A54 stop light control ECU connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A7-16 (STP0) - A54-9 (ACC) Always Below 1 Ω
      A7-16 (STP0) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  12. CHECK HARNESS AND CONNECTOR (SKID CONTROL ECU - STOP LIGHT CONTROL ECU)


    1. Disconnect the A7 skid control ECU connector.

    2. Disconnect the A54 stop light control ECU connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A7-45 (STP2) - A54-1 (OUT) Always Below 1 Ω
      A7-45 (STP2) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  13. REPLACE STOP LIGHT CONTROL ECU


    1. Temporally replace the stop light control ECU with a new or normally function one Click here.


    NEXT

  14. CHECK FOR DTC (PRE-CRASH SAFETY SYSTEM)


    1. Clear the DTCs Click here.

      Tech Tips

      If the detection conditions are not met, the system cannot detect malfunctions.


      • Pre-crash safety system:


        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 / Active Test.

          ABS/VSC/TRC
          Tester Display Test Part Control Range Diagnostic Note
          Stop Light Relay STOP light control ECU ECU ON/OFF Observe the stop lights (do not come on for 2 to 5 seconds).

        6. While performing the Active Test, check the illumination condition of the stop lights and "Stop Light Relay Output" in the Data List.

          ABS/VSC/TRC
          Tester Display Measurement Item/Range Normal Condition Diagnostic Note
          Stop Light Relay Output STOP light control ECU output/ ON or OFF

          ON: Stop light control ECU output on (Stop lights on)

          OFF: Stop light control ECU output off (Stop lights off)

          		 -

    2. Make sure the following conditions are met:


      • Radar cruise control system:


        • The vehicle is being driven at a speed of approximately 50 km/h (31 mph) or more and the distance control switch is on.

    3. Check for DTCs Click here.

      OK
      DTCs C1A4B are not output.

    NG

    REPLACE DRIVING SUPPORT ECU Click here

    OK

    END