PRE-CRASH SAFETY SYSTEM, Diagnostic DTC:C1A4B

DTC Code DTC Name
C1A4B Stop Light Relay Circuit

DESCRIPTION

The stop light switch assembly sends a brake pedal operation signal to the driving support ECU. Based on the signal, the driving support ECU cancels cruise control.

DTC No. DTC Detection Condition Trouble Area
C1A4B

When the power switch is on (IG),

When the skid control ECU (brake booster with master cylinder assembly) detects a malfunction in the stop light control relay circuit, it sends a malfunction signal to the driving support ECU assembly via CAN communication and the driving support ECU assembly stores this DTC.

  • Lighting system

  • CAN communication system

  • Electronically controlled brake system

  • Skid control ECU (brake booster with master cylinder assembly)

  • Stop light control relay circuit

  • Stop light control relay

  • Driving support ECU assembly

WIRING DIAGRAM

B001LKSE11

CAUTION / NOTICE / HINT

Note


  • When this DTC is output, a malfunction in the electronically controlled brake system is suspected. Check if the electronically controlled brake system is functioning normally Click here.

  • When this DTC is output, a malfunction in the lighting system is suspected. Check if the lighting system is functioning normally Click here.

Tech Tips


  • This circuit uses CAN communication. Therefore, be sure to check that the CAN communication system is normal before performing inspection.

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

PROCEDURE


  1. CHECK FOR DTCs (ABS/VSC/TRC)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the intelligent tester on.

    4. Enter the following menus: Chassis / ABS/VSC/TRC / DTC.

    5. Check for DTCs.

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

    6. Turn the power switch off.


    B

    GO TO ELECTRONICALLY CONTROLLED BRAKE SYSTEM Click here

    A

  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

    GO TO LIGHTING SYSTEM (EXT) Click here

    OK

  3. CHECK HARNESS AND CONNECTOR (STOP LIGHT CONTROL RELAY POWER SOURCE)


    1. B001MQ9E01
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Control Relay)

      Disconnect the stop light control relay connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A27-6 (+B) - Body ground Always 11 to 14 V

    3. Reconnect the stop light control relay connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT CONTROL RELAY - STOP FUSE)

    OK

  4. CHECK HARNESS AND CONNECTOR (STOP LIGHT CONTROL RELAY - BODY GROUND)


    1. B001KT8E01
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Control Relay)

      Disconnect the stop light control relay connector.

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

      Standard Resistance (Check for Open)
      Tester Connection Condition Specified Condition
      A27-8 (GND) - Body ground Always Below 1 Ω

    3. Reconnect the stop light control relay connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT CONTROL RELAY - BODY GROUND)

    OK

  5. CHECK HARNESS AND CONNECTOR (STOP LIGHT CONTROL RELAY - STOP LIGHT SWITCH ASSEMBLY)


    1. B001L3HE01
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Control Relay)

      Turn the power switch off.

    2. Disconnect the stop light control relay connector.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      A27-5 (STP) - Body ground Stop light switch ON (Brake pedal depressed) 11 to 14 V
      A27-5 (STP) - Body ground Stop light switch OFF (Brake pedal released) Below 2 V

    4. Reconnect the stop light control relay connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT CONTROL RELAY - STOP LIGHT SWITCH ASSEMBLY)

    OK

  6. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - SKID CONTROL ECU)


    1. B001KVWE01
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Skid Control ECU)

      Turn the power switch off.

    2. Make sure that there is no looseness at the locking part and the connecting part of the connector.

    3. Disconnect the brake booster with master cylinder (skid control ECU) connector.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      A61-6 (STP2) - Body ground Stop light switch ON (Brake pedal depressed) 11 to 14 V
      A61-6 (STP2) - Body ground Stop light switch OFF (Brake pedal released) Below 1.5 V

    5. Reconnect the brake booster with master cylinder (skid control ECU) connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - SKID CONTROL ECU)

    OK

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


    1. Connect the intelligent tester to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the intelligent tester on.

    4. Enter the following menus: Chassis / ABS/VSC/TRC / Active Test.

    5. Select the Active Test on the intelligent tester.

      ABS/VSC/TRC
      Tester Display Test Part Control Range Diagnostic Note
      Stop Light Relay Stop light control relay Relay ON/OFF Stop lights come on

    6. Select the Data List on the intelligent tester.

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

      ON: Relay output on

      OFF: Relay output off

      		 -

    7. Check stop light control relay operation and stop light operation on the Data List while performing the Active Test.

      Result
      Result Proceed to
      Data List content and stop light operation are abnormal or Data List content is normal but stop lights do not turn on or off. A
      Data List content and stop light operation are normal. B

    8. Turn the power switch off.


    B

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

    A

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


    1. Disconnect the stop light control relay connector.

    2. Disconnect the brake booster with master cylinder (skid control ECU) connectors.

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

      Standard Resistance (Check for Open)
      Tester Connection Switch Condition Specified Condition
      A27-9 (ACC) - A61-3 (STP0) Always Below 1 Ω
      Standard Resistance (Check for Short)
      Tester Connection Switch Condition Specified Condition
      A27-9 (ACC) or A61-3 (STP0) - Body ground Always 10 kΩ or higher

    4. Reconnect the stop light control relay connector.

    5. Reconnect the brake booster with master cylinder (skid control ECU) connectors.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT CONTROL RELAY - SKID CONTROL ECU)

    OK

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


    1. Disconnect the stop light control relay connector.

    2. Disconnect the brake booster with master cylinder (skid control ECU) connectors.

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

      Standard Resistance (Check for Open)
      Tester Connection Switch Condition Specified Condition
      A27-1 (OUT) - A61-33 (STP) Always Below 1 Ω

    4. Reconnect the stop light control relay connector.

    5. Reconnect the brake booster with master cylinder (skid control ECU) connectors.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT CONTROL RELAY - SKID CONTROL ECU)

    OK

  10. INSPECT STOP LIGHT CONTROL RELAY


    1. Inspect the stop light control relay Click here.


    NG

    REPLACE STOP LIGHT CONTROL RELAY Click here

    OK

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


    1. B001KTSE01
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Skid Control ECU)

      Turn the power switch off.

    2. Disconnect the brake booster with master cylinder (skid control ECU) connectors.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      A61-33 (STP) - Body ground Stop light switch ON (Brake pedal depressed) 11 to 14 V
      A61-33 (STP) - Body ground Stop light switch OFF (Brake pedal released) Below 1.5 V

    4. Reconnect the brake booster with master cylinder (skid control ECU) connectors.


    NG

    REPLACE STOP LIGHT CONTROL RELAY Click here

    OK

  12. CHECK FOR DTCs (DTC C1A4B)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the intelligent tester on.

    4. Enter the following menus: Body / Pre-Crash 2 / DTC.

    5. Clear the DTCs Click here.

    6. Select the Active Test on the intelligent tester Click here.

      ABS/VSC/TRC
      Tester Display Test Part Control Range Diagnostic Note
      Stop Light Relay Stop light control relay Relay ON/OFF Stop lights come on

    7. Perform the Active Test of the stop light control relay using the intelligent tester.

    8. Select the Data List on the intelligent tester Click here.

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

      ON: Relay output on

      OFF: Relay output off

      		 -

    9. Check for stop light control relay operation using the Data List and stop light operation by performing an Active Test.

    10. Recheck for DTCs.

      Result
      Result Proceed to
      DTC is not output A
      DTC C1A4B is output B

    A

    END

    B

    REPLACE DRIVING SUPPORT ECU ASSEMBLY Click here