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 assembly. Based on the signal, the driving support ECU assembly detects the operation of the brake pedal.

DTC No. DTC Detection Condition Trouble Area
C1A4B

While the engine switch is on (IG).

When the skid control ECU (brake actuator) detects a malfunction in the STOP light 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.

  • CAN communication system

  • VSC system

  • Brake actuator (skid control ECU)

  • Engine room junction block assembly

  • Driving support ECU assembly

WIRING DIAGRAM

A01G6M8E01

INSPECTION PROCEDURE

Note


  • When this DTC is output, a malfunction in the VSC system is suspected. Check if the VSC 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 DTC OUTPUT (VSC SYSTEM)


    1. Check for VSC system DTCs Click here.

      OK
      VSC 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

    INSPECT LIGHTING SYSTEM (STOP LIGHT CIRCUIT) Click here

    OK

  3. INSPECT ENGINE ROOM JUNCTION BLOCK ASSEMBLY


    1. Turn the engine switch off.

    2. Check the Engine room junction block assembly Click here.

      OK
      The Engine room junction block assembly is normal.

    NG

    REPAIR OR REPLACE WIRE HARNESS OR ENGINE ROOM JUNCTION BLOCK ASSEMBLY

    OK

  4. CHECK HARNESS AND CONNECTOR (STP TERMINAL)


    1. A01G4YLE17
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Skid Control ECU (brake actuator))

      Turn the engine switch off.

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

    3. Disconnect the A40 skid control ECU (brake actuator) connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A40-2 (STP) - Body ground Stop light switch assembly ON (Brake pedal depressed) 11 to 14 V
      A40-2 (STP) - Body ground Stop light switch assembly OFF (Brake pedal released) Below 1.5 V

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STP CIRCUIT)

    OK

  5. CHECK HARNESS AND CONNECTOR (STPS TERMINAL)


    1. A01G4SME01
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Engine room junction block assembly (Integration Relay))

      Disconnect the 1F Engine room junction block assembly connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      1F-16 (STPS) - Body ground Stop light switch assembly ON (Brake pedal depressed) 11 to 14 V
      1F-16 (STPS) - Body ground Stop light switch assembly OFF (Brake pedal released) Below 1.5 V

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STPS CIRCUIT)

    OK

  6. PERFORM ACTIVE TEST USING GTS (STOP LIGHT RELAY)


    1. Select the Active Test on the GTS Click here.

      ABS/VSC/TRC
      Tester Display Test Part Control Range Diagnostic Note
      Stop Light Relay Engine room junction block assembly Relay ON/OFF Stop lights come on

    2. Perform the Active Test of the Engine room junction block assembly using the GTS.

    3. Select the Data List on the GTS Click here.

      ABS/VSC/TRC
      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      Stop Light Relay Output Engine room junction block assembly output / ON or OFF

      ON: Relay output on

      OFF: Relay output off

      		 -

    4. Check for Engine room junction block assembly operation using the Data List and stop light operation by performing an 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

    B

    CHECK HARNESS AND CONNECTOR (ENGINE ROOM JUNCTION BLOCK - BRAKE ACTUATOR ASSEMBLY) Click here

    A

  7. CHECK HARNESS AND CONNECTOR (ENGINE ROOM JUNCTION BLOCK - BRAKE ACTUATOR ASSEMBLY)


    1. Turn the engine switch off.

    2. Remove the engine room junction block assembly from the engine room relay block and junction block assembly

    3. Disconnect the A40 skid control ECU (brake actuator assembly) connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      1G-3 (ACC) - A40-31 (STPO) Always Below 1 Ω
      1G-3 (ACC) or A40-31 (STPO) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  8. CHECK HARNESS AND CONNECTOR (ENGINE ROOM JUNCTION BLOCK - BRAKE ACTUATOR ASSEMBLY)


    1. Turn the engine switch off.

    2. Remove the engine room junction block assembly from the engine room relay block and junction block assembly

    3. Disconnect the A40 skid control ECU (brake actuator assembly) connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      1F-11 (STOP) - A40-22 (STP2) Always Below 1 Ω

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  9. PERFORM ACTIVE TEST USING HARNESS AND CONNECTOR (STP2 TERMINAL)


    1. Turn the engine switch off.

    2. A01G4YLE33
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Skid Control ECU (Brake Actuator Assembly))

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

    3. Disconnect the A40 skid control ECU (brake actuator assembly) connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A40-22 (STP2) - Body ground Stop light switch ON (Brake pedal depressed) 11 to 14 V
      A40-22 (STP2) - Body ground Stop light switch OFF (Brake pedal released) Below 1.5 V

    NG

    REPLACE ENGINE ROOM JUNCTION BLOCK ASSEMBLY Click here

    OK

  10. CHECK DTC OUTPUT (PRE-CRASH SAFETY SYSTEM)


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

    4. Enter the following menus: Body Electrical / Pre-Crash 2 / Trouble Codes.

    5. Clear the DTCs Click here.

    6. Select the Active Test on the GTS Click here.

      ABS/VSC/TRC
      Tester Display Test Part Control Range Diagnostic Note
      Stop Light Relay Engine room junction block assembly Relay ON/OFF Stop lights come on

    7. Perform the Active Test of the Engine room junction block assembly using the GTS.

    8. Select the Data List on the GTS Click here.

      ABS/VSC/TRC
      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      Stop Light Relay Output Engine room junction block assembly output / ON or OFF

      ON: Relay output on

      OFF: Relay output off

      		 -

    9. Check for Engine room junction block assembly operation using the Data List and stop light operation by performing an Active Test.

    10. Recheck for DTCs.

      Result
      Result Proceed to
      DTC C1A4B is not output. A
      DTC C1A4B is output (for LHD). B
      DTC C1A4B is output (for RHD). C

    B

    REPLACE DRIVING SUPPORT ECU ASSEMBLY Click here

    C

    REPLACE DRIVING SUPPORT ECU ASSEMBLY Click here

    A

    END