DYNAMIC RADAR CRUISE CONTROL SYSTEM, Diagnostic DTC:C1A4B

DTC Code DTC Name
C1A4B Stop Light Relay Circuit

DESCRIPTION

The skid control ECU (brake booster with master cylinder assembly) outputs a stop light operation signal to the engine room junction block assembly. When the skid control ECU (brake booster with master cylinder assembly) detects a malfunction in the circuit related to the stop light, it informs the driving support ECU assembly via CAN communication and stores DTC C1A4B.

DTC No. DTC Detection Condition Trouble Area
C1A4B

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

When the skid control ECU (brake booster with master cylinder assembly) 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.

  • Stop light relay circuit

  • Engine room junction block assembly

  • Driving support ECU assembly

WIRING DIAGRAM

Refer to DTC C1A05 Click here.

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 GTS to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the GTS on.

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

    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. INSPECT ENGINE ROOM JUNCTION BLOCK ASSEMBLY

    Click here


    NG

    REPAIR OR REPLACE HARNESS OR ENGINE ROOM JUNCTION BLOCK ASSEMBLY Click here

    OK

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


    1. Disconnect the A24 skid control ECU (brake booster with master cylinder assembly) connector.

    2. A0008DHE01
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A24-33 (STP) - Body ground Stop light switch assembly ON (Brake pedal depressed) 11 to 14 V
      A24-33 (STP) - Body ground Stop light switch assembly OFF (Brake pedal released) Below 1.5 V

    3. Reconnect the A24 skid control ECU (brake booster with master cylinder assembly) connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  5. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - ENGINE ROOM JUNCTION BLOCK ASSEMBLY)


    1. Disconnect the 1F engine room junction block assembly connector.

    2. A0009BME01
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Engine Room Junction Block Assembly)

      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 2 V

    3. Reconnect the 1F engine room junction block assembly connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

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


    1. Connect the GTS to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the GTS on.

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

    5. Select the Active Test on the GTS.

      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

    6. Select the Data List on the GTS.

      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

      		 -

    7. Check stop light relay operation and stop light assembly 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 (ENGINE ROOM JUNCTION BLOCK ASSEMBLY - SKID CONTROL ECU) Click here

    A

  7. CHECK HARNESS AND CONNECTOR (ENGINE ROOM JUNCTION BLOCK ASSEMBLY - SKID CONTROL ECU)


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

    2. Disconnect the A24 skid control ECU (brake booster with master cylinder assembly) connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      1G-3 (ACC) - A24-3 (STPO) Always Below 1 Ω
      1G-3 (ACC) or A24-3 (STPO) - Body ground Always 10 kΩ or higher

    4. Reconnect the A24 skid control ECU (brake booster with master cylinder assembly) connector.

    5. Install the engine room junction block assembly to the engine room relay block and junction block assembly.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  8. CHECK HARNESS AND CONNECTOR (ENGINE ROOM JUNCTION BLOCK ASSEMBLY - SKID CONTROL ECU)


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

    2. Disconnect the A24 skid control ECU (brake booster with master cylinder assembly) connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      1F-11 (STOP) - A24-6 (STP2) Always Below 1 Ω

    4. Reconnect the A24 skid control ECU (brake booster with master cylinder assembly) connector.

    5. Install the engine room junction block assembly to the engine room relay block and junction block assembly.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  9. CHECK HARNESS AND CONNECTOR (ENGINE ROOM JUNCTION BLOCK ASSEMBLY - SKID CONTROL ECU)


    1. Disconnect the A24 skid control ECU (brake booster with master cylinder assembly) connector.

    2. A0008BBE01
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A24-6 (STP2) - Body ground Stop light switch ON (Brake pedal depressed) 11 to 14 V
      A24-6 (STP2) - Body ground Stop light switch OFF (Brake pedal released) Below 1.5 V

    3. Reconnect the A24 skid control ECU (brake booster with master cylinder assembly) connector.


    NG

    REPLACE ENGINE ROOM JUNCTION BLOCK ASSEMBLY Click here

    OK

  10. CHECK FOR DTCs (DTC C1A4B)


    1. Connect the GTS to the DLC3.

    2. Turn the power switch on (IG).

    3. Clear the DTCs Click here.

    4. Perform the following to make sure that the DTC detection conditions are met.

      Tech Tips

      If the detection conditions are not met, the malfunction cannot be detected.


      1. Drive the vehicle at a speed for which cruise control operation is possible.

      2. Turn the cruise control system on using the cruise control switch (ON-OFF button).

      3. Push the cruise control switch to -/SET to begin control of vehicle speed using the cruise control system.

    5. Enter the following menus: Powertrain / Radar Cruise / Trouble Codes.

    6. Check for DTCs.

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

    7. Turn the power switch off.


    A

    END

    B

    REPLACE DRIVING SUPPORT ECU ASSEMBLY Click here