PRE-CRASH SAFETY SYSTEM, Diagnostic DTC:C1A4B

DTC Code DTC Name
C1A4B Stop Light Relay Circuit

DESCRIPTION

The brake booster with master cylinder assembly (skid control ECU) sends a stop light operation signal to the stop light control relay.

When the brake booster with master cylinder assembly (skid control ECU) detects a malfunction in the stop light circuit, the driving support ECU assembly stores DTC C1A4B.

DTC No. DTC Detection Condition Trouble Area
C1A4B

Either of the following conditions is met:


  • When the power switch is on (IG), the IG1 terminal voltage is between 11 and 14 V and the stop light illumination output signal (STPO) is output, the signal is not received at terminal STP2 for 0.3 seconds or more.

  • When the power switch is on (IG), the IG1 terminal voltage is between 11 and 14 V and the stop light illumination output signal (STPO) is not output, the signals received at terminals STP and STP2 are different for 0.3 seconds or more.

  • Lighting system

  • Electronically controlled brake system

  • Stop light control relay

  • Driving support ECU

  • Harness or connector

WIRING DIAGRAM

A003Y6RE05

INSPECTION PROCEDURE

Note


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

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

PROCEDURE


  1. CHECK STOP LIGHT OPERATION


    1. Turn the power switch on (IG).

    2. 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 Click here

    OK

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


    1. Turn the power switch off.

    2. Disconnect the A27 stop light control relay connector.

    3. A003VDPE08
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Control Relay)

      Measure the voltage and resistance 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
      Standard Resistance
      Tester Connection Condition Specified Condition
      A27-8 (GND) - Body ground Always Below 1 Ω

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER (SKID CONTROL ECU) - AUXILIARY BATTERY)


    1. Turn the power switch off.

    2. Disconnect the A61 brake booster with master cylinder (skid control ECU) connector.

    3. A003V37E09
      Text in Illustration
      *a

      Front view of wire harness connector

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

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

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

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  4. CHECK HARNESS AND CONNECTOR (STOP LIGHT CONTROL RELAY - AUXILIARY BATTERY)


    1. Turn the power switch off.

    2. Disconnect the A27 stop light control relay connector.

    3. A003VDPE07
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Control Relay)

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A27-5 (STP) - Body ground Brake pedal depressed 11 to 14 V
      A27-5 (STP) - Body ground Brake pedal released Below 1.5 V

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  5. 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. Perform "Active Test" according to the display on intelligent tester.

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

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

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

      ABS/VSC/TRC
      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      Stop Light Relay Output

      Stop light control relay

      ON or OFF

      ON: Relay output on (Stop light on)

      OFF: Relay output off (Stop light off)

      		 -
      Result
      Result Result
      Data List item changes between ON and OFF, but stop lights do not turn on A
      Data List item changes between ON and OFF and stop lights turn on and off B

    B

    CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER (SKID CONTROL ECU) - STOP LIGHT CONTROL RELAY) Click here

    A

  6. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER (SKID CONTROL ECU) - STOP LIGHT CONTROL RELAY)


    1. Turn the power switch off.

    2. Disconnect the A61 brake booster with master cylinder (skid control ECU) connector.

    3. Disconnect the A27 stop light control relay connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A61-3 (STPO) - A27-9 (ACC) Always Below 1 Ω
      A61-3 (STPO) or A27-9 (ACC) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  7. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER (SKID CONTROL ECU) - STOP LIGHT CONTROL RELAY)


    1. Turn the power switch off.

    2. Disconnect the A61 brake booster with master cylinder (skid control ECU) connector.

    3. Disconnect the A27 stop light control relay connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A61-6 (STP2) - A27-1 (OUT) Always Below 1 Ω

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  8. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER (SKID CONTROL ECU) - STOP LIGHT CONTROL RELAY)


    1. Turn the power switch off.

    2. Disconnect the A61 brake booster with master cylinder (skid control ECU) connector.

    3. A003V37E10
      Text in Illustration
      *a

      Front view of wire harness connector

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

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

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

    NG

    REPLACE STOP LIGHT CONTROL RELAY Click here

    OK

  9. CHECK FOR DTCs (RADAR CRUISE)


    1. Turn the power switch off and wait for at least 2 minutes.

    2. Clear the DTCs Click here.

    3. Make sure that the DTC detection conditions are met.

      Tech Tips

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


      • Using the intelligent tester, perform the Active Test "Stop Light Relay" with the power switch on (IG).

    4. Check for DTCs Click here.

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

      Note

      When replacing the driving support ECU, always replace it with a new one. If a driving support ECU which was installed to another vehicle is used, the information stored in the driving support ECU will not match the information from the vehicle. As a result, a DTC may be stored.


    B

    REPLACE DRIVING SUPPORT ECU Click here

    A

    END