PRE-CRASH SAFETY SYSTEM, Diagnostic DTC:C1A4B

DTC Code DTC Name
C1A4B Stop Light Relay Circuit

DESCRIPTION

The brake booster with master cylinder (skid control ECU) sends a stop light operation signal to the stop light switch assembly. When the brake booster with master cylinder (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 vehicle speed is approximately 50 km/h or more, the cruise control switch (ON-OFF button) is on, 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 vehicle speed is approximately 50 km/h or more, the cruise control switch (ON-OFF button) is on, 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

  • Harness or connector

  • Stop light switch assembly

  • Driving support ECU assembly

WIRING DIAGRAM

A005AMYE21

CAUTION / NOTICE / HINT

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. 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 TERMINAL VOLTAGE (POWER SOURCE OF STOP LIGHT SWITCH ASSEMBLY)


    1. Turn the power switch off.

    2. Disconnect the A79 stop light switch assembly connector.

    3. A005DBBE02
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Switch Assembly)

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A79-7 (B) - Body ground Always 11 to 14 V

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A79-2 (GND) - Body ground Always Below 1 Ω

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. CHECK TERMINAL VOLTAGE (STP TERMINAL)


    1. Turn the power switch off.

    2. Disconnect the brake booster with master cylinder (skid control ECU) A58 connector.

    3. A005ELLE01
      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
      A58-33 (STP) - Body ground Brake pedal depressed 11 to 14 V
      A58-33 (STP) - Body ground Brake pedal released Below 1.5 V

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  4. CHECK TERMINAL VOLTAGE (STP TERMINAL)


    1. Turn the power switch off.

    2. Disconnect the A79 stop light switch assembly connector.

    3. A005DWRE02
      Text in Illustration
      *a

      Front view of wire harness connector

      (to Stop Light Switch Assembly)

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A79-1 (OUT) - Body ground Brake pedal depressed 11 to 14 V
      A79-1 (OUT) - Body ground Brake pedal released Below 1.5 V

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

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


    1. Enter the following menus: Chassis / ABS/VSC/TRAC / Active Test.

    2. Perform "Active Test" according to the display on GTS.

      ABS/VSC/TRAC
      Tester Display Measurement Item Control Range Diagnostic Note
      Stop Light Relay Stop light switch assembly (STOP LP) ON or OFF Stop lights come on

    3. Enter the following menus: Chassis / ABS/VSC/TRAC / Data List.

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

      Stop light switch assembly (STOP LP) output/

      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 (SKID CONTROL ECU - STOP LIGHT SWITCH ASSEMBLY) Click here

    A

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


    1. Turn the power switch off.

    2. Disconnect the A58 brake booster with master cylinder (skid control ECU) connector.

    3. Disconnect the A79 stop light switch assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A58-3 (STPO) - A79-4 (ACC) Always Below 1 Ω
      A58-3 (STPO) or A79-4 (ACC) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

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


    1. Turn the power switch off.

    2. Disconnect the A58 brake booster with master cylinder (skid control ECU) connector.

    3. Disconnect the A79 stop light switch assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A58-6 (STP2) - A79-3 (L) Always Below 1 Ω
      A58-6 (STP2) or A79-3 (L) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  8. CHECK TERMINAL VOLTAGE (STP2 TERMINAL)


    1. Turn the power switch off.

    2. Disconnect the A58 brake booster with master cylinder (skid control ECU) connector.

    3. A005E4HE01
      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
      A58-6 (STP2) - Body ground Brake pedal depressed 11 to 14 V
      A58-6 (STP2) - Body ground Brake pedal released Below 1.5 V

    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY 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 GTS, 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 assembly, always replace it with a new one. If a driving support ECU assembly which was installed to another vehicle is used, the information stored in the driving support ECU assembly will not match the information from the vehicle. As a result, a DTC may be stored.


    A

    END

    B

    REPLACE DRIVING SUPPORT ECU ASSEMBLY Click here