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) sends a stop light operation signal to the stop light control relay (STOP relay).

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

DTC No. Detection Item DTC Detection Condition Trouble Area
C1A4B Stop Light Relay Circuit

Either of the following conditions is met:


  • When the vehicle speed is approximately 50 km/h or more, the cruise control main 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 main 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

  • Wire harness or connector

  • STOP relay

  • Driving support ECU assembly

WIRING DIAGRAM

A01I57IE06

INSPECTION PROCEDURE

Note


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

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

  • 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.

PROCEDURE


  1. CHECK STOP LIGHT OPERATION


    1. Check that the stop lights operate Click here.

      OK
      Stop lights come on when the brake pedal is depressed, and go off when the brake pedal is released with the power switch on (IG).

    NG

    GO TO LIGHTING (EXT) Click here

    OK

  2. CHECK HARNESS AND CONNECTOR (POWER SOURCE)


    1. Turn the power switch off.

    2. Remove the STOP relay from the No. 2 engine room relay block and junction block assembly.

    3. A01I39ME01
      Text in Illustration
      *1 No. 2 Engine Room Relay Block and Junction Block Assembly (Relay Holder)

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      Relay holder terminal 5 - Body ground Power switch off 11 to 14 V
      Relay holder terminal 2 - Body ground Power switch on (IG) 11 to 14 V

    4. Turn the power switch OFF.

    5. Reinstall the STOP relay from the No. 2 engine room relay block and junction block assembly.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. CHECK HARNESS AND CONNECTOR (STP TERMINAL)


    1. Turn the power switch off.

    2. Disconnect the A28 skid control ECU (brake booster with master cylinder assembly) connector.

    3. A01I58BE19
      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
      A28-33 (STP) - Body ground Stop light switch assembly on (Brake pedal depressed) 11 to 14 V
      A28-33 (STP) - Body ground Stop light switch assembly off (Brake pedal released) Below 1.5 V

    4. Reconnect the A28 skid control ECU (brake booster with master cylinder assembly) connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  4. CHECK HARNESS AND CONNECTOR (STOP LIGHT VOLTAGE)


    1. Turn the power switch off.

    2. Remove the STOP relay from the No. 2 engine room relay block and junction block assembly.

    3. A01I39ME01
      Text in Illustration
      *1 No. 2 Engine Room Relay Block and Junction Block Assembly (Relay Holder)

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      Relay holder terminal 4 - Body ground

      Stop light switch assembly on

      (Brake pedal depressed)

      		 11 to 14 V
      Relay holder terminal 4 - Body ground

      Stop light switch assembly off

      (Brake pedal released)

      		 Below 1.5 V

    4. Reinstall the STOP relay from the No. 2 engine room relay block and junction block assembly.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  5. PERFORM ACTIVE TEST USING TECHSTREAM (STOP LIGHT RELAY, STOP LIGHT RELAY OUTPUT)


    1. Connect the Techstream to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the Techstream on.

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

    5. Perform Active Test according to the display on the Techstream.

      ABS/VSC/TRAC
      Tester Display Test Part Control Range Diagnostic Note
      Stop Light Relay Stop light control relay (STOP relay) ON or OFF Stop lights come on

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

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

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

      ON: Relay output on (Stop light on)

      OFF: Relay output off (Stop light off)

      		 -
      Result
      Result Proceed to
      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 (STOP RELAY - SKID CONTROL ECU (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY)) Click here

    A

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


    1. Turn the power switch off.

    2. Disconnect the A28 skid control ECU (brake booster with master cylinder assembly) connector.

    3. Remove the STOP relay from the No. 2 engine room relay block and junction block assembly.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      Relay holder terminal 1 - A28-3 (STPO) Always Below 1 Ω
      Relay holder terminal 1 or A28-3 (STPO) - Body ground Always 10 kΩ or higher

    5. Reinstall the STOP relay from the No. 2 engine room relay block and junction block assembly.

    6. Reconnect the A28 skid control ECU (brake booster with master cylinder assembly) connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

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


    1. Turn the power switch off.

    2. Disconnect the A28 skid control ECU (brake booster with master cylinder assembly) connector.

    3. Remove the STOP relay from the No. 2 engine room relay block and junction block assembly.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      Relay holder terminal 3 - A28-6 (STP2) Always Below 1 Ω
      Relay holder terminal 3 or A28-6 (STP2) - Body ground Always 10 kΩ or higher

    5. Reinstall the STOP relay from the No. 2 engine room relay block and junction block assembly.

    6. Reconnect the A28 skid control ECU (brake booster with master cylinder assembly) connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  8. CHECK HARNESS AND CONNECTOR (STP2 TERMINAL)


    1. Turn the power switch off.

    2. Disconnect the A28 skid control ECU (brake booster with master cylinder assembly) connector.

    3. A01I58BE20
      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
      A28-6 (STP2) - Body ground Stop light switch assembly on (Brake pedal depressed) 11 to 14 V
      A28-6 (STP2) - Body ground Stop light switch assembly off (Brake pedal released) Below 1.5 V

    4. Reconnect the A28 skid control ECU (brake booster with master cylinder assembly) connector.


    NG

    REPLACE STOP RELAY

    OK

  9. CHECK FOR DTC (PRE-COLLISION 2)


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

    2. Connect the Techstream to the DLC3.

    3. Turn the power switch on (IG).

    4. Turn the Techstream on.

    5. Clear the DTCs Click here.

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

      Tech Tips

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

    7. Enter the following menus: Body Electrical / Pre-Collision 2 / Trouble Codes.

    8. Check for DTCs.

      OK
      DTC C1A4B is not output.

    NG

    REPLACE DRIVING SUPPORT ECU ASSEMBLY

    OK

    END