PRE-CRASH SAFETY SYSTEM, Diagnostic DTC:C1A4B

DTC Code DTC Name
C1A4B Stop Light Relay Circuit

DESCRIPTION

The skid control ECU (brake actuator assembly) sends a stop light operation signal to the stop light control relay (STOP LP relay). When the skid control ECU (brake actuator 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 While the engine switch is on (IG), the skid control ECU 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.

  • Lighting system

  • Vehicle stability control system

  • Harness or connector

  • Stop light switch assembly

  • Stop light control relay (STOP LP relay)

  • Skid control ECU (brake actuator assembly)

  • Driving support ECU assembly

WIRING DIAGRAM

A018KWNE02

CAUTION / NOTICE / HINT

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 FOR DTC (ABS/VSC/TRC)


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

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

    5. Check for DTCs.


      Chassis > ABS/VSC/TRC > Trouble Codes
      Result
      Result Proceed to
      Vehicle stability control system DTCs are not output A
      Vehicle stability control system DTCs are output B

    6. Turn the engine switch off.


    B

    GO TO DTC CHART (VEHICLE STABILITY CONTROL 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
      Result
      Proceed to
      OK
      NG

    NG

    INSPECT LIGHTING SYSTEM (STOP LIGHT CIRCUIT) Click here

    OK

  3. INSPECT STOP LIGHT SWITCH ASSEMBLY


    1. Inspect the stop light switch assembly.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    OK

  4. CHECK HARNESS AND CONNECTOR (STP TERMINAL)


    1. Turn the engine switch on (IG).

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

    3. Disconnect the A47 skid control ECU (brake actuator assembly) connector.

    4. A018LQJC59
      *a

      Front view of wire harness connector

      (to Skid Control ECU (Brake Actuator Assembly))

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A47-2 (STP) - Body ground Stop light switch assembly on (Brake pedal depressed) 11 to 14 V
      A47-2 (STP) - Body ground Stop light switch assembly off (Brake pedal released) Below 1.5 V

    5. Reconnect the A47 skid control ECU (brake actuator assembly) connector.

    6. Turn the engine switch off.

      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STP TERMINAL)

    OK

  5. CHECK STOP LIGHT CONTROL RELAY (STOP LP RELAY)


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

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

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


      Chassis > ABS/VSC/TRC > Active Test
      Tester Display Measurement Item Control Range Diagnostic Note
      Stop Light Relay Stop light control relay (STOP LP relay) ON or OFF Stop lights come on

      Chassis > ABS/VSC/TRC > Active Test
      Tester Display
      Stop Light Relay

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

    7. Check the Data List for proper functioning of the stop light control relay (STOP LP relay).


      Chassis > ABS/VSC/TRC > Data List
      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      Stop Light Relay Output Stop light control relay (STOP LP relay) output ON or OFF

      ON: Relay output on (Stop light on)

      OFF: Relay output off (Stop light off)

      		 -

      Chassis > ABS/VSC/TRC > Data List
      Tester Display
      Stop Light Relay Output
      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 engine switch off.


    B

    CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - POWER SOURCE) Click here

    A

  6. CHECK HARNESS AND CONNECTOR (STOP LP RELAY - SKID CONTROL ECU)


    1. Remove the stop light control relay (STOP LP relay) from the engine room relay block and junction block assembly.

    2. Disconnect the A47 skid control ECU (brake actuator assembly) connector.

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

      Standard Resistance (Check for Open)
      Tester Connection Condition Specified Condition
      Relay terminal 1 - A47-31 (STPO) Always Below 1 Ω
      Relay terminal 3 - A47-2 (STP) Always Below 1 Ω
      Relay terminal 4 - A47-22 (STP2) Always Below 1 Ω
      Standard Resistance (Check for Short)
      Tester Connection Condition Specified Condition
      Relay terminal 1 or A47-31 (STPO) - Body ground Always 10 kΩ or higher
      Relay terminal 3 or A47-2 (STP) - Body ground Always 10 kΩ or higher
      Relay terminal 4 or A47-22 (STP2) - Body ground Always 10 kΩ or higher

    4. Reinstall the stop light control relay (STOP LP relay) to the engine room relay block and junction block assembly.

    5. Reconnect the A47 skid control ECU (brake actuator assembly) connector.

      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LP RELAY - SKID CONTROL ECU)

    OK

  7. CHECK HARNESS AND CONNECTOR (STP2 TERMINAL)


    1. Turn the engine switch on (IG).

    2. Disconnect the A47 skid control ECU (brake actuator assembly) connector.

    3. A018LQJC60
      *a

      Front view of wire harness connector

      (to Skid Control ECU (Brake Actuator Assembly))

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A47-22 (STP2) - Body ground Stop light switch assembly on (Brake pedal depressed) 11 to 14 V
      A47-22 (STP2) - Body ground Stop light switch assembly off (Brake pedal released) Below 1.5 V

    4. Reconnect the A47 skid control ECU (brake actuator assembly) connector.

      Result
      Proceed to
      OK
      NG

    5. Turn the engine switch off.


    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    OK

  8. CHECK FOR DTC (PRE-CRASH 2)


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Clear the DTCs.

      Click here

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

      Tech Tips

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

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

    6. Check for DTCs.


      Body Electrical > Pre-Crash 2 > Trouble Codes
      Result
      Result Proceed to
      DTC C1A4B is not output. A
      DTC C1A4B is output. B

    7. Turn the engine switch off.


    A

    END (STOP LIGHT CONTROL RELAY (STOP LP RELAY) WAS DEFECTIVE)

    B

  9. REPLACE BRAKE ACTUATOR ASSEMBLY


    1. Replace the brake actuator assembly.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

  10. CHECK FOR DTC (PRE-CRASH 2)


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Clear the DTCs.

      Click here

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

      Tech Tips

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

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

    6. Check for DTCs.


      Body Electrical > Pre-Crash 2 > Trouble Codes
      Result
      Result Proceed to
      DTC C1A4B is not output A
      DTC C1A4B is output B

    7. Turn the engine switch off.


    A

    END

    B

    REPLACE DRIVING SUPPORT ECU ASSEMBLY Click here

  11. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - POWER SOURCE)


    1. Disconnect the A54 stop light switch assembly connector.

    2. A018LLMC01
      *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
      A54-2 - Body ground Always 11 to 14 V

    3. Reconnect the A54 stop light switch assembly connector.

      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - POWER SOURCE)

    OK

  12. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - ECM)


    1. Disconnect the A54 stop light switch assembly connector.

    2. Disconnect the A43 ECM connector.

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

      Standard Resistance (Check for Open)
      Tester Connection Condition Specified Condition
      A54-3 - A43-36 (ST1-) Always Below 1 Ω
      A54-1 - A43-51 (STP) Always Below 1 Ω
      Standard Resistance (Check for Short)
      Tester Connection Condition Specified Condition
      A54-3 or A43-36 (ST1-) - Body ground Always 10 kΩ or higher
      A54-1 or A43-51 (STP) - Body ground Always 10 kΩ or higher

    4. Reconnect the A54 stop light switch assembly connector.

    5. Reconnect the A43 ECM connector.

      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - ECM)

    OK

  13. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - BODY GROUND)


    1. Disconnect the A54 stop light switch assembly connector.

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

      Standard Resistance (Check for Short)
      Tester Connection Condition Specified Condition
      A54-1 - Body ground Always 10 kΩ or higher
      A54-3 - Body ground Always 10 kΩ or higher

    3. Reconnect the A54 stop light switch assembly connector.

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE ECM Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - BODY GROUND)