PRE-CRASH SAFETY SYSTEM, Diagnostic DTC:C1A4B

DTC Code DTC Name
C1A4B Stop Light Relay Circuit

DESCRIPTION

The skid control ECU outputs a stop light operation signal to the stop light control relay. When the skid control ECU detects a malfunction in the stop light circuit, the driving support ECU outputs DTC C1A4B.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

DTC Output from

C1A4B

Stop Light Relay Circuit

  • For the pre-crash safety system:

    • The engine switch is on (IG).

  • For the radar cruise control system:

    • The vehicle is being driven at 50 km/h (31 mph) or more and the ACC main switch is ON.

When the skid control ECU detects a malfunction* in the stop light relay circuit, the skid control ECU sends a malfunction warning signal via CAN to the driving support ECU and a DTC is output.

*: Condition for skid control ECU malfunction warning signal output. When the voltage at the IG1 terminal is between 11 and 14 V and the stop light illumination output (STP0) is ON, there is no input signal to the STP2 terminal for 5 seconds or more, or when the input signals to terminals STP and STP2 are different for 5 seconds or more when the voltage at the IG1 terminal is between 11 and 14 V and the stop light illumination output (STP0) is OFF.

  • Lighting system

  • Harness or connector

  • STOP LP relay

  • Stop light control relay

  • Driving support ECU

Driving Support ECU (Pre-Crash 2)

WIRING DIAGRAM

E260081E01

CAUTION / NOTICE / HINT

Note:

  • When replacing the master cylinder solenoid, perform calibration Click here.

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

  • When replacing the driving support ECU, always replace it with a new one and be sure to perform initialization (Click here). If an ECU which was installed to another vehicle is used, the information stored in the ECU will not match the information from the vehicle, and as a result, a DTC may be stored.

Tip:

  • When DTC C1425 is output together with DTC C1380, inspect and repair the trouble areas indicated by DTC C1425 first Click here.

  • This circuit uses CAN communication. Therefore, if there are any malfunctions in the communication circuit, one or more DTCs in the CAN communication system are output.

PROCEDURE

  1. CHECK FOR DTC (VEHICLE STABILITY CONTROL SYSTEM)

    1. Check for DTCs.

      Click here

      Body Electrical > Pre-Crash > Trouble Codes

      OK

      Vehicle stability control system DTCs are not output.

    Result

    Result

    OK

    NG
    NG

    GO TO VEHICLE STABILITY CONTROL SYSTEM

    Click here

    OK

  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

    Result

    OK

    NG
    NG

    CHECK TERMINAL VOLTAGE AND RESISTANCE (+B, GND)Click here

    OK

  3. READ VALUE USING INTELLIGENT TESTER (STOP LIGHT SW)

    1. Turn the engine switch off.

    2. Connect the intelligent tester to the DLC3.

    3. Turn the engine switch on (IG).

    4. Turn the intelligent tester on.

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

      Chassis > ABS/VSC/TRC > Data List

      Tester Display

      Stop Light SW

      Chassis > ABS/VSC/TRC > Data List

      Tester Display

      Measurement Item

      Range

      Normal Condition

      Diagnostic Note

      Stop Light SW

      Stop light switch

      ON or OFF

      ON: Brake pedal depressed

      OFF: Brake pedal released

      -

    6. Check that the stop light switch condition observed on the intelligent tester changes according to brake pedal operation.

      OK

      The intelligent tester displays ON or OFF according to brake pedal operation.

    Result

    Result

    OK

    NG
    NG

    CHECK TERMINAL VOLTAGE (STP)Click here

    OK

  4. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (STOP LIGHT RELAY)

    1. Turn the engine switch off.

    2. Connect the intelligent tester to the DLC3.

    3. Turn the engine switch on (IG).

    4. Turn the intelligent tester on.

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

      Chassis > ABS/VSC/TRC > Active Test

      Tester Display

      Stop Light Relay

      Chassis > ABS/VSC/TRC > Active Test

      Tester Display

      Measurement Item

      Control Range

      Diagnostic Note

      Stop Light Relay

      STOP LP relay

      Relay ON/OFF

      Observe the stop lights (do not come on for 2 to 5 seconds).

    6. While performing the Active Test, check the illumination condition of the stop lights and "Stop Light Relay Output" in the Data List.

    Result

    Result

    Proceed to

    When Active Test performed, Data List item changes between ON and OFF and stop lights turn on and off

    A

    When Active Test performed, Data List item changes between ON and OFF, but stop lights do not turn on

    B
    B

    INSPECT STOP LP RELAYClick here

    A

  5. CHECK TERMINAL VOLTAGE (STP2)

    1. Disconnect the A7 skid control ECU connector.

    2. C214161C25

      *a

      Front view of wire harness connector

      (to Skid Control ECU)

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

      Standard Voltage

      Tester Connection

      Condition

      Specified Condition

      A7-45 (STP2) - Body ground

      Brake pedal depressed

      8 to 14 V

      Brake pedal released

      Below 1.5 V

    Result

    Result

    OK

    NG
    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  6. RECONFIRM DTC

    1. Clear the DTCs.

      Click here

    2. Start the engine.

    3. Perform a road test.

    4. Check if the same DTC is output.

      Click here

      Result

      Result

      Proceed to

      DTC is not output

      A

      DTC is output

      B
    A

    USE SIMULATION METHOD TO CHECK

    Click here

    B

    REPLACE MASTER CYLINDER SOLENOID

    Click here

  7. INSPECT STOP LP RELAY

    1. Remove the STOP LP relay from the engine room relay block.

    2. A087121C03

      *1

      STOP LP relay

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

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      3 - 4

      Battery positive voltage is applied to terminal 1 and battery negative voltage is applied to terminal 2

      10 kΩ or higher

      Battery positive voltage is not applied to terminal 1 and battery negative voltage is not applied to terminal 2

      Below 1 Ω

      3 - 5

      Battery positive voltage is applied to terminal 1 and battery negative voltage is applied to terminal 2

      Below 1 Ω

      Battery positive voltage is not applied to terminal 1 and battery negative voltage is not applied to terminal 2

      10 kΩ or higher

    Result

    Result

    OK

    NG
    NG

    REPLACE STOP LP RELAY

    OK

  8. CHECK TERMINAL VOLTAGE (STOP LP RELAY POWER SOURCE TERMINAL)

    1. Remove the STOP LP relay from the engine room relay block.

    2. C220884C02

      *a

      Component without STOP LP Relay

      (Engine Room Relay Block)

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

      Standard Voltage

      Tester Connection

      Condition

      Specified Condition

      1 - Body ground

      Engine switch on (IG)

      8 to 14 V

      5 - Body ground

      Always

      11 to 14 V

    Result

    Result

    OK

    NG
    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  9. CHECK TERMINAL VOLTAGE (STPO)

    1. Disconnect the A7 skid control ECU connector.

    2. C214161C27

      *a

      Front view of wire harness connector

      (to Skid Control ECU)

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

      Standard Voltage

      Tester Connection

      Condition

      Specified Condition

      A7-16 (STPO) - Body ground

      Engine switch on (IG)

      11 to 14 V

    Result

    Result

    OK

    NG
    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  10. RECONFIRM DTC

    1. Clear the DTCs.

      Click here

      Body Electrical > Pre-Crash > Clear DTCs

    2. Turn the engine switch off.

    3. Check if the same DTC is output.

      Click here

      Body Electrical > Pre-Crash > Trouble Codes

    Result

    Result

    Proceed to

    DTC is not output

    A

    DTC is output

    B
    B

    USE SIMULATION METHOD TO CHECK

    Click here

    A

  11. REPLACE MASTER CYLINDER SOLENOID

    1. Temporally replace the Master cylinder solenoid with a new or normally function one .

      Click here

    Result

    Result

    NEXT
    NEXT

  12. CHECK FOR DTC (PRE-CRASH SAFETY SYSTEM)

    1. Clear the DTCs .

      Body Electrical > Pre-Crash > Clear DTCs

      Click here

      Tip:

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

      • Pre-crash safety system:

      1. Turn the engine switch off.

      2. Connect the intelligent tester to the DLC3.

      3. Turn the engine switch on (IG).

      4. Turn the intelligent tester on.

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

        Chassis > ABS/VSC/TRC > Active Test

        Tester Display

        Stop Light Relay

        Chassis > ABS/VSC/TRC > Active Test

        Tester Display

        Measurement Item

        Control Range

        Diagnostic Note

        Stop Light Relay

        STOP LP relay

        Relay ON/OFF

        Observe the stop lights (do not come on for 2 to 5 seconds).

      6. While performing the Active Test, check the illumination condition of the stop lights and "Stop Light Relay Output" in the Data List.

        Chassis > ABS/VSC/TRC > Data List

        Tester Display

        Stop Light Relay Output

        Chassis > ABS/VSC/TRC > Data List

        Tester Display

        Measurement Item

        Range

        Normal Condition

        Diagnostic Note

        Stop Light Relay Output

        STOP LP relay output

        ON or OFF

        ON: Relay output on (Stop lights on)

        OFF: Relay output off (Stop lights off)

        -

    2. Make sure the following conditions are met:

      • Radar cruise control system:

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

    3. Check for DTCs .

      Click here

      Body Electrical > Pre-Crash > Trouble Codes

      OK

      DTCs C1A4B are not output.

    Result

    Result

    OK

    NG
    OK

    END

    NG

    REPLACE DRIVING SUPPORT ECU

    Click here

  13. CHECK TERMINAL VOLTAGE (STP)

    1. Disconnect the A7 skid control ECU connector.

    2. C214161C26

      (to Skid Control ECU)

      *a

      Front view of wire harness connector

      (to Skid Control ECU)

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

      Standard Voltage

      Tester Connection

      Condition

      Specified Condition

      A7-7 (STP) - Body ground

      Brake pedal depressed

      8 to 14 V

      Brake pedal released

      Below 1.5 V

    Result

    Result

    OK

    NG
    OK

    REPLACE MASTER CYLINDER SOLENOID

    Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  14. CHECK TERMINAL VOLTAGE AND RESISTANCE (+B, GND)

    1. Disconnect the A6 stop light control relay connector.

    2. C206543C03

      *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

      A6-6 (+B) - Body ground

      Always

      11 to 14 V

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

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      A6-4 (GND) - Body ground

      Always

      Below 1 Ω

    Result

    Result

    OK

    NG
    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  15. CHECK TERMINAL VOLTAGE (STP)

    1. Disconnect the A6 stop light control relay connector.

    2. C206543C04

      *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

      A6-2 (STP) - Body ground

      Brake pedal depressed

      8 to 14 V

      Brake pedal released

      Below 1.5 V

    Result

    Result

    OK

    NG
    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  16. INSPECT STOP LP RELAY

    1. Remove the STOP LP relay from the engine room relay block.

    2. A087121C03

      *1

      STOP LP relay

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

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      3 - 4

      Battery positive voltage is applied to terminal 1 and battery negative voltage is applied to terminal 2

      10 kΩ or higher

      Battery positive voltage is not applied to terminal 1 and battery negative voltage is not applied to terminal 2

      Below 1 Ω

      3 - 5

      Battery positive voltage is applied to terminal 1 and battery negative voltage is applied to terminal 2

      Below 1 Ω

      Battery positive voltage is not applied to terminal 1 and battery negative voltage is not applied to terminal 2

      10 kΩ or higher

    Result

    Result

    OK

    NG
    NG

    REPLACE STOP LP RELAY

    OK

  17. CHECK HARNESS AND CONNECTOR (STOP LIGHT CONTROL RELAY - STOP LP RELAY)

    1. Disconnect the A6 stop light control relay connector.

    2. Remove the STOP LP relay from the engine room relay block.

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

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      A6-8 (OUT) - Engine room relay block STOP LP relay terminal 4

      Always

      Below 1 Ω

      A6-8 (OUT) - Body ground

      Always

      10 kΩ or higher

    Result

    Result

    OK

    NG
    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  18. CHECK TERMINAL VOLTAGE (STOP LIGHT POWER SOURCE TERMINAL)

    1. Remove the STOP LP relay from the engine room relay block.

    2. C220884C02

      *a

      Component without STOP LP Relay

      (Engine Room Relay Block)

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

      Standard Voltage

      Tester Connection

      Condition

      Specified Condition

      4 - Body ground

      Brake pedal depressed

      8 to 14 V

      Brake pedal released

      Below 1.5 V

    Result

    Result

    OK

    NG
    OK

    REPAIR OR REPLACE HARNESS OR CONNECTOR (ENGINE ROOM RELAY BLOCK STOP LP RELAY TERMINAL 3 CIRCUIT)

    NG

    REPLACE STOP LIGHT CONTROL RELAY ASSEMBLY

    Click here