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 ECU. 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

Either of the following conditions is met:

  • When the engine 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 engine 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

  • Vehicle stability control system

  • Harness or connector

  • Stop light control ECU

  • Driving support ECU

Driving Support ECU (Pre-Crash 2)

WIRING DIAGRAM

E284910E01

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.

Tip:

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 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

    GO TO LIGHTING SYSTEM

    Click here

    OK

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

    1. Disconnect the A66 stop light control ECU connector.

    2. E173014C06

      *a

      Front view of wire harness connector

      (to Stop Light Control ECU)

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

      Standard Voltage

      Tester Connection

      Condition

      Specified Condition

      A66-6 (+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

      A66-8 (GND) - Body ground

      Always

      Below 1 Ω

    Result

    Proceed to

    OK

    NG
    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. 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

      11 to 14 V

      Brake pedal released

      Below 1.5 V

    Result

    Proceed to

    OK

    NG
    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  4. CHECK TERMINAL VOLTAGE (STP)

    1. Disconnect the A66 stop light control ECU connector.

    2. E173014C07

      *a

      Front view of wire harness connector

      (to Stop Light Control ECU)

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

      Standard Voltage

      Tester Connection

      Condition

      Specified Condition

      A66-5 (STP) - Body ground

      Brake pedal depressed

      11 to 14 V

      Brake pedal released

      Below 1.5 V

    Result

    Proceed to

    OK

    NG
    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 engine switch on (IG).

    3. Turn the intelligent tester on.

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

      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).

      Chassis > ABS/VSC/TRC > Active Test

      Tester Display

      Stop Light Relay

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

    Result

    Proceed to

    Proceed to

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

    A

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

    B
    B

    CHECK HARNESS AND CONNECTOR (STOP LIGHT CONTROL ECU - SKID CONTROL ECU)Click here

    A

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

    1. Disconnect the A66 stop light control ECU connector.

    2. Disconnect the A7 skid control ECU connector.

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

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      A66-9 (ACC) - A7-16 (STPO)

      Always

      Below 1 Ω

      A66-9 (ACC) - Body ground

      Always

      10 kΩ or higher

    Result

    Proceed to

    OK

    NG
    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

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

    1. Disconnect the A66 stop light control ECU connector.

    2. Disconnect the A7 skid control ECU connector.

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

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      A66-1 (OUT) - A7-45 (STP2)

      Always

      Below 1 Ω

    Result

    Proceed to

    OK

    NG
    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  8. 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

      11 to 14 V

      Brake pedal released

      Below 1.5 V

    Result

    Proceed to

    OK

    NG
    NG

    REPLACE STOP LIGHT CONTROL ECU ASSEMBLY

    Click here

    OK

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

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

    2. Clear the DTCs .

      Click here

      Body Electrical > Pre-Crash > Clear DTCs

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

      Tip:

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

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

    4. Check for DTCs .

      Click here

      Body Electrical > Pre-Crash > Trouble Codes

      Note:

      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 anothervehicle 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.

      OK

      DTCs C1A4B are not output.

    Result

    Proceed to

    OK

    NG
    OK

    END

    NG

    REPLACE DRIVING SUPPORT ECU

    Click here