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Home >> Lexus >> 2017 >> CT 200h Base >> Repair and Diagnosis (Single Page) >> Restraints >> Restraints Control Systems >> Pre-Collision System - Diagnostic Codes & Circuit Tests >> Pre-Collision System >> DTC C1A4B: Stop Light Relay Circuit [08/2014 - ] >> Procedure

DTC C1A4B: Stop Light Relay Circuit [08/2014 - ]: Procedure

  1. CHECK FOR DTCs (ABS/VSC/TRAC) 
    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 / Trouble Codes.
    5. Check for DTCs.

      Result

      Result Proceed to
      DTC is not output A
      DTC is output B
    6. Turn the power switch off.

    Result:  B

    B 

    GO TO ELECTRONICALLY CONTROLLED BRAKE SYSTEM 

    (Refer to How To Proceed With Troubleshooting [08/2014 - ] )

    Result:  A

    A 

    Refer to  2

  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:  NG

    NG 

    INSPECT LIGHTING SYSTEM (STOP LIGHT CIRCUIT) 

    Result:  OK

    OK 

    Refer to  3

  3. INSPECT STOP LIGHT SWITCH ASSEMBLY 
    1. Inspect the stop light switch assembly (Refer to Inspection [08/2014 - ] ).

      OK

      The stop light switch assembly is normal.

    Result:  NG

    NG 

    REPLACE STOP LIGHT SWITCH ASSEMBLY 

    (Refer to Components [08/2014 - ] )

    Result:  OK

    OK 

    Refer to  4

  4. CHECK HARNESS AND CONNECTOR (STP2 TERMINAL) 
    1. Turn the power switch off.
    2. Disconnect the skid control ECU (brake booster with master cylinder assembly) connector.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A61-6 (STP2) - Body ground Stop light switch assembly ON (Brake pedal depressed) 11 to 14 V
      A61-6 (STP2) - Body ground Stop light switch assembly OFF (Brake pedal released) Below 1.5 V
    4. Reconnect the skid control ECU (brake booster with master cylinder assembly) connector.

    Result:  NG

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (STP2 CIRCUIT) 

    Result:  OK

    OK 

    Refer to  5

  5. PERFORM ACTIVE TEST USING TECHSTREAM (STOP LIGHT RELAY) 
    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. Select the Active Test on the Techstream.
      ABS/VSC/TRAC

      Tester Display Test Part Control Range Diagnostic Note
      Stop Light Relay Stop light control relay Relay ON/OFF Stop lights come on
    6. Perform the Active Test of the stop light control relay (stop light switch assembly) using the Techstream.
    7. Select the Data List on the Techstream.
      ABS/VSC/TRAC

      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      Stop Light Relay Output Stop light control relay output / ON or OFF ON: Relay output on
      OFF: Relay output off      		 -
    8. Check for stop light switch assembly operation using the Data List and stop light operation by performing an Active Test.

      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
    9. Turn the power switch off.

    Result:  B

    B 

    Refer to  7

    Result:  A

    A 

    Refer to  6

  6. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - SKID CONTROL ECU) 
    1. Turn the power switch off.
    2. Disconnect the stop light switch assembly connector.
    3. Disconnect the skid control ECU (brake booster with master cylinder assembly) connector.
    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A25-4 (ACC) - A61-3 (STPO) Always Below 1 Ω
      A25-4 (ACC) or A61-3 (STPO) - Body ground Always 10 kΩ or higher

    Result:  NG

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result:  OK

    OK 

    Refer to  7

  7. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - SKID CONTROL ECU) 
    1. Turn the power switch off.
    2. Disconnect the stop light switch assembly connector.
    3. Disconnect the skid control ECU (brake booster with master cylinder assembly) connector.
    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A25-1 (OUT) - A61-33 (STP) Always Below 1 Ω
    5. Reconnect the skid control ECU (brake booster with master cylinder assembly) connector.
    6. Reconnect the stop light switch assembly connector.

    Result:  NG

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result:  OK

    OK 

    Refer to  8

  8. CHECK HARNESS AND CONNECTOR (STP TERMINAL) 
    1. Turn the power switch off.
    2. Make sure that there is no looseness at the locking part and the connecting part of the connector.
    3. Disconnect the skid control ECU (brake booster with master cylinder assembly) connector.
    4. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A61-33 (STP) - Body ground Stop light switch ON (Brake pedal depressed) 11 to 14 V
      A61-33 (STP) - Body ground Stop light switch OFF (Brake pedal released) Below 1.5 V
    5. Reconnect the skid control ECU (brake booster with master cylinder assembly) connector.

    Result:  NG

    NG 

    REPLACE STOP LIGHT SWITCH ASSEMBLY 

    (Refer to Components [08/2014 - ] )

    Result:  OK

    OK 

    Refer to  9

  9. CHECK FOR DTCs (DTC C1A4B) 
    1. Connect the Techstream to the DLC3.
    2. Turn the power switch on (IG).
    3. Clear the DTCs (Refer to DTC Check / Clear [08/2014 - ] ).
    4. Turn the power switch on (IG).
    5. Turn the Techstream on.
    6. Enter the following menus: Chassis / ABS/VSC/TRAC / Active Test.
    7. Select the Active Test on the Techstream.
      ABS/VSC/TRAC

      Tester Display Test Part Control Range Diagnostic Note
      Stop Light Relay Stop light control relay Relay ON/OFF Stop lights come on
    8. Perform the Active Test of the stop light control relay (stop light switch assembly) using the Techstream.
    9. Select the Data List on the Techstream.
      ABS/VSC/TRAC

      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      Stop Light Relay Output Stop light control relay output / ON or OFF ON: Relay output on
      OFF: Relay output off      		 -
    10. Check for stop light switch assembly operation using the Data List and stop light operation by performing an Active Test.
    11. Recheck for DTCs (Refer to DTC Check / Clear [08/2014 - ] ).

      OK

      DTC C1A4B is not output.

    Result:  OK

    OK 

    END 

    Result:  NG

    NG 

    REPLACE DRIVING SUPPORT ECU ASSEMBLY 

    (Refer to Components [08/2014 - ] )

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