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Home >> Lexus >> 2021 >> LS 500h AWD >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Electronically Controlled Brake System (W/O Advanced Park) - Diagnostic Codes (3 Of 3) & Symptom Tests >> ELECTRONICALLY CONTROLLED BRAKE SYSTEM (w/o Advanced Park) >> Brake Control Warning Light does not Come ON [10/2020 - 10/2023] >> Procedure

Brake Control Warning Light does not Come ON [10/2020 - 10/2023]: Procedure

  1. CHECK CAN COMMUNICATION SYSTEM 
    1. Check if CAN communication system DTCs are output.

      Refer to DIAGNOSIS SYSTEM [10/2020 - 11/2021] , or refer to DIAGNOSIS SYSTEM [11/2021 - 10/2022] , or refer to DIAGNOSIS SYSTEM [10/2022 - 10/2023]

      Result

      Result Proceed to
      DTCs are not output. A
      DTCs are output. B

    Result: 

    B 

    INSPECT CAN COMMUNICATION SYSTEM. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [10/2020 - 11/2021]  , or refer to  HOW TO PROCEED WITH TROUBLESHOOTING [11/2021 - 10/2023] 

    Result: 

    A 

    See step  2

  2. PERFORM ACTIVE TEST USING TECHSTREAM (BRAKE WARNING LIGHT / YELLOW (MINOR MALFUNCTION)) 
    1. Connect the Techstream to the DLC3.
    2. Turn the power switch on (IG).
    3. Select the Active Test on the Techstream.

      Refer to DATA LIST / ACTIVE TEST [10/2020 - 10/2023]

      Chassis > ABS/VSC/TRAC > Active Test 

      Tester Display Measurement Item Control Range Diagnostic Note
      ECB Warning Light Brake warning light / yellow (minor malfunction) Warning light ON/OFF
      • Observe combination meter assembly
      • ECB: Electronically Controlled Brake System

      Chassis > ABS/VSC/TRAC > Active Test 

      Tester Display
      ECB Warning Light

      ECB: Electronically Controlled Brake System

    4. Select the Data List on the Techstream.

      Refer to DATA LIST / ACTIVE TEST [10/2020 - 10/2023]

      Chassis > ABS/VSC/TRAC > Data List 

      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      ECB Warning Light Brake warning light / yellow (minor malfunction) ON or OFF ON: Warning light on
      OFF: Warning light off
      ECB: Electronically Controlled Brake System

      Chassis > ABS/VSC/TRAC > Data List 

      Tester Display
      ECB Warning Light

      ECB: Electronically Controlled Brake System

    5. Check the operating condition of the brake warning light / yellow (minor malfunction) when operating it using the Techstream.

      Result

      Result Proceed to
      Brake warning light / yellow (minor malfunction) in the Data List does not change using the Active Test. A
      Brake warning light / yellow (minor malfunction) in the Data List turns ON/OFF using the Active Test. B

    Result: 

    A 

    REPLACE SKID CONTROL ECU ASSEMBLY. Refer to  REMOVAL [10/2020 - 10/2022]  , or refer to  REMOVAL [10/2022 - 10/2023] 

    Result: 

    B 

    See step  3

  3. INSPECT COMBINATION METER ASSEMBLY 
    1. Turn the power switch off.
    2. Perform the Active Test of the combination meter assembly (meter CPU) using the Techstream.

      Refer to DATA LIST / ACTIVE TEST [10/2020 - 11/2021] , or refer to DATA LIST / ACTIVE TEST [11/2021 - 10/2023]

      ECB: Electronically Controlled Brake System

      Body Electrical > Combination Meter > Active Test 

      Tester Display
      ECB Warning
    3. Check the combination meter assembly.

      OK

      The brake warning light / yellow (minor malfunction) turns on or off in accordance with the Techstream operation.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE SKID CONTROL ECU ASSEMBLY. Refer to  REMOVAL [10/2020 - 10/2022]  , or refer to  REMOVAL [10/2022 - 10/2023] 

    Result: 

    NG 

    INSPECT METER / GAUGE SYSTEM. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [10/2020 - 11/2021]  , or refer to  HOW TO PROCEED WITH TROUBLESHOOTING [11/2021 - 10/2023]