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Home >> Lexus >> 2021 >> LS 500 Base, RWD >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Exterior Lights >> Lighting System (Ext) - Diagnostic Codes (3 Of 3), Symptom Tests & Circuit Tests (1 Of 2) >> Lighting System >> Headlight Dimmer Switch Circuit [10/2020 - 10/2023] >> Procedure

Headlight Dimmer Switch Circuit [10/2020 - 10/2023]: Procedure

  1. READ VALUE USING TECHSTREAM 
    1. Using the Techstream, read the Data List.

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

      Chassis > Steering Angle Sensor > Data List 

      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      Light OFF Switch Light control switch DRL-off position signal OFF or ON OFF: Light control switch not in DRL-off position
      ON: Light control switch in DRL-off position
      w/ DRL OFF Switch
      Auto Light Switch Light control switch Auto position signal OFF or ON OFF: Light control switch not in Auto position
      ON: Light control switch in Auto position
      -
      Head Light Switch (Tail) Light control switch Tail position signal OFF or ON OFF: Light control switch in neither Tail nor Head position
      ON: Light control switch in Tail or Head position
      -
      High Beam Main Switch Headlight dimmer switch High position signal OFF or ON OFF: Headlight dimmer switch not in High position
      ON: Headlight dimmer switch in High position
      -
      Passing Light Switch Headlight dimmer switch Flash position signal OFF or ON OFF: Headlight dimmer switch not in Flash position
      ON: Headlight dimmer switch in Flash position
      -

      Chassis > Steering Angle Sensor > Data List 

      Tester Display
      Light OFF Switch
      Auto Light Switch
      Head Light Switch (Tail)
      High Beam Main Switch
      Passing Light Switch

      OK

      Normal conditions listed above are displayed.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  7

    Result: 

    OK 

    See step  2

  2. READ VALUE USING TECHSTREAM 
    1. Using the Techstream, read the Data List.

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

      Chassis > Steering Angle Sensor > Data List 

      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      Head Light Switch (Head) Light control switch Head position signal OFF or ON OFF: Light control switch not in Head position
      ON: Light control switch in Head position
      -

      Body Electrical > Main Body > Data List 

      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      Head Light SW (Head) Light control switch Head position signal OFF or ON OFF: Light control switch not in Head position
      ON: Light control switch in Head position
      -

      Chassis > Steering Angle Sensor > Data List 

      Tester Display
      Head Light Switch (Head)

      Body Electrical > Main Body > Data List 

      Tester Display
      Head Light SW (Head)

      OK

      Normal conditions listed above are displayed.

      Result

      Result Proceed to
      OK A
      NG ("Steering Angle Sensor" side abnormality) B
      NG ("Main Body" side abnormality) C
      NG ("Steering Angle Sensor" and "Main Body" are abnormality) D

    Result: 

    PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to  PROBLEM SYMPTOMS TABLE [10/2020 - 10/2023] 

    Result: 

    REPLACE STEERING SENSOR. Refer to  REMOVAL [10/2020 - 10/2022]  , or refer to  REMOVAL [10/2022 - 10/2023] 

    Result: 

    See step  4

    Result: 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (MAIN BODY ECU [MULTIPLEX NETWORK BODY ECU] - STEERING SENSOR) 
    1. Disconnect the G12 main body ECU (multiplex network body ECU) connector.
    2. Disconnect the G29*1 or G30*2 steering sensor connector.
      1. *1: w/ VGRS
      2. *2: w/o VGRS
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      W/ VGRS

      Tester Connection Condition Specified Condition
      G12-16 (HEAD) - G29-7 (HEAD) Always Below 1 Ω
      W/O VGRS

      Tester Connection Condition Specified Condition
      G12-16 (HEAD) - G30-7 (HEAD) Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU). Refer to  REMOVAL [10/2020 - 10/2022]  , or refer to  REMOVAL [10/2022 - 10/2023] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  4. INSPECT TURN SIGNAL SWITCH 
    1. Remove the turn signal switch.

      Refer to REMOVAL [12/2017 - ]

    2. Inspect the turn signal switch.

      Refer to INSPECTION [10/2020 - ]

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE TURN SIGNAL SWITCH. Refer to  REMOVAL [12/2017 - ] 

    Result: 

    OK 

    See step  5

  5. INSPECT STEERING WHEEL SWITCH HOUSING 
    1. Remove the steering wheel switch housing.

      Refer to REMOVAL [10/2020 - 10/2022] , or refer to REMOVAL [10/2022 - 10/2023]

    2. Inspect the steering wheel switch housing.

      Refer to INSPECTION [12/2017 - ]

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE STEERING WHEEL SWITCH HOUSING. Refer to  REMOVAL [10/2020 - 10/2022]  , or refer to  REMOVAL [10/2022 - 10/2023] 

    Result: 

    OK 

    See step  6

  6. CHECK HARNESS AND CONNECTOR (MAIN BODY ECU [MULTIPLEX NETWORK BODY ECU] - STEERING SENSOR) 
    1. Disconnect the G12 main body ECU (multiplex network body ECU) connector.
    2. Disconnect the G29*1 or G30*2 steering sensor connector.
      1. *1: w/ VGRS
      2. *2: w/o VGRS
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      W/ VGRS

      Tester Connection Condition Specified Condition
      G12-16 (HEAD) or G29-7 (HEAD) - Body ground Always 10 kΩ or higher
      W/O VGRS

      Tester Connection Condition Specified Condition
      G12-16 (HEAD) or G30-7 (HEAD) - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE STEERING SENSOR. Refer to  REMOVAL [10/2020 - 10/2022]  , or refer to  REMOVAL [10/2022 - 10/2023] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  7. INSPECT TURN SIGNAL SWITCH 
    1. Remove the turn signal switch.

      Refer to REMOVAL [12/2017 - ]

    2. Inspect the turn signal switch.

      Refer to INSPECTION [10/2020 - ]

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE TURN SIGNAL SWITCH. Refer to  REMOVAL [12/2017 - ] 

    Result: 

    OK 

    See step  8

  8. INSPECT STEERING WHEEL SWITCH HOUSING 
    1. Remove the steering wheel switch housing.

      Refer to REMOVAL [10/2020 - 10/2022] , or refer to REMOVAL [10/2022 - 10/2023]

    2. Inspect the steering wheel switch housing.

      Refer to INSPECTION [12/2017 - ]

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE STEERING SENSOR. Refer to  REMOVAL [10/2020 - 10/2022]  , or refer to  REMOVAL [10/2022 - 10/2023] 

    Result: 

    NG 

    REPLACE STEERING WHEEL SWITCH HOUSING. Refer to  REMOVAL [10/2020 - 10/2022]  , or refer to  REMOVAL [10/2022 - 10/2023]