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Home >> Toyota >> 2021 >> Highlander LE, 4WD >> Repair and Diagnosis >> Accessories & Equipment >> Exterior Lights >> Lighting System (W/O AFS) - Symptom Tests & Circuit Tests (2 Of 2) >> LIGHTING SYSTEM (w/o AFS) >> Taillight Relay Circuit [12/2019 - 11/2023] >> Procedure

Taillight Relay Circuit [12/2019 - 11/2023]: Procedure

  1. PERFORM ACTIVE TEST USING GTS 
    1. Perform the Active Test according to the display on the GTS.

      Body Electrical > Main Body > Active Test 

      Tester Display Measurement Item Control Range Diagnostic Note
      Taillight Relay Taillight relay OFF or ON -

      Body Electrical > Main Body > Active Test 

      Tester Display
      Taillight Relay

      OK

      Taillights illuminate.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to  PROBLEM SYMPTOMS TABLE [12/2019 - 09/2020]  , or refer to  PROBLEM SYMPTOMS TABLE [09/2020 - 10/2022]  , or refer to  PROBLEM SYMPTOMS TABLE [10/2022 - 11/2023] 

    Result: 

    NG 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (POWER SOURCE - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY) 
    1. Disconnect the 4F instrument panel junction block assembly connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      4F-1 - Body ground Ignition switch off*1
      Always*2      		 11 to 14 V
      1. *1: for HV Model
      2. *2: for Gasoline Model

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  3

  3. INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY 
    GTY945333Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    *a Component without harness connected
    (Instrument Panel Junction Block Assembly)    		 - -
    1. Remove the main body ECU (multiplex network body ECU) from the instrument panel junction block assembly.

      Refer to REMOVAL [12/2019 - 10/2022] , or refer to REMOVAL [10/2022 - 11/2023]

    2. Connect a positive (+) lead from the auxiliary battery to terminal 4F-1.
    3. Connect a negative (-) lead from the auxiliary battery to terminal MB-14 (TRLY).
    4. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      4B-11 - Auxiliary battery negative (-) terminal Always 11 to 14 V
      4D-30 - Auxiliary battery negative (-) terminal Always 11 to 14 V
      4C-32 - Auxiliary battery negative (-) terminal Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU). Refer to  REMOVAL [12/2019 - 10/2022]  , or refer to  REMOVAL [10/2022 - 11/2023] 

    Result: 

    NG 

    REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY. Refer to  REMOVAL [12/2019 - 10/2022]  , or refer to  REMOVAL [10/2022 - 11/2023] 

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