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Headlight Relay Circuit: Procedure

  1. PERFORM ACTIVE TEST USING TECHSTREAM 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Turn the Techstream on.
    4. Enter the following menus: Body Electrical / Main Body / Active Test.
    5. Check that the relays operate.
      MAIN BODY

      Tester Display Test Part Control Range Diagnostic Note
      Headlight Relay Headlight relay OFF or ON -

      OK

      Relay operates. (Low beam headlights illuminate.)

    NG → See step   2 

    OK → See step   6 

  2. INSPECT HEADLIGHT RELAY (H-LP RELAY) 
    1. Inspect the headlight relay. Refer to ON-VEHICLE INSPECTION .

    NG → REPLACE HEADLIGHT RELAY 

    OK: Go to next step 

  3. CHECK HARNESS AND CONNECTOR (HEADLIGHT RELAY - BATTERY) 
    1. Remove the headlight relay from the No. 2 engine room relay block.
      Fig 1: Identifying Headlight Relay On No. 2 Engine Room Relay Block
      GTY345755Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      1 (Headlight relay holder) - Body ground Always 11 to 14 V
      5 (Headlight relay holder) - Body ground Always 11 to 14 V
      TEXT IN ILLUSTRATION

      *1 No. 2 Engine Room Relay Block
      *2 Headlight Relay Holder
    3. Reinstall the headlight relay.

    NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: Go to next step 

  4. CHECK HARNESS AND CONNECTOR (HEADLIGHT RELAY - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY) 
    1. Remove the headlight relay from the No. 2 engine room relay block.
    2. Disconnect the 3B instrument panel junction block assembly connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      2 (Headlight relay holder) - 3B-34 Always Below 1 Ω
      2 (Headlight relay holder) - Body ground Always 10 kΩ or higher
    4. Reconnect the instrument panel junction block assembly connector.
    5. Reinstall the headlight relay.

    NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: Go to next step 

  5. INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY 
    1. Remove the instrument panel junction block assembly.
      Fig 2: Measuring Resistance Of Instrument Panel Junction Block Assembly
      GTY347114Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Remove the main body ECU from the instrument panel junction block assembly.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      3B-34 - 3F-15 (HRLY) Always Below 1 Ω
      3B-34 - Body ground Always 10 kΩ or higher
      TEXT IN ILLUSTRATION

      *a Component without harness connected
      (Instrument Panel Junction Block Assembly)
    4. Reinstall the main body ECU.
    5. Reinstall the instrument panel junction block assembly.

    NG → REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY 

    OK → See step   7 

  6. PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to  PROBLEM SYMPTOMS TABLE 
  7. REPLACE MAIN BODY ECU. Refer to  REMOVAL 
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