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Low Beam Headlight Circuit: Procedure

  1. PERFORM ACTIVE TEST USING TECHSTREAM 
    1. Connect the Techstream to the DLC3.
    2. Turn the engine switch on (IG).
    3. Turn the Techstream on.
    4. Enter the following menus: Body Electrical / Body / Active Test.
    5. Check that the relays operate.
      BODY (MAIN BODY ECU RH)

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

      OK

      Low beam headlights illuminate.

    NG → See step   2 

    OK → See step   7 

  2. INSPECT FUSE (H-LP L LWR, H-LP R LWR) 
    1. Remove the H-LP L LWR fuse from the No. 2 engine room relay block.
    2. Remove the H-LP R LWR fuse from the No. 2 engine room relay block.
    3. Measure the resistance of the fuses.

      Standard Resistance

      Below 1 Ω

    NG → REPLACE FUSE 

    OK: Go to next step 

  3. INSPECT HEAD LP RELAY 
    1. Remove the HEAD LP relay from the engine room No. 1 relay block.
      Fig 1: Inspecting Head LP Relay
      GTY108191Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Specified Condition
      3 - 5 10 kΩ or higher
      3 - 5 Below 1 Ω
      (When battery voltage is applied to terminals 1 and 2)

    NG → REPLACE HEAD LP RELAY 

    OK: Go to next step 

  4. CHECK HARNESS AND CONNECTOR (MAIN BODY ECU RH - BATTERY) 
    1. Disconnect the RL main body ECU RH connector.
      Fig 2: Identifying RL Connector Terminals
      GTY273092Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      TEXT IN ILLUSTRATION

      *1 Front view of wire harness connector
      (to Main Body ECU RH)
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      RL-7 (HRLY) - Body ground Always 11 to 14 V

    NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: Go to next step 

  5. CHECK HARNESS AND CONNECTOR (HEADLIGHT (LOW LH OR LOW RH) - BATTERY AND BODY GROUND) 
    1. Check the wire harness between the headlight (Low LH) and battery, and the headlight (Low LH) and body ground.
      Fig 3: Identifying B12 Connector Terminals
      GTY264891Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      TEXT IN ILLUSTRATION

      *1 Front view of wire harness connector
      (to Headlight Assembly LH)
      1. Disconnect the B12 headlight connector.
      2. Measure the voltage according to the value(s) in the table below.

        Standard Voltage

        Tester Connection Condition Specified Condition
        B12-17 (LO) - Body ground Light control switch in head position 11 to 14 V
      3. Measure the resistance according to the value(s) in the table below.

        Standard Resistance

        Tester Connection Condition Specified Condition
        B12-16 (E) - Body ground Always Below 1 Ω
    2. Check the wire harness between the headlight (Low RH) and battery, and the headlight (Low RH) and body ground.
      Fig 4: Identifying B2 Connector Terminals
      GTY264889Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      TEXT IN ILLUSTRATION

      *1 Front view of wire harness connector
      (to Headlight Assembly RH)
      1. Disconnect the B2 headlight connector.
      2. Measure the voltage according to the value(s) in the table below.

        Standard Voltage

        Tester Connection Condition Specified Condition
        B2-17 (LO) - Body ground Light control switch in head position 11 to 14 V
      3. Measure the resistance according to the value(s) in the table below.

        Standard Resistance

        Tester Connection Condition Specified Condition
        B2-16 (E) - Body ground Always Below 1 Ω

    NG → See step   6 

    OK → See step   8 

  6. CHECK HARNESS AND CONNECTOR (HEADLIGHT (LOW LH OR LOW RH) - HEAD LP RELAY) 
    1. Check the harness and the connectors between the headlight (Low LH or Low RH) and the HEAD LP relay.
      Fig 5: Identifying B12, B2 And No. 1 Engine Room Relay Block Connector Terminals
      GTY256291Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      TEXT IN ILLUSTRATION

      *1 Front view of wire harness connector
      (to Headlight Assembly LH)
      *2 Front view of wire harness connector
      (to Headlight Assembly RH)
      *3 No. 1 Engine Room Relay Block
      *4 HEAD LP Relay
      1. Disconnect the B12 headlight connector.
      2. Remove the HEAD LP relay from the engine room No. 1 relay block.
      3. Measure the resistance according to the value(s) in the table below.

        Standard Resistance (Check for Open)

        Headlight Assembly Tester Connection Specified Condition
        LH B12-17 (LO) - HEAD LP relay terminal (3) Below 1 Ω
        RH B2-17 (LO) - HEAD LP relay terminal (3) Below 1 Ω

        Standard Resistance (Check for Short)

        Headlight Assembly Tester Connection Specified Condition
        LH B12-17 (LO) or HEAD LP relay terminal (3) - Body ground 10 kΩ or higher
        RH B2-17 (LO) or HEAD LP relay terminal (3) - Body ground 10 kΩ or higher

    NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK → REPLACE MAIN BODY ECU RH (COWL SIDE JUNCTION BLOCK RH) 

  7. PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to  PROBLEM SYMPTOMS TABLE 
  8. REPLACE HEADLIGHT ASSEMBLY (LOW LH OR LOW RH). Refer to  COMPONENTS 
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