LIGHTING SYSTEM Headlight Relay Circuit

DESCRIPTION

The main body ECU (multiplex network body ECU) receives headlight dimmer switch information signals and illuminates the low beam headlights.

WIRING DIAGRAM

B0029JAE01
B0029V4E01

CAUTION / NOTICE / HINT

Note


  • Inspect the bulbs and fuses for circuits related to this system before performing the following inspection procedure.

  • When replacing the main body ECU (multiplex network body ECU), make sure to replace it with a new one.

PROCEDURE


  1. PERFORM ACTIVE TEST USING GTS (H-LP RELAY)


    1. Using the GTS, perform the Active Test.

      Click here


      Body Electrical > Main Body > Active Test
      Tester Display Measurement Item Control Range Diagnostic Note
      Headlight Relay Low beam headlight relay ON or OFF -

      Body Electrical > Main Body > Active Test
      Tester Display
      Headlight Relay
      OK
      Headlight relay operates (low beam headlights come on).
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) for LHD: REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) Click here
    REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) for RHD: REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) Click here

    NG

  2. INSPECT HEADLIGHT RELAY (H-LP)


    1. B002AIUN01

      Remove the headlight relay from the No. 1 engine room relay block and junction block assembly.

    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      3 - 5 Battery voltage applied between terminals 1 and 2 Below 1 Ω
      3 - 5 Battery voltage not applied between terminals 1 and 2 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    REPLACE HEADLIGHT RELAY (H-LP)

    OK

  3. CHECK HARNESS AND CONNECTOR (HEADLIGHT RELAY [H-LP] - BATTERY)


    1. Remove the headlight relay from the No. 1 engine room relay block and junction block assembly.

      B0029U8C01
      *A w/o Side Marker Light *B w/ Side Marker Light
      *a

      Front view of wire harness connector

      (to Headlight Relay)

      		 - -

    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      Headlight relay terminal 5 - Body ground Always 11 to 14 V
      Headlight relay terminal 1 - Body ground
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  4. CHECK HARNESS AND CONNECTOR (HEADLIGHT RELAY [H-LP] - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY)


    1. Remove the headlight relay from the No. 1 engine room relay block and junction block assembly.

    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
      Headlight relay terminal 2 - 3B-37 Always Below 1 Ω
      3B-37 - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  5. INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY


    1. B002A1BN09

      Remove the instrument panel junction block assembly.

      for LHD:

      Click here

      for RHD:

      Click here

    2. Remove the main body ECU (multiplex network body ECU) from the instrument panel junction block assembly.

      for LHD:

      Click here

      for RHD:

      Click here

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      A-15 (HRLY) - 3B-37 Always Below 1 Ω
      Result
      Proceed to
      OK
      NG

    OK

    PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE Click here

    NG

    REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY for LHD: REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY Click here
    REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY for RHD: REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY Click here