LIGHTING SYSTEM Headlight Signal Circuit

DESCRIPTION

The main body ECU receives a headlight low switch information signal from the light control switch, and illuminates the low beam headlight.

WIRING DIAGRAM

A003CITE01

INSPECTION PROCEDURE

Tech Tips

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

PROCEDURE


  1. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (HEADLIGHT [LOW])


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the intelligent tester on.

    4. Enter the following menus: Body / Main Body / Active Test / Headlight Relay.

    5. Check that the headlights (low) turn on/off.

      Main Body ECU
      Tester Display Test Part Control Range Diagnostic Note
      Headlight Relay Headlight (low) ON or OFF -
      OK
      Headlights (low) turn on/off.

    NG

    CHECK HARNESS AND CONNECTOR (HEADLIGHT LOW BULB - HEADLIGHT RELAY) Click here

    OK

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

  2. CHECK HARNESS AND CONNECTOR (HEADLIGHT LOW BULB - HEADLIGHT RELAY)

    A003DNEE02
    Text in Illustration
    *1

    Front view of wire harness connector

    (to Front Headlight Low Bulb [w/ AFS])
    *2 for LH
    *3 for RH
    *4

    Front view of wire harness connector

    (to Front Headlight Low Bulb [w/o AFS])

    1. w/ AFS:


      1. Disconnect the A28 or A27 headlight (low) connector.

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

        Standard Voltage
        for LH
        Tester Connection Switch Condition Specified Condition
        A28-4 (LO) - Body ground Light control switch HEAD, dimmer switch low 11 to 14 V
        Light control switch HEAD, dimmer switch not low Below 1 V
        for RH
        Tester Connection Switch Condition Specified Condition
        A27-4 (LO) - Body ground Light control switch HEAD, dimmer switch low 11 to 14 V
        Light control switch HEAD, dimmer switch not low Below 1 V

    2. w/o AFS:


      1. Disconnect the A31 or A30 headlight (low) connector.

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

        Standard Voltage
        for LH
        Tester Connection Switch Condition Specified Condition
        A31-2 (LO) - Body ground Light control switch HEAD, dimmer switch low 11 to 14 V
        Light control switch HEAD, dimmer switch not low Below 1 V
        for RH
        Tester Connection Switch Condition Specified Condition
        A30-2 (LO) - Body ground Light control switch HEAD, dimmer switch low 11 to 14 V
        Light control switch HEAD, dimmer switch not low Below 1 V

    NG

    INSPECT HEADLIGHT RELAY (H-LP) Click here

    OK

    REPAIR OR REPLACE HARNESS OR CONNECTOR (HEADLIGHT LOW BULB - BODY GROUND)

  3. INSPECT HEADLIGHT RELAY (H-LP)

    A003AL0E14

    1. Remove the headlight relay from the engine room No. 1 relay block.

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

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

    NG

    REPLACE HEADLIGHT RELAY

    OK

  4. CHECK HARNESS AND CONNECTOR (HEADLIGHT RELAY - BATTERY)

    A003DH9E01
    Text in Illustration
    *1

    Component without relay connected

    (Engine Room No. 1 Relay Block)
    *2 Headlight Relay (H-LP)

    1. Remove the headlight relay from the engine room No. 1 relay block.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      Headlight relay terminal 2 - Body ground Always 11 to 14 V
      Headlight relay terminal 3 - Body ground Always 11 to 14 V

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  5. CHECK HARNESS AND CONNECTOR (HEADLIGHT RELAY - HEADLIGHT [LOW] BULB)


    1. A003CKDE01
      Text in Illustration
      *1

      Component without relay connected

      (Engine Room No. 1 Relay Block)
      *2

      Front view of wire harness connector

      (to Headlight Low Bulb [w/ AFS])
      *3 for LH
      *4 for RH
      *5

      Front view of wire harness connector

      (to Headlight Low Bulb [w/o AFS])

      Remove the headlight relay from the engine room No. 1 relay block.

    2. w/ AFS:


      1. Disconnect the A28 or A27 headlight (low) connector.

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

        Standard Resistance
        for LH
        Tester Connection Condition Specified Condition
        Headlight relay terminal 5 - A28-4 (LO) Always Below 1 Ω
        Headlight relay terminal 5 - Body ground Always 10 kΩ or higher
        for RH
        Tester Connection Condition Specified Condition
        Headlight relay terminal 5 - A27-4 (LO) Always Below 1 Ω
        Headlight relay terminal 5 - Body ground Always 10 kΩ or higher

    3. w/o AFS:


      1. Disconnect the A31 or A30 headlight (low) connector.

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

        Standard Resistance
        for LH
        Tester Connection Condition Specified Condition
        Headlight relay terminal 5 - A31-2 (LO) Always Below 1 Ω
        Headlight relay terminal 5 - Body ground Always 10 kΩ or higher
        for RH
        Tester Connection Condition Specified Condition
        Headlight relay terminal 5 - A31-2 (LO) Always Below 1 Ω
        Headlight relay terminal 5 - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  6. CHECK HEADLIGHT (HEADLIGHT RELAY - MAIN BODY ECU)

    A003DX3E02
    Text in Illustration
    *1

    Front view of wire harness connector

    (to Main Body ECU)

    1. Disconnect the D79 main body ECU connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      D79-20 (HRLY) - Body ground Always 11 to 14 V

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

    REPLACE MAIN BODY ECU