LIGHTING SYSTEM Headlight Relay Circuit

DTC Code DTC Name
Headlight Relay Circuit

DESCRIPTION

The main body ECU receives the light control switch head signal to control the headlight relay. When the light control switch is in the AUTO position, the main body ECU receives the ambient light level signal from the automatic light control sensor to control the headlight relay.

Tip:

  • If a low beam headlight on only one side does not illuminate, inspect any bulb, fuse or wire harness that is related to the headlight.

  • If both the right and left low beam headlights do not illuminate when the light control switch is turned to the head position, perform the headlight relay Active Test and read the light control switch head signal value in the Data List to determine if the malfunction exists on either the switch side or the relay side.

WIRING DIAGRAM

E270009E01
E270008E02

CAUTION / NOTICE / HINT

Note:

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 RELAY)

    1. Using the intelligent tester, perform the Active Test (Click here).

      Table 1. Main Body

      Tester Display

      Test Part

      Control Range

      Diagnostic Note

      Headlight Relay

      Headlight Relay

      ON / OFF

      -

      OK

      Headlight relay operates (low beam headlights illuminate).

    REPLACE MAIN BODY ECU (INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY)

  2. INSPECT HEADLIGHT RELAY (H-LP)

    1. E108359E02

      Remove the headlight relay from the engine room No. 1 relay block, junction 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 between terminals 1 and 2

      10 kΩ or higher

      3 - 5

      Battery voltage applied between terminals 1 and 2

      Below 1 Ω

    REPLACE HEADLIGHT RELAY

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

    1. E345037E02

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

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

      Standard Voltage

      Tester Connection

      Condition

      Specified Condition

      Headlight relay terminal 1 - Body ground

      Always

      11 to 14 V

      Headlight relay terminal 5 - Body ground

      Always

      11 to 14 V
      Table 2. Text in Illustration

      *1

      Engine Room No. 1 Relay Block, Junction Block

      *2

      Headlight Relay (H-LP)

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  4. CHECK HARNESS AND CONNECTOR (HEADLIGHT RELAY [H-LP] - MAIN BODY ECU)

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

      U184812E02
      Table 3. Text in Illustration

      *1

      Front view of wire harness connector

      (to Main Body ECU)

      *2

      Engine Room No. 1 Relay Block, Junction Block

      *3

      Headlight Relay (H-LP)

      -

      -

    2. Disconnect the H79 main body ECU 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 - H79-20 (HRLY)

      Always

      Below 1 Ω

      H79-20 (HRLY) - Body ground

      Always

      10 kΩ or higher

    PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

    (Click here)

    REPAIR OR REPLACE HARNESS OR CONNECTOR