Lexus IS250 · Service Manual BODY ELECTRICAL

Headlight Relay Circuit

Circuit diagnosis

DESCRIPTION

The headlight relay is turned ON by operating the headlight switch.
When the theft deterrent system is activated, it causes the ECU to turn the headlight relay on and off repeatedly at approximately 0.25 second intervals to flash the headlights.
In this condition, if any of the following operations is performed, the ECU to turns the headlight relay off to stop the headlight from flashing:
  1. Unlock the driver door with a key.
  2. Turn the engine switch on (ACC) or on (IG).
  3. Unlock the doors with the wireless door lock control system.

WIRING DIAGRAM

E123470E01
E123471E01

INSPECTION PROCEDURE


1. PERFORM ACTIVE TEST BY INTELLIGENT TESTER

  1. Connect the intelligent tester to the DLC3.

  1. Turn the engine switch on (IG).

  1. Turn the intelligent tester main switch on.

  1. Select the item below in the ACTIVE TEST and then check the relay operation.

    ACTIVE TEST: Main Body (Main Body ECU RH) 
    Item
    		 Test Details
    		 Diagnostic Note
    Headlight Relay
    		 Headlight relay ON / OFF
    		 -

    OK:
    Headlight assembly (low) illuminates.



 OK
PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE
NG


2. INSPECT FUSE (H-LP L LWR, H-LP R LWR)

  1. Remove the H-LP L LWR fuse from the engine room No. 2 relay block .

  1. Remove the H-LP R LWR fuse from the engine room No. 2 relay block .

  1. Measure the resistance of the fuses.

    Standard resistance:
    Below 1 Ω



 NG
REPLACE FUSE
OK


3. INSPECT HEAD LP RELAY

  1. E108359E01
    Remove the HEAD LP relay from the engine room No. 1 relay block.

  1. 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


4. CHECK HARNESS AND CONNECTOR (MAIN BODY ECU RH - BATTERY)

  1. E108583E05
    Disconnect the RL main body ECU RH connector.

  1. 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
    		 10 to 14 V



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


5. CHECK HARNESS AND CONNECTOR (HEADLIGHT (LOW LH OR LOW RH) - BATTERY AND BODY GROUND)

  1. E108361E07
    Check the wire harness between the headlight (Low LH) and battery, and the headlight (Low LH) and body ground.

    1. Disconnect the B12 headlight connector.

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

      Standard voltage:
      Tester Connection
      		 Condition
      		 Specified Condition
      B12-17 (LO) - Body ground
      		 Turn the light control switch to the ON (HEAD) position.
      		 10 to 14 V

      Standard resistance:
      Tester Connection
      		 Condition
      		 Specified Condition
      B12-16 (E) - Body ground
      		 Always
      		 Below 1 Ω

  1. E108361E08
    Check the wire harness between the headlight (Low RH) and battery, and the headlight (Low RH) and body ground.

    1. Disconnect the B2 headlight connector.

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

      Standard voltage:
      Tester Connection
      		 Condition
      		 Specified Condition
      B2-17 (LO) - Body ground
      		 Turn the light control switch to the ON (HEAD) position.
      		 10 to 14 V

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



OK
REPLACE HEADLIGHT ASSEMBLY (LOW LH OR LOW RH)
NG


6. CHECK HARNESS AND CONNECTOR (HEADLIGHT (LOW LH OR LOW RH) - HEAD LP RELAY)

  1. E123167E01
    Check the harness and the connectors between the headlight (Low LH or Low RH) and the HEAD LP relay.

    1. Disconnect the B12 light 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
      Check for short:
      Headlight Assembly
      		 Tester Connection
      		 Specified Condition
      LH
      		 B12-17 (LO) or HEAD LP relay terminal (3) - Body ground
      		 10 kΩor higher
      RH
      		 B2-17 (LO) or HEAD LP relay terminal (3) - Body ground
      		 10 kΩor higher



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE MAIN BODY ECU RH (COWL SIDE J/B RH)


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