Lexus IS250 · Service Manual BODY ELECTRICAL

Turn Signal Light Circuit

Circuit diagnosis

DESCRIPTION

The main body ECU LH controls the operation of the turn signal flasher. The turn signal flasher blinks the turn signal lights.
The main body ECU LH receives RH/LH turn signal light blink request signals from the combination switch ECU through BEAN communication and sends operation signals to the turn signal flasher.

WIRING DIAGRAM

E123469E01

INSPECTION PROCEDURE


1. CHECK TURN SIGNAL LIGHT (OPERATION)

  1. Turn the engine switch on (IG).

  1. When the turn signal light switch is operated, check that the corresponding turn signal lights flash.

    HINT:
    The front, side and rear turn signal lights share the same drive circuit. Therefore, if either the front or rear turn signal lights do not come on, there may be a problem in the circuit between the turn signal flasher and the bulb, or the circuit between the bulb and body ground.


    Result:
    Result
    		 Proceed to
    Neither left nor right turn signal lights flash
    		 A
    Left turn signal lights do not flash
    		 B
    Right turn signal lights do not flash
    		 C



B
Go to step 6

C
Go to step 11
A


2. 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 on.

  1. Select the item(s) in the ACTIVE TEST, and check the operation.

    ACTIVE TEST: Body No. 3 (Main body ECU LH) 
    Item
    		 Test Details
    		 Diagnostic Note
    Turn Lamp RH
    		 RH side turn signal lights operation ON / OFF
    		 -
    Turn Lamp LH
    		 LH side turn signal lights operation ON / OFF
    		 -

    OK:
    Turn signal lights flash.



 NG
Go to step 3
OK

PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE

3. INSPECT FUSE (LH-IG, TURN-HAZ)

  1. Remove the LH-IG fuse from the cowl side J/B LH.

  1. Remove the TURN-HAZ fuse from the engine room No. 1 J/B.

  1. Measure the resistance of the fuses.

Standard resistance:
Below 1 Ω



 NG
REPLACE FUSE
OK


4. CHECK HARNESS AND CONNECTOR (POWER SOURCE)

  1. E109542E04
    Disconnect the J30 flasher connector.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    J30-7 (E) - Body ground
    		 Always
    		 Below 1 Ω

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

    Standard voltage:
    Tester Connection
    		 Condition
    		 Specified Condition
    J30-4 (B) - Body ground
    		 Always
    		 10 to 14 V
    J30-1 (IG) - Body ground
    		 Engine switch on (IG)
    		 10 to 14 V



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


5. REPLACE TURN SIGNAL FLASHER

  1. Temporarily replace the turn signal flasher with a new or normally functioning one.

  1. Check that the turn signal lights flash.

    OK:
    Turn signal lights flash.



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

END

6. 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 on.

  1. Select the item(s) in the ACTIVE TEST, and check the operation.

    ACTIVE TEST: Body No. 3 (Main body ECU LH) 
    Item
    		 Test Details
    		 Diagnostic Note
    Turn Lamp LH
    		 LH side turn signal lights operation ON / OFF
    		 -

    OK:
    Turn signal lights flash.



 NG
Go to step 7
OK

PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE

7. CHECK HARNESS AND CONNECTOR (MAIN BODY ECU LH - BODY GROUND)

  1. E123382E01
    Disconnect the LA main body ECU LH connector.

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

    Standard voltage:
    Tester Connection
    		 Condition
    		 Specified Condition
    LA-16 (TL) - Body ground
    		 Always
    		 10 to 14 V



NG
Go to step 10
OK


8. CHECK HARNESS AND CONNECTOR (TURN SIGNAL FLASHER - HEADLIGHT)

  1. E108392E08
    Disconnect the J30 flasher connector.

  1. Disconnect the B12 headlight connector.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    J30-3 (LL) - B12-9
    		 Always
    		 Below 1 Ω
    J30-3 (LL) - Body ground
    		 Always
    		 10 kΩ or higher



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


9. REPLACE TURN SIGNAL FLASHER

  1. Temporarily replace the turn signal flasher with a new or normally functioning one.

  1. Check that the turn signal lights flash.

    OK:
    Turn signal lights flash.



 NG
REPLACE MAIN BODY ECU LH (COWL SIDE J/B LH)
OK

END

10. CHECK HARNESS AND CONNECTOR (MAIN BODY ECU LH - TURN SIGNAL FLASHER)

  1. E108389E06
    Disconnect the LA main body ECU LH connector.

  1. Disconnect the J30 flasher connector.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    LA-16 (TL) - J30-5 (EL)
    		 Always
    		 Below 1 Ω
    LA-16 (TL) - Body ground
    		 Always
    		 10 kΩ or higher



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE TURN SIGNAL FLASHER

11. 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 on.

  1. Select the item(s) in the ACTIVE TEST, and check the operation.

    ACTIVE TEST: Body No. 3 (Main body ECU LH) 
    Item
    		 Test Details
    		 Diagnostic Note
    Turn Lamp RH
    		 RH side turn signal lights operation ON / OFF
    		 -

    OK:
    Turn signal lights flash.



 NG
Go to step 12
OK

PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE

12. CHECK HARNESS AND CONNECTOR (MAIN BODY ECU LH - BODY GROUND)

  1. E123382E02
    Disconnect the LA main body ECU LH connector.

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

    Standard voltage:
    Tester Connection
    		 Condition
    		 Specified Condition
    LA-15 (TR) - Body ground
    		 Always
    		 10 to 14 V



NG
Go to step 15
OK


13. CHECK HARNESS AND CONNECTOR (TURN SIGNAL FLASHER - HEADLIGHT)

  1. E108392E09
    Disconnect the J30 flasher connector.

  1. Disconnect the B2 headlight connector.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    J30-2 (LR) - B2-9
    		 Always
    		 Below 1 Ω
    J30-2 (LR) - Body ground
    		 Always
    		 10 kΩ or higher



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


14. REPLACE TURN SIGNAL FLASHER

  1. Temporarily replace the turn signal flasher with a new or normally functioning one.

  1. Check that the turn signal lights flash.

    OK:
    Turn signal lights flash.



 NG
REPLACE MAIN BODY ECU LH (COWL SIDE J/B LH)
OK

END

15. CHECK HARNESS AND CONNECTOR (MAIN BODY ECU LH - TURN SIGNAL FLASHER)

  1. E108389E07
    Disconnect the LA main body ECU LH connector.

  1. Disconnect the J30 flasher connector.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    LA-15 (TR) - J30-6 (ER)
    		 Always
    		 Below 1 Ω
    LA-15 (TR) - Body ground
    		 Always
    		 10 kΩ or higher



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE TURN SIGNAL FLASHER


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