Lexus IS250 · Service Manual ENGINE

MIL Circuit

Circuit diagnosis

DESCRIPTION

The MIL (Malfunction Indicator Lamp) is used to indicate malfunction detections by the ECM.
By turning the engine switch on (IG), power is supplied to the MIL circuit, and the ECM provides the circuit ground which illuminates the MIL.
The MIL operation can be checked visually: When the engine switch on (IG) is first turned to on, the MIL should be illuminated and should then turn off. If the MIL remains illuminated or is not illuminated, conduct the following troubleshooting procedure using the intelligent tester.

WIRING DIAGRAM

A122753E01

INSPECTION PROCEDURE

HINT:
Troubleshoot each trouble symptom in accordance with the chart below.

MIL remains illuminated
 Start inspection from step 1
MIL not illuminated
 Start inspection from step 3

1. CHECK MIL CONDITION (WHETHER MIL TURNS OFF)

  1. Connect the intelligent tester to the DLC3.

  1. Turn the engine switch on (IG).

  1. Turn the tester ON.

  1. Check whether any DTCs have been stored (Click here). Note them down if necessary.

  1. Clear DTCs (Click here).

  1. Check if the MIL turns off.

    OK:
    MIL should turn off.



 OK
REPAIR CIRCUITS INDICATED BY OUTPUT DTCS
NG


2. CHECK HARNESS AND CONNECTOR (CHECK FOR SHORT IN WIRE HARNESS)

  1. A122886E04
    Disconnect the A6 ECM connector.

  1. Turn the engine switch on (IG).

  1. Check the MIL is not illuminated.

    OK:
    MIL is not illuminated.

  1. Reconnect the ECM connector.



 OK
REPLACE ECM
NG


3. CHECK HARNESS AND CONNECTOR (COMBINATION METER - ECM)

  1. A115544E05
    Disconnect the A6 ECM connector.

  1. Disconnect the J35 combination meter connector.

  1. Measure the resistance of the wire harness side connector.

    Standard resistance (Check for open):
    Tester Connection
    		 Specified Condition
    W (A6-8) - EFI (J35-12)
    		 Below 1 Ω

    Standard resistance (Check for short):
    Tester Connection
    		 Specified Condition
    W (A6-8) or EFI (J35-12) - Body ground
    		 10 kΩ or higher



OK
REPAIR OR REPLACE COMBINATION METER ASSEMBLY
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

4. CHECK MIL CONDITION (MIL IS ILLUMINATED)

  1. Check if the MIL is illuminated when the engine switch is turns to on.

    OK:
    MIL should be illuminated.



 OK
SYSTEM IS OK
NG


5. CHECK HARNESS AND CONNECTOR

  1. A122886E04
    Disconnect the A6 ECM connector.

  1. Turn the engine switch on (IG).

  1. Measure the voltage of the wire harness side connector.

    Standard voltage:
    Tester Connection
    		 Specified Condition
    W (A6-8) - Body ground
    		 10 to 14 V

  1. Reconnect the ECM connector.



 OK
REPLACE ECM
NG


6. CHECK HARNESS AND CONNECTOR (COMBINATION METER - ECM)

  1. A115544E05
    Disconnect the A6 ECM connector.

  1. Disconnect the J35 combination meter connector.

  1. Measure the resistance of the wire harness side connector.

    Standard resistance (Check for open):
    Tester Connection
    		 Specified Condition
    W (A6-8) - EFI (J35-12)
    		 Below 1 Ω

    Standard resistance (Check for short):
    Tester Connection
    		 Specified Condition
    W (A6-8) or EFI (J35-12) - Body ground
    		 10 kΩ or higher



OK
REPAIR OR REPLACE COMBINATION METER ASSEMBLY
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR


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