Malfunction Indicator Lamp: Testing and Inspection

DIAGNOSIS
- The "CHECK ENGINE" Malfunction Indicator Lamp (MIL) circuit is in short or open.





TROUBLE SYMPTOM
- Trouble Symptom 1: When Ignition Switch is turned to "ON" (Engine OFF), MIL does not illuminate.
- Trouble Symptom 2: Although MIL illuminates, trouble code is not shown on Subaru Select Monitor or the OBD-II General Scan Tool display.








WIRING DIAGRAM

1. Classify the malfunction. Is it a Trouble Symptom 1 or Trouble Symptom 2?
- If the malfunction shows Trouble Symptom 1, go to step 2.
- If the malfunction shows Trouble Symptom 2, go to step 4.





2. Check output signal from Engine Control Module (ECM).
a. Turn Ignition Switch to "ON".
b. Measure voltage between ECM and body.
[CHECK]: Connector & terminal (B84) No. 31 - Body/ 1 Volts, or less.
[YES]: Go to step 3.
[NO]: If Malfunction Indicator Lamp (MIL) comes on when shaking or pulling ECM connector and harness, repair ECM connector. Check that ECM connector is correctly connected. If the MIL does not come on even when ECM connector is correctly connected, replace the ECM.





3. Check harness connector between ECM and Ignition Switch.
Check the following and repair it necessary.
a. Check that fuse (No. 15) is not blown out.

NOTE: It replaced fuse (No. 15) blows out easily, check the harness for short circuit between fuse (No. 15) and Combination Meter.

b. Check that harness from fuse to Combination Meter is not open.
c. Check that the MIL wiring is not open.
d. Check that harness from Combination Meter to the ECM is not open.
e. Check that the connector (B37) is correctly connected as the wiring diagram shows.

4. Check short circuit of harness.
a. Turn Ignition Switch to "OFF".
b. Disconnect connector from ECM.
[CHECK]: Does the MIL comes on?
[YES]: Repair short circuit of harness between ECM and Combination Meter.
[NO]: Replace ECM.