Chart A-1 No Service Engine Soon Light

Chart A-1:

Check Engine Light Circuit:

CIRCUIT DESCRIPTION:

There should always be a steady "CHECK ENGINE" light when the ignition is "ON" and engine is not running. Battery voltage is applied to the light bulb. The ECM will control the light and turn it "ON" by providing a ground path through the ECM.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Checks to see if ECM is receiving power.

2. Checks to see if ECM is faulty.

3. Checks for an open in WHT/BLU wire between FI relay and ECM.

4. Checks to see if ECM has a good ground.

5. Checks for an open in BLK/WHT wire to I/P and PPL wire to ECM.

6. Checks to see if FI relay switch is receiving power.

7. Checks to see if FI relay coil is receiving power.

8. Checks to see if FI relay or ECM is faulty, or an open in BLK wire between FI relay and ground.

DIAGNOSTIC AIDS:

Be sure to check connectors for contamination, corrosion or bent terminals.