Chart A-1 No Service Engine Soon Light

Chart A-1:

MIL Circuit:

CIRCUIT DESCRIPTION:
There should always be a steady MIL (Service Engine Soon) when the ignition is "ON" and engine stopped. Ignition voltage is supplied directly to the light bulb. The Engine Control Module (ECM) will control the light and turn it "ON" by providing a ground path through CKT 419 to the ECM.

TEST DESCRIPTION: Number(s) below refer to circled number(s) on the diagnostic chart.

1. If the fusible link is open or ECM fuse blown, replace it.

2. Using a test light connected to 12 volts, probe each of the system ground circuits to be sure a good ground is present.

DIAGNOSTIC AIDS:
Engine runs OK, check:

^ Faulty light bulb.
^ CKT 419 open.
^ Gauges fuse blown. This will result in no oil or generator lights, seat belt reminder, etc.

Engine cranks but will not run:

^ Fusible link or ECM fuse.
^ ECM ignition fuse open.
^ Battery CKT 2 to ECM open.
^ Ignition CKT 439 to ECM open.
^ Poor connection to ECM.