A-1 ~ No Malfunction Indicator Lamp (MIL)

Chart A-1 Wiring Diagram:

Chart A-1 No Check Engine Light:

CIRCUIT DESCRIPTION:

There should always be a steady "CHECK ENGINE" light, when the ignition is "ON" and engine stopped. Battery voltage is supplied directly to the light bulb from fuse C-7. The Electronic Control Module (ECM) will control the light and turn it "ON" by providing a ground path through CKT 419 To the ECM.

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

1. Battery feed CKT 240 is protected by a fusible link in relay fuse center under the hood near the battery.

2. If CKT 240 has voltage, the ECM grounds or the ECM are faulty.

3. Using a test light connected to 12 volts, prove 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.
^ Fuse C-7 (10 amp) blown. This will result in no oil or generator lights, seat belt reminder, etc.

Engine cranks, but will not run:

^ Continuous battery fuse or fusible link open.
^ ECM ignition fuse open.
^ Battery CKT 240 to ECM open.
^ Ignition CKT 439 to ECM open.
^ Poor connection to ECM.