Chart A-1 No Check Engine Light

Chart A-1:

ALDL Circuit:

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. The Electronic Control Module (ECM) will control the light and turn it "ON" by providing a ground path through the PPL wire from the ECM to the bulb.

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

1. Battery feed terminals "C16" and "B1" are protected by a fusible link in relay fuse center under the hood near the battery.

2. If terminals "C16" and "B1" have 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.
^ PPL wire open.
^ Meter fuse 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 RED/WHT wire to ECM open.
^ Ignition RED/GRN wire to ECM open.
^ Poor connection to ECM.