Chart A-1 No Check Engine Light

No Check Engine Light:

Chart A-1 Wiring Diagram:

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. Providing a ground should turn the "CHECK ENGINE" light "ON."

2. Checks for B+ from control relay.

3. Verifies B+ to control relay from ignition switch.

4. Test light connected to voltage. Check the ECM for a good ground.

5. The test should be "ON" indicating the control relay is faulty.

DIAGNOSTIC AIDS:

^ Faulty light bulb.
^ Open in violet wire circuit.
^ Engine cranks, but will not run.
^ Battery feed circuit open.
^ Control relay faulty.
^ Ignition circuit open.
^ Poor ECM connects.