Engine Control Module - ECM

Chart A-1:

DLC Connector Circuit:

CIRCUIT DESCRIPTION
There should always be a steady Malfunction Indicator Lamp (MIL) when the ignition is "ON" and engine stopped. Battery voltage is supplied to the lamp. The ECM will control the lamp and turn it "ON" by providing a ground path through MIL control circuit to the ECM.

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

1. This step will isolate the problem in the MIL control circuit.

2. If the battery feed and ignition feed circuits have voltage, the ECM connections, grounds, or ECM is faulty.

3. Using a test light connected to 12 volts, probe each of the system ground circuits to be sure a good ground is present. Refer to ECM terminal end view for ECM pin locations of ground circuits.

4. If the fuse/fusible link is open, refer to ECM wiring diagram for complete circuit.

DIAGNOSTIC AIDS
If the engine runs OK, check:
^ Faulty lamp.
^ The MIL control circuit open, shorted to ground or open fuse.
If the engine cranks but will not run, check:
^ Continuous battery-fuse or fusible link open.
^ ECM ignition fuse open.
^ Battery feed circuit to ECM open.
^ Ignition feed circuit to ECM open.
^ Poor connection to ECM.