With PCM

Chart A-1 MIL (Service Engine Soon) Diagnostic Chart:

MIL (Service Engine Soon) Wiring Schematic:

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 Powertrain Control Module (PCM) will control the lamp and turn it "ON" by providing a ground path through CKT 419 to the PCM.

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step will isolate the problem in CKT 419.
2. If CKTs 440 and 439 have voltage, the PCM connections, grounds, or PCM are 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 Control Module / Connector Views for PCM pin locations of ground circuits. Connector Views

DIAGNOSTIC AIDS
Check PCM grounds for being clean, tight, and in their proper locations.