Chart A-1 No Malfunction Indicator Lamp (MIL)

Chart A-1 No Malfunction Indicator Lamp (MIL):

Malfunction Indicator Lamp Wiring Circuit:

Circuit Description:

There should always be a steady MIL (Service Engine Soon) when the ignition is "ON" and engine is "OFF." Battery voltage is supplied through the ignition switch directly to the lamp. The Powertrain Control Module (PCM) controls the lamp and turns 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. If the fusible link is blown, locate and repair short to ground.
2. Using a test light connected to 12 volts (B+) probe each of the system ground circuits to be sure a good ground is present. See "PCM Terminal End View" in front of this section for PCM pin locations of ground circuits.

Diagnostic Aids:

Engine runs OK, check:
^ Faulty light bulb.
^ CKT 419 open.
^ Gauges fuse blown; this will result in the loss of MIL, brake light, etc. on I/P.

Engine cranks but will not run.
^ Fuse or fusible link open.
^ ECM fuse open.
^ Battery CKT 2 or 440 to PCM open.
^ Ignition CKT 439 to PCM open.
^ Poor connection to PCM.
^ Poor PCM ground.
^ Underhood fuel pump and ECM power fuse.