Chart A-1 No Malfunction Indicator Lamp (MIL)

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

System Check Schematic:

CIRCUIT DESCRIPTION
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. There should always be a steady Malefaction Indicator Lamp (MIL) (Check Engine) when the ignition is "ON" and engine is "OFF."

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

1. If the fusible link is open, locate and repair short to ground.
2. Connecting a test light to (B+) and probing each ground circuit verifies a good ground is present. See Connector Views for PCM pin locations of ground circuits when using breakout box J397OO use overlay #J 39700-112. Connector Views

DIAGNOSTIC AIDS
Engine runs OK, check:
^ Faulty lamp.
^ CKT 419 open.
^ Gauges fuse open; this will result in the loss of etc. on Instrument Panel (I/P).
^ Faulty I/P cluster.

Engine cranks but will not run.
^ PCM ignition fuse open.
^ Battery CKT 480 to PCM open.
^ Ignition CKT 639 to PCM open.
^ Poor connection to PCM.
^ Poor PCM ground.