No Service Engine Soon Light

Diagnostic Chart.:

PCM Wiring:

DESCRIPTION
There should always be a steady SERVICE ENGINE SOON light when the ignition is On and engine stopped. Battery voltage is supplied directly to the bulb. The powertrain control module (PCM) will control the lamp and turn it On by providing a ground path through Circuit 419 to the PCM.

PARAMETERS
^ Lamp will not illuminate if power or ground is lost to the PCM or bulb.
^ Lamp will not illuminate if bulb is shorted or open.


DIAGNOSTIC AIDS

Engine runs OK check:
^ Faulty bulb.
^ Circuit 419 open.
^ Ignition 1 fuse blown.
^ Faulty Quad driver.

Engine cranks but will not run:
^ PCM B fuse blown
^ PCM 1 fuse blown
^ Ignition 4 MAXI fuse blown.
^ Circuits 480 or 439 open.
^ Terminal tightness at PCM.