Chart A-1 No Service Engine Soon Light

Chart A-1 - No "Service Engine Soon" Light:

Wiring Diagram for No "Service Engine Soon" Light.:

CHART A-1 NO -SERVICE ENGINE SOON LIGHT


Circuit Description:
There should always be a steady "Service Engine Soon" (SES) light, when the ignition is "ON" and engine stopped. Battery is supplied directly to the light bulb. The Electronic Control Module (ECM) will control the light and turn it "ON" by providing a ground path through CKT 419 to the ECM.


Test Description: Numbers below refer to circled numbers on the diagnostic chart.
1. "Service Engine Soon" light should be "ON" as the test light provides the ground.
2. Using a test light connected to l2 volts, probe each of the system ground circuits to be sure a good ground is present. See ECM terminal end view in front of this section for ECM pin locations of ground circuits.


Diagnostic Aids:

Engine runs OK, check:
Faulty light bulb
CKT 419 open

Engine cranks, but will not run check:
Continuous battery - fuse or fusible link open
ECM ignition fuse open
Ignition CKT 439 to ECM open
Poor connection to ECM