Chart A-1 No Service Engine Soon Light

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

Wiring Diagram for "Service Engine Soon" Light.:

CHART A-1


NO "SERVICE ENGINE SOON" LIGHT 3800 (VIN C) (PORT)


Circuit Description:


There should always be a steady "Service Engine Soon" 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".

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.


DiagnosticAids:


Engine runs OK, check:


Faulty light bulb
CKT419open

Engine cranks, but will not run:


Continuous battery - fuse or fusible link open

ECM ignition fuse open

Ignition CKT 439 to ECM open

Poor connection to ECM