Chart A-1 No Service Engine Soon Light

Fig. 038 Wiring Diagram for Chart A-1 No "Service Engine Soon" Light:

CHART A-1

NO "SERVICE ENGINE SOON" LIGHT

2.5L (VIN U) (TBI)

Circuit 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 light. 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 light bulb. The electronic control module (ECM) controls the light and turns it "ON" by providing a ground path through CKT 419 to the ECM.

Fig. 037 Chart A-1 - No "Service Engine Soon" Light:

Test Description:
Numbers below refer to circled numbers on the diagnostic chart.
1. This check determines if there is a fault in the "SES" light circuit in the ECM.
2. If CKTs 240 and 439 have voltage, the ECM grounds or the ECM is faulty.
3. Using a test light connected to 12 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 the ECM terminal locations of ground circuits.




Diagnostic Aids:
If engine runs OK, check the following:
a. Faulty light bulb
b. CKT 419 open
c. Gages fuse blown. This will result in no oil or generator lights, seat belt reminder, etc.
If engine cranks but will not run, use CHART A-3.