Chart A-1 No Service Engine Soon Light

Chart A-1:

"Service Engine Soon" Light Wiring Diagram:

***UPDATED BY TSB # 92-6E-26 DATED NOVEMBER 1992




CIRCUIT DESCRIPTION:


There should always be a steady "SERVICE ENGINE SOON" light when the ignition is "ON" and engine stopped. Battery voltage is supplied through the ignition switch 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.

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 12V (B+) probe each of the system ground circuits to be sure a good ground is present.


DIAGNOSTIC AIDS:

Engine runs OK, check:

^ Gauge fuse.

^ CKT 419 open.

^ Faulty light bulb.

Engine cranks but will not run:

^ Continuous battery - fuse or fusible link open.

^ CKT 440 or fusible link open.

^ Ignition CKT 639 to ECM open.

^ Poor connection to ECM.

^ Poor ECM ground.