Regal V6-191 3.1L (1991)
No "Service Engine Soon" Light Or Won't Flash Code 12
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 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.
If the fuse in holder is blown refer to wiring diagram of Code 54 for complete circuit.
2.
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 CONNECTOR
IDENTIFICATION in SCHEMATIC DIAGRAMS/ELECTRICAL AND ELECTRONIC DIAGRAMS for ECM pin locations of ground
circuits.
DIAGNOSTIC AIDS:
Engine runs OK, check:
^
Faulty light bulb.
^
CKT 419 open,
^
Gage fuse blown. This will result in no stop lights, oil or generator lights, seat belt reminder, etc.
Engine cranks but will not run:
^
Continuous battery - fuse or fusible link open.
^
ECM ignition fuse open.
^
Battery CKT 480 to ECM open.
^
Ignition CKT 439 to ECM open.
^
Poor connection to ECM.
