Bonneville V6-3800 3.8L (1991)
Wiring Diagram
CIRCUIT DESCRIPTION:
There should always be a steady "SERVICE ENGINE SOON" (SES) Light when the ignition "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 12 volts probe each of the system ground circuits to be sure a good ground is present. See ECM CONNECTOR
IDENTIFICATION in ELECTRICAL AND ELECTRONIC DIAGRAMS
DIAGNOSTIC AIDS:
Engine runs OK, check:
^
Faulty light bulb.
^
CKT 419 open.
^
Gage fuse #16.
Engine cranks but will not run, check:
^
Continuous battery - fuse or fusible link open.
^
ECM fuse #7 open.
^
Ignition CKT 439 to ECM open.
^
Poor connection to ECM.
