With Throttle Body Injection (TBI)

Fig. 010 Chart A-1 - No "Service Engine Soon" Light:

Fig. 011 - Wiring Diagram for Chart A-1 No "Service Engine Soon" Light VIN O, VIN 2, VIN R, VIN U:

CHART A-1

NO "SERVICE ENGINE SOON" LIGHT

1.8L VIN O 2.5L VIN 2 VIN R VIN U

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 circuit 419 to the ECM.
Engine runs OK, check:
a. Faulty light bulb.
b. CKT 419 open.
c. Gage fuse blown. This will result in no stop lights, oil or generator lights, seat belt reminder, etc.

Engine cranks but will not run.
a. Continuous battery-fuse or fusible link open.
b. ECM ignition fuse open.
c. Battery CKT 240 to ECM open.
d. Ignition CKT 439 to ECM open.
e. Poor connection to ECM.



1. Solenoids and relays are turned "ON" or "OFF" by the ECM, using internal electronic switches called "drivers". Each driver is part of a group of four, called "Quad-Drivers". Failure of one driver can damage any other driver in the set. Solenoid and relay coil resistance must measure more than 20 ohms. Less resistance will cause early failure of the ECM "driver".



Before replacing the ECM, be sure to check the coil resistance of all solenoids and relays controlled by the ECM. See ECM wiring diagram for the solenoids and relays and the coil terminal identification.
When checking TCC solenoid, be sure to raise drive wheels and run above 30 MPH to close third gear apply switch.