1994 GMC Jimmy Owner's Manual - Page 125

Malfunction Indicator Light (SERVICE ENGINE SOON) Cluster Standard Digital Cluster A computer monitors operation of your fuel, ignition and emission control systems. This light should comeon when the ignitionis on, butthe engine is not running, as a check to show it is working. If it does not come on at you all, have it fixed right away.If it stays on,or it comes on while you are driving, the computeris indicating that you have a problem. You should take your vehicle for service soon. in NOTICE: If you keep driving your vehicle with this light on, after a while the emission controls won't work well, your fuel economy as won't be as good and your engine may not run as smoothly. This could lead to costly repairs not covered by your warranty. 2-71