have a 94 2wd 300 six F-150 and the Engine check light came on 2 years ago. The truck runs perfect gets 20mpg . I had it checked and they said it was a sensor that tells me if a expensive $350 vacuum part (named with 3 letters,forget what they were now) is working and it would cost $70 to get and it was $70 to do the test.
I just payed the test and left without fixing anything. I just noticed the CEL(Check Engine Light) is out now but the truck still runs the same.

I rented a new Dodge SUV and its engine light came on so I was told to bring it to a dealer and they told me not to worry about it! and the SUV ran great for it's 500 mile road trip.

Now the other day my friends 2003 Chevy Siverado Engine light came on and the dealership could not find anything wrong said it can happen if it rains or goes through a car wash! They may be right because it was raining and his light went out now.
I think because mine was on for 2 years that the CEL light bulb finally bunt out. [img]/ubbthreads/images/%%GRAEMLIN_URL%%/grin.gif[/img]
I just think these things cause more trouble than they detect.