My check engine light came on?

Ok my truck just failed California smog check because the check engine light does not function. I guess the light is burned out? Is this something that I can replace? I asked at autozone if this was a part that they could get and they told me it was a dealer specific light. Apparently there is some history of the truck that I am not aware of. I bought it used in Wyoming and then moved to California. It is the 3.0 liter V6, automatic and 4X4. Thanks for any help.

2000 Ford Ranger Super, 105,000 miles, 6 cylinder. Just wondering what would cause the check engine light to come on?

The check engine light is governed my emission controls, if some thing causes your emission controls to recieve a signal out of range then it will light your check engine light (if it can not fix the problem itself), there are too many things to list, first I would get the computer scanned for codes and go from there. If you get codes post em, someone here should be able to help ya