2001 Nissan Frontier

Electrical problem
2001 Nissan Frontier 4 cyl Two Wheel Drive Manual 70,000 miles

The other day my service engine soon light came on, and has remained on. I looked it up in my owner's manual, and all it said was to check and make sure my gas cap was screwed on tight. It then stated that after a few trips the light should go off. Well, I did and it hasn't. The only other alternative is to take it in and I am new to my area, and I don't have a mechanic yet. I looked at all of the fuses and checked underneath the hood for any loose connectors, etc. Any suggestions before I take it in?
June 4, 2008.

I would bring it to autozone, or your local parts place for a free scan, then you can post the results to me and we will take it from there, in the mean time make sure all of your fluids are correct.