01 Ranger XLT SuperCab 4.0 4 X 4

I just purchased this vehicle yesterday - nice ride with only 16,700 miles on it! I replaced the serpentine belt last night due a whining noise and it runs ever so quiet right now. My problem is this - the CHECK ENGINE light came on after about 20 miles and hasn't went off since!! I checked the gas cap (due to previous postings mentioning this) and it seems to be fine. I know you can disconnect the battery and reset the system but I'd rather not do this since I've heard that it can wipe out the diagnostics or erase them and make troubleshooting difficult. Is there anything I can do myself? I have an appointment scheduled with a local dealer as its still under warranty but I'm just curious what could be causing this with so low mileage on the vehicle - Thanks

my 2000 3.0l had a fuel sensor set off the check engine light at 20,000 so it could be anything.just for future reference,i had a squeek and it turned out to be the a/c compr clutches.

Techs here at work just ran a check on it .. came back as DPFE and EGR - Sensor issue. Off to the shop tonight .. hope this isn't something I can look forward too often!? Thanks for the insight ..

Well, I dunno what I can tell you other than my experience. Two months ago I bought an 00 4x4 4l 5sp from a dealer with 32" mudders on it and 45k miles. In the glovebox were about a hundred "fix-it" receipts, under warranty of course.
Now, I get the worst mileage ever in a compact pickup and the truck runs hot on the highway. BUT it has not given me a problem.