check engine light

I just got a 99 Ranger....one week has gone by and the check engine light is on.....this happened on my 03 that I just got rid of and it was the gas cap....any other ideas so I don't have to drive 100 miles to where I got the warranty?

Take it to any Autozone store and ask them to check the OBD-2 codes. They do it for free! It will tell you what codes caused the light to come on. The same handheld codescanner can reset the codes to make the light go off, but if there is a problem, it will return. If it seems to be running ok, it probably is a bad oxygen sensor. If so, the computer will even tell you which one. If you just bought it, I'd be suspicious that the dealer may have just reset the codes to get it off the lot. I'd check the codes, then make the dealer fix the problems.