What year is your Jeep? I forget what year it started, but usually you can cycle the key from the ACC position to the ON position 3 times and it will display where the odometer usually is. So, ACC, ON, ACC, ON, ACC, ON, then leave it and it should show you what code/codes is/are stored in the computer. It will run through the code(s) that the computer has then it will say "done". I want to say Jeep (and Chrysler products in general) started doing that in 1999 or so. I'd give that a shot, or run by an AutoZone...I'm pretty sure there's one down in Aspen Hill. I'd run the code for you, but I can't find my scanner to save my life (cheap-o AutoZone one, but it did the trick). As far as scanners go, if all you're looking to do is scan codes and clear them, then the cheapest OBDII one you can find will work just fine.