I just had the same lights on an 03, I found the speed sensor in the rearend was actually broke off. It set a code for something like transmission pressure at 0 mph. Everything seemed to function properly except the speedometer. It seemed to jump up to 5 or 10 mph if you just moved 3 feet and took a few seconds to drop all the way to 0 after stopping. It worked properly otherwise. Hope that helps, sensor was under $40 at Carquest.
Matt