Had same problem on the '02- replace the battery with a fresh one. That cures a host of electrical problems. If that doesn't get it then the gauge is bad. Most 01-04 Sprints had some form of "guess gauge" symptoms. Mine reads full for 80 miles then drops to just above E in 40 miles then stays there until the low fuel light comes on at 180 miles. gave up on accuracy and just click the odo every fillup, watch the miles and the low fuel light.
But if you're having other instruments going flitchy then the new battery will sort that.
cheers