Someone posted this on Yahoo Answers, and it worked!!

TURN THE CAR ON AND MAKE SURE THAT THE MILES READS ON ODOMETER, NOT ON TRIP A OR B. TURN THE CAR OFF THEN HOLD DOWN THE ODOMETER BUTTON AND TURN THE CAR ON. RELEASE THE ODOMETER BUTTON AFTER LIKE 3 SECS. AND THEN THE GAUGE SHOULD START TO COUNT DOWN. THEN IT WILL BE CLEARED