Malfunctioning Speedometer

try unplugging the whole speedo harness and letting it set for a couple of minutes and then plug it in and let it run through it's self configure mode and see if it helps....by chance do you have aftermarket gauge faces in it???

I think if you unhook your battery your computer will reset

take the two screws on the top portion of your bezel out and pull that out. Next there will be four of those star screws (anti theft I forget there actual name) take them out and ease your gauge cluster out. It will barely pull out so next you have to disconnect the two groups of wires in the back of it by pulling up on the big tabs....you might have to get a small screwdriver and pry it the first couple of times. then you can take your gauge cluster out....I suggest cleaning it while you have it out. See if you can find a website that details a white gauge face install because it is the same premise and will probably have pictures. Ohhh yeah the hardest part is the first step actually before taking the two screws off you have to get your headlight knob off....you do this by pulling it out and rotating it until you see a recessed area with metal in the middle....take a screwdriver and press down on this metal and simultaneously pull it off and thats it.