2003 Ford F-150 v6 Auto Reg Cab Sport, Speedometer stays maxed when vehicle is not moving. It stays this way until you reach speeds of 40mph or greater the it shows I'm going 85mph. When in park or turned off its pegged out. I purchased the truck this way and all other gauges function correctly. Any ideas would be greatly appreciated....

 

Not to sure but it kind of sounds like maybe your ground and power wires are switched.

 

At what location would they be switched and how would I go about fixing this?