How to Check VSS Wire

Hello,

I have a 2004 Ford F150 Extended Cab pickup that I am trying to retrofit a 2006 Ford Factory Navigation unit into.  The unit is made by Pioneer as an OEM Navigation unit.  The unit appears to be modeled after the Pioneer AVIC-D1.  Pioneer's part number for this unit is AVIC-XD1. The Ford part number is 6G1T-18K931-AD.  The back of this unit looks exactly like the back of Ford's 6 CD Audiophile stereos.  It has the same three plugs on the back and they plugged right into the factory wiring harness. 

So far everything has gone well and works except that the map does not track with the movement of the truck.  I think the probem lies with the VSS signal.  Can anyone tell me how to check the VSS signal.  I know which wire it is (grey w/black stripe on pin 14 on back of radio)  I'm looking for information on how to see if it is working.  Is it a simple voltage check as the vehicle is moving or is it something more complex?

When I bought the truck it had a single CD factory radio.  So I'm wondering if some of the wires are not hooked up in the harness.

Another question; This unit came out of a 2006 Ford Explorer.  Does anyone know if it is vehicle specific and whether it needs to be programmed or set up for a different vehicle?

Any help would be greatly appreciated.

Thanks,

Willie

The GPS antenna is hooked up.  Its mounted under the dash.  I was tols that as long as there is no metal blocking it it will pick up the satalite signaul throughplastic.  It connects and I get a great signal.  I am able to check it in the diagnostics of the Navigation unit

Is the VSS signal just an open and close signal as in a relay or is it an actual voltage pulse?

Thanks for all your help,

Willie