I found a post that has the VSS location

VSS = Vehicle Speed Sensor. You don’t NEED to connect this. But if you do, the Navigation is supposed to be more accurate.

 

In the Edge, you can find this wire coming from the PCM (Powertrain Control Module), which is under the hood on the passenger side of the engine. It is the purple/orange wire.

Reference:

http://www.fordedgeforum.com/index.php? ... c=728&st=0