I have a Dec 06 unit that had the 2 wire bypass. My installer apparantly forgot to connect the VSS wire. Can you have the VSS wire connected and the bypass still functioning or does it have to be disconnected?

Yes,

You can have them both connected. The VSS wire connection will not affect the by-pass in any way.

The VSS connection will give you more accuracy in ETA times and GPS location accuracy so it really needs to be connected.

Cheers,

Kevin

accuracy is about 3 feet, according to pioneer. but vehicle dynamics wont fully work if vss is not connected