I just had a 120BT installed in a Nissan Xterra (2010). Initially, the installer forgot to install the VSS wire, so I went back yesterday to get that done.
It is connected, as I do get a sensor reading, but it ranges from 0 to 20, no matter how fast I'm going.
Is it supposed to read the actual MPH, and is somehow not connected right, or does the sensor status page represent some other value...?
Thanks
I had the same questions a few months back. See this thread for your answer.
The readings you are seeing are normal and in the range of the pulse output information from your vehicle. The speed sensor feedback is a pulse, not a exact replication of your actual mph. This pulse is sending a signal back to your speedometer and to your ABS controls let it know what the rotation speed of your tires are so they translate correctly. I have my VSS wire connected and what you are seeing is exactly correct and the same readings I get...Your fine.. 
P.S. I read somewhere on the forums where someone heard that the Speed Pulse (VSS Signal) should read twice as high as the actual speed of the vehicle. This is not correct....You should be seeing SP numbers in the range of 0-20 as your speed increases or decreases.
Hope I help put your mind at ease!! Have a Happy 4th!!
Peace ~ HFoM