Video as requested.
You can see the menu has most items grayed out and unavailable. When we reached 22 kph (notice the HUD) driver pushed the hangup button (see post above), and all functions become available. But GPS gets "lost".
http://www.youtube.com/watch?v=rhfu_CxTDk4

Answers! Feeding in no speed signal or a wrong speed signal really messes with the GPS brain - it becomes worse than a standard GPS - you can be off by a km and pointing in the wrong direction. Don't know why, but makes sense to only isolate while using the MMCS for other functions - you only need i...

Inhibiting the speed override is simple. It can be done by cutting the blue-white wire mentioned above and putting a 10k resistor in between the ends. The 10k allows normal operation, but if you put 5V into the MMCS side, the MMCS will operate as if stationary. It will mess up GPS operation so must ...