Hi There I've got the genuine Toyota satnav in my Prado, and a couple of years ago remember reading about this on some of the U.S. forums. Just trying to find this now reveals the most common problem for this is that the Navigation system must have the speed sensor wire connected so it can compute things as it is going along. Without this connection, the symptoms are exactly as you say. From a U.S. site which resells genuine toyota navs : Toyota OEM Audio, Video See Nav Install for details on the speed sensor. It is part of the R12 plug on the back of the stereo. What model is your car? Perhaps it had the navigation system fitted later and this has never worked, or maybe is simply playing up. Anyway, Toyota should be able to fix for you if don't feel like looking for yourself. Hope this is of some use.