Pretty sure there isn't going to be an easy way to unlock the NAV functions like type in a hidden code or anything, this topic has floated around boards for several years without any resolution that was quick and painless. I did notice on the schematic for my car during an audio upgrade, that there is a speed sensor wire that goes from the nav control module to the stereo head unit to the instrument cluster. Perhaps, if that isn't connected at all, the nav will think that the car is not moving...or it may not. I haven't experimented with it to find out. Don't know about the XF wiring charts though, it may be more complex that just that.