Its definitely enabled on the NAV systems... that signal is also used to disable access to some of the NAV functions so you aren't adjusting them in a moving vehicle.. In fact in the discussion for it there is a fair amount of information on the harness and diagrams so people could disable it. Look in the threads on this site for the NAV system and the ones on adding in an iPod... they both have info on the wiring harness. However I think I read that the wiring harness for the NAV vehicles is significantly different than the non NAV system FEH's. It sounds counterintuitive because you'd think a company wouldn't want to have a whole bunch of different parts for different options if it could be avoided... but you might find that even if a NAV vechile has the VSA (I think thats what the signal is called) yours might not have the same signal available.