factory nav no prompts, not working...help!

[amighjm6]

just traded my '00 tahoe in on a 2008 with factory nav, but it's obviously not working as its supposed to. it will let me add a destination, and it does prompt me to follow the route, but then there are no turn by turn directions, and it won't recalculate the route if i detour. it does tell me " you have reached your destination", so i know its not a volume issue and the prompts should work. i've read a few threads about installing a factory unit and having to hook up the vss wire...but i assume that would already be done in a factory installed unit? how do i check to see? any other ideas?
thanks in advance

 

[blueflamed03]

have you had dealer look at it?

 

[amighjm6]

nah, i've only had it a week...at first i thought it was just a crappy system, then i started reading some other people having the same types of problems, but they were all installing the units themselves, i haven't seen a situation where it was a factory installed issue. if i have to, i will take it to the dealer, but i hate to pay the dealer to diagnose and fix something if i can do it myself.