Sorry, I can't answer your question. Although every car I've bought or leased has had On Star (as have many of my rental Caddy's from AVIS), I have never used nor renewed the service. (My reasons are "for another day.) But why not purchase a Garmin C340 GPS on Amazon or some other discount site (not the C330 or C350). It is one of my favorite toys, easily portable in carry-on, recharges off the car's accessory socket, accurate down to 30ft. --- and, besides the clearly readable video display, has a lilting British Lass (if you so choose) who speaks to you step by step till you reach your destination.