1. I can program a destination, but when I start the nav I get a prompt saying something like "the route can not be calculated, you are not on a digitized street." Consequently I do not get any directions, although it will show my starting point and my destination on the map. What does that mean, and why?

2. My position on the map will only change every 30 secs or so.

3. The center cluster will typically say "off road", and the direction arrow for my destination is inaccurate

Fyi; I consistently show betwen 6-8 satellites.

also, my nav disc is not an original; it's a copy that came with the unit as a 2008 map. It does show local streets, etc.

Any help/comments appreciated.

TIA

You will get the first message as long as you are off a road that the Nav DVD does not recognize.

Again the 3rd message will be displayed if you are in a location that the DVD does not recognize.

Maybe try using a different DVD to see if thats the problem.

a tremendous amount of time vs. connecting via headliner or trunk. And I was able to get rid of 4 pounds of useless weight (the OnStar unit itself, which became useless when OnStar switched to digital only).

even with the correct tire size set in channel 1 and the proper speed signal received.