I bought a 2008 Avalanche LTZ with navigation (no DVD) off the dealer and they have been no help with the issue I am having.

From what I can tell the unit it is factory installed.

I have realized that the GPS signal is either non-existent or very limited. I have searched many forums and have come across a couple of main potential causes:

-After market window tint on windshield or windows (which I have both)
-GPS Antenna is poorly located and is not providing or receiving a clear signal.
-VSS wire is not available or connected.
-OnStar may be causing an interference (plan to use the trial version only)

I'm pretty new to all of this so I have a couple of questions:

- Where is the typical GPS antenna unit located for a factory installed nav unit? Some have said near the rear view mirror.

- Shouldn't the factory installed unit have a VSS wire already?

- Can I disable On-Star to see if that is causing the issue?

Any help is appreciated!