2007 silverado factory nav

Depending on the exact nature of the problem a VSS signal may help.  Most navigation systems use GPS to initially locate your current position in the internal maps.  It then ujses the VSS and an electronic compass to move you around inside the maps.  While you are moving it will periodically compare your location to the GPS location and update if necesarry.  But, if you arn't moving it doesn't bother checking the GPS information.

So, if the GPS starts out on your current position but the position never moves I would look in to hooking up the VSS wire.  If the GPS never finds your location maybe the antenna is bad?

First, the GPS antenna must have a line-of-site to the sky.  Under your dash does no good for signals to your GPS antenna.  Place the antenna up on the roof and then drive around with it like this.  If after a few minutes it doesn't get a signal, you most likely have a bad antenna.

What I do to test the accuracy of the navigation, is cover your windows with some newspaper.  Then drive around with nothing but the nav guiding you.  If you don't hit anything, then you're good.

btw....jk.

This baffels me that you get a signal.  Whenever I've tried that or seen it tried by fellow installers, it never works.  I obviously know less about the GPS signal than previously thought.  One of those voo-doo things with me that I know what works for me and I go with it.  Maybe it's not covered by metal material, and the signal goes through the front windshield and the plastic dash?

For example, one of my clients with an 07 camry, had his GPS antenna mounted to the top of his trunk lid.  When he went through the car-wash and they popped the trunk to dry the lid off, the antenna got pushed into the trunk.  He lost his signal immediately and came running back to my shop because "something is wrong with my nav!"  So the antenna didn't have line of sight to the sky, and was underneath the metal trunk lid, no signal.  So maybe the antenna can get a signal through glass and a certain degree of plastic, but is thwarted by metal?

The factory GM nav needs a VSS wire connected. Without it it will not track correctly. You need the brown plug on the back of the nav, it's on that(most times it isn't there unless the truck already came with one). I have one out in the truck if you need pin location in the plug. The easiest place to access VSS is on the back of the distribution block under the dash to the left of the brake pedal. Pull it out and spin it around, it's a GREEN / WHITE wire on the center plug.

The factory location for the GPS antenna is to the left of the defrost vents. That panel pops up easily and there's a spot under it.