GMC Sierra Owners Manual
Global Positioning System (GPS)
• Obstruction of the GPS can occur in a large city with tall buildings; in parking garages; around airports; in tunnels, underpasses, or parking garages; or in an area with very dense trees. If GPS signals are not available, the OnStar system should still operate to call OnStar. However, OnStar could have difficulty identifying the exact location.
• In emergency situations, OnStar can use the last stored GPS location to send to emergency responders.
• A temporary loss of GPS can cause loss of the ability to send a Turn-by-Turn Navigation route.
The Advisor may give a verbal route or may ask for a call back after the vehicle is driven into an open area.