Just remember it's best not to run low on fuel. It's what lubricates your fuel pump. Every time you run down past the low fuel light it shortens the life of your fuel pump.
Brwbier

 

HUH?

 

It uses both. Cell phone for communication with OnStar and GPS for telemetry. The GPS satellites are used to locate the car, but without cell service you cannot contact nor talk to OnStar. The range is typically better than a standard cell phone nowadays.

Here's a LOT more info on OnStar:
http://auto.howstuffworks.com/onstar.htm

 

Quote:
Originally Posted by Brwbier
Every time you run down past the low fuel light it shortens the life of your fuel pump.
Brwbier

HUH?
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The fuel pump has a electric motor, sits low if not on the bottom of the tank. Low fuel level in tank= fuel pump motor runs "dry"(not sitting in fuel),wearing out the motor prematurely.
Never a good idea to run each tank down to get last drops outa it.

 

Charge the phone with my ciglight adapter and walk until I get signal.