See also:

Cellular and GPS Antennas
Avoid placing items over or near the antenna to prevent blocking cellular and GPS signal reception. Cellular reception is required for OnStar to send remote signals to the vehicle. ...

Ignition Transmission Lock Check
While parked, and with the parking brake set, try to turn the ignition to LOCK/OFF in each shift lever position. • The ignition should turn to LOCK/OFF only when the shift lever is in P (Park). †...

Speedometer
The vehicle's speed can be selected to display on the Driver Information Center (DIC) and the speedometer in either kilometers per hour (km/h) or miles per hour (mph). Telltales on the speedom ...