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. ...

Customer Assistance Offices (U.S. and Canada)
GMC encourages customers to call the toll-free number for assistance. However, if a customer wishes to write or e-mail GMC, the letter should be addressed to: United States GMC Customer Assistance ...

Remote Keyless Entry (RKE) System Operation
The Remote Keyless Entry (RKE) transmitter will work up to 60m (195 ft) away from the vehicle. There are other conditions which can affect the performance of the transmitter. See Remote Keyless E ...