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 ...

Exterior
While GM is trying to differentiate the Silverado and Sierra, the common silhouette is hard to overcome, even with unique front fenders, grille, bumpers, headlamps, cargo box and taillamps. There' ...