See also:

Onstar.com
The website provides access to account information, manages the OnStar subscription, and allows viewing of videos of each service. Get subscription plan pricing and sign up for OnStar Vehicle Diag ...

Units
Press the vehicle information button until UNITS displays. This display allows you to select between metric or English units of measurement. Once in this display, press the set/ reset button to selec ...

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 ...