Horn
Pressa 
on the steering wheel pad
to sound the horn.
See also:
When It Is Time for New Tires
Factors, such as maintenance, temperatures, driving speeds, vehicle loading, and road conditions affect the wear rate of the tires.
Treadwear indicators are one way to tell when it is time for new ...
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 Diagnos ...
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 ...