Reactivation for Subsequent Owners
Push 
and follow the prompts to speak to an Advisor as soon as possible after acquiring the vehicle.
The Advisor will update vehicle records and will explain the OnStar service offers and options available.
See also:
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 ...
Doors Liftgate
WARNING
Exhaust gases can enter the vehicle if it is driven with the liftgate or trunk/hatch
open, or with any objects that pass through the seal between the body and the trunk/hatch
or liftgate. ...
Using the “Delete” Command
1. Press and hold for two seconds.
2. Say “Delete.” 3. Say the name tag you want to delete. ...