See also:

Using ABS
Do not pump the brakes. Just hold the brake pedal down firmly and let ABS work. You might hear the ABS pump or motor operating and feel the brake pedal pulsate, but this is normal. ...

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 ...

Manual Operation of Power Liftgate
To change the liftgate to manual operation, turn the mode switch to the OFF position. With the power liftgate disabled and all of the doors unlocked, the liftgate can be manually opened and closed. ...