See also:

Footnotes — Maintenance Schedule Additional Required Services — Normal
a) Or every two years, whichever comes first. More frequent replacement may be needed if the vehicle is driven in areas with heavy traffic, areas with poor air quality, or areas with high dust levels. ...

Turning the System On and Off
The system can be disabled through the Driver Information Center (DIC). See “Park Assist” under Vehicle Personalization (With DIC Buttons) on page 5‑46 for more information. URPA defaults ...

New for 2011
The Sierra Hybrid gets GM's OnStar 9.0 telematics system that GM says provides better voice recognition. GM also said they have worked to cut down on the amount of wind noise occupants hear. ...