2005 GMC Sierra 1500 Pickup Owner's Manual - Page 145

Mirrors {CAUTION: Manual Rearview Mirror Four-wheel drive vehicles with the transfer case in NEUTRAL will allow the vehicle to roll, even if your automatic transmission shift lever is in PARK (P). So, be sure the transfer case is in a drive gear - not in NEUTRAL. Always set your parking brake. Follow the proper steps to be sure your vehicle will not move. See Shifting Into Park (P) (Automatic Transmission) on page 2-49. If you are pulling a trailer, see Towing a Trailer on page 4-68. Pull or push the tab under the mirror to adust it to the night or daytime setting. In the nightime setting, the glare from headlamps behind the vehicle will be less intense. Automatic Dimming Rearview Mirror with OnStar®, Compass and Temperature Display Your vehicle may have this feature. When on, an automatic dimming mirror automatically dims to the proper level to minimize glare from lights behind you after dark. The mirror also includes a dual display in the upper right corner of the mirror face. The compass reading and the outside temperature will both appear in the display at the same time. P (On/Off): This is the on/off button. 2-55