2008 GMC Yukon Owner's Manual - Page 147

Mirrors {CAUTION: Four-wheel drive vehicles with the transfer case in NEUTRAL will allow the vehicle to roll, even if the shift lever is in PARK (P). So, be sure the transfer case is in a drive gear - not in NEUTRAL. Always set the parking brake. Follow the proper steps to be sure your vehicle will not move. See Shifting Into PARK (P) on page 2-44. If you are pulling a trailer, see Towing a Trailer on page 4-49. Automatic Dimming Rearview Mirror with OnStar®, Compass and Temperature Display Your vehicle may have this feature. When on, the automatic dimming mirror dims to the proper level to minimize glare from lights behind you after dark. The mirror has a dual display in the upper right corner of the mirror face that shows the compass reading and the outside temperature. Control buttons for the OnStar® system are at the bottom of the mirror. See OnStar® System on page 2-60 for more information about the services OnStar® provides. P (On/Off): This is the on/off button. 2-49