2005 GMC Yukon Owner's Manual - Page 120

The three modes you can choose between are: This button is used to enable or disable the StabiliTrak® and is also used to shift the transfer case into Neutral (N). For more information on using StabiliTrak®, see StabiliTrak® System on page 4-10. d (StabiliTrak®): {CAUTION: Shifting the transfer case to NEUTRAL can cause your vehicle to roll even if the transmission is in PARK (P). You or someone else could be seriously injured. Be sure to set the parking brake before placing the transfer case in NEUTRAL. See Parking Brake on page 2-35. N (Neutral): Shift the vehicle's transfer case to NEUTRAL only when towing your vehicle. See Recreational Vehicle Towing on page 4-62 or Towing Your Vehicle on page 4-62 for more information. Indicator lights in the buttons show which mode you are in. The indicator lights will come on briefly when you turn on the ignition and one will stay on. If the lights do not come on, you should take your vehicle to your dealer for service. An indicator light will flash while the transfer case is shifting. It will remain on when the shift is complete. If for some reason the transfer case cannot make a requested shift, it will return to the last chosen setting. f (All-Wheel Drive): This button allows the transfer case to distribute power to all four wheels as needed depending on road and driving conditions. 4 n (4LO): This button allows the transfer case to deliver extra torque to the wheels, and provides for precise control of wheel speed by engine braking. You may never need this setting. It sends maximum power to all four wheels. You might choose four-wheel low if you are driving off-road in deep sand, deep mud, deep snow, and while climbing or descending steep hills. 2-32