2009 GMC Yukon Owner's Manual - Page 144

2 m (Two-Wheel Drive High): This setting is used for driving in most street and highway situations. The front axle is not engaged in two-wheel drive. This setting also provides the best fuel economy. AUTO (Automatic Four-Wheel Drive): This setting is ideal for use when road surface traction conditions are variable. When driving your vehicle in AUTO, the front axle is engaged, but the vehicle's power is primarily sent to the rear wheels. When the vehicle's software determines a need for more traction, the system will transfer more power to the front wheels. Driving in this mode results in slightly lower fuel economy than Two-Wheel Drive High. 4 m (Four-Wheel Drive High): Use the four-wheel high position when you need extra traction, such as on snowy or icy roads or in most off-road situations. This setting also engages your front axle to help drive the vehicle. This is the best setting to use when plowing snow. 4 n (Four-Wheel Drive Low): This setting also engages the front axle and delivers extra torque. You may never need this setting. It sends maximum power to all four wheels. You might choose Four-Wheel Drive Low if you are driving off-road in deep sand, deep mud, deep snow, and while climbing or descending steep hills. The vehicle has StabiliTrak®. Shifting into Four-Wheel-Drive Low will turn Traction Control and StabiliTrak® off. See StabiliTrak® System on page 4-6. { CAUTION: Shifting the transfer case to N (Neutral) can cause the vehicle to roll even if the transmission is in P (Park). You or someone else could be seriously injured. Be sure to set the parking brake before placing the transfer case in N (Neutral). See Parking Brake on page 2-42. N (Neutral): Shift the vehicle's transfer case to N (Neutral) only when towing the vehicle. See Recreational Vehicle Towing on page 4-44 or Towing Your Vehicle on page 4-44 for more information. If the SERVICE 4 WHEEL DRIVE message stays on, you should take the vehicle to your dealer/retailer for service. See "SERVICE 4 WHEEL DRIVE message" under DIC Warnings and Messages on page 3-64. 2-38