2003 GMC Yukon Owner's Manual - Page 121

You can choose among four driving settings: h (2HI): This setting is used for driving in most street and highway situations. Your front axle is not engaged in two-wheel drive. This setting also provides the best fuel economy. AUTO 4WD: This setting is ideal for use when road conditions are variable. When driving your vehicle in AUTO 4WD, the front axle is engaged, but the vehicle's power is sent only to the rear wheels. When the vehicle senses a loss of traction, the system will automatically engage four-wheel drive. Driving in this mode results in slightly lower fuel economy than 2HI. The transfer case buttons are located to the left of the instrument panel cluster. Use these switches to shift into and out of four-wheel drive. G (4HI): Use the 4HI 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 your vehicle. This is the best setting to use when plowing snow. 2-27