2003 GMC Sierra 1500 Pickup Owner's Manual - Page 123

An 4WD indicator light will illuminate when you shift into four-wheel drive and the front axle engages. An indicator on the bezel near the lever shows you the transfer case settings: 2-Wheel High (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. 4-Wheel High (4HI):: Use 4HI 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 use when plowing snow. I- Some delay between shifting and the indicator's lighting is normal. Recommended Transfer Case Settings Transfer Case Settings *See Recreational Vehicle Towing on page 4-53or Towing Your Vehicle on page 4-53 for further information. Shllklng the transfer case to hcJTRAL can cause your vehicle to roll even if the transmission is in PARK (P), or if you have a manual transmission, even if you are in gear. You or someone else couldbe seriously injured. Be sure to set the parking brake before placing the transfer case inNEUTRAL. See "Parking Brake" in the Index. 2-36