2005 GMC Yukon Owner's Manual - Page 121

If the SERVICE 4WD message stays on, you should take your vehicle to your dealer for service. See SERVICE 4WD under Driver Information Center (DIC) on page 3-54. Shifting Out of Four Wheel-Low To shift from Four-Wheel Low to All-Wheel Drive, your vehicle must be stopped or moving less than 3 mph (5 km/h) with the transmission in NEUTRAL (N) and the ignition in RUN. Press and release the all-wheel drive button. You must wait for the All-Wheel Drive indicator light to stop flashing and remain illuminated before shifting your transmission into gear. If the All-Wheel Drive button is pressed when your vehicle is in gear and/or moving, the All-Wheel Drive indicator light will flash for 30 seconds but will not complete the shift unless your vehicle is moving less than 3 mph (5 km/h) and the transmission is in NEUTRAL (N). Shifting Into Four Wheel Low To shift to the Four-Wheel Low position, the ignition must be in RUN and the vehicle must be stopped or moving less than 3 mph (5 km/h) with the transmission in NEUTRAL (N). Press and release the Four-Wheel Low switch. You must wait for the Four-Wheel Low indicator light to stop flashing and remain on before shifting your transmission in gear. Notice: Shifting the transmission into gear before the Four-Wheel Low indicator light has stopped flashing could damage the transfer case. To help avoid damaging your vehicle, always wait for the Four-Wheel Low indicator light to stop flashing before shifting the transmission into gear. If the Four-Wheel Low button is pressed when your vehicle is in gear and/or moving, the Four-Wheel Low indicator light will flash for 30 seconds and not complete the shift unless your vehicle is moving less than 3 mph (5 km/h) and the transmission is in NEUTRAL (N). After 30 seconds, the transfer case will return to the setting last chosen. When in Four-Wheel Low, StabiliTrak® is automatically disabled. For more information see StabiliTrak® System on page 4-10. Shifting Into NEUTRAL To shift the transfer case to NEUTRAL, do the following: 1. Make sure the vehicle is parked so that it will not roll. 2. Set the parking brake. See Parking Brake on page 2-35 for more information. 3. Start the vehicle or turn the ignition to RUN. 4. Put the transmission in NEUTRAL (N). 5. Shift the transfer case to All-Wheel Drive. 2-33