2003 GMC Yukon Owner's Manual - Page 122

5(4LO): This setting also engages your front axle and delivers extra torque. You may never need this setting. It sends maximum power to all four wheels. You might choose 4LO if you are driving off-road in deep sand, deep mud, deep snow and climbing or descending steep hills. {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 2-34. NEUTRAL: Shift the vehicle's transfer case to NEUTRAL only when towing your vehicle. See Recreational Vehicle Towing on page 4-55 or Towing Your Vehicle on page 4-54 for more information. Indicator lights in the switches show which setting 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 shifting the transfer case. It will remain illuminated 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. If the SERVICE 4WD message stays on, you should take your vehicle to your dealer for service. See ″Service 4WD message″ under Driver Information Center (DIC) on page 3-53. Shifting into 4HI or AUTO 4WD Press and release the 4 hi or AUTO 4WD switch. This can be done at any speed (except when shifting from 4LO), and the indicator light will flash while shifting. It will remain illuminated when the shift is completed. Shifting into 2HI Press and release the 2 hi switch. This can be done at any speed (except when shifting from 4LO). 2-28