2003 GMC Envoy Owner's Manual - Page 96

If the SERVICE 4WD light on the instrument panel cluster stays on, you should take your vehicle to your dealer for service. See Service Four-Wheel Drive Warning Light on page 3-47 for further information. 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" in the Index. Shifting into 4HI or A4WD Turn the knob to 4HI or A4WD. This can be done at any speed and the indicator light will flash while shifting. It will remain illuminated when the shift is complete. Shifting into 2HI Turn the knob to 2HI. This can be done at any speed. NEUTRAL: Shift the vehicle's transfer case to NEUTRAL only when towing your vehicle. See Recreational Vehicle Towing on page 4-45 for more information. An indicator light in the knob will show you which position the transfer case is 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. Shifting into 4 L 0 To shift to 4L0, the vehicle's engine must be running and the vehicle must be stopped or moving less than 2 mph (3.2 km/h) with the transmission in NEUTRAL (N). The preferred method for shifting into 4LO is to have your vehicle moving 1 or 2 mph (1.6 to 3.2 km/h). Turn the knob to 4L0. You must wait for the 4LO indicator light to stop flashing and remain illuminated before shifting your transmission into gear. If you turn the knob to 4LO when your vehicle is in gear and/or moving, the 4LO indicator light will flash for 30 seconds and not complete the shift unless your vehicle is moving less than 2 mph (3.2 km/h) and the transmission is in NEUTRAL (N). After 30 seconds, the transfer case will return to the setting last chosen. 2-27