2003 GMC Sonoma Owner's Manual - Page 104

Electronic Transfer Case If your four-wheel-drive vehicle has the electronic transfer case, the transfer case buttons are to the right of the steering wheel on the instrument panel. 4LO: You may never need 4L0. This setting also engages your front axle to give you extra traction. It sends the maximum power to all four wheels. You might choose 4 L 0 if you were driving off-road in sand, mud or deep snow and ciimbing or descending steep hills. Indicator lights in the buttons show you 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 in for service. An indicator light will flash while shifting. It will remain illuminated when the shift is completed. Shifting from 2HI to 4HI Press and release the 4HI button. This can be done at any speed, and the front axle will lock automatically. Use these buttons to shift into and out of four-wheel-drive. You can choose among three driving settings: 2HI: This setting is for driving in most street and highway situations. Your front axle is not engaged in two-wheel drive. When this light is turned on, it is about one-half as bright as the others. Shifting from 4HI to 2HI Press and release the 2HI button. This can be done at any speed, and the front axle will unlock automatically. 4HI: This setting engages your front axle to help drive your vehicle. Use 4HI when you need extra traction, such as on snowy or icy roads, or in most off-road situations. 2-29