2003 Chevrolet Avalanche Owner's Manual - Page 11

You can also reshape the back wing area of the lower seatback. To increase support in the wing area of the lower seatback, press and hold the top of the control. Let go of the control when the lower seatback reaches the desired level of support. Heated Seats To decrease support in the wing area of the lower seatback, press and hold the bottom of the control. Let go of the control when the lower seatback reaches the desired level of support. a - Your vehicle may have heated front seats. The buttons used to control this feature are located on the front doors. The engine must be running for the heated seat feature to work. To heat the entire seat, press the horizontal button with the heated seat symbol. Press the button to cycle through the temperature settings of high, medium and low and to turn the heated seat off. Indicator lights will glow to designate the level of heat selected, three for high, two for medium, and one for low. 1-4