Steering Wheel Controls
WARNING: This page is about a different car, the 2003 Pontiac Montana, 2003 Oldsmobile Silhouette, and 2003 Chevrolet Venture. However, it is still accessible from the selected car via links, so may be relevant.
The Steering Wheel Controls consist of multiple momentary contact switches that connect a series of resistors so that each switch selection corresponds to a fixed resistance value. These fixed resistance values allow the radio to identify which switch has been pressed.