Steering Wheel Controls
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
Some audio functions are available using the steering wheel controls. The steering wheel controls consist of multiple momentary contact switches that connect a series of resistors. When a steering wheel control button is pressed, a specific resistance value is noted by the body control module (BCM). This results in a generated voltage, unique to the particular button. The BCM alerts the radio that the button has been pressed, and the radio responds, just as if the corresponding radio front panel button had been pressed.