Circuit/System Description
WARNING: This page is about a different car, the 2011 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
The sunroof ventilation position select switch is connected directly to the controller and provide detent positions for open, off and close. The control switch completes the circuit provided by the control module, a reference ground Input and a pull-up voltage provided by the analog to digital switch input. The control switch places a different resistor ladder network in the circuit depending on the function selected. The controllers analog to digital switch input reads the resulting voltage range and determines the function.