Steering Wheel Controls
WARNING: This page is about a different car, the 2011 Lincoln MKT. However, it is still accessible from the selected car via links, so may be relevant.
The steering wheel controls consist of a series of resistors. Each steering wheel control switch function corresponds with a specific resistance value within the switch. When a switch is pressed, the ACM (or the APIM) monitors the change in reference voltage to determine the requested function.