Steering Wheel Controls
WARNING: This page is about a different car, the 2007 Ford Pickup, 2007 Ford F550 Super Duty, 2007 Ford F450 Super Duty, and 2007 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
The steering wheel controls consist of multiple switches that have a specific resistor value for each button function creating a voltage divider. When a button is pressed, a specific reference voltage is sent to the audio unit. The audio unit then uses this reference voltage to determine which control input function has been selected. The steering wheel controls are located on the steering wheel.