Theory Of Operation
WARNING: This page is about a different car, the 2016 Dodge Durango. However, it is still accessible from the selected car via links, so may be relevant.
The Body Control Module (BCM) provides a ground path for the wiper park switch sense circuit through a pull - down resistor that is connected to ground. The Wiper Park Switch switches the signal circuit to voltage when the wiper motor is active and in the park position.