So in an aha moment I decided to clean the rear window of my car. With the drought making it illegal to wash your car and the weather being so hit or miss with rain, etc. the car had gotten pretty dirty.
Low and behold with a clean rear window the sensor seems to be working as it should. I'm guessing the scatter from the dirt and grime was enough to through it off. Duh.
'08 Starfire Pearl ISF