R2D2

I just touch the top of the door handle closest to the door edge, works with any door. Not sure if you have that on your vehicle, it might have been part of a package  I think it is called "Intellegent Access". It is listed on my window sticker and it is in the owners manual. I tried posting the picture from the OM but can't do that.... I am attaching an image file showing where the sensor is, click on the thumbnail image to enlarge :)
 
Also living in Florida I have little use for pre-warming the car with remote start (I see you are in Chicago....brrrrr)

Should be on page 86 of your owner's manual.
 
If you don't have one, you can download it from here
 
http://www.fordservicecontent.com/Ford_Content/catalog/owner_guides/13zhyom2e.pdf