2008 Kia Sorento code P0504

My ESC light has been going off on its own and today my check engine light came on with the code P0504. Definition :1. A/B brake switch correlation 2. Open/short circuit or 3. Poor electrical Connection 4. brake switch is faulty.

I have no clue where this part is on my car or how to replace it. If anyone could give me some pointers or a site that would lead me through the process I would be very grateful. We are having a lot of bad weather out here and I need my car working. Thanks in advance.

Its probably very similiar to this.
http://www.justanswer.com/kia/6jl8g-kia-amanti-replace-adjust-brake-light-switch.html

Ok thanks so much! Found out this is a recall on my car and Kia will fix for free. Hope that helps the ESC stay on too. We will see.