There is a wiring diagram here, page 20:
https://docs.google.com/file/d/0B9SE...TNk/edit?pli=1
When you say "rear fog lights" do you mean rear park lights?
Lift up the fuse box lid and you will find the schematic and fuse list on the underside of the lid. I have it here in .xps formate but it wont let me upload it. It appears the park lights are fed individually, M17, M18, and these fed other circuits so if you only have issue with park lights, fuse probably not the issue. Could be a ground connection (but again, unlikely because ground connections on the rear light cluster are common). As suggested, make sure you are operating them correctly.