No rear brake lights but third brake light works

[JD123]

2007 GMC Sierra Classic 2500HD. Rear brake lights do not work. Third brake light mounted above the rear glass does. Checked bulbs and fuse. Did these models experience the problems with the turn signal multifunction switch that plagued earlier models? Sound like that's what it is?

 

[shadyowl2]

First thing i would check is your brake light switch. Make sure you are getting the 12 volt reference to one side. if you are, jump the switch, if your lights work then it's the switch.