I got an 06 dually and noticed today my driver and passenger side brake lights don't work. The third brake light does though. I got the truck 2nd hand and it had a brake contoller in the cab bit the took it out. Also has several trailer light connections. Any ideas on where to start checking. Also I've already checked the fuses under the hood. Thanks

 

Check the bulbs, look at the bases real close to see if the little wires have melted into the plastic bases and not makeing contact in the sockets. On my 03 there is a plug on the drives side just behind the mud flap open the plug and use a test light and see if you get lights there if yes then your have a short from there to the back and have to start unrapping the harness and lookin at the wires. If no power at plug its before the plug, and need to check wires ahead of there. Brake controler shouldn't be the problem because my 03 has a factory plug you just wire the controler to a pigtail and plug it into the factory socket.

 

My 06 had a plug under the dash and just plugged the controller in. There is a multi-pin plug between the one Kowalski is talking about and the control box, if the power does not reach the back one you can check at this one to see if the problem is between them.
Does your brake light come on or your back up lights when you press the brake pedal? If not, the issue could be the plug in the back is disconnected.
Good luck.

 

Well thanks for all the help guys. I feel like an idiot it turns out both brake lights were out what's the odds of that lol