I've done a bunch of reading and have not found the answer so I figured I would ask... my wife has a 2008 Suburban LT she had someone in traffic tell her she had no brake lights so she brought it home and I verified.. I threw a brake light switch in it figuring it was a $15 cheap fix but no go I also realized that the power liftgate has stopped working I drove the truck the day before and the liftgate was working checked all the fuses everything's good check the wiring in the headliner above the lift gate no apparent issues I have power and ground at the brake light switch as long as the interior lights are on when the interior lights go out I lose power at the brake light switch but regardless still no brake lights I was thinking body control module but that doesn't explain the tailgate not working. I checked the grounds for the rear of the truck took them off clean them and put them back on no luck. I have turn signals and running lights. And all lights come on when I exit the vehicle (courtesy lights) any help would be appreciated

 

Welcome to the forum. Best guess is you have an open some where and the interior lite circuit is back feeding the brake circuit.

 

Just wanted to follow up so I made an appointment to take it to my buddy's shop that morning I got in and I turned the hazards on so I can drive with no brake lights decided to try the hatch it was working normally drove to my buddy's shop when I got there he said your brake lights are working fine so he scanned it and said that there was a generic code and the dashboard had stopped talking to the body control module but it was a history code and everything seems to be working again so I'll just keep an eye on it for now

 

Spray the body module connectors with an electronics cleaner / lubricant. Lots of GM vehicles in the '08 to '12 time frame suffered from fretting corrosion in connectors.
Some like Malibu's even had recalls for no brake lights for that issue.