I have a 2005 Jeep Cherokee that recently had both brake lights go out at the same time however the top brake light works. We have checked the bulbs, fuses and even replaced the Brake Light Switch. All 4 lights work when using flashers as well as the running lights, and reverse lights. I have been reading forums for almost a week now and from what I am seeing it can one of the following:

- Issue w/ ground
- Signal switch could be going bad causing issue w/ the brake lights
- Wiring harness

Anyone have any suggestions? I have had everyone I know look at it (i.e. Father, ex husband, etc) and no one can seem to figure it out. I'd rather not have them rewiring things if I can find the issue. Thanks in advance!!

I would suspect a Fuse or the signal head. The brake switch may be the culprit if you have more than 2 wires on it.
I believe the third light is from the brake switch, and the lower brake lights go through the Combination switch(signal head/signal switch) then to the brake lights.
Try your 4 way flashers and walk around vehicle and view bulbs flashing.
If they work, wiring from signal head is good.

Or both bulbs are bad?

I did try the hazard lights and they all work. From what I have read, if the hazard lights work then the bulb and wiring is working. Is that accurate? Also if the flasher, blinkers, and running lights work, does that eliminate a faulty Signal switch?

I will check if there are two wires coming from the Brake Light Switch, which I have already replaced.

Some one else said possibly the relay? Is that w/ in the fuse box?

You don't have any ABS issues? The ABS lamp on the dash is off?
The feed to the high mount lamp is slightly different than the main rear brake lamps in that the rear lamps go through the Integrated Power Module but the high mount doesn't.
(These vehicles have a high failure rate for that module)
I would recommend taking this to a shop that has electrical knowledge.

Since All bulbs work with the flashers, that tells you the wiring and bulbs are good from the signal switch.
How many wires on brake switch?
It doesn't eleminate the switch, however, I think I would suspect a fuse?
I have a few jeep manuals, will see if I can locate a diagram and or fuse location.