I've checked everything suggested, but I can't find where the problem is. I've checked the cables from the brake light to the front door under the sill. There's no short circuit, but there's not enough voltage either. The cable that powers the brake light is about 0.5V short compared to the left brake light. I measure about 10.35V, and on the left one that works, about 10.85V. I've also disassembled and cleaned the fuse box by the battery, and I've also replaced the brake light panel. The ground is fine, I've cleaned all the ground points both front and rear. Is there anything else that can be checked or does the body have to be checked to make sure something hasn't oxidized? Where exactly do the cables that are under the sill on the right side and enter under the dashboard towards the engine compartment go?