Hey all, I know this is an older post but wondering if anyone ever found a fix for this? I just had this crop up in my 2002 Ram 1500. I really hope it's not the FCM. I am not really savvy with working on my truck but I do have a couple of things to add from the above. So my two rear brake lights are not working (bulbs are fine) and the third brake light works fine. There was a trailer harness hooked up, certainly was aftermarket but looks like it could have been a dealer that did it, it looks great up until the last six inches but that works fine. all other lights on the back in work fine as well just the brake lights don't.
I took off the tail light assembly to check the the harness there and that gets a bit weird too. I get power from the reverse lights and tail lights (running lights or whatever they are called, when i turn my lights on). The other two have a constant 9V of power coming out of them (both the left and right tail light assembly do this). That just doesn't seem right but like I said, not savvy at all!