This happened to me--same year jeep.
But I had a starting prob. It affected the rear lights: runners, heads, parking.
I chased ALL the leads from the battery and wrenched them down. Problem solved.
Hope you are that lucky. A Chilton's auto repair guide for your jeep is available in every parts store. They are fairly worthless, but they have extensive electrical/switch diagrams if that doesn't work.
If it's not a simple matter of wrenching, or a simple fuse, then it's a switch.
If it's not headlights or runners and only brake lights my only other guess is your brake lights became un-grounded. I had my runners but no brakes and that was the cause.
Crawl under your beast for an hour---it might become clear.--Good luck.