Hmmm. I have earlier models ('79 and '83), but I recall that my warning light was on because of a failed sensor under the master cylinder. I guess it could be the hand brake sensor? I'm assuming that there isn't an actual leak or failure in the brake system, of course. Good luck!
Typically it is a failure of one of the (2) sensors on the bottom of the brake master. They are difficult to replace. When mine went out in my 82, I just replaced the master, as it came with new switches pre-installed.