does the grand prix brake light say e brake or just brake like my regal? if so you could just need brake fluid. maybe check the master cylinder fluid level.
This.
The BRAKE light in the dash isn't just to tell you the ebrake is on, its to tell you the fluid is low
2011 Mitsubishi Lancer GTS - DD mode
1991 Mitsubishi 3000GT - Many mods to come