On my 1997 Taco the brake idiot light comes on for a few seconds then off at semi random times. Usually when taking off first thing in AM but randomly throughout the drive. Been doing it for years. I thought it was the park brake that was loose. It used to be that it quit if I pushed the park brake handle in firmly. I tightened the cable by the book and now the on/off shows up. It may have been there all along too. Is there a sensor for vacuum assist? Could I have a vacuum leak to the tank? I'm hoping this is not related to ABS.
I also have a sharp vibration when braking hard. That may be the rotors. I had them turned at last pad change and they may be too thin and warping. Don't know what the ABS feels like.