Brake lights stay on - 2000 Hyundai Sonata

The most probable cause is a sticking brake light switch. The brake light is activated by a small switch mounted under the driver's side, up near the leg of the brake pedal. That switch is spring backed so that when you depress the pedal the shaft of the switch is let forward and turns on the brake light. That switch sometimes comes loose or half cocked in the housing and stays activated all the time until you let the brake pedal loose and the leg of the pedal depresses the switch shaft just enough to turn off the brake light. The solution is to replace the switch, at about 15 bucks at your Advance Store. or 10 bucks plus shipping on the internet. You can check when you leave the vehicle to see if the brake lights are still on. Mind you, this does not happen all the time as sometimes it is cured by the action of the brake pedal knocking the shaft back in line