Why wont the brake lights on the 2002 explorer xls turn off?

Chances are you have a defective brake light switch. The switch should be found under the dash touching the upper part of the brake pedal lever. I would unplug it , see that the lights are off, and circuit test both sides. Most auto parts stores have these. I hope this helps you. Mark

This can be caused by a sticky brake pedal that does not retract fully to the original position. It happened to me and the solution was to spray some silicone or w40 on the rubber boot that is found under the steering wheel.