Why is your Brake light not working on 2001 Toyota Highlander?

If none of the three stop lights are working I would first suspect the fuse for the brake light system - but assuming you've already checked that - I would move on to the brake light switch. Look carefully at the suspended brake pedal and follow it up under the dash. Towards the top you should see a push switch with a plastic plunger coming out of it that rests against the pedal rod. It may be out of adjustment or it may have gone bad. Lastly - rare, altho possible, the three bulbs may have failed.