Look at the top part of the brake pedal, you will see a black plastic switch.
In order to remove it, you have to twist it 90 degrees.
Once you have it outside, press and release it to see if it moves smooth.
Check if the light is working properly.
Most of the chances you will fine the switch stays stuck on its “pressed” position.
this is how it looks:
10$-20$ at Pelican parts