Why won't your brake lights turn off?

I have had several Nissans in the past. On at least 2 of them, I had the same issue. What it turned out to be was: On the brake pedal shaft, there is a small hole where a small plastic piece should be located. This plastic piece pushes on a small plunger that turns the break lights on and off. With all the temperature changes, this plastic piece can crack and fall out. Now, the plunger just sticks thorough the hole. I put a bolt/lock nut through the hole.... Issue fixed... Stoplights are usually turned on by a switch mounted above the brake pedal. When the pedal is fully released, it presses on the switch and it breaks the circuit. When you press the pedal, it releases the switch and the circuit completes, turning on the lights.

Most likely cause of this is that the switch is either broken or misaligned.

Adjust the switch to be depressed when the pedal is up. If the lights turn off, you're done.

If this does not fix it, unplug the switch from the wiring harness. If this makes the lights go off, your switch is broken, buy a new one. If it does not, you have a short circuit in the wiring. You will need to trace the harness, find the damage and repair it by splicing or replacing the harness.