If your vehicle is showing brake lights stay on after releasing the pedal, here are the most likely causes and the parts you'll need to fix each one.
Many vehicles use a small plastic or rubber button on the brake pedal arm to depress the brake light switch. Over time, this pad becomes brittle and shatters, leaving a hole that allows the switch plunger to extend fully, keeping the lights on.
The brake light switch located behind the brake pedal can fail internally. The electrical contacts inside can weld together or the internal spring can break, causing the circuit to stay closed even when the pedal is released.
If the brake light switch was recently replaced or the pedal assembly was serviced, the switch may not be threaded or pushed in far enough to make proper contact with the brake pedal arm when it is fully released.
Forcing a single-filament bulb into a dual-filament socket (or vice versa) can bridge the tail light and brake light circuits. This causes the brake lights to stay illuminated whenever the headlights or parking lights are turned on.
The brake pedal may not be returning to its fully resting position due to a weak return spring, a binding pivot, or a failing brake booster/master cylinder holding slight hydraulic pressure.
In modern vehicles, the brake light switch sends a signal to the BCM, which then powers the lights. A short circuit or a stuck internal solid-state relay in the BCM can keep the lights powered continuously.