It is better to check the performance of the brake light lamps with two people, but you can check it yourself. In the first case, you need to apply the brakes, while the assistant monitors the brake lights. In the second case, you need to drive the back of the car to the garage door or fence wall and apply the brakes, watching through the rear-view mirror for the red reflection of the brake lights on. If one lamp does not light, it must be replaced. If both lamps do not light up, check the operation of the limit switch.