master cylinder is bad or you have a leak
Sounds like you have a problem with your brake light switch under the dash, mounted on your brake pedal metal arm assembly. I know if I get my head down near the brake pedal and push the pedal with my hand I can hear a loud click noise when the brake lights come on. I'm not a mechanic, but I've wondered if the brake fluid level is down in the master cylinder, does the brake pedal drop enough for the brake light switch to turn on the brake lights ?
The piece that activates the brake lights when you push the brake pedal is called the brake light switch. This switch is typically located near the brake pedal assembly and is designed to complete the electrical circuit, illuminating the brake lights to signal to other drivers that the vehicle is slowing down or stopping.
There is an electronic relay switch which turns on the rear brake lights-It's located behind the brake pedal- It clicks when you push the pedal down, making contact.
THE BRAKE LIGHT SWITCH IS NOT PUTTING OUT BATTERY WHENEVER THE BRAKE PEDAL IS PUSHED DOWN. CHECK TO SEE IF BRAKE LIGHTS COME ON WHEN BRAKE PEDAL IS PUSHED DOWN. IF BRAKE LIGHTS COME ON, THEN YOU SHOULD BE ABLE TO SHIFT IT OUT OF PARK. IF NO BRAKE LIGHTS, THEN IT WON'T SHIFT OUT OF PARK. IF THIS IS THE CASE, THEN REPLACE BRAKE LIGHT SWITCH.
Check the brake light switch down on the brake pedal.
Sticking Brake LightsI had this very same problem when I owned a Nissan 300zx. There is a switch in front of the brake pedal that when the brake pedal is pressed the metal part of the pedal presses down on a little button which turns the brake lights on when pressing the pedal. What I did was I got under the dash, took a flashlight and put a little piece of tape in between the pedal and the switch. It acted as a cushion because the pedal wasn't pushing down on the switch as it was pushing on the tape and when I pressed on the pedal the lights would come on but the tape pushed the pedal back to shut the switch off. If you want to avoid all this consider having your brake pedal adjusted. If your brake lights come on still consider having your cars wiring checked out.
put your foot on the brake pedal and press down while some one looks at the brake light to see if it lights up
Look under the dash on the driver's side, half way down the brake pedal. When you depress the brake pedal, the pedal moves away from this switch, which allows the brake light pedal circuit to complete, and your brake lights come on. This brake light switch is always hot/on, as required by federal law, so that even with no key in the ignition, if you hit your brake pedal, the brake lights will come on.
There is a switch down at the brake pedal, It's most likely bad. This is true. There is a switch under the brake pedal that probably needs to be adjusted or replaced. I have this same problem in my 1998 mercury villager. I have not replaced or adjusted the switch...not sure the cost or how hard it is to do. However, I have found that once you are in park, if the brake lights do not go off, I press down hard on the brake pedal and the lights go off.
Adjust or replace the stoplight switch at the upper end of the brake pedal under dash area
check fuses if no luck check the brake pedal switch down under the dash by the pedal or check for a loose ground
Your brake lights are actuated by a switch that is connected to the brake pedal or to the hydraulics. It's sticking in the closed position. Just follow the pedal down until you see the wire.