Four Possible reasons...
Low brake fluid - check the brake fluid level in the master cylinder
Emergency brake is on - check emergency brake
Low brake fluid pressure - such as a broken brake line or a bad wheel cylinder. Check the master cylinder to see if it is empty. If you add fluid and pump the pedal you will probably see brake fluid on the ground or on the inside of the tires.
Possibly a bad master cylinder. - The fluid will stay full but you will have no or little brake pressure.
Could be air in the system as well.
BE CAREFUL If you happen to add Power Steering fluid or Transmission Fluid to the master cylinder instead of brake fluid you will destroy the system. Make sure you use ONLY brake fluid and clean the master cylinder cap off with a clean rag first so no dirt gets into the braking system.
Disconnect your battery and reconnect it and try pulling up on your parking brake.
If it's the brake light in the boot lid then you have to take the cover off the inside of the boot lid and then you will have access to the light bulbs. If it's the brake light in the rear quarter panel then you open boot lid and unscrew the two bolts holding the light cluster and slide it backwards, then you will have access to the bulbs
The light may be the low fluid level for the master cylinder also. Check the fluid level.
When the ABS light is on it is for a reason, a sensor could be bad, or another major problem. The light wont go off until the problem is corrected or until the light burns out
possible faulty brake light switch...sticking....usually located on top of metal arm connecting to your brake pedal. $10 part. There's a rubber bumper that the brake pedal switch hits against to turn off. When the bumper gets old it falls off (you will notice the pieces on the floor when you get in). Without the bumper in place the switch post just goes through the hole that the bumper is supposed to be in and is never depressed and the brake lights don't shut off.
IS it the BRAKE LIGHT or the Parking Brake Light? If it is the BRAKE LIGHT, then your pedal must be going down far enough to hit a sensor that sets off the brake light to tell you your brakes need serviced. Normally this means you are low on brake fluid. If you are low on brake fluid FIND OUT WHY! You may have excessive brake pad wear, or a leaking brake cylinder, or your master cylinder may be going out. If you keep pumping the brakes and then stand on it hard, feel for the pedal to eventually go soft, if it does, then normally the seals in the master cylinder are going out. If you pump the brakes and the pedal never gets hard, then you have a serious brake fluid leak. If the Parkign Brake light stays on, then your parking brake is not fully releasing, at least where the contacts are to remind you it is on. This can be adjusted.
The brake light is controlled by a relay switch. If the relay switch is bad the brake lights will stay on. The brake light switch simply plugs in and out. Unplug the brake light switch until you can replace it.
There is a reason why it is on. Check the fluid level, it may be low. This would be an indication that you need to have the brakes checked soon.
is your e-brake on?
The brake light switch is broken or out of adjustment.
change ur brake pads?
Brake light switch went bad.
Might be a stuck brake light switch its located at the top of the brake pedal
You can reset the brake warning lights, on your VW Jetta, by backing up 20 feet and using the brakes. The automobile will sense the new pads and the warning light will go off.
Check the brake light switch down on the brake pedal.
You need to find and fix the problem. Either your emergency brake is not completely off or you have a problem in your cars brake system. That warning light is there to warn you that a serious problem exists.
Check the brake light switch adjustment.
There is a sensor in the top of the brake cylinder where you put in the fluid. Replace it and the light will go away.