What to Do When Your Brake Light Comes On

The first thing to check, and by far the most common reason the light comes on, is kind of a "duh" moment.

© Chaiyagorn Phermphoon/Shutterstock

By Mark Johanson, The Family Handyman

Why is my brake light on?

If the brake light illuminates on your dashboard, don't panic. But, take it seriously, as brakes are probably the most important safety feature on your car. The first thing to check, and by far the most common reason the light comes on, is kind of a "duh" moment: You've left the parking brake fully or partially engaged. Pull the brake release and see if that solves the light issue. In most cases it does.

Next on the checklist of causes for an illuminated brake light is the brake fluid level. Under normal conditions you should not have to add brake fluid, as it works in a sealed system. But, if a leak develops, the system will lose fluid which impairs the stopping power of the brakes. You can add fluid as a stop-gap, but if you have a leak in your pneumatic braking system, you need to have it repaired or you may lose enough fluid to cause your brakes to fail.

Finally, as with "Check Engine" lights, brake lights themselves can fail or false indicate. Or, the sensors that trigger the light may be faulty. Don't assume at the onset of the light that a bad sensor or readout light is behind it, but if there appears to be no other problem, have your service provider investigate the indicator light itself and the sensors.

ABS (automatic brake systems) 

Modern cars have automatic brake systems that prevent the brakes from locking up in emergency braking situations. Most ABS systems have their own indicators, so if you have an issue with your ABS you'll likely see the brake light illuminated as well as an ABS indicator light. ABS systems have sensors in the brakes that are linked to a chip in your car's computer system, so dealing with them requires servicing at a car service center that can read engine codes. 

If you are a very dedicated home mechanic, consider investing in your own code reading device. They range from basic models that simply give you a numeric readout that you can look up, to more sophisticated ones that display the nature of the code issue or engine problem.