7 Reasons Why Your Brake Light Might Be On

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If your brake light is on, it could be the result of worn brake shoes, defective sensors, or low brake fluid. 
Your brake light is not something you want to ignore. If neglected long enough, brake problems could lead to brake failure—and that’s not a situation you want to find yourself in when you come to a red light at a busy intersection.
To help you avoid a dangerous situation, the car insurance super app Jerry is breaking down the top 7 possible causes to help you answer the question “Why is my brake light on?”

1. Your parking brake is on

The most common reason for your brake light being on is a pretty simple one: you left your parking brake one. You may have forgotten to release your parking brake or didn’t disengage it completely.
Over time, driving with the parking brake on can overheat your brakes and speed up brake shoe wear. It also degrades your brake fluid faster.

2. Your brake shoes are worn

When brake shoes wear down, a sensor wire touches the rotor and causes the brake light to come on. Worn brake shoes cause reduced stopping power and rotor damage.
Symptoms of worn brake shoes may include squeaking, grinding, vibration, and spongy brake pedal feeling.
You can typically diagnose worn brake shoes with a quick visual inspection. If the indicator groove is completely worn away, it is time for a new set of brake shoes.
Pro Tip Brake shoes are usually good for about 30,000 to 35,000 miles in urban use. If yours haven’t been replaced in a while, have a mechanic assess their condition.

3. Anti-lock braking system malfunction

A malfunction with your ABS that’s causing your brake light to come on can be a little more difficult to diagnose. You’ll need to take the car to a technician who can read OBD codes that are stored on the computer to track down the exact source of the malfunction. 
Common causes of ABS problems include faulty or dirty speed sensors and low fluid levels.
The worst-case scenario is that the ABS module itself needs replacement, which can cost anywhere from $200 to upwards of $1,000.
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4. Bad master cylinder

If you are experiencing a pedal that sticks down when you press it, low brake fluid, and uneven brake pad wear, your brake light could be on because of a bad master cylinder.
 A bad master cylinder leads to contaminated brake fluid as well. If you suspect your master cylinder is bad, you should have your vehicle looked at by a mechanic right away. 

5. Defective sensors

ABS sensors—also known as wheel speed sensors—are crucial to your braking system. These sensors can become clogged with debris and brake dust, and their connecting wires can become damaged
If your brake light is related to a defective sensor, a visual inspection may reveal problems with the sensor or its wire harness. Otherwise, you’ll need an ohmmeter to test for electrical shorts or open circuits. 

6. Low brake fluid

If your brake fluid is low, you’ll probably see a yellow “!” on your dashboard. When the brake fluid is dangerously low, that symbol will become red. Low brake fluid can be due to leaks, clogged lines, or other hydraulic issues
If your brake fluid is low, you will need to determine the reason why before adding more fluid. You may need to have leaks repaired, do a brake fluid flush, or have a technician troubleshoot the hydraulic system.

7. Rear brake lights need to be replaced

Some vehicles alert you when rear brake lights need replacement or repair. To check if your rear brake lights are working properly, simply have a friend stand behind your vehicle and tell you if your lights come on when you push the brakes. 
If any of the brake lights fail to come on, you are likely dealing with a blown bulb. This is an easy, inexpensive fix—check your manual if you’re unsure how to replace the bulb yourself. 
If a blown bulb isn’t the problem, you could be dealing with shorted-out electrical connections or blown fuses.

What do I do if my brake light is on?

If your brake light is on when you start the car, try to locate the problem or contact a mechanic before driving. The light indicates that brake failure is a possibility—and continuing to drive risks your safety, the safety of others on the road, and damage to your brake system.
If you are already driving when your brake light comes on, stay calm and pull over somewhere safe where you can try to diagnose the problem.

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Car insurance is a key part of keeping yourself safe while on the road—and there’s no easier way to find a great car insurance policy than with Jerry.
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FAQs

No. Brakes are one of the most important safety features your car has, and you should not drive if a warning light signals a problem with them. 
If your brake light is on, problems like low brake fluid and ABS malfunctions could lead to brake failure. Driving with your brake light on raises your risk of being involved in an accident and could cause further damage to your brake system.

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