Why Is My Brake Light On?

If your car’s dash has the brake light on, there could be a few reasons why. When the brake light is on, it means there may be a problem with the brakes, like low brake fluid, broken brake system parts, leaking brake fluid, or a parking brake left on. If the brake light turns on, you do not want to drive the car in case the brakes stop working. The tips in this article and video can help you inspect the system yourself and possibly fix it without having to bring it to a professional.

What to Do If the Brake Light Is On

How to diagnose a flashing brake light on the dash

  1. Stop Driving

    If the brake light is on, you want to stop driving and have the vehicle towed to a safe location or a professional to inspect the brakes, since driving with bad brakes is unsafe for you and other drivers. The brake light may turn on and stay on, it may flash, or it may flash and then turn off.

    If the brakes work fine the brake fluid may just be low, which means you can just top it off with the right brake fluid. Air in the brake system can cause the brake pedal to feel spongy or soft, or it may not fully pause once the vehicle is at a stop, and this is a sign that parts in the brake system may be leaking.

  2. Check the Brake Master Cylinder

    Some brake master cylinders have a sensor that measures and records the brake fluid level. When the brake fluid level drops too low, this sensor will trigger the brake light.

    If the brake fluid level is low, top off the brake fluid with the appropriate type (likely DOT 3 or DOT 4), which can be found in the owner’s manual.

    If the brakes work fine, the brake fluid probably wasn’t maintained or it may not have been topped off during a brake job, but it’s still a good idea to check the rest of the brake system for leaks.

  3. Check the Brake Lines

    Inspect the brake flex hoses and steel lines for leaking. The flex hose leads from the caliper to the steel lines, which lead to the brake master cylinder, and the brake lines will be the smaller of the steel lines underneath the vehicle (the larger steel lines being the fuel lines). Check the lines and hoses on both sides of the vehicle for breaks, cracks, or signs of a fluid leak, and check the steel lines for softness.

  4. Check the Brake Drum

    If your car has a brake drum in the rear, meaning the brake shoes are inside the rotor and the rotor does not have brake pads on the outside, you’ll have to remove the tire and the drum to check the wheel cylinders, or you can visually inspect them from behind. Check the backside of the backing plate for darker spots or wetness. You’ll more than likely find moisture around where the brake line enters the drum or on the backside of the backing plate. The wheel turning will cause the fluid to spurt out.

  5. Check the Brake Caliper

    The brake caliper has a dust seal that protects a second seal embedded in the caliper. This second seal prevents brake fluid from leaking out of the caliper. If this inner seal is damaged, brake fluid will leak out of the dust boot and will manifest as low brake fluid and a spongy brake pedal.

    If part of the dust boot has signs of dampness and brake fluid leaking, the inner seal is damaged and the entire brake caliper needs to be replaced.

  6. Check the Parking Brake

    If the brake light is on on the dashboard, check the parking brake. Sometimes this light turns on when the parking brake is engaged. Disengaging the parking brake should turn it off.

  7. Check the Brake Light Bulbs

    Some vehicles engage the brake light if the brake light bulbs have burned out. Put the car in Park, and then have an assistant stand behind the car enough to see the brake lights. Press the brake pedal and see if the lights turn off. If not, replace the burnt out brake light bulb.

  8. Check the ABS system

    If your vehicle doesn’t have a separate light for the ABS system, which can be confirmed by checking the owner’s manual, it may turn on the brake light when there is a problem with the ABS.

    Read more about how to inspect the ABS wheel speed sensors

Do More than Fix a Brake Light That’s On: Learn to Replace Brake Parts and More Yourself

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Summary
Brake Light On? How to Check the Brake Light - Expert Tips - 1A Auto
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Brake Light On? How to Check the Brake Light - Expert Tips - 1A Auto
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If your brake light is on on your dashboard, this guide and video from our expert mechanics explains why it might be on and how you can fix it yourself
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1A Auto
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