What to Do When Your Brake Warning Light Is On

Your brakes are responsible for slowing and stopping your vehicle. They’re its most important safety system.

When your car detects a problem with the brakes, one or more warning lights will come on to alert you. They’ll typically light up briefly when you first start your car, but if you see them stay on or if they come on while you drive, you might have a problem with your braking system.

Brake problems are serious business, so if you see warning lights or experience other issues such as brake noise or vibration, get your car checked out at a repair shop right away. And if the brake system doesn’t respond right, or if the pedal suddenly goes to the floor or requires pumping to stop the car, stop driving it and get it towed to a repair shop.

When the main brake warning light is triggered by a fault in the system, it will be illuminated in red. It appears as a circle, with a “!” in the center, and parentheses on either side.

If your brake fluid level is too low, typically you will see a similar warning light, only it will be yellow or amber instead of red.

Anti-lock brakes, which automatically pump the brakes many times per second for better stopping in slippery or emergency conditions, have their own warning light. It’s usually depicted as a circle, with “ABS” in the center, and parentheses on either side. It will be orange or yellow when lit.

How the braking system works

Your braking system uses hydraulic fluid to transmit the pressure of your foot on the brake pedal, through a sealed system filled with brake fluid, to the brake discs or drums on each of your vehicle’s wheels.

Friction material in each brake pushes against the rotating disc, reducing the wheel’s speed. The harder you press on the brake pedal, the faster you slow down or stop.

Why the brake warning light comes on

There are several possible reasons why your brake warning light can come on. Some may be obvious, while others may be hard to track down.

Here are some common causes of brake warning lights:

Your parking brake is on or malfunctioning

One of the everyday functions of your brake warning light is to let you know that your parking brake is on. It acts as a reminder to release the parking brake before you drive off. If you forget to release it, or don’t release it completely, the light will stay on.

Some parking brake systems may have their own warning light. This will appear as a red circle, with a “P” in the center, and parentheses on either side.

Solution: If you continue to drive with the parking brake on, you will eventually wear it out and need to have your mechanic repair it. Check that your parking brake has been fully released. On vehicles with automatic parking brake release mechanisms, there is a manual release lever near the top of the pedal assembly in case the automatic release fails. Occasionally, the switch that turns off the brake warning light when you disengage the parking brake can malfunction or need adjustment, making the light stay on. Your mechanic can fix this for you.

Your brake fluid is low or is leaking

Maintaining the correct amount of brake fluid is essential. You can find your brake fluid reservoir under the hood. This reservoir is usually made of translucent plastic, which lets you check the level of the fluid inside against the “MAX” and “MIN” marks that are molded into it.

The clear tank is convenient, but it’s also meant to minimize the number of times you need to open it. By keeping it shut as much as possible, you keep the system free of dust and water that can enter when the cap is removed and then contaminate the fluid.

If your brake fluid level is near, at or below the “MIN” mark, you need to add some immediately. Not having enough brake fluid can trigger your brake warning light.

Solution: Top up your brake fluid. Check your owner’s manual for instructions, and use only the brake fluid type specified in the manual. Never use a lower number fluid than the system requires; however, if the specified fluid is not available (for example, DOT 3), it could be replaced with DOT 5, but the system should be bled soon after to remove any mixed fluid.

Low brake fluid can also be caused by worn brake pads. As the friction material wears, the brake fluid pushes the pistons out against the thinner pads farther into the brake disc to generate enough stopping power. This displaces the brake fluid, and causes the fluid level to drop in the reservoir. Replacing the brake pads first may resolve this particular problem. Topping up the fluid can be done afterward, if it’s still necessary. Your mechanic can figure this one out.

If there’s no other related issue, the light should go away; however, if the fluid level gets low, and your pads show little wear, it’s possibly you have a brake fluid leak. You’ll want to have the system checked out.

You or your mechanic should look around the brake fluid reservoir, the brake lines, their connections, any mechanical proportioning valves (usually found on the frame or differential of trucks, near the rear brakes), the rubber hoses near the wheels, and the brake mechanisms at each wheel. If you notice a clear or amber-colored liquid oozing out or dripping onto the ground, repairs are urgently needed. Don’t drive the vehicle until the brakes are repaired.

Your brake pads are worn out

Some carmakers design the braking system to alert you when their brake pads are worn and need replacing by turning on the warning light. You may also hear squealing noises when you apply them.

Don’t wait to get the brake pads replaced. If you totally wear out the friction material on your brake pads, it’ll result in metal-to-metal contact. This will damage or destroy parts of your braking system, resulting in a very expensive repair job.

Solution: Replace your worn brake pads with a fresh set. The sensors may also need replacing. Additionally, the brake discs should be checked out. If necessary, the discs can be machined, or be replaced if they’re too worn.

Your brake light bulb has burned out

Most vehicles have several bulbs in the brake lights. If one or more bulbs burn out, the computer will see a resistance change in the circuit and turn on the brake warning light.

Solution: Always use high-quality bulbs of the correct type when replacing them so the resistance returns to normal. Replacing conventional bulbs with LED bulbs on this type of system will require a mechanic to deal with the electrical changes.

Can I drive with the brake warning lights on?

If the light is red, no, you can’t. Your braking system is not working the way it should, making it too dangerous to get on the road. If it's yellow, you should check your brake fluid and get the vehicle diagnosed if you suspect a leak.

You have to be able to stop your car, for your safety and the safety of other drivers. As soon as you notice your brake warning light has come on, stop driving it. Call your mechanic for further guidance, and schedule repairs right away.