Brake Warning Light On? What It Means and What to Do

When a brake warning light comes on, start with the color. A red warning light on your dashboard means one of three things: the parking brake is on, the brake fluid is low, or the hydraulic system has lost pressure. A yellow ABS light means the anti-lock system has a fault, and your normal brakes still work. Here's how to tell which, whether it's safe to drive, and what fixes it.

What is the brake system warning light?

It's the dashboard light that tells you the brake system needs attention, and US law spells out when it must come on. Under Federal Motor Vehicle Safety Standard 135, an indicator has to activate for a loss of brake fluid or pressure, an electrical failure in the anti-lock brake system, and whenever the parking brake is applied (49 CFR 571.135, S5.5.1).

The same rule requires a bulb check. When you start your car, every brake light in the cluster should flash on for a second or two and then go out. If one never appears at start-up, the bulb or circuit has failed and the warning can't reach you.

What do the different brake warning lights mean?

Most cars have more than one, and the color matters. FMVSS 135 requires red for the main brake indicator and yellow for a separate ABS indicator.

Common reasons the brake warning light comes on

In our experience at WeBrakes, a brake warning light most often indicates low brake fluid. Our technicians investigate the root cause, which is often a fluid leak or simply worn brake pads that have lowered the fluid level.

The parking brake is engaged

This is the simplest cause to check first. A partially engaged parking brake, from a lever that isn't fully lowered or a pedal that hasn't fully released, will keep the light on. Try releasing the parking brake and applying it again, then check that the parking brake is fully disengaged. If the parking brake light stays on after that, the switch on the lever may be stuck or out of adjustment. On cars with an electronic parking brake system, a fault in the motor or switch can trigger the warning too.

Low brake fluid

A float in the reservoir, the brake fluid level sensor, turns the warning on when the fluid drops. Fluid goes down slowly as pads wear, because the caliper pistons sit further out. A sudden drop is different. It usually means a leak in a hose, line, or caliper, and a leak can lead to brake failure. Old, water-logged fluid is a separate problem; a brake fluid flush replaces it.

Worn brake pads

On many cars a pad sensor trips at about 3 mm of material (Haynes). Cars without sensors use a metal tab that squeals instead. Here's how to check your brake pads, and why brakes squeak.

A fault in the anti-lock brake system (ABS)

If the amber light marked ABS comes on by itself, a wheel speed sensor, its wiring or the ABS module has a problem. The car will still stop, but the wheels can lock in a hard stop on a wet road. A dirty or damaged wheel speed pickup is the usual culprit.

A faulty sensor or loose wiring

Sometimes the brake components are fine and the messenger is wrong. A failed float, a corroded connector or a pad wear lead that wasn't replaced with the pads can all keep the warning on. The warning light may also flicker over bumps when a wire is loose.

Warning light on but the parking brake is off?

If the parking brake is fully released and the red warning is still on, the next suspects are low brake fluid levels and a hydraulic problem. Check the reservoir: if it's below MIN, look for wet spots inside the wheels or under the car. If the fluid is full and the pedal feels normal, a sticking switch or a faulty brake sensor is likely. If the pedal feels soft or sinks, don't drive the car.

ABS and brake light on at the same time

When the red warning and the yellow ABS light come on together, treat it as a red-light problem. On many cars, the system that balances braking between the front and rear wheels runs through the ABS, so an ABS fault can switch on both. Low fluid can also trigger both. Check the fluid and the pedal, and have the brake system inspected before you drive any distance.

Is it safe to drive with the brake warning light on?

Not with a red light, until you know why. Brake problems were the critical reason in about 22% of crashes that investigators traced to the vehicle (NHTSA, DOT HS 812 506, 2018). A red light with a normal pedal and a full reservoir is often just the parking brake. A red light with a soft, low or sinking brake pedal is a possible brake system failure. Stop your car and don't drive it.

A yellow ABS warning on its own is less urgent. Your regular brakes work as normal. Drive gently, leave more room, and have the brake system inspected soon.

What to do when the light comes on while driving

1.  Test the pedal. Press the brake pedal gently. If it feels firm and the car slows normally, you have time to pull over calmly.

2.  Stop the car somewhere safe. A parking lot or a wide shoulder, not a live lane.

3.  Check the parking brake. Make sure it's fully released. With an emergency brake pedal, push and release it once.

4.  Check the brake fluid level. The reservoir is usually on the driver's side of the engine bay. The fluid should sit between MIN and MAX.

5.  Look for a leak. Wet patches inside a wheel or a puddle under the car mean fluid is escaping.

6.  Decide. Low fluid, a leak or a soft pedal means call for help. A full reservoir and a firm pedal means you can drive carefully to get it checked.

Topping up the fluid may turn the light off, but it doesn't fix the reason the fluid was low.

Warning light still on after new brake pads?

Three reasons come up. The pad wear sensor wasn't replaced, and a tripped sensor stays tripped. The fluid wasn't topped up after the caliper pistons were pushed back. Or the car needs its service reminder reset, which on many newer models takes a scan tool.

Brake warning lights in Philadelphia and the Bay Area

Greater Philadelphia. Years of winter road salt corrode steel brake lines, and a corroded line that starts to weep is one route to a low-fluid warning on older cars. If your light comes on after a winter, look for wet, rusty spots along the lines under the car. WeBrakes doesn't repair brake lines, so if an inspection finds a leaking line, we'll tell you what we found. WeBrakes covers Philadelphia, Delaware, Bucks, Montgomery and Chester counties, Wilmington and Camden County, NJ: mobile brake repair in Philadelphia.

San Francisco Bay Area. San Francisco requires you to curb your wheels when you park on a grade over 3% (SFMTA), and most drivers set the parking brake hard on every hill. If you don't fully release the brake before you pull away, that's the first thing to check. WeBrakes covers San Francisco, San Mateo, Santa Clara, Alameda, and Contra Costa counties: mobile brake repair in San Francisco.

How much does it cost to fix a brake warning light?

It depends entirely on the cause. Releasing a parking brake costs nothing. A sensor is a small job. Brake pad replacements, a brake hose replacement or an ABS repair cost more, in that order. Start with a diagnosis so you pay for the right brake repair, not a guess: a WeBrakes mobile brake inspection is $75, applied to your repair if you book it. For typical prices, see our brake repair prices and the brake pad replacement cost guide; for pads, see brake pad replacement.

Brake warning light FAQ

Can low brake fluid cause the brake warning light to come on?

Yes. It's one of the most common causes. The level sensor trips before the reservoir is empty, so you get a warning while the brakes still work. Find out where the fluid went before you top it up.

Why is my brake light on when the parking brake is off?

Usually low brake fluid, a hydraulic problem or a faulty switch or sensor. Check the fluid level and the pedal feel. If the pedal is soft or sinks, don't drive the car.

What does it mean when the ABS and brake light are on at the same time?

Treat it as a red-light problem. An ABS fault can disable the system that balances front and rear braking, and low fluid can trigger both lights. Get it inspected before you drive any distance.

What's the difference between the brake light and the ABS warning light?

The red brake light covers the basic hydraulic brakes and the parking brake. The yellow ABS light covers only the anti-lock function. One means your ability to stop may be affected; the other means you've lost a safety aid.

What does the brake warning light mean on a BMW?

BMW uses the same colors as everyone else. A yellow brake symbol usually points to a service item such as pad wear. Red means stop and check the fluid and parking brake. The iDrive screen normally names the fault.

Can you come to me if I shouldn't drive the car?

Yes. WeBrakes is a mobile brake service. A technician comes to wherever the car is parked in Greater Philadelphia or the San Francisco Bay Area, inspects it for $75 (applied to your repair if you book it) and can usually fix it the same day, getting any missing part from our parts vendor. WeBrakes doesn't repair brake lines.

Do brake shoes trigger a warning light?

Rarely. Drum brakes with brake shoes don't usually have wear sensors. Worn shoes show up in regular brake inspections, which are the cheapest brake maintenance there is, or as a parking brake that pulls up higher than it used to.