Why does the brake light come on when accelerating or braking?

This article will cover the most common reasons why your parking brake light might come on just when you are accelerating or braking and how you can identify and fix the problem yourself.

In short, the most likely cause for a brake light to turn on when you are accelerating, or braking is a low brake fluid level. While stationary, the fluid level might be just enough for the sensor to not throw a warning light, but when the car is moving, the G force can cause the fluid to move around, resulting in a warning light on your dashboard.

Brake system warning light in car dashboard

Here is what can cause a brake warning light when the car is moving

1. Low brake fluid level

The most common cause for the brake light to turn on your dashboard is a drop in your brake fluid level. Inside the brake master cylinder is a sensor that will ensure that your braking system has enough fluid to function correctly.

However, over time the car might lose brake fluid due to leaks in the braking system. Whether it is a damaged hose, a crack in the master cylinder, or the brake fluid reservoir, there are quite a few parts that can fail and leak.

I suggest parking your car on a clean surface for a couple of hours, then move it and check on the ground for any yellow to brownish fluid.

Additionally, you might want to check the brake calipers as these are prone to leaking after years of wear, vibrations, and dust.

Lastly, you want to check the brake fluid reservoir and the master cylinder for any cracks.

If you can’t see any problem, you should also consider that as the brake pads wear down, they get closer to the rotor resulting in fluid level drop.

2. Parking brake is on

It is probably the first thing you should check, but ensure your parking brake, also known as the emergency brake (e brake), is not engaged.

It can happen that in a rush, you might forget to release your parking brake or not release it properly.

Driving with your parking brake on for more than a couple of minutes will damage your car’s brakes.

Even if slightly engaged, the warning light will stay on your dashboard while driving your car.

If this was your problem, depending on how long you have been driving, you might need to get it inspected by a mechanic for any potential damage to your braking system.

3. Failing sensors

A failing sensor can also cause your warning light for the braking system to turn on. It might be the sensor measuring the brake fluid level, not sending an accurate reading.

I recommend checking your brake fluid level by opening the reservoir and visually check if the level is below the limit. Your owner’s manual will tell you how to measure the brake fluid level correctly.

While at it, you might also check the color of the fluid. A darker color will indicate that you need to perform a fluid change soon.

The parking brake sensor might be failing as well, indicating incorrectly that your parking brake is engaged.

Replacing either of these sensors will range from $100 to $150, depending on the car model and how easy it is to work on it.

4. Worn brake pads

Although rare, you should consider that worn-out brake pads will cause the level of fluid to drop.

When pressing the brake pedal, the caliper piston will travel farther to activate the brake pads.

As a result, the brake fluid level might drop just under the limit and cause your brake light to turn on when braking.

Ideally, you will want to replace your brake pads every 40,000 miles, but this heavily depends on your driving style. As with everything else, the quality of the brake pads will impact their lifespan too.

Although newer cars have sensors to tell you when your brake pads have worn out, some older models will not indicate this.

5. Issues with your ABS

Although your car has an ABS warning light, sometimes issues with your ABS will cause just the brake light to turn on.

If you checked the brake fluid and it is within limits, your parking brake is off, and you have enough depth on your brake pads, it is most likely a problem with your ABS or a faulty sensor.

Unfortunately, these sorts of issues are harder to diagnose. Hence I recommend taking your car to a specialist for a proper inspection. He will be able to hook your vehicle to an OBD scanner and look for error codes.

What should you do when your brake light turns on?

Knowing how to deal with a warning light can save you thousands of dollars in damages. As soon as your brake light turns on, you should safely pull over and perform a quick inspection.

The most obvious thing to do is to ensure your parking brake is not engaged.

Secondly, you will want to check that your brake fluid level is not low. If needed, top up accordingly and see if the warning light goes away. Make sure you check with the owner’s manual to ensure you use the correct brake fluid.

If you are finding that the light turns on only when accelerating or taking a sharp turn, it is possible that this was your problem.

After performing these checks, restart your car and see if the warning light is still on.

If the light didn’t go off, I recommend checking your brake pads. If they are worn out, this will turn your brake light on, especially as you are braking. This will cause the brake fluid to drop lower than the recommended limit.

At this point, I recommend driving your car to a repair garage and have a professional inspect the problem. If you feel your brakes don’t behave normally, it is important not to drive the car and have it towed.

Is it bad to drive with your brake light on?

The braking system is the most important feature of your car, allowing you to stop safely in an emergency. The brake light on will indicate a possible fault, and driving your car around is not recommended under any circumstance.

Unless the problem was a low brake fluid level which you manage to fix yourself, you should be driving your car straight to a mechanic to have it inspected.

A car technician will tell you whether you need to replace one of the sensors or if your car brakes need replacing.


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