Informational Guide

How Does Anti-Lock Brakes (ABS) Work?

Most modern vehicles are equipped with anti-lock brakes, but how does ABS work? Find out in this detailed guide.

Most modern vehicles are equipped with anti-lock brakes, but how does ABS work? We will look at the role ABS has and how it works. Once you read our comprehensive guide, you will know everything there is about how ABS works. 

Four-channel, Four-sensor ABS

This ABS sensor has a different valve associated with each wheel, including a separate speed sensor for each. This is the preferred system because there is monitoring occurring with each wheel, ensuring that optimized braking force is always used.

Three-channel, Three-sensor ABS

This ABS gives both front wheels an individual valve and speed sensor but shares one between the two rear wheels. Many pickup trucks feature this type of system. However, both rear wheels must be locked for the system to be triggered.

One-channel, One-sensor ABS

This standard ABS system only includes one valve and speed sensor for all four wheels. Usually, it is located on the rear axle. You can tell what vehicles have this system because there will be one brake line running to the rear wheels with the use of a T-fitting.

Benefits of Anti-Lock Brake Systems

You might be asking - "what is abs in cars and how does it work?" But, more importantly, you want to understand the benefits of the ABS. First, you have better stopping power and traction control, which is important if you drive on slippery or icy roads. You might also have lower insurance rates as this safety device prevents accidents. Cars with ABS also tend to have higher resale values, which puts more money in your pocket when you are ready to sell.

Main Components of Anti-Lock Brake Systems

ABS Speed Sensor ABS Valves

How does an ABS sensor work? It consists of a magnet and a toothed ring surrounded by a coil. The sensor determines the speed of each wheel, while the valves control the amount of pressure each receives. As you press the brake pedal harder, the valves are responsible for limiting pressure.

ABS Electronic Control Unit (ECU)

This controller is where all of the information from the sensors is processed. As a wheel loses traction, signals are sent to the controller so action can be taken. This controller is responsible for limiting the amount of braking force and activating the ABS modulator for better traction and drivability.

Hydraulic Control Unit

When you brake normally, the ABS system remains dormant. However, when skidding is detected, the controller alerts the hydraulic modulator to ensure the wheels don't lock up. The modulator comes with two valves per brake caliper to allow fluid through as needed.

alloy wheel

How Do Anti-Lock Brakes (ABS) Work?

What is an ABS system and how does it work? In most vehicles, the ABS operates the same way, whether you are driving a car or riding a motorcycle. Sensors are located on the wheels or axles to detect when locking is occurring. The ABS then pumps the brakes at a speed of hundreds per second to stop the wheels from skidding. When this happens, the driver regains control over the vehicle. Basically, the ABS works across three stages.

  1. 1
    You engage the brake.
  2. 2
    Wheels begin to skid or lock up.
  3. 3
    ABS starts pumping the brakes to regain control.

Here's a helpful video that further illustrates the system.

How to Know the ABS System Is Bad: Warning Signs

Unresponsive Brakes

When the ABS module fails, your brake pedal could become unresponsive. This isn't the case with all vehicles, but something to be aware of. Sometimes, the brake pedal stops working slowly, giving you time to repair the system.

Wheels are locking up

When the ABS works right, the wheels shouldn't lock up. As the ABS module becomes faulty, it can cause locking up, even under normal driving conditions. You might also notice random clicking noises associated with this problem.

Brake pedal needs more force

When the ABS system works correctly, you don't need a lot of force to engage the brake pads. However, as the system begins to breakdown, you might have to push the pedal harder to achieve the same amount of force.

ABS light is on

The ABS Light comes on to alert you of a problem. It's the Check Engine Light for brakes but won't tell you exactly what the problem is. Instead, you will need a code scanner that detects these issues.

Speedometer Fails

Faulty wheel speed sensors can cause the ABS Light and ESP light to illuminate. It is also a cause for the speedometer to stop working, which puts you in danger.

People Also Ask (FAQs)

What does it mean when an ABS light is on in a semi-trailer?

As you answer - how does the ABS light work on a semi-trailer, you see that the systems are similar to that of a passenger vehicle. If the ABS light has come on, there is something wrong with your system that should be checked out.

How do you know if your Harley has ABS?

Many people ask, how does motorcycle ABS work, more specifically, how does Harley ABS work. Interestingly enough, only some bikes come with ABS. If your Harley motorcycle contains the proportioning valve under either of the side covers, the bike likely has ABS. Now, all that's left to do is figure out - how does ABS work on a motorcycle?

How do you use ABS on a motorcycle?

If you ride a bike, you want to know - how does ABS on a motorcycle work? The systems are very similar to that on a passenger vehicle, except you have fewer wheels to control.

When are anti-lock brakes most effective?

The best time to use anti-lock brakes is when you are driving in slippery, icy, and wet conditions when traction is more difficult.

Can I drive my car with a bad ABS module?

If the ABS light is on your vehicle, you should have it checked out before driving any further. Without anti-lock brakes, you are putting yourself at risk on the road.

What happens if my car doesn't have ABS?

Without ABS, the tires can't grip and the wheels lock up, which causes the tires to slide. When this occurs, the vehicle becomes out of control. That's why drivers who don't have ABS are taught to pump the brakes if traction is lost.

Can low brake fluid cause ABS light to come on?

The ABS light might come on if the brake fluid level is low. You might also notice a spongy, soft brake pedal when this happens.


How does an ABS pump work? We've looked at various types of anti-lock brake systems to show you the differences. Understanding this vital safety system helps you remain safe on the road.