ABS System Parts – A Comprehensive Guide

In a quest to make vehicle owners and road users safe, many safety features have been placed in cars by car manufacturers. One of which is the ABS system. So what does an ABS system do? The ABS system is a safety device that helps drivers avoid skidding by preventing wheel lock during an abrupt stop.

Before the introduction of ABS, the wheels could lock up and skid when a driver suddenly hit the brakes. But not anymore, as the ABS now gives driver control in such situations. The ABS system, however, comprises several components that help ensure your car stops safely. But before we discuss the ABS system parts, let’s see the types of ABS systems.

abs system in car

Types of ABS

The anti-locking brake system works in different ways, depending on the number of channels used to help your car stop in challenging situations.  There are basically three types of ABS systems, which are as follows.

One-channel one-sensor ABS

The one channel one-sensor ABS system is commonly found in trucks using rear-wheel ABS. It has a one-speed sensor and a valve, with the speed sensor located in the rear axle.

With this setup, the controller monitors both rear wheels simultaneously, which means both wheels must lock before it acts. So what happens when only one rear wheel is locking or losing road traction? The ABS will fail to release pressure to stop your car, invariably limiting braking effectiveness.

Three-channel three-sensor ABS

This ABS system is commonly found on pickup trucks with four ABS wheels and utilizes only three speed sensors and three valves. Here, each front wheel has a valve and a speed sensor, while the two back wheels use one sensor and a valve. The speed sensor for the back wheels is placed on the rear axle.

The controller can regulate the front wheels individually for effective braking since they have a separate valve and speed sensor. However, since the back wheel shares one valve and sensor, both rear wheels must be locking or sliding before the controller swing into action. And what if only one of the rear wheels locks? It’s simple; the ABS system will not act, resulting in poor braking.

Four-channel four-sensor ABS

This system uses four-speed sensors and four valves, with one sensor and one valve on each wheel. This allows the controller to manage each wheel independently, allowing effective braking.

Of all the types of ABS systems, this is the best because it can regulate brake action on only the affected wheel(s).

When the controller detects that any wheel is losing road traction or sliding, it immediately acts by providing power for that wheel. However, in the other types of ABS systems using the one-speed sensor, both wheels must be locking before the ABS system comes into play.

ABS system parts name

The ABS system comprises different parts working together to effectively stop your car at a short distance.  So here are the ABS components and functions.


Cars with ABS have valves on their wheels, and how many valves depend on the type of ABS system. The valves are responsible for allowing, blocking, and releasing pressure on the brakes using three different positions depending on the ABS system. They include the close, open, and release position.

In the open position, the valve opens and releases pressure from the master cylinder into the brake. In the block position, the valve blocks the line, separating the brake from the master cylinder, invariably preventing pressure from rising more even if the drive pushes harder. In the release position, the valve let out some pressure from the brake.

Wheel speed sensors

The anti-lock braking system sensor is placed on your wheels and monitors how fast or slow your wheels are going. How many sensors you use depends on the ABS system type. Typically, when a wheel is about locking, the speed sensor notifies the controller.

ABS Sensors

Controller (Electronic brake control module)

The controller, also called an electronic brake control module, is the brain and processor of the ABS system and connects directly to the brake line.  It uses information from the individual wheel speed sensors to determine whether to pump the brakes or not.


The pumps of an ABS system help release hydraulic pressure to the brake lines when the valves are released. Generally, when the valves are released, hydraulic pressure drops, so there has to be a way to return back the pressure. Hence, the need for a pump. When the valve reduces pressure, the pump helps restore the pressure back.

Hydraulic motor

While not a main component, the hydraulic motor is an important ABS brake parts. So what does it do? The hydraulic motor is a component of the hydraulic system through which the ABS builds back pressure. It works in synchrony with the ABS pumps.

Hydraulic fluid

The hydraulic brake fluid is a component of the hydraulic system and is useful in building braking pressure. It is used in transferring force into pressure and to boost braking force. Here, the brake fluid helps transfer pressure from the hydraulic brake line to other brake components near the wheels. It is also useful in regulating brake heat. As the brake heats, the fluid’s high boiling point ensures the brake still works optimally.


Q: What are the six major parts of an ABS modulator

The ABS system comprises several components that help prevent wheels from locking during an abrupt stop. However, the six basic parts of ABS are the controller, valve, pump, wheel speed sensor, brake caliper, and hydraulic motor. And here is how they work collectively.

The speed sensor helps detect the wheel speeds and relates this information to the control module. The control module then acts by releasing the valves to reduce pressure. As the pressure reduces, it loosens up the grip on the locking brake, giving your wheels more traction to slow down and stop well.

Q: What are the 4 main stages of ABS operation

The four main stages of ABS operation are the sensing stage, pressure reduction stage, pressure maintenance stage, and pressure boosting stage. In the sensing, the wheel speed sensor detects when the wheel is about to lock and informs the controls module. In the pressure reduction stage, the ABS control module releases the valve causing a reduction in pressure.

In the pressure maintenance stage, the control module allows the valves to retain pressure, so it doesn’t increase, no matter how much the driver hits the pedal—allowing the car to slow down and stop.

In the pressure increment stage, the control module allows the pump to recover the pressure lost when the valves were released.

Q: What is inside an ABS module

The ABS module, which is the brain of the anti-locking brake system, uses information from the wheel sensors to determine when to release brake pressure from a wheel that wants to lock up and skid. It is located in the engine compartment or on the frame rail of the driver’s side of the vehicle.

It, however, houses several components to do this effectively. So what is inside an ABS module? An ABS module has a sensor and other electrical connectors and wires helping it to function well. If these sensors are dirty or there is an issue with the wires or electrical connectors, the ABS module will not work as intended.

Q: What is a 4-channel ABS system?

A 4-channel ABS system is an ABS system that controls each wheel independently. This ABS system uses four-wheel sensors and four valves, with each wheel having its own sensor and valve. In this type of ABS system, the controller regulates each wheel independently. So when the controller senses any wheel is skidding, it immediately swings into action to stop that wheel from locking up.

Q: What is a dual and single-channel ABS?

A dual and single-channel ABS is an ABS system that controls the two front wheels independently while controlling both rear wheels together. This ABS system uses three-speed sensors and three valves.

Here, the two front wheels have their own sensor and valve, while the two rear wheels use a single sensor and valve. In this ABS system, the controller regulates the front wheels individually since they have their own valve and sensor.

On the other hand, the two back wheels are regulated together because they share one valve and sensor. This means the controller will only swing into action only when the two back wheels are locking up. So what happens when only one rear wheel is locking up? The ABS will not supply power to the locking, which invariably affects your braking performance.


An ABS system practically ensures you brake within the shortest time and safely. It does this by providing power to any lagging or locking wheel. The system, however, consists of several components to work effectively. So what are the components of an ABS system?

They include valves, speed sensors, controllers, pumps, hydraulic motors, and hydraulic fluids. Therefore, for your ABS system to properly brake on slippery terrains or in emergencies, all ABS system parts must be functioning properly. So, if you notice any ABS brake problems, immediately take your car for proper diagnosis and possible repair of any brake components.


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