ABS Pump Users Guide

ABS Pump

When you are looking to buy an ABS (anti-locking brake system) pump to replace your old one it is important to match up the part numbers to be sure it’s the correct one for your car. Get it right the first time – You do not want to purchase the wrong one and then go though the process of finding the correct one all over again.

At Your Car Spares Ltd  – What we test and look for!!!!

As the ABS pump is an electrical part testing it can be more difficult and the best method of testing it is by using a diagnostic equipment. If there is a problem with the ABS then it should give you a fault code which allows you to identify where the problem lies. If the ABS light remains illuminated on your dashboard then this means there is a problem with the ABS. Before you take it to get professionally looked at you should check that the fuse hasn’t blown. If the fuse hasn’t blown then you need to get it looked at because if there is a fault with the ABS then it will shut off until it is fixed.

Where to find the Part Number

An ABS pump will have a few part numbers that you need to match up to ensure you are getting the right one for you car. There will be a part number on the ECU / control module and the main body of the ABS pump.  Below we will show you an example of the part numbers on an ABS pump. 

Pump parts number

Where to find the ECU part number.


Pump serial number

Close up of a sample serial number for an ABS pump part.

How does an ABS Pump work?

The anti-lock braking system ensures that the wheels are always in tractive contact when driving by preventing the brakes from locking up and avoid skidding. The ABS pump consists of an ECU which monitors the speed of the rotation of each wheel and a hydraulic unit / pump which puts pressure on the brakes. If the ECU identifies that a wheel is rotating at a quicker pace than the other wheels then it causes the valves , which are inside the brake lines , to increase the hydraulic pressure on the brakes of that wheel to slow it down. Alternatively , if the wheel is moving at a slower pace it will lower the pressure to speed it up. The valve in the brake lines has three different positions , as follows :

  • In the first position , the valve is open and this allows the brake master cylinder to send pressure directly to the brakes without any changes in the pressure.
  • In the second position , the valve will close the lines. This means that the brake master cylinder isn’t able to put any pressure on the brakes therefore the pressure will not increase if the driver presses the brake pedal more.
  • In the third position , the valve will levitate the pressure on the brakes.

The most common problem with the vales are that they sometimes get blocked which will render them unavailable to open , close or reduce pressure on the brakes.

Not all of the anti-locking brake systems are the same , below we will go through 5 different schemes:
Four-channel , four ABS Sensors – This scheme is the most effective because it allows each wheel to be overseen by an individual ABS sensor and valve. This allows the ECU / controller to ensure that the maximum braking force is achieved.

Three-channel , four ABS Sensors – This system isn’t as common as it is mainly used in older cars. This system , like the four-channel and four ABS sensor system , has an individual sensor on each of the wheels but only the front wheels have a dedicated valve , whereas the rear wheels have a shared valve.

Three-channel , three ABS Sensors – This is a scheme that is often found on pick-up trucks. It has dedicated ABS sensors and valves on the front wheels but a shared sensor and valves on the rear. The shared sensor can be found on the rear axle. Due to the rear wheels sharing a sensor they both need to lock up before the ECU will reduce or increase the pressure on the brakes.

Two-channel , four ABS Sensors – This is a system found in cars manufactured between the late 1980s and early 2000s. It uses individual sensors on each of the four wheels but two valves , one for the front and one for the rear. If one of the wheels locks up then the controller will make an adjustment to the brake pressure of both of them.

One-channel , one ABS Sensor – This system is another one which is found on pick-up trucks. It uses one valve and one sensor for the rear wheels. The controller will only respond if both wheels lock up.

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