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ABS sensor - What is it?

ABS sensors are crucial for the ABS System to work. This system prevents the wheels to lock when braking in dangerous situations. In this way, the driver remains in control of the car. ABS sensors are composed of a toothed ring and a magnet.

The ABS sensors are placed on each wheel of the car: Their function is to monitor the wheels' rotation speed. Depending on the information sent by the ABS sensor to the engine computer, the computer will adapt the braking pressure. This information about the wheel speed will also be useful for both the engine system, the transmission system, or the navigation system for example.

Therefore, the ABS sensors are indispensable for your safety while driving, as well as your comfort.

ABS sensor replacement

In the case of a bad ABS sensor, you should have it changed as soon as possible. Before the replacement, it will first be necessary to clean the sensor with a metallic brush. Then, you can install the new ABS sensor, and make sure the sensor cable is well placed. For mechanics, or for handy car owners, the ABS sensor replacement is relatively quick and simple and should take about ten minutes.

To make sure the ABS sensor in your car is correctly changed, let a qualified mechanic do it for you.

Symptoms of a bad ABS sensor

After a while, the toothed ring and the magnet can wear out and will alter the ABS sensor performance. Some signs can indicate that one or several ABS sensors are faulty.

  • The ABS light is turned on in your car's dashboard.
  • It gets harder to brake when it’s raining or on an icy road.
  • The braking distance is longer than usual.
  • In case of strong braking, the wheels are locking, and you are losing control of the car.

But how to tell which ABS sensor is bad? In order to find out, you will need to test each ABS sensor.

How to test an ABS sensor?

Different methods exist in order to test the ABS sensors of your car: This test can be done with a voltmeter which will measure the current, with an ohmmeter which will measure the electrical resistance, or with an oscilloscope. The easiest method is to use a voltmeter for the test.

First of all, you need to find the location of the ABS sensor you want to test: Usually, they are fitted on the wheel hub. When this is done, disconnect the wires on the sensor and attach the voltmeter to the sensor. Then, you can perform the test by spinning the wheel, as you can read the voltage.

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