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How to test abs sensor?

December 15, 2023
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The ABS sensor is a safety device that prevents your wheels from locking in the event of an emergency stop. They are located on each wheel. However, they can sometimes malfunction. To prevent this from happening, you can use special equipment to test your ABS sensor. In this article, you will learn what the symptoms of a faulty ABS sensor are and how to diagnose it.

What are the symptoms of a bad ABS sensor?

If the ABS sensor is defective, the ABS will not engage. Symptoms of a faulty ABS sensor may include

ABS warning light on:One of the most common signs of an ABS sensor malfunction is the ABS warning light on your vehicle's dashboard. This indicates a problem with the ABS.
Wheel locking during hard braking:If you notice that your wheels lock or partially lock during hard braking, this may be a sign of an ABS sensor malfunction.
Abnormal noise or vibration during braking: A faulty ABS sensor can also cause abnormal noise or vibration during braking. This may be because the ABS is not working properly to regulate the brake pressure on the wheels.
Loss of vehicle control when braking:If you experience loss of vehicle control when braking, this may also be a sign of a faulty ABS sensor. The ABS is designed to help you maintain control of your vehicle during an emergency stop, and a faulty sensor can compromise this functionality.
Your vehicle is unstable in the rain or when it freezes: the ABS sensor is not transmitting the information needed to keep the vehicle stable, and you will lose traction on ice or wet roads.
Longer stopping distances: the ABS HS sensor prevents the ABS from activating in time during heavy braking.
Braking is not evenly distributed to all four wheels: the ABS sensor does not distribute braking evenly.

What causes a sensor to fail?

The ABS sensor is a delicate part. If it's not a wearing part and you don't plan to replace it regularly throughout the life of your car, the ABS sensor can become clogged or damaged over time. Some of the causes of ABS sensor failure include:

Wear and tear: Like any electronic component, ABS sensors can wear out over time due to exposure to the elements, vibration, and normal wear and tear.
Physical damage: ABS sensors can be damaged by impact, collision, or road debris. Cables and connectors can also be damaged.
Electrical malfunctions: Electrical problems such as short circuits, cable cuts, or problems with the vehicle's electrical system can cause the ABS sensor to malfunction.
Dirt or debris:ABS sensors use magnets to detect wheel rotation. If these magnets become dirty or covered with debris, it can cause detection errors.
Bearing problems: Worn or damaged wheel bearings can cause vibration or abnormal wheel movement, which can mislead the ABS sensor.
Connection problems: Connection problems between the sensor and the brake system or between the sensor and the ABS control module can cause malfunctions.

To test an ABS sensor

Step 1: Preparation

Make sure the vehicle is turned off and the ABS is disengaged. You'll need to locate the ABS sensor you want to test. It's usually located near the wheels, near the brake rotors or hubs.

Step 2: Disconnect

Disconnect the ABS sensor's electrical connector. This will give you access to the sensor pins for measurement.

Step 3: Adjust the multimeter

Set the multimeter to measure resistance (ohmmeter). Some multimeters have a special function for testing ABS sensors.

Step 4: Measure the resistance of your ABS sensor

Testing your ABS sensor can be necessary in many cases: when a warning light comes on, when brake pressure is not regulated properly, when your wheels lock under hard braking when the diagnostic unit displays a fault code. You can perform your check by first checking the installation of your ABS sensor.

To do this, place a repair cable equipped with PIN contacts on the tester and connect the sensor socket to the other end. Then measure the resistance of the contacts and verify that the results match the information in the service manual.

Step 5: Perform a voltage test

To check the performance of your ABS sensors, you'll need to perform a voltage test on each one. To do this, connect the pin lead to a tester and spin the wheel at 1 rpm. Then make sure that your multimeter reads between 0.20 and 0.25 V. As the rotation increases, the voltage reading on your tester's screen should also increase.

If you have an oscilloscope instead, the resistance level will be indicated by the amplitude on a graph. Note, however, that this type of equipment is more expensive and more suitable for professionals due to the complexity of maintenance.

Step 6: Do a final test on a flat road

Once you've measured the resistance and performed your voltage test, we recommend that you ride on a flat road to perform the final check. The idea is to rotate the wheel 360°. You'll need to brake at a speed of between 20 and 400 km/h by pressing the brake pedal down. You'll feel a slight vibration on the pedal and hear a noise coming from your brake pads.

How do I clean the ABS sensor?

Another possibility for an ABS problem is a dirty sensor. ABS sensors are very exposed to dirt due to their location on the wheels. There are several steps you can take to clean the sensors:

Raise the vehicle, remove the wheel, and remove the ABS sensor.
Clean the ABS sensor with soapy water and possibly a brush.
Clean the sensor housing
Dry with a microfiber cloth
Replace the ABS sensor

When and how to replace the ABS unit?

The ABS unit can be replaced when it breaks or fails, as it is an essential safety feature of the vehicle. Replacing the sensor may be all that's needed, but it may also be necessary to repair the ECU or the hydraulic system.

Repairs can be more or less expensive depending on the parts involved and the type of vehicle. It is therefore advisable to get a professional estimate to get a better idea of the costs involved. It's also possible to buy used parts for this type of equipment. For example, there are vehicles with ABS blocks in perfect condition that can be salvaged for a more economical installation.