How to check the ABS sensor

A braking system equipped with ABS (anti-lock braking system) technology is what every driver who cares about increased safety while driving desires. It works well in situations where heavy braking is needed, and also makes it easier to stop the car on an icy road.

ABS systems coordinate braking force using sensors. What are they and how to check the ABS sensors in your car? Modern sensor technology is much more advanced than just a few years ago.

How it works

Today, the job of the ABS sensor in most vehicles is to place two magnetically interacting elements:

  • sensor;
  • drive gear.

The sensor contains magnesium and a phase-sensitive detector, as well as a cable that sends data to the ABS computer. It is connected to a drive gear (or sometimes a magnetic wheel) that rotates to provide information about wheel speed or braking force. The sensor captures this information by changing the electromagnetic field caused by the moving “teeth” of the wheel.

Unfortunately, since the anti-lock braking system sensors are located near the wheel, they are subject to dirt, turbulence and other factors that, sooner or later, can cause a breakdown or incorrect operation.

What is the resistance of the ABS sensor?

Resistance is a physical quantity that informs about the resistance to the flow of current. This is the drag force used to capture any variability in a spinning wheel. With ABS sensors, the wire resistance measurement is typically between 1000 and 2000 ohms.

A relatively constant reading indicates a good sensor. If the measured resistance changes (decreases or increases) for no apparent reason, this may indicate a damaged or dirty sensor that should be cleaned or replaced.

How to Check an ABS Sensor

Modern vehicle and component manufacturers are trying to simplify the diagnosis of individual components as much as possible. That is why in many cars access to the ABS sensor connectors is located inside the cabin next to other electronics.

As for the rear sensors, the connectors for them can be located under the rear seat or inside the trunk. However, it often happens (in older models of cars) that in order to check the ABS sensor, you have to remove the wheel, use a pit or lift on the rack.

For example, to check the ABS sensor on a BMW e46, just use the controls on the dashboard. You need to turn on the ignition and wait a while. If two ABS lights and a triangle with an exclamation point in a circle and an arrow light up, you can be sure that the front ABS sensor has failed. If the third indicator lights up additionally, indicating that the handbrake is tightened (and the handbrake is not tightened), then you need to look at the rear ABS sensor

A much more accurate method of checking the sensor is computer diagnostics. Sometimes it may happen that the ABS sensor is working, but the computer has problems reading the data. In order to determine the exact causes of ABS failure, you need to contact a specialized car service.