ABS Sensor

What is a ABS Sensor?
The ABS sensor is also known as the Wheel Speed Sensor. The job of the sensor is to provide a digital signal to the car's ECU that reports the speed of each wheel.

This function is vital for ABS to operate as without speed readings from the wheels the ECU cannot determine whether a wheel is locking up under braking. When the ECU detects a wheel is turning at a speed slower than is possible relative to the other wheels it will engage the ABS system to manage braking on the wheel. Once the wheel then returns to a normal speed it will re apply the brake (via the abs pump). This process repeats up to 20 times per second and is responsible for the grinding sensation you sometimes feel when you apply the brakes.

If the sensors malfunction this vital safety system cannot work correctly. It's not always clear if the sensors are failing as other issues can make them appear to be the culprit. Any problems or warnings from the ABS should be investigated by a qualified mechanic.
What problems can be caused by this part?

Car skids and brakes lock up when braking hard

When pressing the brakes hard in an emergency stop situation the wheels lock up and the car skids along rather than stop quickly in a straight line.

Check Brakes warning light shows on dashboard

The check brakes warning sign is showing on the dashboard. The sign looks the same as or very similar to the icon on this page.

ABS warning light shows on dashboard

The ABS (Antilock braking system) warning light has appeared on the dashboard and stays illuminated while driving.

How much does it cost to replace the ABS Sensor?
The ABS sensor is another part that varies hugely in cost depending on the manufacturer, they can range from £500 to £3500. They will usually take a couple of hours to replace.
We have 105 owner problems that mention the ABS Sensor