Wheel speed sensors

When the wheel speed sensor fails, the ABS fault signal lights up on the dashboard, and a fault code – specific to each brand – is stored in the ECU’s memory, to be read and interpreted later by a compatible diagnostic kit. More specifically, although the light may be yellow / orange and not red, we cannot stress enough that you should not drive for long with a non-functioning ABS sensor. This is for your own safety, as the brake pressure regulation will be affected; and of course, in case of sudden emergency braking, your front wheels will lock.

Firstly, we strongly advise you to visually check the wheel speed sensor; i.e., the body of the sensor (visible dents, cracks or any kind of blow), its connector (is it subject to poor connection or loosening), and its wiring (presence of damaged wires).

Secondly, using a multimeter (in millivolt mode), you can take a first measurement of the sensor, then several others by turning the wheel of the car little by little each time. The aim here is to check all the polarities after the wheel has been rotated through 360°, and if the sensor is working correctly, the voltage will rise the same amount each time you turn the wheel.

If the above tests are not conclusive, then it would appear that you need to replace your vehicle’s wheel speed sensor.

Although the ABS sensor is particularly durable by design, as it needs to resist constant external stresses, it can sometimes cease to function properly. For example, due to excessive dirt, or a break in the connection due to friction or excessive vibration, short-circuiting or even impact with external debris. It can also be compromised by stresses caused by mechanical or thermal stress, internal overheating of the sensor, or problems with the wheel bearing and/or the ABS module.

We recommend the following steps to replace your wheel speed sensor as efficiently as possible and to limit possible mistakes:

1. Raise the vehicle, for example with a jack and a stand.
2. Remove the wheel by removing the nuts, and locate the wheel speed sensor.
3. Remove the bolts securing the sensor to the suspension – with de-sealer, if necessary.
4. Dismantle your sensor using circular movements and pliers.
5. Place the new sensor and attach it to the suspension.
6. Refit your wheel.

In order to extend your wheel speed sensor’s durability, we strongly advise you to observe the following installation recommendations:

• Be careful not to damage your new wheel speed sensor during installation;
• When cleaning the sensor, only use soapy water, a microfiber cloth and a brush – also take care not to break it when removing it with the pliers;
• Refit the wheel using the torque recommended by the manufacturer and take this opportunity to check your tyre pressure at the same time.