ABS sensor BOSCH VOLVO S40

DIY repair is only possible if the ABS malfunction is caused by faulty wheel speed sensors. Due to their location, they are highly exposed to moisture and dirt and therefore often fail. In some cases, it is enough to clean the sensitive element with a dry soft lint-free cloth. If this doesn’t work, replace the component.

If a malfunction of the anti-lock braking system is caused by a failure of the electronic control unit or a hydraulic unit, you will need professional assistance. Visit a car repair shop.

First, inspect the component. Cracks on its housing, torn and oxidised wires, and a damaged connector indicate a malfunction.

Use a multimeter for thorough diagnostics. Before you start testing the component, check how the wheel speed sensors are installed in your car. You can find this information in the vehicle repair manual.

You will need to raise the car and most likely to remove the wheel in order to access the part. Next, disconnect the wire from the ABS control unit. Connect the multimeter probes to the sensor contacts and measure resistance. Compare the received values with nominal data – they are usually specified in the car owner’s manual. As a rule, these values vary within the range of 0,5–2,0 kiloohms.

The next step of testing is measuring the voltage on the sensor contacts. To do this, rotate the wheel with your hand at a frequency of about 1 cycle per second. With this frequency, the voltage should be 0,25–0,50 V.

This procedure is determined by the vehicle make and model. Typically, the steps are the following:

1. Engage the parking brake and secure the axle opposite to the one on which you’re going to replace the component with wheel chocks. Raise the car.
2. Remove the wheel.
3. Unscrew the fasteners of the brake caliper, pull it aside and secure with a wire.
4. Remove the brake pads and a disc.
5. Unscrew the sensor fastening bolt and remove the component from its mounting seat.
6. Disconnect the wire from the ABS control unit and car body.
7. Install a new part by following all steps in reverse order.