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Published on May 29, 2015
A brief teardown and look inside an ABS pump.
The Anti-lock Braking system in your car prevents your wheels from locking up during braking. Preventing a skid is key to maintaining steering control and stability during a maneuver.
Wheel speed sensors feed an ABS computer to monitor if your wheels are skidding during braking. When the brake pedal is depressed, brake fluid flows through the master cylinder to the ABS pump and out to the wheels.
If the ABS computer detects the car is skidding, it activates a relay in the ABS motor, temporarily releasing brake pressure up to 15 times per second, preventing a skid.
Opening up the ABS unit reveals a heavy duty DC motor that is responsible for building brake pressure and 12 solenoids, three for each wheel.
ABS wheel speed sensors are a magnetic sensor that function similar to a hall effect sensor. It responds to changes in the magnetic field from the splines in the driveshaft or hub, which generate a voltage that the computer can read.
The ABS system also functions as part of the vehicle stability control, brake assist, pre-collision braking, traction control and active cruise control among other safety features in modern cars.