ABS Sensors

Monitoring Wheel Speed: The ABS sensor continuously monitors the speed of each wheel. It detects how fast each wheel is rotating and sends this information to the ABS control module.
Preventing Wheel Lock-up: During braking, if one or more wheels start to lock up (cease rotating due to excessive braking force), the ABS sensor detects the difference in speed compared to the other wheels. Wheel lock-up can lead to a loss of traction and control, especially on slippery surfaces.
Maintaining Control: When a potential wheel lock-up is detected, the ABS control module adjusts the braking pressure to the affected wheel(s). It rapidly releases and re-applies the brake, preventing the wheel from locking and allowing the driver to maintain steering control.

Magnetic Inductive (Passive) Sensors: These consist of a toothed ring (also known as a tone wheel or reluctor ring) and a magnetic coil. As the wheel rotates, the teeth pass by the magnetic coil, creating an alternating current (AC) signal. The frequency of this AC signal corresponds to the wheel speed.
Magnetoresistive (Active) Sensors: These are more advanced and use a semiconductor device that changes resistance in the presence of a magnetic field. They generate a digital signal (a series of voltage pulses) directly proportional to wheel speed.

For magnetic inductive sensors, the passing teeth of the tone wheel cause fluctuations in the magnetic field, inducing an AC voltage in the sensor coil.
For magnetoresistive sensors, the sensor detects changes in a magnetic field as the wheel rotates, producing a digital signal.
Data Transmission: The generated signals (either AC or digital) are transmitted to the ABS control module. This data is analyzed in real-time to assess the speed of each wheel.
Feedback Mechanism: Based on the data received from the ABS sensors, the control module modulates the braking force applied to each wheel. This feedback loop ensures that each wheel maintains optimal traction with the road surface, thereby enhancing vehicle stability and control during braking.

Enhanced Safety: By preventing wheel lock-up, ABS sensors help maintain traction and steering control, reducing the risk of skidding and improving overall vehicle safety.
Shorter Stopping Distances: On slippery or uneven surfaces, ABS can shorten stopping distances by preventing the wheels from locking and maximizing the contact with the road.
Vehicle Stability: ABS sensors contribute to maintaining vehicle stability during sudden or hard braking, especially in emergency situations.
Improved Tire Wear: Preventing wheel lock-up also helps reduce uneven tire wear, as the wheels are less likely to drag across the surface of the road.

Sensor Malfunction: Over time, ABS sensors can become dirty, damaged, or fail due to exposure to harsh driving conditions. Common symptoms of a faulty ABS sensor include the ABS warning light on the dashboard, loss of ABS function, and unusual brake behavior.
Regular Checks: Regular maintenance and checks can ensure that ABS sensors are functioning correctly. Cleaning the sensors and checking the wiring for damage can prevent potential issues.
Replacement: If an ABS sensor fails, it typically needs to be replaced to restore proper ABS function. This should be done by a qualified technician to ensure correct installation and calibration.