What is an ABS Sensor?
The anti-lock braking system uses an ABS sensor or wheel sensor to monitor the wheel speed and send this information to the ABS computer. The ABS computer uses this information to prevent the brakes from locking during an emergency stop. If wheel speeds are not equal, the computer modulates the anti-lock feature until the speeds are equalized.
Where are these sensors located?
The ABS sensor is typically located in each wheel hub/rotor on a four channel ABS system. Some rear wheel drive applications have the sensor mounted in the rear differential.
Will a malfunctioning ABS sensor illuminate the check engine light or affect vehicle operation?
Yes, a failing sensor can illuminate the Malfunction Indicator Light (MIL) or ABS warning lamp, and may cause failure of the anti-lock braking system to operate safely and properly.
What are the common causes of failure?
Typically these sensors will fail as a result of clogging from metallic debris, brake dust or dirt due to exposure to the harsh elements.
How to determine if these sensors are malfunctioning?
An ABS sensor can be visually inspected and the wire winding and sensor harness can be tested for opens, shorts and proper factory specified resistance with an ohmmeter.
Check out this video showing a typical ABS speed sensor replacement.
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Photo courtesy of Wikimedia Commons.