In some cars with an Anti-lock Braking System (ABS), there’s a part called the ABS differential speed sensor. Think of it as a special sensor that measures how fast a key spinning part inside your car’s differential (a part that helps wheels turn at different speeds) is moving. It then sends this speed information to the ABS control module (the computer that runs the ABS system). The ABS computer uses this data to figure out how fast your car is actually going.

Simple Signs of a Bad or Failing ABS Differential Sensor

If this sensor isn’t working correctly, you might notice these problems:

The ABS Warning Light Comes On: This is usually the most obvious sign. If the car’s computer detects a problem with the ABS differential sensor or the information it’s sending, it will light up the ABS warning light on your dashboard.
ABS Acts Up (Improper Activation): Because this sensor helps the ABS system know your car’s speed, if it’s faulty, the ABS might get confused. This could cause the anti-lock brakes to activate unexpectedly (when you’re not braking hard) or fail to activate when they should.

Important Advice About ABS Differential Sensors

Here’s a key point to remember about these sensors:

Not All Cars Have One: It’s important to know that not every car with ABS has an ABS differential sensor. Many modern cars use individual wheel speed sensors (one sensor on each wheel) instead of a single sensor mounted on the differential. So, if you’re troubleshooting an ABS light, your mechanic will check which type of sensor system your vehicle uses.

In simple terms, the ABS differential sensor tells your car’s ABS computer how fast you’re going. If it fails, your ABS warning light will likely come on, and your ABS might act strangely. Just remember that not all cars use this specific type of sensor; many rely on individual sensors at each wheel instead.