How to Tell Which ABS Sensor Is Bad

ABS also known as the anti-locking brake system is an essential component in your car, and it ensures your vehicle’s brake does not lock up if you stop quickly.

When your car’s abs light is on, it indicates something is wrong, and the ABS will not function, so when you try stopping, your wheels may lock up.

Therefore, immediately you tell which abs sensor is bad, you should fix it.

Is it proving difficult to find the ABS sensor with an issue?

This article will help you learn how to tell which abs sensor is bad, replace it, and ensure the abs light does not come on again after the replacement.

What Is An ABS Sensor?

An ABS sensor is an enhanced braking system, mostly in new vehicles.

An anti-lock brake sensor, also known as a wheel speed sensor, is a type of tachometer used to measure the speed of a wheel and pass it to the vehicle’s ECM (Engine Control Module).

Since the wheels do not turn at an equal speed, the abs sensor is responsible for reporting the speed of the four wheels to the ECM.

Applying abs break is quicker compared to manual brakes.

Therefore, some vehicles will emit a grinding noise if the ABS is engaged.

Where Is ABS Sensor In Your Car?

The ABS sensor is situated on a four-channel ABS in every wheel hub. It is fitted in the rear differential in some rear-wheel-drive applications.

The sensors were outside the wheel hub in either the differential housing or the steering knuckle in the older configurations.

The abs sensor is usually paired with a ring gear. The ring is mounted on devices like brake drum and brake rotor.

However, the ABS sensor is mounted in the wheel hub in the newer systems. Based on the mode of the braking system, automobiles can have one or up to four abs sensors.

What Happens When Your ABS Sensor Goes Bad?

The abs sensors help to measure the speed of the wheel. Therefore if it goes bad, there is likely to be trouble.

Here are the signs which will tell if your abs sensor is bad.

1. Illuminated Warning Lights

There are essential lights on your dashboard that are crucial in alerting you in danger.

If your abs wheel speed goes bad or fails, the first sign you will get is the ABS light. First, the ABS warning light will come on, but the traction and stability control warning lights will also come if the other systems stop working properly.

However, it is only rare, like when the ABS wheel speed sensors stop registering the speedometer.

2. Pulsating Brake Pedal When Braking

If the abs sensor goes, it will cause wrong speed reading on either one or more tires. It is because the abs sensors help measure each wheel’s speed.

So, if the abs sensor goes bad, it tricks the Abs control module hence assuming the car is on slippery ground.

Therefore, the traction and abs control will kick in, and you will realize it by pulsating brake when you try braking.

3. Loss of Anti-lock Brakes

If the abs sensor fails, the anti-lock brakes will get difficult to operate.

When a fault comes up, the system will cause an alert, and the ABS warning light will come on. Therefore, your vehicle’s electronic control module will not receive crucial information from the sensor. Your automobile’s computer depends on the data to tell whether the wheels lock up and need any support.

Since the system does not know what is happening, the abs sensor will shut down until you repair your car.

4. Loss of Traction

Apart from losing anti-lock brakes, your car will also lose traction control, stability control, hill-start assists as well as roll stability.

When the sensor fails to send the data, the computer also shuts down the other systems.

You can also experience issues without the Abs light on.

Therefore, your abs sensor has gone bad if you struggle to maintain stability in adverse weather conditions or handle problems when you brake quickly.

It can also result from bad wiring connections that run from the sensor to ECM.

How To Tell Which ABS Sensor Is Bad?

To tell which abs sensor is bad, use a car diagnostic scan tool or a voltmeter.

Here is how to tell which abs sensor is bad

Car Diagnostic Scan Tool

You can use a car diagnostic tool to test a vehicle’s wheel Abs sensor.

I highly recommend you check out Amazon for various car diagnostic scan tools.


  1. Connect the Car Diagnostic scan tool to your vehicle.
  2. On the main screen, press the Diagnostics and choose the model of your car. Now choose the system selection and allow the device to communicate with your car.
  3. Select your geographical area and now wait for the diagnostic system to start.
  4. Now you can press the control unit, choose ABS VSA and wait for the loading of system information.
  5. Next, press the read codes, and the diagnostic tool will show you the fault codes. For instance, code C0037:14 indicates a short to ground or an opening in the sensor signal return circuit.
  6. You can now fix or replace the faulty ABS sensor to rid all the dashboard’s fault codes and the warning lights.

Voltmeter or Multimeter

If you can’t access a scan tool, use a multimeter test to check for the voltage of the wheel’s abs sensor.

Some basic car repair skills are necessary for this process since you will have to remove the wheel to test the abs sensor.

I highly recommend a digital multimeter; it is an advanced tester and can test automotive electrical problems.


  1. Park your vehicle on level ground, turn off the engine, and hit the emergency brakes.
  2. Ensure the abs fuse filament is intact in your car’s main fuse block. If it’s blown, replace it.
  3. Loosen the lugs of your car’s wheels using a tire iron. Next, jack up the car and support it using a good quality pair of jack stands. You can now remove the lug nuts using a tire iron and put them aside.
  4. Check under the brake disc and wires of the wheel speed sensor; you will get the sensor fitted on the rotor. Use your fingers to pull apart the wire to disconnect it. You can now inspect the two-pin connector.
  5. Clamp the voltmeter probes to the connection on the ABS sensor. Now turn on the voltmeter and set it to altering current. To obtain an accurate reading, ensure the probes do not touch each other.
  6. When the voltmeter is turned on, it should read zero. Once the system reads zero, it is ready for the test.
  7. Spin the wheel hub slowly rotating with your hand to test the abs sensor. The spinning hub creates a charge that is measured by the voltmeter. If the sensor is functioning, it should read about 400 volts. The reading varies on the car and speed you will spin the hub.
  8. If you get the right reading on one sensor, move on and test the next.

Here are tips to help you get an accurate reading;

  • Check the abs reluctor, a gear with teeth located behind the wheel
  • Ensure the teeth are in the right position and are do not have any damage
  • Clear all metal shavings from the abs reluctor and repeat testing the abs sensor

Final Thoughts on How to Tell Which ABS Sensor Is Bad

Generally, driving a vehicle with a bad abs sensor is not safe.

At the same time, it can be challenging to tell which ABS sensor is bad since a vehicle has four sensors that help to tell if any of the wheels require more brake power.

The sensors are essentially the main components of your vehicle’s Anti-lock Brake System.

So, if your sensor has a problem, do not get worked up.

It is possible to tell which ABS sensor has a problem using a voltmeter or a diagnostic tool and replace it immediately.

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