How To Tell Which ABS Sensor Is Bad

180 Automotive is reader-supported. This post contains affiliate links. As an Amazon Associate I earn from qualifying purchases.

The antilock braking system sensor, or simply ABS sensor, has a significant role it plays in your car engine. There are two ABS sensors in your car: passive and active ABS sensors.

Your overall safety on the road also depends on the proper functioning of this important component. It is a part of the ABS that receives and sends a signal to help prevent the brakes from locking.

Besides, the ABS sensor monitors the amount of power in your car braking system. This way, it can keep in check the brake power.

Essentially, the sensor measures the amount of speed in the car wheel. But it does more than that and I will shed more light on that shortly. But suffice it to say that when an ABS wheel speed sensor goes bad, it portends great danger for your safety.

My focus in this article is to look at the symptoms of a faulty ABS speed sensor. I’ll talk about its functions, working principles, as well as the consequences of its malfunctioning.

How To Know Which ABS Sensor Is Bad

To tell which of your car’s ABS wheel speed sensors is bad, you’ll need to be on the lookout for the ABS warning light that comes up on your car dash.

That’s not all the symptoms. Don’t forget to also see if there is utter damage to the anti-lock braking system.

Another sign to tell if your ABS wheel speed sensor is failing is the energetic feel and response of the brake pedal each time you hit your foot on it.

Last but not least, you’ve got to pay attention to the loss of control and traction. Apart from these symptoms, there are other details you’ll also need to be on the lookout for. Nothing should be too much to give to your safety and the overall health of your car, isn’t it?

Loss Of Traction And Stability

The first important sign that your ABS sensor is failing is loss of stability control and traction control. Here’s how the thing works.

The electronic stability control system and electronic traction control system are two important systems in the ECM.

The ABS sensor interacts with these systems to ensure vehicle safety, especially at high speeds. Besides, they ensure hill-start assist and roll stability.

However, when your car’s ABS sensor stops functioning, the ECM won’t receive any information about the wheel. The consequence is that the two systems will shut down.

Once the ABS sensor gets bad, you’ll struggle with control and stability in poor weather conditions. Handling will also be an issue.

Anti-Lock Braking System Failure

No doubt, there’s a direct digital interaction between the ABS and its sensor. The failure of the latter naturally leads the former to stop functioning until it is repaired or replaced.

You won’t be able to operate the ABS as soon as the ABS sensor fails to send a signal to the computer. Once there’s an issue with the ABS sensor, you’ll get an indication on your dash through the ABS warning light that comes on.

The ECM fails to receive any signal from the sensor. If that happens, the computer won’t get any hint as to which wheel needs support. Essentially, you will notice the erratic work of the ABS.

ABS Warning Light Comes On

One of the earliest signs of a faulty ABS wheel speed sensor is that the ABS warning light will illuminate. You’ll receive the indication that something is wrong with your braking system.

The sensor is the first culprit when this light comes on. The speedometer may also either indicate a wrong recording or stay on at 0 mph.

Longer Braking Distance

The failure of the ABS wheel speed sensor causes your vehicle to take more time to come to a safe, quick stop.

The entire braking system, including the sensor, is programmed to slow down your vehicle or bring it to a quick stop.

However, when the sensor is bad, your vehicle will require longer distances to stop.

Pumping Brake Pedal

When you hit your foot on the brake pedal, you may feel some pulsating response. In other words, the brake pedal will give some pumping feedback when you brake.

The reason is that the ABS control module is not receiving any data about the speed on the car wheel. As a result, it tricks the car into thinking that it’s operating on slippery terrain.

The failure of any of the ABS sensors is the cause. So, you may experience that the vehicle becomes unstable under normal driving conditions. In this instance, you’ll notice the increased pedal effort.

Remember, your brake pedal needs a minimal hit to slow down or stop your vehicle.

Now, I want to go back to explain the different functions of the ABS speed wheel sensor and what its functions are.

What Is ABS And How Does It Work?

An absolutely great question to start with! The ABS sensor of your car is essentially a linking measuring component between your car wheel and the Engine Control Module (ECM).

It primarily functions to calculate the amount of rotational speed present in your car wheel and thereafter sends information to the ECM.

Otherwise called brake sensor, the device communicates with the ECM to determine which wheel is locking up. Since your car wheels rotate at different speeds, the sensor alerts the ECM about each wheel.

Depending on the configurations of your car, the location of the ABS sensor differs from car to car. Newer models have their ABS sensor located in the wheel hub assembly.

However, older configurations had the ABS sensor mounted in differential housing, steering knuckles, or any part outside the wheel hub.

Whether new or old models, vehicles can have between 0ne and four ABS sensors.

The mode of operation of this component is simple. The ABS sensor generates a signal when there is a contract between the magnet and the toothed ring enclosed in a coil in the ABS.

The digital signal gets to the ABS monitor which in turn determines how much speed is in a wheel. The ABS generally controls the braking power of your car wheel.

So, as the sensor transmits the digital signals about a certain wheel to the ECM, the ECM will reduce the braking force on the wheel.

How To Test ABS Sensor

Testing the ABS sensor is a way to find out what is actually wrong. This way, you can avoid presumption and applying the wrong treatment.

To start with, the damage to your ABS sensor can be physical in which you will only need a visual inspection.

The damage may also be a buildup of dirt, debris, or carbon deposit around the sensor. The riskiest and most dangerous damage that can happen to your ABS is an internal failure.

In the case of physical damage, you should first check from under the car hood the ABS sensor wiring and electrical connections. It’s possible there are broken, corroded, or frayed wires. A simple check from beneath the car is what you need.

In the case of ferrous deposit buildup around the ABS sensor, you’ll need to clean, sometimes with chemicals. Here, you’ll need to remove the sensor from its location. If cleaning doesn’t work, we can take the next and best step which is using a scan tool.

Testing ABS With Multimeter

Assuming, the damage on your ABS sensor is internal, here’s how to test it using a multimeter. A scan tool is another option. Let me guide you through how you can carry out the test, whether it’s.

Preliminary steps

  1. Jack up the car and remove a wheel (some vehicles will let you access the sensor harness without jacking).
  2. Disconnect the ABS wheel speed sensor.
  3. Inspect the inner strut towers if you’re testing the front ABS sensor.
  4. If you’re testing for the rear ABS sensor, check inside the truck or beneath the rear seat cushion.

Test On Passive And Active ABS Sensor

Under normal conditions, the passive or 2-wire ABS sensor gives off reading in the range of 800-2000ohms. For the active ABS sensor, the reading should be between 1,000 and 2,500 ohms.  

These are the readings for the ground leads and resistances across the signals. Any readings below or above these ranges mean your ABS sensors are bad and will need to be repaired or replaced.

If the readings fluctuate, you’ll also need to repair the sensors also. The other indication the multimeter will produce is a no-resistance reading.

In this instance, the diagnosis tool will show an open or short circuit. The reasons may be moisture intrusion, an internal short, or a cracked shell.

The good news is that carrying out the ABS sensor test is pretty simple. You can save a lot of money on labor and parts if you do a proper inspection. A DIYer procedure should be a starting point before approaching a dealer or mechanic.

Is Flashing ABS Light A Bad Sign?

No, an ABS light coming on and off intermittently doesn’t indicate a bad. Most vehicles are programmed to routinely indicate the ABS light as soon as you start the car.

The indication is by design a way shows that the ABS is active. But you need to constantly carry out a visual or physical inspection.

Final Thoughts

Now, we’ve both walked this short journey together and I hope you find it amazing. So, from now on, you should be able to easily tell which ABS sensor is bad in your car.

It doesn’t matter whether it is the 2-wire (passive) or 2 or 3-wire (active) ABS sensor that’s faulty. The symptoms remain the same. The procedure for testing doesn’t equal change.