ABS sensor

Understanding ABS sensor

The anti-lock brake (ABS) system makes use of sensors to transmit information to the ABS module, which activates the ABS system during wheel lock, this sensor is known as the ABS sensor. These sensor mechanisms, which are typically made of two components, are mounted at the wheel.

ABS sensor

In order to convey information to the ABS control module, there will be a reluctor wheel or tone ring situated on the axle that spins with the wheel and either a magnetic or hall effect sensor. The reluctor wheel may deteriorate or get dusty over time to the point where it is unable to provide an accurate reading.

Well, in this article, We’ll be discussing the following;

  • What is an ABS sensor?
  • What is the function of an ABS sensor?
  • ABS sensor diagram
  • What are the working principles of an ABS sensor?
  • Where is the ABS sensor located?
  • What are the symptoms of a bad ABS sensor?
  • How do you test an ABS sensor?
  • How do you replace an ABS sensor?
  • ABS sensor replacement cost

Read more: Things you need to know about car sensors

Ok then, let’s dive in!


What is an ABS sensor?

An anti-lock brake sensor, typically known as an ABS sensor, measures the rotational speed of a wheel and sends the data to the engine control module of the vehicle (ECM). The wheel speed sensor and ABS brake sensor are other names for the ABS sensor.

The ABS sensors communicate the speeds of all four wheels to the ECM, which uses this information to evaluate whether the wheels are locking up since no wheel rotates at the same speed. Compared to traditional brakes, the ABS brake applies more quickly. As a result, in some cars, the ABS generates a grinding sound when activated.

The hydraulic valve automatically releases the pressure on the brake fluid when the speed sensor detects that a wheel has been locked, releasing the braking pressure. The pump activates to generate pressure when the wheel is rotating, and the braking system applies the brakes again.

What is the function of an ABS sensor?

The main function of the Anti-lock Braking System (ABS) speed sensors is to magnetically read each wheel’s rotational speed and relay the information to the vehicle’s electronic control unit. The ABS system intervenes when a wheel begins to lock up and/or skid, gradually releasing and reapplying the brake multiple times per second to help preserve optimal braking effectiveness and directional control.

If an ABS sensor malfunctions, the vehicle switches to normal braking with no possibility of ABS monitoring or pressure modulation when a wheel, or wheels, lock up while braking. In slick and/or gravel-like circumstances, a wheel will automatically lock up without ABS, and the car may lose stability and directional control.

Read more: Everything you need to know about a car ABS light  

ABS sensor diagram



What are the working principles of an ABS sensor

Most new cars have an anti-lock braking system (ABS). To determine how quickly the wheels rotate, ABS wheel sensors are fitted to the wheels or axle. Most ABS sensors have a magnet and toothed ring encased in a coil. The signal that is sent to the ABS controller is produced when the magnet and ring make contact and an electric field is produced.

The controller then determines how fast each wheel or axle should go. The Engine Control Module then receives this information (ECM). The ABS is turned on when the ECM detects that a wheel is locking up. It runs so quickly that it frequently produces a grinding noise and pulsating sensation.

The traction control system and the ABS sensor work together to control how the car moves in unstable conditions. The system will engage when one wheel moves more slowly than the others, which will happen when traction is lost.

In order to avoid trouble, the computer decreases the amount of brake force applied to the wheel. The wheel can restore grip and resume normal rotation when this force lessens. The stability control systems in contemporary cars are also controlled by these sensors.

Read more: Understanding the working of anti-lock braking system (ABS)

Where is the ABS sensor located

location Some ABS wheel speed sensors are mounted directly on the axle, while others are mounted at the wheel, behind the brake rotor. The number of ABS wheel speed sensors in each car varies. On a four-channel ABS system, the ABS sensor is normally found in each wheel hub or rotor. The sensor may be installed in the rear differential in some rear-wheel-drive applications.

What are the symptoms of a bad ABS sensor

Here are the most common signs and symptoms of a bad ABS sensor:

  • ABS Warning Lights appear on the dashboard
  • Anti-lock Brakes become inoperable
  • Loss of Traction or Stability Control
  • Pulsating Brake Pedal while braking

ABS Warning Lights appear on the dashboard

There are several significant lights on your dashboard that might warn you of impending danger. The ABS light is most likely one of the first signs of a bad ABS wheel speed sensor that you will notice when it fails. It might initially only result in the ABS warning light turning on. The traction and stability control warning lights, however, might also come on if the other systems stop working properly. In a few rare instances, bad ABS wheel speed sensors can make the speedometer stop reading.

Anti-lock Brakes become inoperable

The anti-lock brakes become inoperable when an ABS sensor fails. The system sends out a warning whenever a defect is discovered, and the ABS warning light turns on. The electrical control module of the vehicle ceases getting useful data from the sensor at this point. This data is used by the computer to assess whether the wheels are locking up and need help. The ABS shuts off until the repair is completed since the system doesn’t understand what’s going on.

Read more: Understanding automotive braking system

Loss of Traction or Stability Control

Other features, including stability control and traction control, may also be lost, in addition to anti-lock brakes. These systems are also turned off by the computer when the sensor stops transmitting data. However, even without the ABS light on, issues can arise. The ABS sensor may be to blame if you experience handling problems when you stop suddenly or struggle to retain traction in bad weather. Damaged electrical connections between the sensor and the ECM may also be to blame.

Pulsating Brake Pedal while braking

Each wheel’s speed is measured by the ABS sensors, and if one of the sensors malfunctions, it will report the incorrect wheel speed on one or more wheels. As a result, the ABS control module will be misled into believing the vehicle is sliding over a slick surface. You will be able to tell whether the ABS and traction control are engaged by the brake pedal’s pulsing or pumping sensation.

Read more: Everything you need to know about Electronic Stability Control (ESC) system

How do you test an ABS sensor?

Here’s how to test the ABS sensor in a simple process:

  • Lift The Vehicle With A Jack
  • Set The Multimeter To The 20k Ohms Range
  • Disconnect The ABS Cable and then Place Probes On the ABS Terminals
  • Evaluate Results

Lift The Vehicle With A Jack

You engage the emergency brake and park the car’s transmission for safety purposes to prevent it from moving while you are under it. Now, you also need to raise the car where the sensor is positioned in order to get access to it and conveniently conduct a diagnosis on it.

The sensor may be found under one of your wheel hubs depending on your automobile, but you may check your owner’s manual to find out exactly where it is. To prevent confusing the ABS sensor with other sensors, you need also to be aware of how the ABS sensor in your car looks. While performing these checks, slide a mat under your car to keep your clothes clean.

Set The Multimeter To The 20k Ohms Range

Set the meter to the Ohms value denoted by the omega (Ω) symbol. The measurement range is indicated by a set of numbers in the meter’s Ohms section (200, 2k, 20k, 200k, 2m, and 200m). To acquire the most accurate measurement, set the meter to the 20k ohm range because that is the typical resistance of an ABS sensor.

Disconnect The ABS Cable and then Place Probes On the ABS Terminals

To expose the terminals for the test, you now detach the anti-lock braking system from its sensor cable. Now, you delicately separate the wire harnesses from where they are connected and shift your focus to the wheel side harness. You can put your meter probes on any of the terminals for the sensor because polarity is irrelevant for measuring Ohms.

Evaluate Results

You now look at the meter’s reading. 800 to 2000 Ohms is the standard range for ABS sensors. However, you choose the appropriate specifications based on the sensor model for your car to assess whether or not you are receiving the correct value.

If the sensor is in good condition, the meter will display a steady value between 0.8 and 2.0 when set to the 20k Ohms range. The sensor has to be replaced if the value is outside of this range or fluctuates. If you also get an “O.L” or “1” reading, the sensor needs to be replaced because its wire harness has a short, break, or too much resistance.

Read more: Understanding crankshaft position sensor

How do you replace an ABS sensor?

With a few tools, you can easily replace the ABS wheel speed sensor on your own. This can be a task worth taking on in your garage if you have some basic mechanical expertise. You’ll need Jack and Jack stands, a ratchet and socket set, wheel chocks, a repair manual or access to a repair database, a torque wrench, and safety glasses to perform the task.

Well, here’s a process to guide you on how to replace the sensor:

Removing the ABS sensor

  • Put on the safety glasses.
  • Disconnect the negative battery cable.
  • Use a jack and jack stands to safely lift and support the car. Lock the rear wheels and engage the parking brake.
  • From the ABS sensor harness, disconnect the electrical connector.
  • Use a ratchet to remove the ABS sensor retaining bolt. You should also take out any bolts that are holding the wiring harness for the sensor in place.
  • Now remove the vehicle’s ABS sensor.

Fitting the replacement ABS sensor

  • To confirm that both have the same design, compare the new and old ABS sensors.
  • Fit the replacement ABS sensor in.
  • Reinstall the ABS sensor retaining bolt and any other fasteners that hold the wiring harness in place.
  • Tighten all fasteners in accordance with the manufacturer’s specifications using a torque wrench.
  • Reconnect the electrical connector for the ABS sensor.
  • Lower the car while keeping the jack stands in place.
  • Reconnect the negative battery cable.
  • Clear any associated diagnostic trouble codes using a scan tool or code reader (DTC).

Read more: How to reset airbag light in six simple steps

ABS sensor replacement cost

Depending on the vehicle you drive, replacing an ABS sensor can cost anywhere between $100 and $150, plus an additional $100 to $300 for labor. Luxury car ABS wheel speed sensors can frequently cost more, and some models can be more difficult to service, which increases labor costs.

Read more: Brake pad and rotor replacement cost


What happens if the ABS sensor is faulty?

The ABS Light turning on reduced stopping distances, and impaired stability in icy or rainy conditions are common symptoms.

What is an ABS sensor?

An ABS sensor is a wheel speed sensor that aids in determining when to activate the ABS system in your car. The ABS system is intended to activate during emergency braking maneuvers to assist in preventing wheel locking. As a result, you can keep control of your car and prevent collisions.

Can I drive with the ABS sensor light on?

As regular braking is unaffected by the ABS light, you can continue to drive the vehicle while it is illuminated. However, since your ABS system aids in stopping control and driving without it can be risky, we wouldn’t advise you to do this.

Can you drive with a broken ABS sensor?

It is not advised to drive the vehicle if both the ABS and brake warning lights are illuminated since both brake monitoring systems are having problems and require quick attention. At this stage, we advise against driving the car and instead suggest towing it to a mechanic.

How do I know if my ABS sensor has gone?

Measuring the resistance between the signal and ground leads on a passive ABS sensor typically produces a result between 800 and 2000 ohms. A reliable sensor is one that consistently reads within this range. The sensor is broken if the resistance on the meter is constantly varying or rising.

How do I know if my ABS sensor is working?

With a car jack, raise the vehicle, disconnect the sensor cable from the ABS, switch the multimeter to the 20k Ohms range, and attach the probes to the sensor terminals. If the ABS is in good shape, the proper reading should range between 800 and 2000 Ohms.

What causes an ABS sensor to come on?

This light normally illuminates for one of four reasons: either the ABS module is broken, the fluid reservoir is low on fluid, the wheel speed sensors are damaged, or the system is off. In fact, the traction control system in your car and the ABS have certain crucial parts in common.

Can ABS sensors be repaired?

If one ABS sensor needs to be fixed, it will likely be the ABS sensor wire. You must solder the damaged wire on the ABS sensor in order to complete the repair. The ABS sensor wire may occasionally, nonetheless, be beyond repair, in which case a complete replacement will be required.

That is all for this article, where we get to discuss the following

  • What is an ABS sensor?
  • What is the function of an ABS sensor?
  • ABS sensor diagram
  • What are the working principles of an ABS sensor?
  • Where is the ABS sensor located?
  • What are the symptoms of a bad ABS sensor?
  • How do you test an ABS sensor?
  • How do you replace an ABS sensor?
  • ABS sensor replacement cost?

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