Why is My ABS Light On? (5 Common Causes)

Last Updated on March 14, 2023

ABS is an abbreviation for the Anti-lock Braking System. The ABS is one of the systems in your car that is responsible for keeping you safe and in control of your vehicle in case of emergency due to heavy braking.

The first symptom of a problem with the ABS system is that the ABS light will come on in the instrument cluster in your dashboard. For more information about how an ABS system works and the common causes of an ABS light coming on, please continue reading.

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See Also: Why is My Traction Control Light On?

How an ABS System Works

The main role of the anti-lock braking system is to keep you safe from the any accidents and to make sure that you do not lose control of your car (like skidding) in case of any emergency braking.

The ABS is a safety system which has the ability to recognize a stop in the rotation of the wheels during braking while the car is still in motion, and release the brake fluid pressure which allows the wheels to start rotating again.

The system is capable of this because it is fully automated.  This operation may sound simple at first but its importance lies in the controlled stoppage or slowdown of the vehicle while greatly reducing the chances of losing control of the car.

This will allow the car wheels to avoid getting locked up and skidding uncontrollably. But a vehicle’s ABS is also prone to wear and tear and can fail. If you see the ABS light come on, the best course of action is to resolve the issue as soon as possible.

Common Causes When an ABS Light Comes On

#1 – Faulty Wheel Speed Sensor

bad wheel speed sensor

One of the various reasons for the ABS light to illuminate and stay on is a faulty wheel speed sensor. Wheel speed sensors are located inside the center of the wheel and in some cases, inside the transmission.

The Anti-lock Braking System depends on the data from the wheel speed sensor. The wheel speed sensors decide the rate at which the wheels of your vehicle are moving.

They transmit that data to the ABS which, upon receiving it from one or more wheels, determines that one or more wheels are moving slower as compared to the others and it releases the pressure of the brake fluid.

This allows the wheels to resume their movement. If there is problem with the wheel speed sensor, whether is covered is grime from regular driving or damaged in some way, the ABS will not get any data from it to control the movement of the wheels.

The wheel speed sensor is mounted really close to the braking system which makes it vulnerable to damage due to high heat caused by the brakes. This damage to wheel speed sensor could cause the ABS light to come on.

Related Trouble Codes: C0035, P0500

#2 – Unresponsive Hydraulic Pump or Valve

bad ABS pump

The ABS releases a hydraulic valve to increase the brake fluid pressure to hinder the wheels from losing friction with the ground when it receives the data from the wheel speed sensors.

This valve or pump is more susceptible to damage probably due to internal wear and tear. One of the causes of this internal wear could be the dirt brake fluid. This could make ABS light to come on.

#3 – Blown Fuse

blown fuse

Like most any system or electrical component, the anti-lock braking system will have its own fuse. Before attempting to replace expensive parts or spend time troubleshooting, make sure the fuse for the ABS is not blown or burnt. A quick check in the fuse box can save you a big headache.

#4 – Faulty ABS Module

bad ABS module

Another reason for the ABS light to come on is ABS module itself being faulty. This could happen due to the corrosion on the wires which could increase their resistance causing delays or no communication between the wheel speed sensor and the ABS.

Even a small amount of corrosion is enough to keep the system from working. The worst case scenario includes the replacement of the computer in the module.

#5 – Low Brake Fluid

brake fluid change

Like most of the braking system, the ABS too relies on hydraulic brake fluid in order to control the pressure. A low level of fluid in the reservoir could prevent ABS from doing its job which can make the ABS light stay on. Too much air in the system is another probable cause of it.

See Also: DOT 3 vs DOT 4 Brake Fluid

Mark Stevens
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16 thoughts on “Why is My ABS Light On? (5 Common Causes)”

  1. You forgot worn through wire. When the shop forgets to put the wire back into the holder ontop of the hub and just leaves it to rub ever so lightly on a rotating wheel part…it may take it more than a year to wear through the rubber and then the wire itself.

  2. the abs light on my 95 honda civic is coming on and off it is not staying on what are the possible outcomes if this is really an abs problem i have not had any braking problems and this has only been occurring for about a week

    • There should be a code stored for that ABS light that will help you narrow down the problem. You can scan it like a regular check engine light using an OBD2 scanner.

  3. That is very informative.

    I have a problem with ABS. As I plug it the ABS module, continuous vibration is coming through engine even though the engine is not on. What can be the cause?

    The mechanic is asking me to replace the airbag module before figuring out what’s the issue with ABS but how are they even connected?

    • I’m not sure I understand. Do you know approximately where the vibration is coming from?

      Did you ask the mechanic why he wants you to replace the airbag module first? Is the airbag light on?

  4. What is the most likely cause of an ABS light that is only on sometimes? The only other symptom is that sometimes while braking at low speeds the brakes pulsate. 2006 Chevy Uplander. Thanks!


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