Symptoms of a Bad ABS Sensor & the Replacement Cost

Driving a car is not all just about speeding, braking is an important aspect too. And when it comes to braking, your car’s ABS brakes are the hero.

The Anti-Lock Braking System is widely found in vehicles today and it helps you reduce your car’ speed without jamming the wheels. This results in fewer accidents and quicker stops.

However, ABS brakes work under a system, where ABS sensors send information to the car’s computer and the computer makes the decision to activate the ABS function.

These special sensors are located near the wheels and consist of two vital parts: the tone ring and the magnetic sensor. Both of these parts work together to ensure the ABS’s efficient functionality. However, these components are exposed to wear and tear and with time, their performance can deteriorate.

If any of these components fail to function, you can be in big trouble but fortunately for you, there are ways you can detect their failure. Every car is different so while some symptoms might show in your car where they won’t in other cars. Check out the ABS sensor failure symptoms below and expand your knowledge.

Signs of a Bad ABS Sensor

All the symptoms will do is help you diagnose an ABS sensor failure. At the end of the day, you would have to find a solution yourself or schedule a visit to the nearest workshop.

1. The ABS Light Illuminates

This is the most common symptom when it comes to ABS sensors. When there is even the slightest problem with the ABS sensor, your car’s onboard computer will catch the malfunction and switch on the ABS light.

This light is similar to the check engine light that comes on in your car’s dash when there is an engine related fault. Naturally, if this light flashes, you should think about visiting your mechanic as soon as possible or read the trouble codes at home. The longer you prolong the ABS sensor issue, the more you will be prone to accidents. You can find a suitable OBD2 scanner to read the codes here:
OBD2 Scanner

2. Vehicle Will Take More Time to Stop

The ABS system is placed to help stop your car quicker. It only comes into play when you press the brakes hard enough. Therefore, any fault in the ABS sensor will not activate the ABS system on time and you will find your car taking longer to stop than usual. You might also sense your car skidding and losing traction when you brake hard.

3. Pumping Brake Pedal on Braking

If an ABS sensor sends a faulty signal, you can experience pumping in the brake pedal when braking. This is caused by that the sensor makes the brake control unit think that the car is slipping, but in reality, it is not.

4. Vulnerability on Wet Roads

The ABS sensors transmits valuable information to the ABS system which allows it to maintain your car’s stability and traction on less grippy surfaces. Wet and icy roads are the biggest enemy of your brakes and your ABS system is probably the only shield against losing traction other than the use of winter tires.

Therefore, if you feel you are losing control when braking on wet roads, it shows your car’s ABS sensors are not in optimum condition. However, it could be the module that is not functioning properly. To find out, you will need to visit a mechanic and ask for a checkup.

What Is an ABS Sensor?

The core function of the ABS speed sensor is to monitor, record and transmit the information about the manner in which the tires rotate. If there is a slippage between the wheels of your vehicle, the ABS sensor would quickly alert the ABS system. The message is generated from the difference sensed by the ABS sensor and it is transmitted to the ABS control unit. As a result, the ABS would engage and override the manual braking of your vehicle.

Basically, the ABS speed sensor consists of a magnetic sensor which carries out the principal function. Upon the principle of induction, when the tone ring slots pass from within the magnetic lines of forces of the magnetic sensor present in the ABS sensor, a voltage will be induced. This voltage then generates a signal for the ABS control system. Although this is the most common principle, in some vehicles the design may use a different approach. Usually, such a sensor is mounted on everything that has a rotating body. It is essentially a safety anti-skid braking system.

Where Are the ABS Sensors Located?

Typically, in most modern vehicles the common design requires the ABS speed sensors to be mounted near the wheels. Technically, this is the most suitable place for mounting the ABS speed sensors on your vehicle. There may be an exception in certain vehicles, such as the trucks which have solid axles.

Replacing a Failed ABS Sensor

If the ABS sensor is not working properly in terms of monitoring the sync between the wheel and the brakes, it should be replaced by a new one. If you are willing to do the replacement by yourself, here is a brief step by step guide to how you can go about replacing the ABS sensor of your vehicle. The replacement instructions can differ a lot between different car models. This is a general guide.

• Make sure that you have all the materials with you that are required.
• Refer to the service manual of your vehicle to locate and identify the sensor.
• By diagnostic procedure, identify which sensors have failed and need replacement. This is usually done by testing each sensor individually.
• Remove any obstacles to gain access to the sensor.
• Remove all the electrical connection and the wirings from the sensor.
• Remove the sensor by unmounting it from the wheel.
• Make sure you keep a record of the wiring and the places from where you disconnected the wires.
• Thoroughly clean the tone ring and the sensor mounting hole to remove the dust accumulated on it or the brake lathe particles.
• Math the old sensor with the new one
• Install the new sensor from where you removed the old one by inserting it into the mounting hole.
• Be gentle in order to prevent it from breaking.
• Connect the connectors back on the right places and route the sensor wires along the correct path.
• Attach the connections of the sensor to the vehicle.
• Clear the error code from the scan tool of your vehicle.
• Take a test drive to make sure everything works accurately.

Diagnosis of a Bad ABS Sensor

The diagnosis is important for the ABS sensor as it will help us understand exactly where the problem lies. Here is a brief procedure that can help you diagnose a bad or a failing ABS sensor.

• Park your vehicle on a levelled ground.
• Keep the engine turned off.
• Acquire the tools required and the service manual of your vehicle.
• Locate the ABS sensor.
• Find all the connectors and electrical wires. Remove them one by one.
• Use the voltmeter and attach the probes gently to the sensor.
• After attaching the switch, set the voltmeter to AC voltage.
• Allow the voltage to fluctuate and then drop to zero.
• Once it is at zero, perform the test by rotating or spinning the hub or axle.
• Due to the rotation, a voltage should be produced and readings will show on the meter.
• If the readings do not appear and remain at zero, the ABS sensor has failed and should be replaced by another one.

Once you know of the problem, it is wise to start thinking about solving it. However, solving ABS related problems is not everyone’s cup of tea, therefore there is only so much you can do. Here is a list of things you can do to solve your ABS sensor failure.

Read the trouble codes

While an OBDII scanner is usually used to diagnose ECU related problems, there are some OBDII scanners available on the market that can also diagnose ABS sensor problems. Invest in such a scanner wisely, as they cost a lot of money but they are extremely useful. When you connect one to your car, it will show you a particular code on its screen telling you where the problem lies. At times, simply resetting the error code sent by the ABS system can solve the problem; however, if the problem still persists, you can visit your nearest mechanic for a quick solution. You can check out our article Best OBD2 scanners to find a suitable scanner for you.

Clean Your Wheel Arch

The ABS sensor/s is/are located near the wheel where the rest of the suspension is situated. Most of the time, a sensor can become unresponsive if dirt gets accumulated near it. You can use a blower to clean off the dirt from your suspension and wheels or you can go to a service station, pay a few bucks and get your car cleaned from underneath with a pressure pipe. If you are lucky, your car’s ABS light will go away.

However, if even after trying everything, you are still unlucky, it is time to visit a seasoned mechanic. Mechanics are car doctors and as such, they charge exorbitant rates for their service. But when you have no choice, you have to spend money.

ABS Sensor Replacement Cost

The cost of replacing the ABS sensor can be different depending on the vehicle you are using since the ABS sensors are replaced along with the complete control module. This again depends on the type of underlying problem and the design of the ABS system installed in your vehicle.

In the case where you can and need to replace only one ABS sensor, you may need to pay an amount ranging from $100 to $200 on average for most vehicles. This does not involve the labour cost. If you are not doing it by yourself and have a mechanic to do the job for you, it can cost you another $50 to $150 depending on the time it takes to replace it and the amount that the mechanic or car repair shop would charge you. If you need to replace an entire ABS control module, the cost for it can go higher, from $200 to as much as $600 in certain vehicles. For luxury vehicles, you should expect a relatively higher price for the devices and parts.

Magnus Sellén

Hello I'm Magnus, the owner and the writer of this website. I have been working with cars since I was 16 and I'm specialized with in-depth Automotive diagnostics. Also been driving drifting for the last 6 years. I'm here to give you answers to all your automotive questions and I hope that you enjoy our content.