Symptoms of a Faulty Anti-lock Braking System Sensor – A vehicle is designed with an array of sensors at different points that provide crucial information to the control unit and other modules in the vehicle. These sensors help the ECU take actions that will make driving hassle-free.
One of these sensors is the anti-lock braking sensor, also referred to as the ABS wheel speed sensor. The ABS sensor is a vital part of the anti-lock braking system that detects the speed on each wheel and sends that information to the control module. The ABS sensor performs various important roles in the anti-lock braking system and the car as a whole, making it an essential component.
The ABS sensor (see Symptoms of a faulty ABS control module) is designed to last the lifespan of the car but just like other sensors, it might become faulty after some time. A faulty sensor will begin to show some signs and these signs must not be ignored, to avoid hazardous situations. This article will explore some basic facts about the ABS sensor.
What is the Anti-lock Braking System Sensor and what does it do?
The ABS sensor is a component of the anti-lock braking system that detects or monitors the speed of the wheels when they are rotating and transmits this information to the control module.
The ABS sensor ensures the wheels do not lock up, by sending appropriate data to the control module and prompts the control module to adjust the brake pressure on the wheels. It ensures braking is smooth to prevent skidding.
The ABS sensor is usually addressed as the wheel speed sensor because of its role in detecting wheel speed and rotation. Since all wheels might not rotate at the same pace sometimes, the sensors are mounted on all four wheels to monitor the speed on each wheel. These differences and fluctuations are sent to the control module which will direct the required brake pressure to each wheel to enhance their performance.
Information from the ABS sensor is also shared with other components like the chassis control system, transmission, and engine to ensure efficiency and optimal performance of a car.
How does the Anti-lock Braking System Sensor Work?
Most modern vehicles are equipped with four ABS sensors, each sensor mounted on the four wheels of the vehicle. The sensors make use of a toothed metal ring and a magnet that is attached to the car wheels. When the wheels rotate, the metal ring comes in contact with the magnet and generates signals that inform the control module of how fast the wheels are rotating.
The ABS sensor calculates the wheel speed and measures it in RPMs. The pulses created by the toothed metal ring and magnet are converted and sent to the control module which uses the data to monitor the wheel speed and effectively manages brake pressure.
Each time the ring and magnet spin past the sensor, the sensor picks some signal which is translated as wheel speed reading. This signal is captured by the ABS control module and is used to balance the brake pressure on the wheels.
Symptoms of a Faulty Anti-lock Braking System Sensor
The ABS sensor is a vital component of your car and when it fails the symptoms are quite noticeable.
A faulty ABS sensor will make the ABS dashboard light come on and a whole lot of other indicators.
Symptoms of a faulty anti-lock braking system sensor include but are not limited to:
Failure of traction and stability control system
The ABS sensor supports the traction and stability system and any problem with the ABS sensors will affect these components as well.
If any of the ABS sensors go bad, you will find it difficult to accelerate on slippery surfaces, icy or wet conditions or you will lose stability when trying to take a sudden brake.
A faulty ABS sensor will cause problems when braking. The sensors are supposed to activate when skidding is detected due to hard braking.
On a slippery surface, a functional ABS sensor is supposed to cause some form of vibration under your feet when you press on the brakes. However, if you do not feel this vibration and the car takes a while to slow down, it indicates there is a problem with the ABS sensors.
ABS light illuminates on the dashboard
A faulty ABS sensor will lead to the illumination of the ABS dashboard light.
The ABS light will alert you when there’s a problem with the ABS and might be one of the first indicators of a faulty ABS sensor.
The ABS works inconsistently
The anti-lock brake system might work sometimes and fail to work other times due to a faulty ABS sensor.
This can be very risky because you will not know when it will work and when it won’t and can fail when it is most needed. It is important to get this fixed after experiencing it a few times.
Failure of the anti-lock brake
The ABS control module stops receiving information from the sensor when the sensor is faulty. The information sent from the sensor is supposed to guide the control module on when to activate the anti-lock brakes.
If the sensor is faulty, the module will not detect a locking wheel. Failure to do this will cause the entire ABS to shut down.
An anti-lock brake sensor activates when braking
The ABS sensor is supposed to activate when your vehicle is skidding or sliding.
However, a faulty ABS sensor will activate the anti-lock anytime you press on the brake pedal. This happens because the ABS sensor is sending wrong signals and speed reading to the ABS control module which will then activate the anti-lock inaccurately.
Troubleshooting a faulty Anti-lock Braking System Sensor
Before thinking of replacing the ABS sensors, it is important to conduct a test on each sensor. Doing this is important because a car has more than one sensor and not all sensors might be faulty at the same time.
To determine which sensor is faulty, you will be required to use an OBD-II scanner to read error codes from the control module. Common OBD-II scanners that can be used to diagnose ABS-related problems include the launch Creader, Autel MaxiDAS DS708, and Airbag scan tool.
Road debris, dirt, or grease will affect the functioning of the ABS sensor. When troubleshooting, if you notice dirt or grease on these components, it is important to clean up the sensor first and observe if the ABS dashboard light still beams.
If the problem is not solved after cleaning, inspect the wiring harness that connects to the ABS sensor for corrosion or disconnection. If you notice any of these, have it fixed before going further.
If there is no problem with the wiring, then you will scan the ABS control unit with an OBD-II scanner to read fault codes and replace the component if required.
How to replace a faulty Anti-lock Braking System sensor
Rather than causing more damage to your car, if you feel you cannot carry out the replacement on your own, take your car to an auto repair shop.
Here are the steps to replace a faulty ABS sensor.
- Disconnect the negative terminal from the battery and fix your car on jack stands to make work easy.
- Locate the ABS sensor on each wheel, for cars that have 4 sensors, you must have scanned and read the codes from the control unit to know which sensor needs replacement.
- Disconnect electrical connectors, bolts, and other things that hold the sensor and wiring harness together.
- Take off the old and faulty sensor you wish to replace and install the new one. Tighten the bolts and ensure the sensor and harness are secured.
- Reconnect the connector to the new sensor and the negative terminal to the battery, then drive your car to test if the issue has been resolved.
Anti-lock Braking System Sensor Replacement Cost
Replacing the ABS sensor will cost between $200 to $400. The sensor will cost between $100 and $150 while labor costs $100 to $300.
However, these price disparities depend on the model and make of your vehicle.
Frequently Asked Questions
Where is the anti-lock braking system sensor located?
Some vehicles are designed with up to four ABS sensors while some others have three or two. For vehicles with four sensors, the ABS sensors are mounted on each wheel of the vehicle behind the brake rotor. In other vehicles with three sensors, some of the sensors are installed directly on the rear axle.
How many anti-lock braking system sensors are in a car?
The number of ABS sensors installed in a car varies based on the car’s make and model. Most cars have four sensors which implies that each wheel has a sensor installed in them. Some other cars have three sensors, with one each on the front wheels and one mounted on the rear axle to monitor both rear wheels.
Can the anti-lock braking system sensor be cleaned?
Yes! The anti-lock brake sensor can be cleaned. This can be done with warm water, soap, and a soft cloth or wire brush for stubborn dirt. After cleaning, it is important to dry it up properly to prevent corrosion.
What causes the anti-lock braking system sensor to fail?
There are different reasons for the ABS sensor failure. The most common is an internal defect in the sensor. Other causes of anti-lock brake sensor failure include loose or broken wiring, faulty ABS relay or fuse, low battery voltage, bad ABS motor, and ABS module.
Can I drive with a bad anti-lock braking system sensor?
Technically, you can drive a few miles with a bad ABS sensor, but this is not advisable. When the ABS sensor is faulty, the entire anti-lock brake system will be affected, and this is quite risky as the ABS may fail when needed and cause a very dangerous situation.
Can a faulty anti-lock braking system sensor cause transmission problem?
Yes! A faulty ABS sensor can cause transmission problems because the transmission system also uses signals from the sensor to determine the correct gear, based on the wheel speed and engine RPM. A faulty ABS sensor will cause the transmission to shift improperly or unable to increase gears.