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Parking sensors guide – history, working, types, problems, replacement

Driving in the current era, I am sure you would have heard about parking sensors; they alert you of obstacles while parking and assist in avoiding unintentional dings, scrapes, and accidents. Also known as proximity or reversing sensors, most modern vehicles have them fitted on the rear bumper. However, some also feature them on their front bumper and fenders.

Although most modern vehicles have some type of parking assist system pre-installed on them, many cars still do not have them. That said, you can always buy aftermarket systems and install them yourself.

Today, we will tell you how this technology came into existence. How do these sensors work? What issues can you face with these? Are they fixable once broken? Can you replace them yourself?

Read on to find answers to all these questions and more!

First let me through light on the history of parking sensors:

Rear parking sensors might seem like a recent invention but they have been around since the 1970s. Its inventor, Dr. Heyes, was an employee at the Blind Mobility Research Unit in the UK. He got the inspiration for this invention while developing a similar technology to help guide the visually impaired.

When Dr. Heyes first introduced the technology, people were hesitant to adopt it. Although a few car companies did use the technology into their vehicles, it wasn't until 2003 that the first mainstream car with this feature was launched. It was a Toyota Prius

What are the advantages and limitations of parking sensors?

Parking today is so much easier than it was 15 years ago, and reversing sensors have played a significant part in this. A parking assist system helps you see rear objects in your blind spots to avoid damage to your vehicle or property.

While these reversing sensors do make parking much easier than before, relying too heavily on them would be unwise. Sensors have their limitations and are prone to failure, especially when covered with snow or mud, etc. They may also fail to detect flat or thin objects. Some sensors use soundwaves to spot obstacles, therefore fail if the obstacle is soft or sound dampening.

How do parking sensors work?

The moment you put your car in reverse gear, the rear parking sensors start working. They initiate to transmit either an ultrasonic or an electromagnetic signal (depending on the system you have installed). These signals bounce off nearby objects and if the sensor recaptures the transmitted signal too quickly, you will receive a warning.

The sensors alert you in two ways: audio and visual warnings. The audio warnings are generally beeping sounds, which increase in frequency, as you get closer to an object. The visual warnings are either LCD or LED lights, which blink faster as your vehicle draws closer to obstacles, or they are on-screen warnings via the back-lit LED display. These sensors are usually installed on the back bumper but some cars have them on the front as well. Sometimes, they’re also on the flanks to detect obstacles all-around. The front sensors usually can detect obstacles up to 4 feet away while back sensors can pick up objects up-to 8 feet away.

Parking sensors. Parking assist system. Three  differing positions of vehicle and signals. Car reversing backwards towards cone


Types of sensors:

There are two main types of reversing sensors.

  • Ultrasonic parking sensors:

These make use of high-frequency soundwaves to calculate the distance between your car and the objects around it. The system records the time elapsed between emitted and reflected wave detection. The lesser this length of time is, the closer is the object. The sensors connect to an alarm system. Along with audio warnings, the advanced ultrasonic sensors also warn in a pictograph on the car’s infotainment screen.

  • Electromagnetic parking sensors:

These sensors make use of electromagnetic frequencies to discover obstacles in the path of your car. Since these sensors are capable of picking different wavelengths at a time, they do not have the same limitations as ultrasonic sensors have and can detect more types of obstacles.

Both types of sensors work when your car is either in reverse gear or you’re driving at low speed. They stop transmitting information once you start moving forward to pick up your speed.

Common problems with parking sensor and their solutions:

Due to the positioning of parking sensors, they’re very susceptible to damage. While some issues might be straightforward such as physical damage, others are more complex.

Damaged or dirty sensors:

Your sensor system may have come with some manufacturing faults or it might have developed these issues because of improper use or trauma. For example, the sensors might get debris buildup, which prevents them from functioning properly. A sensor may also lose specific parts, requiring you to get new parking sensors fitted in your vehicle.

Solution: Take out the sensors and clean them with a soft cloth to remove dirt or impurities from them. If the sensors are damaged, get a new parking sensor kit or replace the damaged parts.

Poorly installed sensors:

Occasionally, the issue with a sensor system is not a malfunction but rather a faulty installation. In these instances, you might notice that your car alarm goes off every time you put your car in reverse, even with no visible obstacles in sight.

Solution: The sensors on your vehicle need to be at least 18 to 24 inches above the ground or they will keep picking the ground as an obstacle and generate warnings. So, you need to either take your car to a specialist or remove and reinstall the sensors in a higher position yourself.

How to replace your parking sensors:

Not all issues with parking sensors have solutions and sometimes the only option is to replace them. Now we do recommend you get professional help if you're not well-versed with automobiles. However, if you're confident about your car repair skills, then the parking sensor replacement is pretty straightforward and you can do it yourself at home.

Here are six simple steps to get the job done:

1. Find the broken down sensor:

You're unlikely to face issues with all your sensors in one go. However, if you do, the problem might be electrical and not related to the sensors at all. Determining which sensor is malfunctioning is easy. Put your car in reverse, or press the brake (you might need a friend to help you with this part). Once you've done this, simply place your ear on the sensors to listen for a buzzing sound. If you do not feel like putting your ear near them, just place your hand on your bumper and feel for vibrations. Any sensor, which does not make a buzzing sound or vibrate, is the broken one.

2. Determine the make and model of the sensors used:

Rear parking sensors come in many different sizes and types. Therefore, make sure the parking sensor kit you buy is compatible with your car. It is wise to invest in original and high-quality sensors because they are more reliable than aftermarket products.

3. Locate the sensors:

Not all sensors will require you to dissect your vehicle. You can replace certain sensors by accessing the wires and sensors from underneath the bumper without having to remove the bumper itself. If this is the case, skip the next step and move to the one after.

4. Remove the bumper if necessary:

In case you cannot access the sensor directly, you'll need to remove the bumper. It should not be a problem since most modern vehicles come with easy to remove and reattach plastic bumpers. All you'll need is a screwdriver and plenty of patience!

5. Replace the sensor:

Reversing sensors connect to your vehicle's internal system via wiring. There will often be a plastic connector between the sensor wires and your car wires. You simply have to detach the connectors, remove the sensor, place the new sensor in place of the old, and the entire process will take just a few minutes!

6. Test everything:

Before you wrap up, make sure you test the new sensors to verify proper installation. Testing will also help you determine the functionality of the sensors.

In six simple steps, you have installed new sensors and you’re now ready to roll!


Parking a car especially in a tight or parallel space has always been a chore. With the advent of parking assist technology, this laborious task has become much less daunting and the chances of you damaging your vehicle have significantly dropped. However, parking sensors are only the first step toward easier parking and in recent years, we have witnessed a vast advancement in this field. But, that’s a story for a different time.