How to Test Parking Sensors with a Multimeter (Guide)

Parking sensors are position sensors that help the driver recognize nearby objects when parking a car. They are commonly installed on the bumpers of automobiles. As a definition, these devices are classified as park assist sensors.

Nevertheless, parking sensor issues might occasionally occur, challenging driving. It may be hard to diagnose these issues, one of the easiest ways to find out what’s wrong is by using a multimeter.

In general, to test parking sensors with a multimeter:

  • Set the multimeter into electrical resistance mode, then remove the sensor from the car.
  • Locate the three-contact parking sensor (plus, signal, minus).
  • The resistance of a functional sensor between “plus” and “minus” will exceed 0.5 megohms. On the other hand, there should be a 2 – 40 kOhm between the “minus” or “positive” and the signal contact.
  • If the value on either test dramatically changes, the parking sensor is damaged and must be replaced.

Park assist sensor testing may be complex. This learning material will guide you on how to use a multimeter to test parking sensors and what to look for when they are damaged.

How Does the Park Assist Sensor Work?

sound waves in car

With car dimensions expanding and parking spots reducing, these sensors are becoming increasingly common. There are two primary types of sensors, depending on their location:

  1. Front bumper sensors
  2. Rear bumper sensors

These sensors operate on either an ultrasonic or an electromagnetic principle. The rear parking sensors activate and send ultrasonic waves when the driver shifts into reverse. When these waves collide with a nearby object, they are reflected and recaptured by the sensors. The ECU determines the distance of the item from the vehicle based on the time elapsed between transmitting and recapturing waves. (1)

When the car gets close to an object, the parking system warns the driver with an audible tone or a visual indicator. As the vehicle approaches the object, the loudness of the alarm tone increases, urging the driver to stop suddenly.

Aside from these sensors, some car makers use reverse parking sensors cameras to offer a more precise picture of the environment behind the vehicle. Vehicle reverse parking sensors are often built to provide an update from a significant distance away from other objects. (2)

Testing Parking Sensors with a Multimeter in 6 Steps

faulty car parking assistance system

A car’s parking sensors are a vital safety feature. The most efficient approach to assess their accuracy is to use a multimeter.

To achieve this:

  1. In this test, you will configure your multimeter to electrical resistance measurement mode.
  2. Remove the parking sensor from your car. 
  3. Locate the three-contact parking sensor (plus, signal, minus). The two most frequent types of parking sensors are three-contact (pink wire) and four-contact (ground straight ahead in the front bumper).
  4. The resistance of a functional sensor between “plus” and “minus” should be greater than 0.5 megaohms (the higher – the better).
  5. There should be resistance on 2 – 40 kOhm between the “minus” and the signal contact (depending on the sensor).
  6. There will be a resistance of around 2 – 40 kOhm between the signal contact and the “positive.”

diagram for car parking

When using the abovementioned equipment to check for problems, there must be no break or short circuit at any of these connections. Otherwise, they will not perform as intended when placed on the car again and can even put one in danger if they malfunction while driving out of the garage.

Advantages of Park Assist Sensors

Parking sensors have the following advantages:

  • The reduction of blind areas surrounding the car makes the complex process of parking in tight places more accessible.
  • While parking a vehicle, this technique lowers driver fatigue.

A better understanding of the environment behind the vehicle decreases the possibility of harm to the car or any surrounding items.

Ultrasonic vs Ultramagnetic Parking Sensor

Ultrasonic Parking SensorUltramagnetic Parking Sensor
Ultrasonic sensors produce ultrasonic waves that bounce off any item in their path. 

Four or six sensors are commonly mounted on the bumper.

When the sensor detects a reflection, it transmits information to its central unit. It finds how far away the item is based on the time difference between the arrival of each wave back to the sensor.

It is common in most automobiles. 

These sensors do not require drilling.
Electromagnetic parking sensors are more current and dependable, but they are more expensive. 

Electromagnetic parking sensors are installed on the inside of a bumper.

They are not as widespread as ultrasonic parking sensors 

They’re so uncommon that most people will have no idea what it signifies to see one on an automobile.

Drilling is typically necessary for ultrasonic sensors. However, these sensors are rugged and engineered to survive harsh weather conditions.

Take a look at some of our related articles below.

(1) electromagnetic principle –
(2) environment –

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About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gCertifications: B.E.E.
Education: University Of Denver - Electric Engineering
Lives In: Denver Colorado

Electrical engineering is my passion, and I’ve been in the industry for over 20 years. This gives me a unique ability to give you expert home improvement and DIY recommendations. I’m not only an electrician, but I also like machinery and anything to do with carpentry. One of my career paths started as a general handyman, so I also have a lot of experience with home improvement I love to share.

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