Troubleshooting Mercedes Parking Sensor Parktronic Problem

In this article, you will learn how to troubleshoot Mercedes Parktronic (not to be confused with Active Parking Assist).

Common problems and faults Mercedes owners often experience with the parking system. How to replace Mercedes bumper parking sensors yourself. Which by the way is very easy and you can save hundreds of dollars by doing yourself.

How does Mercedes-Benz Parktronic work

mb parking assist parktronic system

The first generation of Mercedes Parktronic system uses sensors on the bumper to detect objects nearby. It provides a visual and audible warning as the distance between the object and the car decreases. 

Parking assist only works if the vehicle is in drive or reverse and Emergency/Park brakes are released.

  • If the transmission is in Drive the front warning indicators are enabled. 
  • If the vehicle is in Reverse the rear warning indicators are enabled. 

The Parktronic system starts to beep as you get close to objects. The frequency of the beeps and tone start to increase as you get closer to objects in front or back of the car. 

Mercedes Parktronic system does not work at speeds over 15 mph. The system will automatically turns off and gets enabled again when you slow down. The system is deactivated if you set the shifter to Park. 

Common Symptoms

  • Parktronic beeping constantly
  • Red LED indicators on all the time
  • Mercedes parking sensors not working
  • Two yellow lines always on at low speed
  • Beep when you place car in Reverse 
  • Random beeping from Mercedes parking sensor 
  • Parking Assist Malfunction
  • Mercedes Parking Assist not working
  • Mercedes park assist inoperative
  • Mercedes parking sensor keep beeping

Mercedes Parktronic Problems

mercedes parktronic system

If there is a fault in the system you will need a Professional Diagnostic Scanner that can diagnose Mercedes systems.

mercedes parktronic fault

When you read the fault codes, you may get error codes such as:

  • B8/8 Inner rear right DTS ultrasonic sensor error
  • 9023 / B1023 / 36899 Parking System Fault 
  • B1248 B1252
  • 9005 A42B2 Left Center Sensor. Front Bumper. The sensor is not properly fastened, assembled or there is an obstacle near the sensor. 
  • 9042 At the control unit the supply voltage for warning elements is outside the permissible range. 
  • 900E A42B5 Right center sensor, front bumper. The sensor is not properly assembled or there is an obstacle.
  • 901A A43b9 Left inner sensor, rear bumper. 

Common Causes

  • Unplugged parking sensor
  • Parking sensor has poor contact or is loose
  • Sensor or cable is faulty or has high resistance
  • Sensor is missing or damaged
  • Wiring issue
  • Blown fuse
  • Bad ground connection
  • Damaged parking sensor due to water intrusion
  • Rain and dirt on the parking sensors

Troubleshooting Steps

mercedes parking assist problem

It is simple to spot when only one of the parking sensors on a Mercedes-Benz is defective. You will see one of the warning bars always lit up.

In which case you need to check the sensor that corresponds to the bar that always stays lit up. The bigger challenge is what to do when the Parktronic system doesn't work at all. Below you will find a few items that you need to check when Mercedes Parktronic doesn't work at all.

Check Parktronic fuse

mercedes parktronic problem fuse ok

Check the fuse for the Parktronic system. In most cases, the fuse for Parktronic will be in the fuse box found in the trunk. The fuse is labeled Parktronic and typically is a 10A fuse. If the Parktronic fuse is not in the rear fuse box, check fuses on the side of the dashboard, under the rear seat or in the engine bay.

Check Power Supply

Use a digital multimeter to check for power at the Parktronic fuse.

Check Bumper Sensors

mercedes parktronic bumper sensor

Remove the bumper and check the wiring on the back of the sensors. Make sure all the sensors are plugged in. None of the wires are damaged or cut due to an accident or previous repair work. Unplug the electrical connector and check the terminals/pins on the sensor for corrosion. If you are missing one of the sensors, replace it with a genuine Mercedes Parking Sensor

If you are expecting problems only when it rains, it is because water is getting into one or more of the parking sensors and causing that certain sensor to stop working.

Check Parktronic Switch

mercedes park sensor parktronic not working turn off

The parktronics switch can get sticky or stop operating. You may want to go further and remove the switch to check the operation with a multimeter.

Further Troubleshooting

If the range of your Mercedes-Benz parking system is poor, clean the sensor first.

If the sensor still doesn't pick up objects until you get very close, identify which sensor is not picking up the object. Front or rear? Left or right? You can't adjust the range of the parking sensor. If the sensor is faulty or not picking objects it will need to be replaced.

In the following video, you will learn how to use a Level 3 OBD2 Scanner to troubleshoot Mercedes-Benz Parktronic. Note that diagnostic can also be performed with Level 2 OBD2 Scanner that is designed for Mercedes-Benz cars such as iCarsoft MBII which is a cheaper alternative. 

Additional Resources

  1. How to replace parking sensor on Mercedes S-Class W220
  2. Pictures of various Mercedes sensors 


Pete, 2019-05-08

Great info. However I don't see any mention to the buzzer volume. I recently came across a car where the rear Parktronic had very low buzzing sound while the front system had a clearly audible sound. Can the sound o the buzzer adjusted?

Revvy, 2019-06-17

The local MBZ dealer quotes me $600 to replace on front sensor. Is this reasonable or robbery?

A robbery for sure, especially if you owned a simple Toyota or Honda before. However, spending $600 on something as simple as this is common for Mercedes owners.

It's best to try and learn to do these simple things ourselves to save thousands over the years

Peter , 2019-06-19

The bleep seems to start VERY late in the process. Can the range when the bleep starts be adjusted?????

I think a bad fuse is probably one of the most common causes of this issue. However, where can we find these? If we want to do this ourselves and not to go to an expensive dealership?

Rich, 2019-07-05

Is there a way for this stupid system to be auto-turned off. I hate having to press it each day, and multiple times a day, to turn it off if I take the key out of the car. If you live in any tight city, it is going off all the time and the beeping inside, is worse then the honking, outside. I can't seem to find a way to default it to 'off' though...

Vicki Bristow, 2019-07-16

Our parking sensors go off and flash red on the far right panel every time I press the footbrake. A continuous beep for about 8 seconds and then goes off. The same thing happens every time you press the brake.... Driving us nuts!!!

By YOUCANIC on Apr 25, 2019


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