Control+ connection bug when testing 42100 during building

UPDATE – The bug was fixed in version 1.0.3 of the Control+ app

When you are building the LEGO Technic 42100 Liebherr R 9800 set the app has a verification process built in after every batch of bags. This is a great addition because you can see whether the motors built in are working correctly or not.

Unfortunately there’s a bug in the current version as of 05/10/2019 (version 1.0.2 on both Android and iOS ), after the second batch of bags at page 367 you should only have one XL motor (color code red) connected to the hub in the superstructure.

When you try to run the test it won’t connect, here’s how it looks like:

The solution is to connect all 3 remaining L motors to the hub. After that the second test will run properly (it will only test one L motor connected to port 1).

After the test you can disconnect the 3 L motors.

At the third test you already should have all motors connected to the second hub based on the instructions so that will run properly, just like the fourth test.

If you have any questions or have a different experience please let me know in the comments.



  1. hi I cant get the first motor to connect to the app did you have an issue when first testing the 1st bag setup

  2. Hi,

    1/ It looks like it works well when use on iphone but not on Ipad ?

    2/ when I check the motors with my iphone the controller checks motor calibration but never stops. The motor is ran for hours.

  3. Hi my son finished the build without testing any motors, can I get around this ?

  4. I have version 1.1.0 and the bug would seem to be back! Lego have made a real mess of this control system. It has clearly been rushed out without soak testing.

  5. Unable to pair to liebherr r 9800 excavator. on multiple phones and an ipad. Interchanging solid blue light with white blinking lights over and over. the green sliding progress indicator continues to almost make it then starts over.

    • Did you check all motors and ports? Every motor should be connected to the proper port according to the instructions, otherwise the app won’t connect.

  6. unable to stop motor on occasion and have to remove batteries, turning off the app does nothing

  7. Use the BuWizz app. It works perfectly!!!

    • Unless you want to use the visual control of the arm, or enjoy the benefits of the calibration when the motor stops before the actuator starts to crack etc.

  8. Rich

    So I built the whole set before I I tested it and it won’t connect for the body. The base worked fun but the body is stuck between blue and blinking white. I’m sure I con text everything right

  9. Great article. Thanks

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