ER16 - The Z axis is stuck or the limit switch is broken

This error refers to a problem with the Z limit switch, which is located underneath the Z stage. This switch sets the 'home' or '0' position of the build plate and ensures the build plate won’t move down any further when it is at the bottom of the printer.

The ER16 message indicates that the Z limit switch is not activated or released when expected. This can refer to a problem with the switch, an obstruction, or the movement of the build plate.

Check for obstructions

Objects under the build plate, such as printed parts or tools, can prevent the build plate from lowering completely. This means the Z limit switch will not be activated at the end of a print or during maintenance actions, such as build plate leveling.

Make sure the bottom of the printer is cleared of all objects. Never store items inside an Ultimaker printer. Additionally, check for small pieces of filament around the Z switch. A piece of filament stuck in the limit switch can keep the switch activated, leading to an ER16 message.

Limit switch diagnostic

The Ultimaker 3 diagnostics menu contains a limit switch test. In the Ultimaker 3 menu, go to System - Maintenance - Diagnostics and select the limit switch test.

The menu will show an overview of the X, Y, and Z limit switches and their activation state. If the switch is pressed, it will show an [X]. If the switch is not activated, it shows blank.


Manually lift up the Z stage. Check that the display indicates that the Z switch is not activated. Then manually press the Z limit switch in the back of the printer. Check that the display indicates that the switch is activated.

If the diagnostic test responds correctly to the state of the switch, the limit switch is connected correctly and it is not defective. If the test shows the switch as always or never activated, there is a problem with its connection, or the switch is defective.

Check the connection

If the diagnostic test indicates a potential connection problem you will need to access the electronics at the bottom of the printer.

UM3-Turn-printer.jpg UM3-Mainboard-cover.jpg UM3-Limit-switches-mainboard.jpg
1. Place printer on its side 2. Remove cover 3. Check connections

Gently place the printer on its side, then manually lift up the Z stage.


From the inside of the printer, remove the two bolts that secure the cover and place the cover aside.


The Z limit switch is the short black wire. Ensure it is connected to the connector marked 'Z-stop'.


Check the build plate movement

This error can also appear when the build plate is not moving when instructed. To test this, manually lift up the Z stage. In the Ultimaker 3 menu, go to System - Build plate. Try lowering the build plate via this menu. If it does not move or does not lower completely, the ER16 will reappear. In this case, there could be a problem with the Z motor or the mainboard. Please contact support or your local reseller for further assistance.

Note: If problems persist after taking the steps on this page, contact support or your local reseller. Ensure to include the error number and the log files of your printer.

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