ER34 - Print head communication error

When this error appears, it means that the print head and electronics cannot communicate properly with each other. This is most likely due to a faulty connection between the print head and electronics.

The most common cause for the ER34 error message is a poorly connected print head cable. This may have occurred during transport of the printer, or rough handling of the print head.

Note: When removing the Bowden tubes from the print head, for example for print core cleaning, make sure not to accidentally pull at the print head cable.

Fortunately, this error can often easily be resolved by reseating the print head cable. This only takes a few minutes, and you just need the 2 mm hex screwdriver. Follow the steps below:

  1. Remove the print head screws
Use the 2 mm hex screwdriver to loosen and remove the two long screws at the back of the print head. Only the bottom part of the screw is threaded, so this won't take too long.
  1. Remove the cable cover
Hold the cable cover at the back of the print head and slide it straight upward to remove it.
  1. Disconnect the print head cable
If the print head cable is already loose, proceed to step 4. If not, it helps to fully disconnect the cable before reinserting it. Place the screwdriver behind the cable, against the inside of the back of the print head. Push to disengage the clip locking it in place.
  1. Check for damage
When the print head cable is out, inspect it for signs of damage. Ensure no wires are broken. If the clip is missing, the cable cannot be secured properly. In case of any damage, the print head cable must be replaced. Contact support for further assistance.
  1. Reinsert the print head cable

Place the print head cable into the print head. The clip must face toward the back of the printer. Align it with the connector on the PCB and push it down until you hear it click.

Tip: It can help to use the screwdriver to gently push it into the connector. Be careful not to damage any wires.

  1. Align the cable cover
Take the cable cover and align it with the print head. Slide it straight down to place it.
  1. Secure the print head screws
Insert the two long bolts into the back of the print head and secure them using the hex screwdriver. Be careful not to overtighten the bolts; this can reduce the lifespan of the bearings in the print head.
ER34-Remove-bolts.jpg ER34-Remove-cable-cover.jpg Print-head-cable.jpg
Remove the bolts at the back of the print head Slide the cable cover straight up to remove it Note the clip on the print head cable's connector


You can also check the video below. This shows how to reseat the print head cable on the Ultimaker 3. For S-line printers, the process is very similar.

Note: There are two main differences between the Ultimaker 3 and S-line printers that affect this process, these are listed below.

Cable cover
On older Ultimaker 3 models, the cable cover must be tilted to remove it (like in the video). On newer Ultimaker 3 print heads and S-line, you must slide the cable cover straight upwards to remove it.
Cable orientation
On the Ultimaker 3, as shown in the video, the clip on the print head cable's connector faces toward the front. On S-line printers, the clip on the print head cable must face toward the back.

Check the print core connections

If reseating the cable does not solve the issue, continue troubleshooting by swapping out the print cores. There could be a bad connection between the print cores and the print head PCB.

Note: Never touch the PCB at the back of the print cores with your hands / fingers.

You can clean the contact points using a cotton swab and (isopropyl) alcohol.


Print core

Remove the print cores from the print head. Gently wipe the contacts at the back of the print cores with the cotton swab to clean them.

Print head PCB

Also carefully wipe the pins on the PCB inside the print head. Make sure to brush with upward strokes to avoid damaging the pins.


Need further support?

If the ER34 errors persist after reseating the cable and cleaning the connections, there might be a hardware problem. It is likely that the print head cable must be replaced, or reseated at the mainboard. Contact support by submitting a ticket for further assistance.

For the most efficient help, please share the following information:

  • How often the error shows up
  • During which process(es) you see the error
  • The printer's log files
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