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                  1. Support
                  2. Printer troubleshooting
                  3. Factory Reset (MMU)
                   

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                  Factory Reset (MMU)

                  Relevant for

                  MMU2S
                  MMU3
                  10 comments
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                  This procedure is the same for the MMU3 and MMU2S units running firmware 3.0.0 or newer. In case you are running MMU2S with older FW, please go to Factory reset (MMU2S pre firmware 1.0.6).

                  When upgrading the MMU2S firmware from firmware 1.0.6 (or lower) to 3.0.0 (or higher), or when you find a severe issue with the MMU, you might need to perform a factory reset.

                  1. On the MMU unit, hold the left side button and reset the unit by pushing the button on the right side of the MMU with an Allen key.
                  1. Keep the left side button pressed for a few seconds. You will see the LEDs on the MMU flashing quickly in a "snake" motion.
                  2. Release the MMU left-side button. As soon as you release it, the MMU EEPROM will be cleared and overwritten with factory default values and will do the selftest.

                  You have successfully reset the MMU. No indication will be shown on the MMU or on the printer.

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                  Topics

                  • Troubleshooting
                    • Printer troubleshooting
                      • Factory reset (MMU2S pre firmware 1.0.6)
                      • MMU2S idler unable to move freely
                      • MMU2S Selector not moving
                      • MMU2S LEDs meaning
                      • Firmware updating issues (MK2.5S/MK3S+/MMU2S/MMU3)
                      • IR filament sensor calibration (MMU3, MMU2S)
                      • FINDA setup and troubleshooting
                      • Filament jam (MMU2S)
                      • Logging data over serial line (MMU2S)
                      • FINDA: Filament Stuck #04102 (MMU)
                      • MMU Overcurrent #31310 (CORE One) #35310 (CORE One L) #26310 (MK4S) #13310 (MK4) #27310 (MK3.9S) #21310 (MK3.9) #28310 (MK3.5S) #23310 (MK3.5)
                      • Tangled filament
                      • Status LED explained (MMU3)
                      • Factory Reset (MMU)
                      • TMC driver shorted #04304 (MMU)
                      • TMC driver shorted #04314 (MMU)
                      • TMC driver shorted #04324 (MMU)
                      • Blue Screen of Death (BSOD) #31538 (CORE One) #35538 (CORE One L) #36538 (CORE One INDX) #26538 (MK4S) #13538 (MK4) #27538 (MK3.9S) #17538 (XL) #21538 (MK3.9) #28538 (MK3.5S) #23538 (MK3.5) #12538 (MINI)
                      • Service menu - Factory Reset
                      • Service menu - Individual Filament Calibration
                      • SD cards and USB drives
                    • Diagnostics
                    • Print Quality Troubleshooting
                    • QR Error codes
                    • Print Error Messages

                  5 comments

                  Log in  to post a comment
                  egadgetguy
                  •
                  Can confirm Mk4S with MMU3 fw 6.5.3? this doesn't work!!! now I can't print anything :( :( :(
                  I tried all the troubleshooting steps I know and the ones found on this and other forums. Still won't detect my MMU
                  Reply
                  Hansompants
                  •
                  I've been having the exact same problem since I upgraded my MK4 to 6.5.3 a few weeks ago. I can't get it to detect the MMU3 no matter what I do.
                  Reply
                  Jan Kratochvíl
                  •
                  Hello. Is the MMU updated to the firmware 3.0.4?
                  Reply
                  Hansompants
                  •
                  Hi Jan. No, the MMU firmware is an older version. The issue is that I can't update it to the newer firmware because PrusaSlicer won't detect the MMU when I connect it to my computer via a USB connection.
                  Edit: For context, I am using PrusaSlicer 2.9.5 and my MK4 is on version 6.5.3. I have used multiple cords between MMU3 and my computer, and I have tried restarting / resetting the MMU3 while attempting to flash.
                  Reply
                  Jan Kratochvíl
                  •
                  Hmmmm...try connect the MMU to the computer and make sure, it is also connected to the printer and turn the printer on. If that doesn't help, try contact our support team via livechat for more direct communication.
                  Reply
                  Sgudcreator
                  •
                  As it turns out, I had bent the micro-USB on the buddy board, I managed to hold it in place one last time and flashed the firmware.
                  Reply
                  njmck01
                  •
                  This was actually my issue too! gently pulled the cable forward and it connected and flashed. Thank you!
                  Reply
                  Tango
                  •
                  This doesn't work on my MMU3 on an MK3.5 (upgrade from 3S+). I try it and hold the Allen key in and get an error that the MMU is not communicating and I have to either restart or disable the MMU. Do I press and release the button on the right? I'm not even getting the snake movement of the LEDs.
                  Reply
                  Swing King Design
                  •
                  It doesn't work, it wouldn't run at zero point. Even if I turned on the power to the machine it wouldn't run at zero point. Resetting the mmu3 doesn't factory reset it.
                  You have to start over Prusa
                  Reply
                  Nicolas Duarte
                  •
                  This did not work as described.  I had a BSOD and had to hold the button combination on the MMU while powering up (press and hold before the startup progress bar went past the 50% point).  After that I was able to pass the BSOD.  I did the button combination again and was able to re-flash the firmware, however the main MMU LEDs did not flash in a "snake" motion.  There was flashing inside the box but it was not visible as a snake motion and only seemed to restart the MMU (it performed the same motions as it does on proper startup).
                  Reply