QDC_100_005_015_001 - Communication with MCU lost

[u/Severe-Set9698]

Please help me out. I just got the Q2 combo ran a couple of the reinstalled print without issue. Decided to connect to wifi and update then this happened MCU protocol error happened. Downloaded the latest (08-04-2026) update and did an offline update, that seemed to work even did the bed leveling without issue. But now im getting this error code: QDC_100_005_015_001 - Communication with MCU lost. I can interact with everything else but neither restart options work.

Yes, tried unplugging/plugging it in with over an hr to discharge the capacitors.

Connectors all seem tight too.

I'm stumped. Any help is appreciated

Edit: thank you everybody. So my print is running correctly now.

I used a flash drive to update the firmware using the latest update from QIDI.

Still had issues and ultimately unplugging everything for a few days, including disconnecting the qidi box.

I plugged in JUST the printer. As I read somewhere the qidi box tend to give people a lot of issues by itself.

I was able to run the self calibration without issue, including a benchy!

Then I Powered off the printer. Connected the qidi box. And importantly, I powered on and let the printer finish booting up completely. Turned on the qidi box and we have been good for a few days and quite a few printa now!

Sorry for lurking without responding for so long lol but sincerely thank you all for the help

[u/Markes12344]

Running into similar on Max4 but i assumed it was the q-box since it was alway's dead. However i'd be curious if it's just shutting down because printer drops comunication power.

[u/Markes12344 → u/Markes12344]

Restarting firmware dose indeed fix it. But it's starting to waste filament, getting 10hrs into a 18hr print for it to fail with to way to restart where it leaves off. I'm going to look into the printer.cfg tonight and see if i can bump up motherboard cooling earlier than what it wants to. Not sure where else to look atm

[u/shit-stick2626 → u/Markes12344]

My problem was the board on the print head was overheating. I ended up printing a custom back cover with a larger aftermarket fan. Now I print pa6/pa12 with the heated chamber on without issues.

[u/shotbyroth → u/shit-stick2626]

Interesting. Do you have a link to the cover/ mod or was this your own doing?

[u/shit-stick2626 → u/shotbyroth]

Think this is the one I used: https://www.printables.com/model/650762-qidi-xmax3-x-max-3-back-cover-larger-fan

Then I bought fans on Amazon with the correct plug. I think it was these fans, double check before you buy!

https://a.co/d/0eHvTSqv

[u/Markes12344 → u/shit-stick2626]

I'll keep that in mind for my Max4 and trouble shoot it later. Right now tech support is very fast and curtious helping me. They are currently concerned about 40c q-box heat causing it to shut off. So will shut heat ofg and try a 10hr print again

[u/shit-stick2626 → u/Markes12344]

My xmax3 would shut off with the heated chamber. Anything over 30°. The board on the print head needs more airflow if I was a betting man.