I have the same issue. I’m printing with ASA through the 0.8mm nozzle. I got about an hour or more into a print and it threw up this error. I can resume the print but after a couple of minutes it does it again. I checked connections again because I had swapped out the 0.4mm to the 0.8mm nozzle and they all seemed pretty secure. I speculated that the chamber temperature might be high enough that it’s inhibiting the hotend cooling but I might be way side of the mark with that.
After canceling the print, checking connections etc and starting all over again it seemed to fail at exactly the same point on the print again. After resuming the print I monitored it and I noticed what looked like a very gradual temperature drift on the hotend. Nozzle temperature gradually dropped from 270C to 256C over about 2-3 minutes and it coded out again.
That seems more like a degraded hotend thermistor or a bad connection that degrades with heat. With ASA - particularly large ASA prints like the one I’m trying to do, the chamber temperature should be quite warm to prevent warping. Regardless, I opened the door on the printer and resumed the print to see if that made any difference. That dropped to 252C and threw up the same error code.
I can’t tell if the thermistor is faulty or if the heater cartridge is actually loosing temperature. Would certainly be interested to find out what BambuLabs have to say about it.
UPDATE:
I did a little digging around and I found this thread:
Different printer but the same symptoms. “Eldrick” suggests the part fan might be causing the issue in that instance so I decided to resume my print and adjust the part fan speed on the fly to see if I could stabilise the hotend temperature. Having reduced the speed from 80% to 30% my hotend temperature has stabilised at 270C +/- 1C and it’s been printing again so far without issue.
Now I’m wondering if there’s a software / firmware issue at the root of this. If for some reason the hotend can’t maintain temperature, the part cooling fan should back off - or at least have an option to automatically back off or speed up as it might do in the event of a thermal runaway right?
I’d also be curious to find out why it seems to take over an hour for this issue to present itself.
I don’t think backing off the part cooling fan should be considered a permanent solution but for now I’m hoping it will allow me to complete this print. I hope this suggestion helps you guys out for now but please update me here when BambuLabs respond.