HMS 1A00-2000-0002-0001: Power Outage Occurred During Hotend Replacement
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HMS 1A00-2000-0002-0001 means power was lost in the middle of a hotend swap, and Bambu asks you to restore the setup by following its guide, warning that printing may otherwise fail. The machine is telling you it does not know where the hotend ended up, and it will not guess.
Of all the faults in this group this is the one where doing nothing and pressing on is genuinely risky.
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Why this state is special
A swap is a sequence: release, move, place, confirm. Power lost partway leaves the hardware in a position that matches none of those steps, and the record of which slot holds what is now unreliable. Everything downstream — placement, calibration, the next swap — is built on that record.
Restore it deliberately, not by printing
Follow the recovery procedure rather than starting a job and hoping the machine sorts itself out. The reason the warning is there is that a wrong record turns the next swap into a collision, and a collision costs a mount rather than a plate.
Check the hotend before putting it back
A hotend that was mid-move when power dropped may have landed somewhere. Look at the mounting faces and the top for damage and residue before reseating, because a burred face is what causes the drop fault HMS 1A00-0100-0002-0025 on the next attempt.
What HMS 1A00-2000-0002-0001 tends to cause next
The most common follow-on is the machine finding a hotend where it expected a free bay, which is HMS 1A00-0100-0002-0004. Seeing that code straight after a power cut is a sign the recovery was skipped rather than a new fault.
Preventing the state entirely
A printer that swaps tools has a short window in every job where an interruption is expensive, and that is a reasonable argument for putting it behind a UPS. Even a small one carries the machine through the brownouts that cause most of these. How this generation compares with the single-hotend machines is in the X1C against the H2D, and hotend construction is in 3D printing hotends.
HMS 1A00-2000-0002-0001 FAQ
Can I just restart and print?
Not safely. Restore the setup first; the warning in the message is about the next swap, not this one.
Was the print lost?
The plate almost certainly is. The recovery here is about the machine, not the job.
Would a UPS have saved it?
For a brief cut, yes. That is the main argument for one on a tool changer.
Does it damage anything by itself?
The outage usually does not. Printing afterwards without restoring is what does.
Not every rack fault is an interruption. HMS 1A00-E000-0001-0006 means homing ran too far, and Bambu names a loose timing belt as the likely cause.
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