HMS 1A00-1000-0002-0001: Toolhead or Hotend Rack Has Not Finished Homing
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HMS 1A00-1000-0002-0001 means a hotend swap was requested before either the toolhead XY axes or the hotend rack had finished homing, so the machine refused. It is a precondition message: nothing is broken yet, and something is preventing one of those two from completing.
The code names two candidates. Working out which one has not homed is most of the job.
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Watch a homing cycle
Trigger homing and watch. The XY axes and the rack home separately, and seeing which one stops short tells you where to look. A cycle that completes cleanly and still produces this message points at a stale state rather than at mechanics, and a full power cycle clears that.
If the rack is the one
Rack homing has its own failure code with its own guidance: HMS 1A00-1100-0002-0002, where obstruction and belt tension account for nearly everything. Clear the travel path with the power off before anything else.
If the XY axes are the one
Look for an obstruction on the plate, a cable caught on the gantry, or filament debris at a limit position. Endstops are simple switches, and a switch that is not being reached reads exactly like a switch that has failed — the general approach to printer sensing is in bed levelling sensors.
Why HMS 1A00-1000-0002-0001 blocks the swap specifically
A tool change needs both halves to agree on where they are, to within the tolerance of a mechanical mount. Without homing there is no shared reference, so the machine declines rather than approximating. That is the same instinct that produces the calibration refusals in this group.
Before you retry
Power cycle fully, let the machine home both axes and the rack, and only then start the plate. Starting a job and hoping homing catches up is how an unhomed rack meets a mounted hotend. The platform is described in the Bambu Lab H2D.
HMS 1A00-1000-0002-0001 FAQ
Can I force the swap?
No, and you should not want to. The refusal is protecting the mount.
Does a restart fix it?
Often, when the cause was a stale state after an interrupted job. It costs nothing to try first.
Which homes first?
Watch a cycle on your own machine rather than assuming. The order matters less than which one stalls.
Is this the same as a calibration failure?
No. Homing finds zero; calibration finds the slots — see HMS 1A00-1200-0002-0001.
Homing is not the only motion that gets blocked. HMS 1A00-0100-0002-0035 means the rack met resistance mid-fetch, and purge debris in the travel path explains nearly all of them.
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