HMS 0300-1600-0001-0001: extruder servo current sensor abnormal
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HMS 0300-1600-0001-0001 means the printer cannot trust its reading of how much current the extruder servo motor is drawing. Bambu points at the hardware sampling circuit, and that is usually right. But the extruder is also the one motor that regularly meets real resistance, so it is worth ruling out a genuinely dragging motor first.
Affected machines: A2L, P2S and X1. The extruder motor pushes filament against whatever is happening in the melt zone, so unlike the motion motors it works against a load that changes minute to minute. That is exactly why the printer measures its current.
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Telling a sensing fault from a dragging motor
A sensing fault appears at power-up and does not care what you are printing. A dragging motor appears under load: mid print, on a retraction, or when the filament path is tight. If you can reproduce the code by loading filament and cannot reproduce it cold, the mechanism is the story and not the board.
Check the path before the motor. A worn PTFE liner, a nozzle that is half blocked, or a spool binding on its holder all make the extruder pull more current than the firmware expects. Those cost nothing to find and are far more common than a failed circuit.
Printer reports an extruder current sensor fault, at power-up or during filament moves
Failed sampling circuit on the board, or an extruder dragging against a restricted filament path
- Power off, cool the hotend and unload the filament by hand.
- Turn the extruder gear by hand where the design allows. It should move smoothly with no notchy spots.
- Unplug the extruder motor and measure resistance across both coil pairs, then from each pin to the motor can.
- Check the filament path: the PTFE liner, the nozzle and the spool. Anything that adds drag adds current.
- If the motor and the path are healthy and the code still appears at power-up, the sampling circuit has failed and that is a service item.
- If the motor measures unevenly or turns roughly, fit the replacement and re-run an extrusion calibration.
If you do fit a motor, re-check extrusion afterwards. A new extruder motor sits at a slightly different tooth engagement, and the flow number that was right before will be a little out.
The resistance version of this fault is abnormal extruder motor resistance, which is a clearer motor failure. Our page on the hotend covers the melt path that loads this motor, and the troubleshooting index covers the rest.
HMS 0300-1600-0001-0001 FAQ
Is this the same as a clogged nozzle?
No, but a clog can trigger it. Clear the path first, then decide whether the sensing circuit is at fault.
Does the code appear only during printing?
A dragging motor shows up under load. A failed sampling circuit shows up at power-up, before anything moves.
Which extruder motor fits?
Match it to the model. The X1 and P1 share a part; the A2L and P2S use their own.
Do I need to recalibrate after fitting one?
Yes. Run an extrusion or flow calibration, because the gear engagement changes slightly.
LayerWalker
Print defect diagnosis, calibration procedures and parts that actually fit. Corrections welcome through the contact page.
