HMS 0300-0900-0002-0002: extrusion resistance too high
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The extruder motor is having to push harder than it should. Treat this as a blockage report, not a motor fault: work from the spool forwards, and check the nozzle last rather than first.
Modern Bambu machines measure how hard the extruder is working rather than waiting for a print to fail. When the force needed to push filament rises past the expected band, the printer raises this code. That is useful, because it usually fires before the print is ruined.
Affected machines: A2L, H2, H2S, P2S.
Work forwards from the spool, not backwards from the nozzle
Most people reach for the nozzle immediately and find nothing wrong with it. Resistance accumulates along the whole path. A spool that has crossed a strand over itself binds at the holder. A tight bend in the feed tube adds drag. Filament that has absorbed moisture swells slightly and grips. Only after those are ruled out is the melt zone the likely culprit, and by then you have spent five minutes instead of taking the hotend apart.
Code appears mid-print, often alongside a visible drop in extrusion just before it
Bound spool, restricted feed path, damp filament, or a partial blockage in the melt zone
- Unspool half a metre by hand and feel the drag. A spool that fights you is the whole problem.
- Follow the feed path and remove any tight bend or kink in the tube.
- Check whether the filament is damp. Wet filament swells and grips; drying it fixes a surprising share of these.
- Only now heat the hotend and push filament through by hand. If it needs real force, treat it as a partial clog and clear it.
Do not raise the extruder force or flow rate to push past this code. The measurement exists to stop the drive gear grinding a flat into your filament, which turns a clearable restriction into a jam you have to dismantle the toolhead to reach.
Abrasive filament makes this code recur
If the code keeps returning on carbon fibre or glass filled material, the cause may be a worn nozzle rather than a blockage. An abraded nozzle bore loses its clean profile, and the extra turbulence shows up as extra force at the extruder. Brass wears within a spool or two on filled filament.
Wrong code? The full Bambu HMS code index lists all 588 codes with the subsystem each one points to and which printers show it.
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