How to Fix HMS 0700-4000-0002-0004: AMS Filament Runout or Missing

Bambu Lab HMS error code 0700-4000-0002-0004 is an AMS filament presence failure within the 0700-4000 detection subgroup. Suffix 0002-0004 specifically signals that a slot that was expected to have filament loaded is now reporting empty — either because the spool has genuinely run out, or because the filament detection sensor has lost contact with the filament.

What the Error Means

This error is the AMS-specific equivalent of a traditional filament runout event. The detection sensor registered the absence of filament at a position where filament is required. If the spool is not empty, the filament may have broken inside the AMS slot, retracted too far to be in contact with the sensor, or the spool edge ended and no more filament can unwind. In multi-color printing, this triggers an automatic filament change if a backup slot is configured, or pauses the print for manual intervention.

Step-by-Step Fix

  1. Open the AMS cover and check the spool in the reported slot. If the spool core is visible with no remaining filament, the spool has run out — replace it with a new spool.
  2. If the spool is not empty, examine the filament path from the spool to the AMS sensor. Look for a break in the filament strand.
  3. If the filament snapped, trim the exposed end on the spool cleanly and reload using the manual load function.
  4. Check whether the filament retracted too far during a previous color change and is now positioned behind the sensor. Advance the filament manually until the sensor registers it.
  5. Confirm the spool is not locked or too tightly wound — a spool that cannot rotate freely can cause the filament to snap under feed tension.
  6. For transparent or natural filaments, clean the sensor lens since these colors can be difficult for optical sensors to detect reliably.
  7. Resume the print once the slot is confirmed loaded.

Parts Required

  • Replacement filament spool if the previous spool is empty

No other replacement parts are typically required. Contact Bambu Lab support if a properly loaded spool consistently shows as empty after sensor cleaning.