Bambu Lab HMS error code 0700-4000-0002-0002 is an AMS filament sensor checkpoint failure within the 0700-4000 detection subgroup. Suffix 0002-0002 specifically indicates that during an expected filament feed or retract operation, the filament did not reach or pass the sensor checkpoint within the expected time — the sensor was never triggered, meaning the filament movement did not happen as commanded.

What the Error Means

This error is a motion confirmation failure: the AMS commanded the filament to move to a specific position (advancing past a sensor), but the sensor did not register the filament arriving. This is the detection subsystem’s way of confirming what error 0002-0004 in the motor subgroup reports from the motor side. Root causes include the same feed path issues — filament tip too large to enter the PTFE tube, excessive tube friction, motor slippage — but now confirmed from the sensor side.

Step-by-Step Fix

1. Remove the filament and trim its leading tip squarely to remove any deformation from a previous incomplete load.
2. Manually thread the filament a short distance into the AMS slot to confirm the first section of the path is clear.
3. Run the manual load function from the printer menu and watch the AMS slot status icon for when it transitions to “loaded.” If the status never updates, the filament is not reaching the sensor.
4. Attempt a slow, manual feed and watch for the filament exit appearing at the AMS hub PTFE tube outlet. If it does not appear within a reasonable distance, the blockage is upstream of the sensor.
5. Inspect the PTFE tube at the AMS exit for any blockage from a previous filament stub.
6. Clean the sensor lens as described in the 0002-0001 guide.
7. If the filament consistently reaches the sensor position but the sensor does not trigger, the sensor has failed and requires replacement.

Parts Required

• Replacement AMS optical sensor
• PTFE tube if path friction test shows degradation

Contact Bambu Lab support if sensor replacement does not resolve the checkpoint failure.