HMS 0300-1800-0001-0001: extruder eddy current sensor frequency too low
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The eddy current sensor is not seeing metal where the nozzle should be. Before you order a sensor, confirm the nozzle is actually installed and fully seated — that is the cause far more often than a hardware fault.
Bambu describes this as the extruder eddy current sensor frequency being too low, with the nozzle possibly not installed or the heat sink sitting too far from the sensor. The sensor works by detecting metal at a fixed distance; low frequency means nothing conductive is close enough.
Affected machines: A1 mini, A2L, H2, H2S, P2S.
Where to buy
8Pcs 3D Printer Upgraded Hardened Steel MK8 Nozzles w/DIY Tool Storage Box
Three physical causes, in order of likelihood
Machine reports the nozzle is missing, or homing fails immediately
No conductive surface within the sensor's detection range
- The nozzle is not installed. Obvious, but this error most often follows a maintenance session that was interrupted.
- The nozzle is installed but not seated. Push it fully home before locking it; a partially inserted nozzle sits millimetres too low for the sensor.
- The heat sink has shifted. If the toolhead was dropped or reassembled, the sensor-to-heatsink gap may be outside range.
- Debris in the gap. Purged plastic building up between sensor and heat sink changes the reading.
If you are deliberately running without a hotend
There is a legitimate case for heating the assembly with no hotend fitted — a maintenance or diagnostic session. Bambu provides a maintenance mode in settings for exactly this. Use that rather than looking for a way to suppress the error, because the same sensor reading is what stops the machine heating an empty heater block.
Do not bypass or tape over this sensor to silence the error. It is one of the checks that prevents the printer heating a heater block with no thermal mass attached, which is a fire path, not an inconvenience.
When it really is the sensor
If the nozzle is present, seated, clean and the gap looks right, the remaining causes are a broken MC-to-toolhead communication link or a failed sensor. At that point the diagnostic stops being something you can do with a hex key and becomes a cable and board question for support.
LayerWalker
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