HMS 0300-0200-0001-0007: hotend temperature sensor fault
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The nozzle temperature sensor is not returning a believable value. A standard 100k NTC thermistor reads close to 100k ohm at room temperature; open or near-zero readings both trigger this code. Check the connector before assuming the sensor died.
Every hotend runs closed loop: the heater pushes energy in, the thermistor reports the result, and the controller adjusts. If the sensor reading stops making sense the printer has no safe way to continue, so it halts immediately rather than heat blind.
Affected machines: A2L, H2, H2S, P2S, X1 series, X2D.
What the meter should show
A 100k NTC thermistor reads near 100,000 ohm at 25 degC and falls steeply as it warms. That steep curve is what makes the sensor useful, and it is also why a partially damaged sensor can read plausibly at room temperature and fail once hot. Measure cold, then watch the printer reported temperature during a slow warm-up if it will let you.
Code appears at power-on or as soon as heating begins, before the nozzle reaches temperature
Disconnected or damaged thermistor, or a broken lead at the toolhead
- Power off at the wall and let the hotend cool to room temperature.
- Unplug the thermistor and measure across its pins. A 100k NTC should be near 100k ohm when cold.
- Reseat the connector at both ends and check for a crimp that has backed out of the housing.
- Inspect the thin sensor leads where they leave the heater block. They are the most fragile wires on the machine and they break at the strain point.
Never fit a thermistor of a different type to get the printer running again. The controller converts resistance to temperature using a fixed curve, and the wrong sensor will read a wrong temperature confidently, which is how hotends overheat.
Why this is not a nozzle problem
A clogged or worn nozzle produces extrusion faults, not temperature faults. If the code points at the sensor, the extrusion path is a distraction. Fix the measurement first, then judge print quality afterwards.
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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