HMS 0300-0200-0001-0001: hotend heater short circuit
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The printer measured the hotend heater as a short circuit. A healthy 24 V cartridge reads roughly 10 to 15 ohm; a short reads near zero. Stop, unplug at the wall, and inspect the lead where it flexes before powering on again.
A heater cartridge is a resistive element, and the printer knows what current to expect from it. Ohm law sets the target: a 24 V, 40 W cartridge is about 14 ohm, a 60 W cartridge about 10 ohm. If the measured draw implies far less resistance than that, the controller reads a short and cuts the circuit.
Affected machines: A2L, H2, H2C, H2S, P2S, X1 series.
Where a heater short actually happens
Almost never inside the cartridge body. The failure point is the pair of leads between the cartridge and the toolhead board, at the spot where they flex on every travel move. Insulation there is thin, it rubs against a screw head or a cable tie, and the two conductors eventually touch. A second common cause is a solder blob or a strand of stray wire bridging the connector pins after someone has swapped a nozzle.
Printer halts during heat-up and reports the code before the nozzle reaches temperature
Shorted heater cartridge lead, or bridged pins at the toolhead connector
- Power off at the wall socket and let the hotend cool completely.
- Unplug the heater cartridge and measure across its two pins with a multimeter. Roughly 10 to 15 ohm is healthy. Near zero confirms a shorted cartridge.
- If the cartridge measures correctly, the fault is in the wiring. Run the lead through your fingers and look for shiny, flattened or split insulation at every bend.
- Inspect the connector housing for a bridge across the pins, and for browning that would indicate the short has already been arcing.
Heater cartridges pull several amps. A short that has been running is hot enough to scorch a connector. If you find melted plastic or brown discolouration at the housing, replace the housing as well as the cartridge, and never bypass a heater fault to finish a print.
Why replacing the nozzle will not help
The nozzle and the heater are separate parts. A short is an electrical fault in the cartridge circuit and a new nozzle changes nothing about it. Swapping the nozzle first is the most common wasted step on this code. Measure the resistance, and only then decide what to buy.
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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