Nozzle or bed temperature errors (HMS 0300-0200-… and 0300-0100-…)

Symptom

The printer shows a nozzle temperature error (for example 0300-0200-0001-0001, heater short circuit, or 0300-0200-0001-0007, sensor open circuit; the A1 usually shows «Nozzle Temperature Malfunction») or a bed error (0300-0100-0001-0007, the bed reads 0 °C), or the bed will not heat.

Likely causes, from most to least likely

1. Thermistor (NTC) or heater connector loose or misaligned, or a broken wire.
2. Faulty thermistor or heater.
3. Hotend silicone sock missing or torn.
4. On the X1 with a V8 toolhead board, a loose or burnt 10-pin connector; on the P1 and on the X1 with a V9 board, a badly seated flat cable (FPC).
5. On the bed: loose bed, sensor or power cable, a faulty bed or a failed AC board.

Checks to tell which one it is

• Read what the code says: heater (short or open circuit), sensor or over-temperature, and whether it is the nozzle or the bed.
• If the bed reads 0 °C, the temperature reading is failing (sensor or its cable); if it shows a value but does not rise, the heater power is failing.
• Check the silicone sock: if it is missing or badly damaged, replace it.
• If you own a multimeter and know how to use it, measure cold with everything disconnected: the nozzle ceramic heater is about 12 Ω on the X1, 10 Ω on the P1 and 7 Ω on the A1; the thermistor about 100 kΩ (50-100 kΩ on the X1) at room temperature.

Before you start

Before taking anything apart, cleaning or adjusting it, switch the printer off and unplug it, unless a step says otherwise, and do not touch the nozzle, the heater block or the bed until they have cooled down. If in any doubt about electricity, heat or moving parts, stop and ask a professional.

Step-by-step fix

1. Check the silicone sock

   With the nozzle cold, check that the silicone sock is fitted and intact; replace it if it is torn or comes off easily.

   Check: The alert does not return when heating.

   If that does not fix it: Check the connectors (next step).

2. Reconnect the thermistor

   Switch the printer off and unplug it. Reconnect the nozzle thermistor (NTC) cable with the connector correctly aligned in its socket.

   Check: After power-on, the temperature reads correctly and the alert is gone.

   If that does not fix it: Remove the hotend using the guide for your model and check whether the thermistor or its wire is broken.

3. Check the toolhead board connection

   With the printer off: on the X1 with a V8 board, reseat the 10-pin connector (remove the silicone with tweezers first and look for burn marks); on the P1 and on the X1 with a V9 board, reseat both ends of the flat cable. It sometimes needs doing several times.

   Check: The error disappears.

   If that does not fix it: If the heater or thermistor readings are out of range, replace the hotend or heater assembly; if they are fine, contact Bambu Lab support.

4. If the bed won't heat or reads 0 °C

   Switch the printer off and unplug it. On the X1 the bed is heated directly by mains voltage: only with the printer unplugged, and following the Bambu Lab guide (the rear cover has to come off), check the bed cable and sensor connectors; they are fixed with white silicone and, if they are not tilted and no pins have backed out, simply press them home. On the A1, do not force the bed cables while checking them.

   Check: After power-on, the bed reads room temperature and heats up.

   If that does not fix it: AC board and mains voltage checks are dangerous: leave them to a professional or to Bambu Lab support, which also handles cable or bed replacement.

5. Early-batch A1 printers

   In 2024 Bambu Lab recalled early-batch A1 printers because the bed cable could be damaged when bent and short-circuit, with a risk of electric shock or fire (in the US, those sold before 30 January 2024 with an A as the sixth character of the serial number). If your A1 is from that period and its bed was not replaced, stop using it and contact Bambu Lab support; do not replace the bed yourself.

   Check: You know whether your A1 was affected and whether it has been fixed.

   If that does not fix it: Contact Bambu Lab support or the shop where you bought it.

Prevention

• Do not bend or force the toolhead and bed cables when cleaning or moving the printer.
• Always keep the silicone sock fitted: it keeps the nozzle temperature stable.
• After changing the hotend, check that every connector goes in straight and aligned.

Still not fixed?

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Printers it applies to

Bambu Lab X1 Carbon, X1, X1E, P1S, P1P, A1 and A1 mini.

Official sources

This guide summarises the official documentation linked here:

• HMS_0300-0200-0001-0007: The nozzle temperature is abnormal, the sensor may be open circuit. · Bambu Lab
• HMS_0300-0200-0001-0001: The nozzle temperature is abnormal, the heater may be short circuit. · Bambu Lab
• HMS_0300-0100-0001-0007: The heatbed temperature is abnormal; the sensor may have an open circuit. · Bambu Lab
• Troubleshooting of heatbed not heating up - X1 series · Bambu Lab
• Troubleshooting guide for A1 heatbed not heating up · Bambu Lab
• A1 recall · Bambu Lab