Pulse Hotend Thermistor Check
If you receive an error message reading "Error:heating failed, system stopped! Heater_ID:0" and the issue is not related to a missing silicone sock or a nearby fan blowing on the printer, the following steps should be taken to determine if the thermistor is at fault.
Turn on the printer and connect it to MatterControl using the provided USB cable. Does the error message appear immediately, or does the printer read an idle room temperature of roughly 21-28°C?
Navigate to the Terminal tab in MatterControl. You should see a constant stream of data showing the temperature updates roughly once every second. If you do not see this stream of data, click on Visibility Options and check-mark Temperature Responses. The temperature (labelled T: for the hotend, and B: for the bed) should be consistently reporting to the Terminal and should never jump more than one degree.
If you notice an inconsistency or fluctuation in the temperature reporting, slowly move the wire harness on top of the printhead by hand and monitor any change in the temperature readout. A bad section of the wire harness will result in a large fluctuation in the temperature readout as the harness is moved around. You may also flex the blue wires coming off of the heater block to see if the readings change at all. If either of these cable movements change the readings in the Terminal, then the corresponding cable section or connector between the cables is going to be the cause of the thermistor issue.
Note: a disconnected or broken thermistor will read as 21.0°C and never change temperature readings in the Terminal. Below is an example of the temperature changes you may expect to see: