"Err: MAXTEMP: E1" when THERMAL_PROTECTION_HOTENDS is disabled
#define THERMAL_PROTECTION_HOTENDS is for thermal runaway. When the temperature &quot;should&quot; be climbing or falling at a predicable rate, or holding steady once at running temp.
#define HEATER_0_MAXTEMP defines the maximum temperature Marlin will allow the extruder to get to before initiating a shutdown. This is ALWAYS active for an active extruder (E0) This setting is what will throw MAXTEMP if it is exceeded.
MAXTEMP error when there is no heat on is usually from a short in the thermistor cable.