flexi-bot/docs/marlin/_gcode/M149.md

tag	title	brief	author	requires	group	codes	notes	parameters	examples
m0149	Set Temperature Units	Set temperature units to Celsius, Fahrenheit, or Kelvin.	thinkyhead	TEMPERATURE_UNITS_SUPPORT	units	M149		tag optional description C true Celsius tag optional description F true Fahrenheit tag optional description K true Kelvin

Set temperature units to Celsius, Fahrenheit, or Kelvin. Celsius is the default.