TMPIN is usually the name for an external temperature sensor header. That's what it is on my M6F. Check the manual.
The reading out of bounds suggests either:
Nothing is plugged in to the header and the reading is garbage
The wrong resistance sensor is attached and giving distorted readings
The attached sensor, the header or the sensor chip on the board has a short circuit, which translates to an extremely high temperature
If you have nothing attached or just want to be rid of the annoying reading, there is probably a setting in BIOS (M6F has it on the temperature monitor tab.) BIOS can be set to IGNORE that sensor input. I think that will keep OS apps like HWMONITOR from seeing it.
Jeff