Chosen Solution
Hallo My iMac fans starts running after i opened an application not immediately i bootet up the iMac. Only the CPU Fan and the ODD fan. When i run the ASD i get this ERROR several times: ERROR–13009 SMC error TM_Temp_below_min, the temperature read from the sensor is too frequently below some minimum threshold.
I would reset the SMC, unplug the iMac hold the power button for 10-20 seconds (unplugged) then Start the iMac as usual. https://support.apple.com/en-us/HT201295
