Fan runs full speed.

Dear everyone,

I had a 27” iMac late2015 which has an issue of fan running full speed and takes all the cpu %.

Had tried to do the SMC reset. It works out well the first couple times but not now. I had tried reinstall the system, checking if there is virus things were doing good.

But this time I find that there was some new issues. I try to go to the Hard Disk selected mode by passing the option key to check if there was any problem with the hardware systems, since the fan should not run full speed under this area.

But it did run full speed now. Even under the safe mode. I than run the hardware test and it shows there is an issue with my SMC code - PMF006.

Does anyone have idea which part if my mac need to be repair. thx!