It appears one of your temperature sensors has gone bad.
To debug the error code you need this writeup: AHT error codes. So in your case 4SNS is a system sensor after the : mark T is temperature and the h is heat pipe (heat sink).
I would install a good temperature sensors & fan monitoring software to double check things. I like Temperature Gauge which you can download from the Apps store. There are others out there that are just as good. See what it tells you and let us know too.
I recommend backing up your system and after that you may want to open your system up to inspect it for dust and debris build up on the fans & heat sink fins as well as the logic board it self. If things look clean then the sensor most likely needs to be replaced. It's a bit of work here as you need to pull the logic board out to get to the heat sink and you should apply a fresh coat of thermal paste on the chips if you go this far. Review this IFIXIT guide Heat Sink Replacement
If you do see a lot of stuff you should get a can of can'ed air and a soft paint brush to lightly scrub the fan, fins & logic board and using the can'ed air blowing out the junk.