Sensor error Tp2H, heatpipe, power supply

Hey all,

I've got an iMac late 2012 and to date it worked without any problems.

But after having updated to High Sierra, more and more problems appeared.

The system became slower and unresponsive. Today it reached the climax.

The screen turned black several times in a row, as if it would hibernate.

I started the Apple Hardware Test and it gave me this:

4SNS/1 /40000000 Tp2H-127.875

This means, that the powery supply / heatpipe reached a level of 127°C.

But I'm pretty sure that the sensor is just broken. I bet the system would blow up, if the temperature was real.

Now the question is, can this be easily fixed or does that mean the whole LogicBoard needs to be replaced? And is this worth it ($$$)?

Cheers,

Stephan