Northbridge 2 temperature sensor fail

Thank you for your answer. I have a donor logic board for replacing any chips. My question is where and how to look for the faulty chip on the logic board?

@totyamuri If you have to ask it's very likely you don't have the skills, nor the equipment to replace it. It's the second biggest chip on the board after CPU, with hundreds of solder joints, you'd need a rework station worth a few thousands $/€ just to get it off the board.

@arbaman Thanks for your answer, then my question is: on the board there are 2 large chips, the CPU and the GPU, the GPU has the PCH inside or what?

@totyamuri It's the other way round, PCH handles graphics, backlight, clock and a number of other tasks. That's probably the reason why iStat improperly refers to it as Northbridge, which doesn't really exist as such on that kind of logic board, time for an update for the app ? ;) By the way..I didn't notice it earlier since I relied on your description, but I see the battery sensors show the same temperature, which is a weird coincidence. Did you try running the Mac with battery unplugged from the logic board by any chance ? If not, please try.

@arbaman When the picture has been made there was no battery inside, even the battery is dead which one I have, if I plug it in the temps are the same. The Northbridge 2 not always shows 128°, when I turn on the Mac it shows 30-40°, after some minutes it starts showing 128°.