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Level 1

1 points

error code 4sns/1/40000000:tcbh-127.902

I have an early 2008 mac pro 3,1 running OS X El Capitan version 10.11.3 with 16GB ram memory, and a 2 x 2.8 GHz Quad-Core Intel Xeon processor. I have a problem with the exhaust fan and the cpu fan. They are running at max speed. (upwards of 2700rpm.) I ran the hardware test and got error code "4sns/1/40000000:tcbh-127.902". I have looked everywhere I can think of to identify what this code means and cannot find any definition that makes sense. Can anyone please shed some light on what this codes definition may be or is and what I can do to fix the out of control fan speeds. Cpu temp is running between 79 to 88 degrees.

That You for your help,

Loucarr

Mac Pro, OS X Mavericks (10.9.2)

Posted on Feb 1, 2016 7:34 PM

17 replies

Mar 1, 2016 11:17 AM in response to loucarr

That guy in the center of the board is likely the northbridge chip. That chip handles the signals into and out of the processor chips for I/O and RAM, so basically every important signal goes through it really fast, and it tends to be the hottest chip in the machine even when it is working properly.

Some Readers have reported really wonky behavior in the somewhat different 2009 model, if the black plastic pins that secure that heatsink firmly to the Nothbridge chip get old, brittle, and snap. That heatsink can become noticeably wobbly, and on dual chip models can be detected with the processor heatsinks still in place.

If you bought a spare board, I urge you to try it and make sure it really is a viable spare (although I have no reason to believe it is anything other than just fine).

loucarr Author

Level 1

1 points

Mar 1, 2016 12:58 PM in response to Grant Bennet-Alder

Thanks, I will try it. Makes sense to do so.

error code 4sns/1/40000000:tcbh-127.902