Hey there. I have a Mac Pro 3.2 ghz Quad Intel Xeon 5,1 that has been randomly shutting off for about a month now. So far I have run hardware tests, taken it to a Mac store, cleaned it, etc. First, I was able to keep it on long enough to run a hardware test. This error code came up. 4SNS/1/40000001:Ip6M-0.972 I was told on another forum that my problem was probably a heat sensor. I tried to ask more specific questions, but no one ever replied again. Then, the Mac store said there was a bad sector in my hard drive. So I replaced my hard drive. About a week later it shut down again. But, when I run the hardware test it comes back with no errors. I continued to look online, typing in my symptoms. I thought maybe it was overheating, because it shuts down and then doesn't usually come back on until the next day. So I installed a fan regulator (smcFanControl). I turned up the fan on CPU1 a bit, since that seemed to be the hottest spot. Temp seemed to stay pretty normal... aaaaaaand then it shut down in the middle of the night while no programs were running. I tried to turn it on later that day and it just shut off during start up... which is normally what it does after it shuts off. So now I'm thinking power supply, right? Or still a sensor? I mean, it can't be the logic board, cause it works most of the time. Or can it? I attached a couple of screen shots from iStat to see if maybe someone who knows better can shed some light on this for me. Thank you for any help!