Mac G5 Desktop Spontaneously Shuts Down
So, for a while now, my Mac G5 desktop machine has been spontaneously shutting down at random times. Sometimes it runs for a few days, sometimes it only runs for a few hours, but I'll come back in my office, and it will be completely shut down. Why would a Mac start shutting itself down?
The system.log file always shows this entry:
ApplePMU::PMU FORCED SHUTDOWN, CAUSE = -122
or, as reported for later model G5's:
AppleSMU -- shutdown cause = -122
No need to panic - here's the results of days of research and troubleshooting!
Please note: I have written a new article in this blog that incorporates the user experiences posted here, along with some additional information, and specific troubleshooting tips. Please see the new article, "Troubleshooting the Mysterious '-122' Error" to get the latest information!If you're looking for a quick troubleshooting guide, here's a direct link to the troubleshooting section of that new article.
Doing a Google search on this has not turned up much, other than a few other people getting the same behavior, and being led to believe by others that it has to do with some variation on a failing power supply, a failing motherboard, etc. I'm here to tell you that I don't think that's the case. I did come across one other user who thought that this code implicated the power supply outside of the G5 - as in the UPS or the wall.
If you keep looking, it seems difficult or impossible to find via Google a list of Apple Error Codes that includes a PMU error -122. One red herring is a document at Apple that shows -122 as an HFS error (badMovErr: move into offspring error) which some folks have thought means their disk is in trouble. NOT! If you go to the top of that document at Apple, you'll clearly see the label "This document applies to Mac OS 9 and earlier."
Around the same time this behavior started, I noticed that my UPS was not too happy. OK, "noticing" is perhaps understating it - the damned box started beeping at me three times a day. The failure code on the UPS is telling me that it needs a new battery. I know, it's kind of a "duhhh" moment to wonder why your Mac is shutting down when the UPS is yelling for help, but I'm lazy and cheap and have been holding off getting the new battery.
The new battery arrived today, and I'm going to install it. I'll leave a comment to this post on whether the problem seemed to go away, and hopefully anyone else googling that failure code will come across this post!
UPDATE 1: 10/29/2005 - - - - -
It's important to note that the syslog message I'm seeing about the ApplePMU is occuring after I power on the Macintosh, so this code is being written at BOOT TIME, not at shutdown time.
That being said, I have come across one reference now (forgive me, this is hearsay) where the user said that Apple told him that an ApplePMU cause of -93 isn't actually an error, rather it's the firmware sending the restart command to the PMU. I know, it's not exactly my situation, since my cause code is -122, but I feel that I'm closing in on this.
UPDATE 2: 10/29/2005 - - - - -
I found a reference on an Apple mailing list where an Apple Tech Support representative replies that the ApplePMU driver source is private...which may explain why I can't find the cause codes that appear in the syslog anywhere in the Darwin source!
UPDATE 3: 10/29/2005 - - - - -
OK, so it looks like Apple does not openly publish their "cause codes" for ApplePMU messages in the syslog.
Two possibilities seem likely:
- ApplePMU somehow "knows" it lost external power and manages to write out this state in the last milliseconds of life; or
- ApplePMU reports a cause code of -122 for all mysterious shutdowns; that is, a value of -122 is stored (perhaps in PRAM) while the Mac is running, and unless someone specifically changes it (as in a normal shutdown, or an emergency thermal shutdown, etc.), when the Mac reboots it reads in that last value of -122, which means it is used for ALL mysterious shutdowns of the system. Someone should take a look at the PRAM documentation more closely and perhaps this mechanism is explained there, but for now I'm googled-out, so I'm going to let this go.
UPDATE 11/03/2005 - - - - -
One final note to close out this posting: it has now been 5 days, and the problem of the system just being "off" without warning (not to mention those scary syslog errors regarding the ApplePMU) have not returned, even once. My conclusion: the CAUSE = -122 notation in the system log was indeed a symptom of an EXTERNAL power problem, rather than anything internal to the Mac itself.
..Chris..