iMac (Retina 5K, 27-inch, Late 2015) Randomly Restarts Without Errors

Seems if it is a logic board issue, it must be a very obscure one. The problem does not always manifest itself under load, or even when in use. That would also rule out a thermal issue, unless there actually is a background process run amok and that doesn't appear to be the case.

Power related seems more likely. Either one of the power rails is sagging for some reason or something else.

Still no fix for me. Waiting to try and catch a restart so I can send another set of logs.

Really would just like a replacement machine. Apple has deep pockets - they should just replace these machines for all of us. And it seems the problem is mounting. More and more post each day...

If it is the logic board - getting the okay to replace it seems to be the sticking point. Those that had their's replaced report that the restarts have stopped.

Hello Jeremy et al.,

I strongly suggest that no one rush to any judgements and start demanding hardware repairs. There is no evidence of any hardware problem. It would be most unfortunate if people badgered Apple repair techs into replacing their perfectly good logic boards with refurbished replacements only to find out later that was just a bug in the OS the whole time.

With the number of machines that Apple sells, a random software failure, or rare hardware defect, can look like the same thing. Apple has really not been doing its best software work since the release of 10.9. Personally, I've had all kinds of strange failures since then that I never had before. However, I am confident that new OS updates will improve the situation. EtreCheck isn't much help with these problems and neither are log files. No one outside Apple knows what log files mean and few people inside Apple do either. This is a problem that needs engineering support and that takes months.

If you want to take some action, make sure to maintain good backups. I strongly recommend Time Machine. These days, I find myself restarting my Mac more often than I have since the mid-1990s. Apparently the operating system thinks regular restarts are a good idea too if it is doing them spontaneously. But Mac repairs are like surgery. Don't go cracking something open unless you and your doctor are sure that the problem will be resolved. Otherwise, you may find yourself still dealing with the same old problem, and a few new ones.

Interesting perspective etresoft––what's your opinion on the restarts people have been experiencing with this following users over multiple different software updates or restores to a previous OS? I went from 10.11.5 back to 10.11.3––and the restarts, that began with the update to 10.11.5, have dogged me ever since. Nothing, from a complete restore, to restoring to a Time Machine backup, to blaming my 3rd party RAM and re-installing the RAM that came with the machine, have fixed the problem.

If that's not a hardware issue, what is it? None of the diagnostics seem to reveal a software problem, but the restart issue remains!

I for one want this issue to go away with my iMac––it's supremely irritating, distracting, and compromises my work. I've used Macs for 15 years for my creative projects for business and pleasure.

I spec'd my iMac out over $4,000 to be my rock solid, 4k video editing machine––and it was working fantastically until the dreaded 10.11.5 update, which, undoubtedly, bricked something.

It's not reassuring to tell people experiencing this debilitating problem with their expensive, top of the line Macs that a software update, which we have no ETA on, possibly months away, will "improve" the situation. An improvement is not a solution.

No software fix has presented itself in the almost three weeks this has been happening to me, and if, as you believe, a software solution is somehow inevitable, that leaves me with little if any confidence in the Apple system that constantly and irritatingly pushes notifications at me to "update to the latest software." It's as if Apple software updates have become a game of Russian Roulette.

I'm not seeking to poke holes in your judgement––however, the only permanent "fix" with people to this problem in this thread has been a hardware solution.

Interesting perspective etresoft––what's your opinion on the restarts people have been experiencing with this following users over multiple different software updates or restores to a previous OS? I went from 10.11.5 back to 10.11.3––and the restarts, that began with the update to 10.11.5, have dogged me ever since. Nothing, from a complete restore, to restoring to a Time Machine backup, to blaming my 3rd party RAM and re-installing the RAM that came with the machine, have fixed the problem.

Hello bendean,

I have no opinion. I don't have that machine and have never experienced anything like that. I have experienced other kinds of lockups under heavy CPU usage. And in general, I've been quite unhappy with Apple's operating system quality since 10.9 was released.

My concern is with people using EtreCheck to demonstrate some kind of systematic hardware failure. I wrote EtreCheck and I don't think that is a valid interpretation of its results. If people want to use some other diagnostic method with interpretations that may or may not be valid, that's their prerogative. Just leave EtreCheck out of it.

Ah, interesting––thank you for that enlightening reply! I was looking up EtreCheck earlier. I somehow didn't notice it was a tool that was being used in a way unintended by people posting in this topic.

Hello again bendean,

I just discovered it by accident. These types of threads have a long history here on Apple Support Communities. I try to avoid them like the plague. Now I'm going to get notified of updates for weeks. There is a logical fallacy where millions of people have the same hardware and software, a few of those have problems, some of those problems look the same, and a few of those people converge on this site (for obvious reasons), find a dozen or two like-minded people, think there is a trend, and start talking class-action lawsuit. Any event with a high number of samples is going to have some degree of observable, but unlikely results. Just because you are one of the few to observe an unlikely result doesn't mean it is anything more than chance.

It might be a manufacturing defect. I don't know. I just know EtreCheck doesn't know either. I want EtreCheck to help people find and fix problems with their computers. These threads never have a good outcome for anyone involved and therefore, I don't want to be involved.

Eresoft, seeing a lot of these kinds of things, as I'm sure you do, I can imagine your default response is skepticism. And sure, I can also imagine that you don't want your (really helpful) software to be used willy-nilly as an excuse to hound and badger Apple. Nonetheless, I take issue with your characterization of the thoughts of this group as a "logical fallacy". Yes, in the general case, that analysis is correct, and it is always dangerous to make a leap of logic from correlation to causation. Still, in this case, it doesn't seem completely unwarranted. It is a VERY specific problem, manifesting in exactly the same way, affecting users of the exact same generation of iMac with the exact same factory specs. Sure, it is not definitive proof that we're all experiencing a hardware/manufacturing flaw with the machine. And no one is suggesting a class-action lawsuit or anything hysterical. But given the really shoddy level of technical proficiency at Apple Stores, as well as the dense and thorny support protocol Apple users are forced to endure, it is not unreasonable to, after MANY attempts at getting support through the usual channels, to try to marshall evidence of a general problem that they appear to be unaware of/unresponsive to, and by joining together to demonstrate that this is not an isolated incident, try to get higher-level support to pay attention to the problem. That seems entirely reasonable to me, and, in this case in particular, not based on any logical fallacy.

Another, more recent, turn up to this is that I now get sleep/wake failures where the iMac won't come out of sleep mode at all. Not clear there is any correlation with the reboot problem but....

I don't have that problem, Greg (related to PowerNap change you made perhaps?), but I was having problems with external disks not being ejected properly when computer slept. I installed an app called Jettison, though, and that seems to have solved the issue.

Possibly related. When I reenabled PowerNap, I set the power settings back to defaults. Put hard disks to sleep was previously unchecked. Very odd.

Hello again Jon,

Take a close look at the title of this thread. What other kinds of responses would you expect to see here? If you go looking, you will find similar reports from other machines. People who go looking are going to gravate towards similar responses. In your case, you didn't have to go looking. Someone gave you a link and planted the suggestion. That someone has a history of making these kinds of claims.

The danger in such claims is that they do escalate. Supposedly, no one is suggesting anything hysterical. But in your very next sentence you make a claim about the proficiency of Apple technical and support services. As many consumer surveys show, and anyone who has ever dealt with Apple and companies that aren't Apple can confirm, those claims could be accurately labelled as hysterical. Apple is as good as it gets, warts and all.

By accounts in this thread, Apple is making efforts to investigate the problem. I say let them investigate. Apple regularly issues extended repair programs when they discover systematic problems. But it is quite rare that any similar 8-page thread in Apple Support Communits correlates with an extended repair program. If this thread had 280 pages, then it might be a different story. My suspicion is that it is a software problem more closely associated with 10.10 and 10.11 than any particular type of hardware. I regularly see reports of random restarts on all machines, but I don't remember seeing them until the past couple of years.

Apple will have a new OS available in a couple of months. Maybe that will run better, maybe worse. No way to tell. You can choose to let Apple investigate and see how 10.12 runs on your machine in the fall. Or you can get a refurb logic board and see how 10.12 runs on that in the fall. Just remember that whatever tests Apple runs on your current machine will also be run on the refurb. Whether that is good or bad depends on your perspective.

I am having the same problem, I have to unplug and plug it back in to get it to wake up. I told the representative that I talked to that it has happened several times. I thought maybe there was something with the new UPS that I had it plugged into But I guess it's not since you are having the same problem.

I'm going directly to the wall outlet.

It is getting a sleep failure when this happens;

2016-06-30 06:59:14 -0700 Failure Sleep Failure [code:0x11006C00]:

But it looks like it tries to come out of sleep state, 6:59 is when I came in a started tapping the keyboard to wake it;

2016-06-29 23:02:29 -0700 Assertions PID 53(powerd) Created InternalPreventSleep "com.apple.powermanagement.acwakelinger" 00:00:00 id:0x0xd00000bbb [System: PushSrvc SRPrevSleep kCPU]

2016-06-29 23:02:29 -0700 Assertions PID 301(UserEventAgent) Created BackgroundTask "com.apple.Safari.SafeBrowsing.Update" 00:00:00 id:0x0xb00000bbe [System: PushSrvc BGTask SRPrevSleep IPushSrvc kCPU]

2016-06-29 23:02:30 -0700 Assertions PID 301(UserEventAgent) Created BackgroundTask "com.apple.suggestions.harvest" 00:00:00 id:0x0xb00000bc0 [System: PushSrvc BGTask SRPrevSleep IPushSrvc kCPU]

2016-06-29 23:02:31 -0700 Assertions PID 301(UserEventAgent) Released BackgroundTask "com.apple.suggestions.harvest" 00:00:00 id:0x0xb00000bc0 [System: PushSrvc BGTask SRPrevSleep IPushSrvc kCPU]

2016-06-29 23:02:32 -0700 Assertions PID 301(UserEventAgent) Released BackgroundTask "com.apple.Safari.SafeBrowsing.Update" 00:00:02 id:0x0xb00000bbe [System: PushSrvc SRPrevSleep IPushSrvc kCPU]

2016-06-29 23:02:34 -0700 Assertions PID 53(powerd) Released InternalPreventSleep "PM configd - Wait for Device enumeration" 00:00:05 id:0x0xd00000bb9 [System: PushSrvc SRPrevSleep kCPU]

2016-06-29 23:02:39 -0700 Assertions PID 53(powerd) TimedOut ApplePushServiceTask "Powerd - Wait for client pushService assertions" 00:00:10 id:0x0xa00000bba [System: PushSrvc SRPrevSleep kCPU]

2016-06-29 23:02:39 -0700 com.apple.sleepservices.sessionTerminated SleepService: window has terminated.

2016-06-29 23:02:39 -0700 Summary- [System: SRPrevSleep kCPU] Using AC

Sleep/Wakes since boot at 2016-06-29 00:40:36 -0700 :14 Dark Wake Count in this sleep cycle:6

Time stamp Domain Message Duration Delay

========== ====== ======= ======== =====

UUID: (null)

2016-06-30 06:59:13 -0700 Start powerd process is started

2016-06-30 06:59:13 -0700 Summary- [System: No Assertions] Using AC

2016-06-30 06:59:13 -0700 Assertions Kernel Idle sleep preventers: IODisplayWrangler

Sleep/Wakes since boot at 2016-06-30 06:59:13 -0700 😁 Dark Wake Count in this sleep cycle:0

Time stamp Domain Message Duration Delay

========== ====== ======= ======== =====

UUID: Unknown UUID

2016-06-30 06:59:14 -0700 Failure Sleep Failure [code:0x11006C00]:

It's clear that there is a common pattern involving the iMac17,1. It doesn't affect everyone. I agree with the view expressed earlier that "etrecheck" contributes nothing. But the finding of multiple abnormal shutdowns with "Previous shutdown cause: -128" in the log is about as strong an indication as there can be of either a hardware defect or a bug in the firmware or OS. Apple has taken responsibility for manufacturing errors in other products, such as the MacBookPro6,2 and the iMac12,2, after a long delay during which owners were steadfastly told that nothing was wrong with their devices.