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

Apple is going to replace my logic board. Finally. They are actually sending a tech out to my house to do it. I am supposed to get an appointment in the next 48 hours. Will update everyone when logic board is replaced and if the restarts stop - which I am confident from others like you who say the reboots have stopped with this fix.

I am pleased and hopeful.

I have been having this problem very sporadically, maybe once a week or so. When I go to the console, which log would look at to see if there is a -128 error?

I have no external monitors or devices connected other than a usb hub.

My one year warranty runs out in October so I want to make sure I get this resolved before then.

Thanks!

Just use the search box on the upper right corner and type "-128". Should be easy to find immediately after a reboot.

Thank you.

This is what I get when I do that:

It seems like this is saying my computer shutdown at these 7 times throughout the day today. But, as far as I know this isn't true. When it reboots the startup login screen comes up with my user name and the other user options. However, each time I went to use it today it was at the wake up screen where I'm prompted for my password to wake it from sleep.

Hope this makes sense.

Is the the home service part of AppleCare or will they also do this under normal warranty work?

Hi folks

I dropped my iMac off at the Genius Bar tonight (don't hold out much hope of it demonstrating the problem but hey ho).

A couple of (possibly) useful snippets of information however:

The Genius I talked to went to research the shutdown cause of -128 and came back quite forcefully suggesting that *I* must have shut the machine down because that cause related to "an application cancelled shutdown". Now that's clearly nonsense, as the machine did in fact restart, but it does make *some* sense as there was no way to quit the apps before the machine restarted? Take with a large pinch of salt, YMMV etc.

One other point - the "Previous shutdown cause" message does appear to be generated at multiple times, and doesn't get changed *until* another restart type occurs, e.g. a clean shutdown or a reboot will change it to 5 or 0 (can't remember which way round).

Cheers

Mike

Just had my logic board replaced by an In-Home Technician . Yay! This is his fourth logic board replacement on the late 2015 5K Imac... says this should solve the issue as the Logic Board (Mother Board) has everything on it - basically the body of the computer.

Says the three other ones they replaced are running without the random restart issues. I am hopeful that the problem is now resolved. He suggest Apple Care as it includes in home service. Pretty fast too, less than a 48 hour turn around for the appointment and it took him 45 minutes to do the swap.

Just keep on Apple until they okay the Logic Board replacement. You can see from the photo it has the Video Chip, memory slots, USB connections, etc.

I'm squarely in the Apple box of runaround with my problem, sounds the same as yours. I did os x reinstall with apple online, then took it to apple authorized dealer who did it again plus tests, but couldn't figure it out, now it is with apple store for hardware testing - but wait, they want to do another re-install, but not from my backup - but some hardware tests being done. This is unacceptable, it's now going on a few weeks of this back and forth. Apple should just give me a new refurbished unit now, and throw my machine away. Very frustrating. Not a great customer experience.

Looking in the logs I found one other interesting snippet. My machine was rock solid stable until 10.11.4 was installed, like many reported here. But that Mac OS X update included a firmware change. And the 10.11.5 update that stabilised many or most of the MacBook problems also included a firmware update. I wonder if the firmware changes are at the root of this issue?

From /var/log/install.log, installation of Mac OS X 10.11.4

Mar 22 21:35:06 Mikes-2015-iMac Installer[93316]: OSXUpdCombo10.11.4 : 1.0.0.0.1.1457768702

Mar 22 21:35:06 Mikes-2015-iMac Installer[93316]: FirmwareUpdate : 1.0.0.0.1.1457768702

Installation of Mac OS X 10.11.5

May 18 20:52:54 Mikes-2015-iMac Installer[16240]: OSXUpdCombo10.11.5 : 1.0.0.0.1.1462426507

May 18 20:52:54 Mikes-2015-iMac Installer[16240]: FirmwareUpdate : 1.0.0.0.1.1462426507

Installation of Mac OS X 10.11.6

Jul 20 20:16:19 Mikes-2015-iMac Installer[12662]: FirmwareUpdate : 1.0.0.0.1.1468031924

Jul 20 20:16:19 Mikes-2015-iMac Installer[12662]: FullBundleUpdate : 1.0.0.0.1.1468031924

Emptynet,

I've been wondering if this is due to a bad firmware update, too. Replacing the logic board would certainly be one way to get working firmware. This could explain why the 10.11.4 update broke our systems and why some have found a fix with a new logic board. If the replacement board came with pre-10.11.4 firmware, then it'll be running firmware that doesn't exhibit this problem. As long as an update having the 'bad' firmware isn't installed after the logic board was replaced, then the system would continue to run with the firmware that came with the replacement board. Also, if it's a problem with a firmware update, then it would be much easier to get a firmware update from Apple to fix this than to get Apple to replace all of our logic boards, so that would be good.

So, one question we should try to answer is if those who have had their logic boards replaced are now running a different version of firmware than those of us having this problem. It would be helpful if someone who has the logic board replacement that fixes this problem would post their firmware version. This can be found in the main  menu under 'About This Mac', then clicking on the 'System Overview...' button. Here, there will be a 'Hardware Overview' page with the following two lines:

Boot ROM Version: IM171.0105.B08

SMC Version (system): 2.34f2

Logic board replaced first week of June. Came back with 10.11.5 installed. NO restarts in 7 weeks. Hope this helps.

Logic Board replacement seems the solution. Tech who did mine says it is bad firmware.

The Apple supervisor arranged for an in home repair. It is part of Apple Care (which I didn't have) but apple can authorize it for you. You just need to be persistent. In home is easy and great. I will be getting Apple Care also for future protection.

My machine is still under warranty and I have Apple Care but it was determined that there were no in-home repair options close enough to me. So I have to pack up my machine and make the hour+ drive to the closest repair center. If I had known that in advance, I wouldn't have paid for Apple Care. Sigh.

I am fortunate to be in So Cal where there are 3 Apple Stores within 25 minutes of my house plus a bunch of local computer stores working with Apple. But the Tech with 17 years of experience says it is the Firmware for sure.