Late 2015 iMac is rebooting on its own. Only Finder running, OSX 10.11.6. (2) 8GB RAM sticks. Got to catch it in the act today.

After reboot I find kernel: Previous shutdown cause: -128

That doesn't appear to correspond to anything useful in the old MacOS error codes documentation from 1998:

-128 userCanceledErr User canceled an operation


The is a refurb unit, hoping it doesn't need to go back for another refurbishment.


  • Can you please reinstall MacOS? – At0mic Sep 23 '16 at 1:09

The precise meaning of the shutdown cause codes is not publicly documented, so linked error about userCanceledErr isn't correct, as these are different list of codes.

The shutdown cause -128 in general is related to the unknown hardware issue (e.g. RAM). If it happens repeatedly, you should take it to the repair.

See also:

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