Last week my iMac began restarting immediately after entering my login credentials at startup.
After lots of debugging and experiments I have found that the reboot happens when it establishes a network connection. It happens with both ethernet cable and wifi. If I unplug the ethernet cable and shut off wifi, the iMac starts and I can log in with no problems.
Once it is ready, if I plug in the ethernet cable or activate wifi, it restarts almost immediately.
If I boot in safe mode, the problem does not occur, and I can use network functions.
My searching has not found anyone else describing a problem like this. Does it sound familiar to anyone here?
The iMac is a mid-2011 21.5 inch, model 12,1 core i7. It has been running without issue until this.
What I have done so far:
- reset SMC
- reset PRAM
- unplugged all external accessories
- unplugged ethernet cable
- shut off wifi
- booted to recovery partition, ran Disk First Aid
- booted to recovery partition, reinstalled Mac OS 10.13.6
Logs related to power shutoff
$ log show --predicate 'eventMessage contains "Previous shutdown cause"' --last 48h Filtering the log data using "eventMessage CONTAINS "Previous shutdown cause"" Skipping info and debug messages, pass --info and/or --debug to include. Timestamp Thread Type Activity PID TTL 2019-03-05 12:32:36.742263-0700 0xb2 Default 0x0 0 0 kernel: (AppleSMC) Previous shutdown cause: 5 2019-03-05 12:38:45.725639-0700 0xb2 Default 0x0 0 0 kernel: (AppleSMC) Previous shutdown cause: 0 2019-03-05 13:14:54.760970-0700 0xb2 Default 0x0 0 0 kernel: (AppleSMC) Previous shutdown cause: 0
The above rows are repeated many times in the full log output.
https://georgegarside.com/blog/macos/shutdown-causes/ says 0 means "power disconnected" which makes me wonder if there's a glitch in the network hardware that causes an electrical problem.
System network components report
Broadcom 57765-B0: Name: ethernet Type: Ethernet Controller Bus: PCI Vendor ID: 0x14e4 Device ID: 0x16b4 Subsystem Vendor ID: 0x14e4 Subsystem ID: 0x16b4 Revision ID: 0x0010 Link Width: x1 BSD name: en0 Kext name: AppleBCM5701Ethernet.kext Firmware version: 57765-a1.54 Location: /System/Library/Extensions/IONetworkingFamily.kext/Contents/PlugIns/AppleBCM5701Ethernet.kext mDNS offload capable: c8:2a:14:28:c6:55 Version: 10.3.1 WiFi report: Software Versions: CoreWLAN: 13.0 (1350.1) CoreWLANKit: 13.0 (1350.1) Menu Extra: 13.0 (1361.7) System Information: 12.0 (1300.1) IO80211 Family: 12.0 (1200.12.2) Diagnostics: 1.0 (805) AirPort Utility: 6.3.8 (638.9) Interfaces: en1: Card Type: AirPort Extreme (0x168C, 0x9A) Firmware Version: Atheros 9380: 18.104.22.168-P2P MAC Address: e4:ce:8f:51:8c:c8 Locale: FCC Country Code: Supported PHY Modes: 802.11 a/b/g/n Supported Channels: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 36, 40, 44, 48, 52, 56, 60, 64, 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140, 149, 153, 157, 161, 165 Wake On Wireless: Supported AirDrop: Supported Status: Off
Update: I also found that the WiFi networks listed in network preferences cannot be deleted. All named SSIDs and the delete button are disabled.