User Guide

iMac (27-inch, Late 2009) Symptom Charts — Startup and Power 34
2009-12-16
Intermittent Shutdown
Quick Check
Symptoms Quick Check
Intermittent Shutdown
Powers o during startup.•
Powers o during desktop use.•
Computer restarts •
spontaneously.
Powers o when waking from •
sleep.
Make sure that power cord is securely attached 1.
to the back of computer, and is not hindered by a
desk or other furniture.
Plug computer directly into an AC outlet to test if 2.
a surge protector or UPS is causing issue.
Open System Preferences > Energy Saver > 3.
Schedule and make sure that a “Shut Down”
event is not scheduled.
Isolate OS by starting up from original install 4.
media for this computer, from a same-model
computer in Target Disk Mode, or from a
compatible known-good OS on an external drive.
Both AirPort and Bluetooth services are available
when booted from the Install disk.
Reset SMC and PRAM to clear any stored, 5.
corrupted information.
Start up in Safe Mode by holding shift key down 6.
during startup to load only required kernel
extensions and disable all startup and login
items. See kBase #HT1564: Mac OS X: What is
Safe Boot, Safe Mode?
Deep Dive
Check Result Action Code
Verify improper shutdown 1.
by opening the system.log
located in /var/log. Filter log
for “shutdown cause”. Entries
of value “0” or a negative
value indicate an improper
shutdown. Verify if you nd
recent entries of an improper
shutdown in log le.
Yes Determine if user caused
improper shutdown. Use
known-good AC power cord
and AC outlet. Go to step 2.
No Revisit Quick Check examples
for possible software issues.
Check if user is running
other automating software
that may be shutting down
system. Verify issue and jump
to appropriate symptom
ow. No repair needed under
current symptom ow.