iMac (21.5-inch, Late 2009) Symptom Charts — Startup and Power 33
2010-11-18
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.
1. Make sure that power cord is securely attached
to the back of computer, and is not hindered by a
desk or other furniture.
2. Plug computer directly into an AC outlet to test if
a surge protector or UPS is causing issue.
3. Open System Preferences > Energy Saver >
Schedule and make sure that a “Shut Down”
event is not scheduled.
4. Isolate OS by starting up from original install
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 disc.
5. Reset SMC and PRAM to clear any stored,
corrupted information.
6. Start up in Safe Mode by holding shift key down
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
1. Verify improper shutdown
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.
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