Quick Check
Symptoms Quick Check
Kernel Panic / System Crashes
• Computer displays a kernel panic alert message See Apple Support article HT1392: “You need to restart your computer” (kernel panic) message appears (OS X v10.5, 10.6)
• Computer freezes during use
• Computer freezes upon wake from sleep
• Computer freezes when AirPort is enabled or activated
1. Collect details from user regarding the kernel panic or crash: when does it happen; what peripherals are in use; what applications are in use; what actions are taking place at the time;
and try to establish a set of circumstances so you can recreate the issue effectively.
2. Check for and apply the latest software and firmware updates.
3. Remove suspected external devices.
4. Verify memory configuration matches actual amount of installed physical memory.
5. Hold Shift key during startup to start computer in Safe Mode. See Apple Support article HT1564: OS X: What is Safe Boot, Safe Mode?
6. Start up from known-good bootable device with an up-to-date OS X version and proper build. See Apple Support article HT1159: OS X versions (builds) for computers.
7. Check kernel panic log file to look for crash cause.
See Apple Support articles HT2546: OS X: How to log a kernel panic, and HT1392: “You need to restart your computer” (kernel panic) message appears (OS X v10.5, 10.6).
8. If issue cannot be easily reproduced, run Apple Service Diagnostic (ASD) for longer, looping or OS tests.
Deep Dive
Check Result Action Code
1. Start up computer to Apple Hardware Test (AHT) on internal hard drive or an inserted Install DVD by holding down the D key at startup. Verify whether computer boots up from any of these volumes.
Yes Run extended tests and proceed with results. If AHT passes or boots with a kernel panic, go to step 2.
No Go to step 2.
iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 44 2011-08-29
2. Remove all peripheral devices including keyboard and mouse.
Verify whether computer starts without kernel panic.
Yes Add peripheral devices one at a time until kernel panic repeats. Replace device causing issue.
No Go to step 3.
3. Use known-good memory in the system. Verify whether computer start without kernel panic now.
Yes Install user’s memory one by one and retest. If kernel panic repeats, replace affected memory. Verify whether correct memory specification is being used.
X01
No Go to step 4.
4. Wait for 20 seconds after shutdown and disconnect AirPort card from logic board.
Verify whether computer starts without kernel panic now.
Yes Go to AirPort Card Kernel Panic.
No Go to step 5.
5. Disconnect data cable from hard drive and startup to the Install DVD in the optical drive or from an external volume.
Verify whether computer starts without kernel panic now.
Yes Go to Hard Drive or SSD Not Recognized.
No Go to step 6.
6. Disconnect Bluetooth/camera/
sensor cable and microphone cable from logic board. Verify whether computer starts without kernel panic now.
Yes Go to AirPort Issues, Bluetooth Issues, Camera Issues or Microphone Issues symptom flow as appropriate.
No Go to step 7.
7. Disconnect SD cable on logic board. Verify whether computer starts without kernel panic now.
Yes Go to SD Memory Card Not Recognized.
No Go to step 8 8. Disconnect optical drive and
test. Verify whether computer starts without kernel panic now.
Yes Go to Optical Drive Not Recognized.
No Replace logic board. M06
iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 45 2011-08-29
No Video
Unlikely cause: hard drive, optical drive, speakers, camera
Quick Check
Symptoms Quick Check
No Video
• Power but no video visible on display
• Fan, hard drive spin or optical drive reset sounds audible
• Caps Lock key on wired keyboard illuminates when pressed
1. Press F2 key on wired keyboard to increase screen brightness.
2. For no-video issues, connect a compatible external display to verify if iMac video circuitry is functioning. If image appears on external display go to Backlight Issue/No Backlight.
3. Reset SMC.
4. Reset PRAM by holding down Command-Option-P-R keys while rebooting, until you hear the startup sound for the second time.
Deep Dive
Check Result Action Code
1. Verify startup sound present and fans running when computer powered ON. (Reset SMC and PRAM, reseat battery on logic board if necessary and retest for proper start up.)
Yes Power ON self test OK. Boot sequence started.
Go to step 2.
No Go to No Startup.
2. Verify whether image is visible
on built-in LCD panel. Yes Video present. Verify computer functionality and return to user or jump to appropriate troubleshooting flow.
No Go to step 3.
3. Connect supported external display. Verify whether image appears on external display when computer is started up.
Yes External display detected by system. Video circuitry on logic board functional.
Inspect DisplayPort cable connection to back of LCD panel. Reseat and test again.
If you continue to have problems go to Backlight Issue/No Backlight.
No Go to step 4.
iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 46 2011-08-29
4. Disconnect AC, remove glass and LCD panel to access diagnostic LEDs on center of logic board. Reconnect AC and verify if LED #3 turns on shortly after computer powers on.
Yes Logic board communicating with video card. Go to step 5.
No If LED #3 does not turn ON reseat video card and retest, then replace video card and repeat step 4. If issue persists, replace logic board.
M03 M03 5. Locate diagnostic LEDs on
logic board and verify if LED #4 turns on shortly after computer powers on.
Yes Logic board communicating with LCD panel. Go to Backlight Issue/No Backlight.
No Replace DisplayPort cable.
Go to step 6. X03
6. Locate diagnostic LEDs on the logic board and verify if LED #4 turns on shortly after computer powers on.
Yes Video controller functional and communicating with LCD panel. Go to Backlight Issue/
No Backlight.
No Video controller unable to communicate with LCD panel.
Reseat cables first. If issue persists, replace LCD panel.
Retest.
L03
iMac (27-inch, Mid 2011) Symptom Charts — Startup and Power 47 2011-08-29