Apple MD094LL/A manual Symptoms Quick Check Won’t Start Up, Safe Boot, Safe Mode?

Won’t Start Up

Quick Check

Symptoms	Quick Check
Won’t Start Up	1.	Isolate OS by starting up from original install
• No startup chime.		media for this computer, from a same-model
• Error tones during startup.		computer in Target Disk Mode, or from a
		compatible known-good OS on an external drive.
• Grey screen with fan noise, or
		Both AirPort and Bluetooth services are available
other noise.
		when booted from the Install disk.
• Will not progress beyond
	2.	Reset SMC and PRAM to clear any stored,
Apple logo or spinning gear.
		corrupted information.
	3.	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?
	4.	If system generates error tones there may be an
		issue with the SDRAM. See kBase #HT2341: Intel-
		based Mac: Power On Self Test RAM error codes
	5.	Identifying when in the startup process the
		computer hangs can help isolate the issue.
		See kBase #HT2674: Intel-based Mac: Startup
		sequence and error codes, symbols for
		information on the Macintosh startup sequence,
		and error codes and symbols used.
	6.	Run latest available service utilities.

Deep Dive

Check		Result	Action	Code
1.	Boot computer to Apple	Yes	Run the extended tests
	Hardware Test on the internal		and proceed with results. If
	hard drive or an inserted Install		AHT passes or boots with a
	DVD by holding down the D		memory error, go to step 2.
	key at startup. Verify if system
		No	Go to step 2.
	boots up from any of these
	volumes.
2.	Remove installed SDRAM, and	Yes	SDRAM issue. Reinstall one	X02
	test with known-good SDRAM.		of user’s SDRAM modules
	Verify if computer starts up		and retest. Proceed one by
	properly now.		one to find the faulty SDRAM
			module, and replace it.
		No	Go to step 3.

2010-09-09 iMac (27-inch, Mid 2010) Symptom Charts — Startup and Power  37