My iMac 2011 21.5 is freeze with a white screen during the startup, before the apple logo.
Watching the diagnostic leds, I reallize that the first led is allways on. After press the power button, led 2 is on, and a bit after, at the same time the chimes sounds the led 3 turns on too. Led 4 is off all the time.
iMac 21.5″, macOS 10.13
IIRC correctly it means the LCD Panel is not receiving a video signal. LED# 3, I believe means the video card is communicating with the Logic Board. Most likely the LCD Panel is bad (or the cable/connectors if you had disconnected them previously for a repair or upgrade since they are easily damaged). Cannot 100% eliminate the video card though.
For reference (there are other references online and perhaps even a service guide can be found, but the moderators will not allow us to link directly to most of those sites):
https://logi.wiki/index.php/iMac_Logic_Board_LED_Indicators
Also, for completeness I see you already had another thread open discussing the issues with this same iMac where you were already advised that this iMac is not worth fixing (you should have first asked about the diagnostic LEDs there & waited for a response....I tried to reply earlier, but your first diag LED post was removed):
iMac 2011 21,5 white screen. No keys comb… - Apple Community
You definitely have some sort of hardware issue if the diagnostic LEDs are not all lit. First I would carefully inspect the cables & connectors for video cable(s), and on the Logic Board to see if they show any signs of damage, plus making sure they are fully seated. If reseating cables does not help and there is no obvious signs of damage, then there is no way to know for sure which part is bad without trying a known good part.
Thank you for the response.
I tried that. No keys combination response (cmd+r or alt, or alt+cmd +r or shift, etc.)
I performed different test, like remove the RAM, sounding the beeps, remove the hard disks, card reader and optical unit to force the folder image with the interrogation or another symbol, but the folder does not appear, keeping the white screen.
And after that, I saw the diagnostic leds, and the led 4# off.
What is the ultimate goal here? Are you wanting to wipe the drive and install a fresh OS? Simply reinstall the OS? or What exactly?
The last section of the article says:
Contact us
If the issue continues, contact Apple Support.
Have you done that? If so what did Apple support recommend? If you haven't ... why not? it's a natural step in the process and you can't just ignore it and expect problems to go away.
Your Mac is 12 years old, obsolete and not repairable by Apple. It's time to get a new, or newer, Mac.
Thank you for your response.
The first diag LED post was removed by the moderators. It was too similar to the other post.
Very usefull the link. I am still trying to fix the iMac. I will update this post whatever happens, if finally it works or not.
Like this but white: If your Mac starts up to a blank screen - Apple Support
Diagnostic led 4# do not lit on iMac 2011 21.5
