Chosen Solution
I have a Late 2009, 27" iMac. It has been a solid machine and served me quite well over the years. Finally over the last year, I started having some issues with it. Most recently it is failing to boot up. It plays the chime, gets half-way through the progress bar, then glitches out to a white/gray screen. Then it sits there for a few minutes and then tries to reboot itself. After trying a few possible fixes, such as PRAM and SMC reset etc, I decided to run the Mac Hardware diagnostics. That gave me the following two errors. Quick Test: 4MOT/4/40000003: HDD-1276 Extended Test: 4MOT/4/40000003-HDD-1319 I am trying to see what these errors mean. I know that a 4MOT error has to do with fans. And the HDD part makes me think this has to do with the Hard Disk fan. What I am trying to figure out is the numeric part of the error code. Is it telling me that the fan unit has stopped working, or if this a temperature sensor issue/something else. I am hoping someone with access to these codes, or prior knowledge about them can help decode these for me. Thanks!
Worth a try I guess but personally I would open up the unit and give a through cleaning. As you say Googling seems to indicate fan(s) issue or hard drive fan issue but the posts I read also indicated dust build up for the whole unit which would of course be a possible source of thermal related problems. The following link seems to indicate the OP’s problem was solved; whether it applies to your unit or not I am not sure. https://discussions.apple.com/thread/382… PS There was one small reference on a German site regarding video card being affect but that could also be heat related.
Could be a burnt out Temperature Sensor, which would explain why it’s a fan and HDD error. Try booting off an external disk to see if it’ll run longer in that way. (Eliminates possibility of dead drive) Good luck!
The error 4MOT/4/40000003: HDD you are getting is a Motor problem within the HDD fan. Its not turning as SMC expects, ether its jammed up or the bearing has ceased. You’ll need to pull the HDD drive out and move the logic board forward so you can reach it (one screw). I use a small ratchet driver with the needed Phillips bit so I don’t need to fully remove the logic board.
Here’s the needed part iMac Intel 27" (Late 2009-Mid 2011) Hard Drive Fan
