iMac 27 inch Core i7 (Mid 2011) Won't boot

Question

iMac 27 inch Core i7 (Mid 2011) Won't boot

It seems like this is an issue with the iMac 27" (Mid 2011) not booting anymore. Since the install of High Sierra, It gets to the grey screen with the Apple logo for a while and then reboots again, again and again. I've tried all the known secrets: resetting PRAM, Diagnostics etc. (Please don't offer those in your reply). It work flawless for many years even after I replaced the RAM to 32gig and installed an SSD drive. Slowly, years later...... it would crash, reboot and then to the point where it wouldn't boot at all. Here are a few of my error codes when I started troubleshooting:

4MEM/9/0000000: 0X887cff18

4SNS/1/40000000:TCOH-86.250

4SNS/1/40000000:TH00-9.000

4MEM/62/0000000: 0X8882ef18

4MEM/62/4000000: 0X88857a98

4MEM/62/4000000: 0X8840ca18 (05-19-19)

After Thermal Sensor installed:

4MEM/9/4000000: 0X8881f118

4MEM/9/4000000: 0X88837398

4MEM/9/4000000: 0X887e8518

4MEM/9/4000000: 0X886e118

Test on 12/27/18

4MEM/9/4000000: 0X8841598

Specs:

Model: iMac 12,2

CPU Type Quad-core Intel Core i7

4 cores

CPU Speed: 3.40GHz

L2 Cache 256K

L3 CPU Cache 8MB

Boot Rom Version: 1M121.88Z.004E. B00.1802022050

By looking at these codes, it points to bad memory for the most part. I've tried replacing to original RAM and spinning drive but no cure. Some people have had luck baking the logic board. Rumor has it there was a time when Apple had removed an ingredient from their solder and this might be the culprit since this is an erratic behavior and unrepairable to this day. I've already had a dialog with Apple over a chat session and they can't figure it out and can't offer any solution other than a certified repair center. I know a lot about this iMac so I would like to repair myself. It already paid for itself so I do not intend spending money to get no results. If I can salvage this iMac, I will. I've searched endless forums and have tried all the prescribed remedies suggested so please before you start blasting try this or that (see below), you're wasting time. I would appreciate only absolute solutions to this problem if you have one.

If your fix DOES NOT have anything to do with these solutions listed, I'm all ears:

Resetting or running diagnostic, or safe mode by pressing keystrokes during bootup (Yawn)
Replacing logic board
Replacing graphics card
Replacing drives
Replacing RAM
Thermal Sensors
Cleaning
Reinstalling O/S
Booting from external drive
Striking the iMac
Staring at it and hoping it will boot normal

Thank you for your time and I hope we can collaborate on a solution together.

iMac, OS X 10.11

Posted on May 24, 2020 10:11 AM

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Answer 1

HWTech

Level 9

69,302 points

May 24, 2020 12:52 PM in response to videocraftpro

videocraftpro wrote:

I would appreciate only absolute solutions to this problem if you have one.

If your fix DOES NOT have anything to do with these solutions listed, I'm all ears:

FYI, this is a bit contradictory. Besides no one can give you an absolute solution. It is impossible unless someone gets extremely lucky with their guess.

Assuming you cleaned the memory slots and the contacts on the RAM (you did not specify what you actually cleaned), then try using just a single stick of RAM and testing (again you did not specify this explicitly). Test the single stick in each slot as well. If it fails on each one, then try another stick of RAM. See if any of the memory will work when installed by itself. You need to determine if any of the memory will work and if all the slots behave the same way. Maybe the issue only occurs when multiple modules are installed. Doing this with the original memory is best, but it is Ok to try the 8GB modules you've been using for years as well. Mixing the original memory and the third party memory is not recommended during testing since they may be incompatible with each other.

The next thing would be to test the memory in another Mac if you have one which uses the same spec memory.

Try plugging the AC cord directly into the electrical outlet on the wall to bypass any surge strip/UPS. Also try plugging the computer into another electrical circuit (that is one which uses a different circuit breaker or fuse) and a circuit which isn't shared with a household appliance or laser printer. Make sure the AC cord fits snugly into the back of the iMac. Maybe even try another AC cord.

Otherwise you most likely have a power supply issue or a Logic Board issue. Personally I wouldn't bake the Logic Board as it would at most be a temporary "fix" and it risks damaging the other components on the Logic Board. Carefully check the power supply and Logic Board for any leaking or bulging electrolytic capacitors. The power supply can retain a dangerous charge in its capacitors for an hour (possibly more).

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Answer 2

May 25, 2020 6:02 PM in response to videocraftpro

Ok great news. I have officially fixed and upgraded my Mid 2011 iMac (mac id 12.2) to Catalina and it is working fine. Final steps to resolve were installing the original mac os 10.7 and installing a Catalina Patch from dosdude1 http://dosdude1.com/catalina/

Conclusion: There really wasn't a major issue but maybe a corrupted MAC OS. The error codes may have been from a faulty thermal sensor and may have contributed to the random crashing or from a corrupt MAC OS (High Sierra).

Thanks for your time. Feel free to reach out to me with any questions.

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Answer 3

May 25, 2020 10:50 AM in response to HWTech

FYI, this is a bit contradictory. Besides no one can give you an absolute solution. It is impossible unless someone gets extremely lucky with their guess.

See that's what I'm talking about. Someone who thinks outside the box. Thanks for your reply and offering your suggestions. Fortunately, I've tried all that. Since yesterday after my cry for help, I spent the day poking around. I did make progress and it was simple stupid (telling that to myself) fix. Sometimes when you try to fix a problem that you already fixed, you end up creating more and overlook the simple explanation. As of yesterday before I began troubleshooting I've noticed the MAC will boot to a "no drive/mac os" symbol. Even when I cloned a drive from a newer mac os. I tried "Start up from macOS Recovery" but didn't work. Crashed to a blue screen. Backing up a step, I had an SSD drive installed. I formatted it Mac OS Extended (Journaled) from another newer MAC. That was all. No OS installed yet. Unlike before when it did, it would boot to the apple logo and crash leading me to believe there was a problem elsewhere. So I decided to ignore past history and do a fresh install to see how it goes. I had to locate an original Mac OS install USB. Borrowed from a friend and started the installation. Note: You can't just install the latest MAC OS. In my research, you need to build up to the version it is compatible with. In this case, I started with 10.7. Installation went and currently building my way to El Capitan then up to High Sierra. I doubt I'll be able to install Catalina. If that is the case, this iMac will go up for sale since I will not be able to keep up with the latest editing software I need for work. Unless I find a hack.....anyone? I know it's being done on the old 2009 Mac Towers.

Turns out when I started the installation, my SSD was not coming up in the destination. In disk utility, from the boot up disk, I had to create a partition first. Ain't that some old school stuff. Once I did that I was able to Install. Come to think of it, I probably could have used the "Start up from macOS Recovery" since the blue screen crash was telling me there was no partition. Once the first installation was done and no crash to report, I disconnected the thermal sensor to the SSD and bypass that connector. Later I will replace to see if I can mimic the problem in the past. If it happens, I know it would be a bad thermal sensor and that my friend would be the culprit to my issue or I could have just had a corrupted MAC OS.

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iMac 27 inch Core i7 (Mid 2011) Won't boot

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