Chosen Solution
So, the bloody grey screen. no Apple logo! Now I thought it was either the HDD or the infamous cable. Without doing anything, the folder and question mark icon starts flashing after a long pause on the grey screen upon startup, then auto shuts down after awhile. If I remove the HDD, then I get a forbidden icon… again, it auto shuts down after awhile. I created a Mojave USB installer without realizing this 13” MacBook Pro (early 2011) isn’t supported and managed to get it to boot a couple times, after holding on the the button for a loooooooog time. In Disk Utility, it didn’t detect the old HDD, I put in a WD HDD I had lying around, and it showed up! So I was really, really hoping it would be the HDD. Went to get a Lexor SSD and put it in. Managed to get the USB drive to boot up, and got as far as formatting the SSD in preparation for Mojave install. Then I got some kind of error msg (i forgot what, something like install file is corrupted) just when I clicked to install Mojave to the SSD and from then on, even the USB drive has refused to boot. Even if its a faulty hdd cable, the USB installer should still be able to boot right? What gives?! I am really really stumped! Disclaimer; this MBP belongs to my friend; I’m just trying to help fix it. Seems like all I’ve done is make it worse :( So please, revered Gods of iFixit. Help me to fix this!
You have a Trifecta of issues here! Trying to run to new a macOS that Apple does not support nativelyUsing an expired OS installerNeed a new HD SATA cable #1 - You should not try running the wrong OS on your system. There are elements within your system that will encounter issues. Stick with either Sierra or High Sierra. Frankly I only recommend Sierra on these older SATA based MacBook Pro’s. High Sierra introduces APFS which has issues on SATA based systems. #2 - ‘‘‘Apple made a big blunder! And you fell into it!’’’ If you’ve got an old macOS install image, it will probably stop working today. Here’s the updated image files: How to upgrade to macOS SierraHow to upgrade to macOS High Sierra Jump to Step 4 to get to the file link. Create a new OS installer USB Thumb drive following this guide: How to create a bootable macOS Sierra installer driveHow to create a bootable macOS High Sierra installer drive #3 - A very common issue in the Unibody series is the cable chaffing rubbing on the rough aluminum uppercase. In addition, mis-handling of it can also damage it! So the first step is to get the better cable MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable this one is rated for SATA III drives. The next thing is to help protect it by placing a strip of electricians tape on the uppercase where the cable crosses over Your Hard Drive Cable Is A Ticking Time Bomb. The next issue is the bends! Most people crease the cable folding it and rubbing the edge so the cable has a nice crisp edge - Wrong! Wrong! All you’re doing is damaging the thin foil wires inside the sandwich of the cable. What you want is a nice arc! I use a BIC pen ink straw as my form forming the bend around it No sharp bends! So there is your Trifecta! Each needs to be fixed. If you really want to run Mojave on your system you need to first get your system working with Sierra first then look at DosDude1 patcher. While its a fun thing to try, I don’t recommend trying to run a business on it! You’ll need to boost the system RAM to no less than 12 GB.
I can’t really figure how you managed to go through “installing” Mojave on that Mac, it should just show the forbidden access side at boot..did you try a modified installer ? First thing I’d suggest is to forget Mojave for the time being and try a Sierra or High Sierra bootable pen drive. Before installing, open up the terminal in the Utilities screen and run the Set Date command to take back the clock to let’s say 2017 and turn Wifi off, that should prevent the corrupted install file. If you’re planning to put an Ssd you’ll have to change the HD and replace it with that of 2012 model. Avoid formatting the Ssd with APFS, little to gain and potential problems ahead, so stick with Mac Os extended.
