Chosen Solution
Ok, here’s a weird one: Last week I was using my 2011 15” MBP as normal with no issues on battery power. I was checking email when a family emergency presented itself, so I left the MBP on the kitchen counter. Needless to say, when I returned, the MBP had gone into deep sleep as the battery had died. I plugged in my power adapter and waited until the battery was fully charged. Upon restart, I noticed that the computer was EXTREMELY sluggish, to the point of non-usability, so I restarted the MBP. After the chime, I got a dim grey screen with no Apple logo. NVRAM resets and SMC resets did not improve the situation. I removed the Samsung SSD and replaced it with the old hard drive I had removed years ago, and the MBP booted as normal, ruling out other possible hardware issues. I installed the suspect Samsung SSD into another test 13” 2012 MBP, and it exhibited the same issue, although after about 5 minutes I got the blinking folder with question mark symbol. I have also tried placing the SSD in an external USB enclosure, but in this configuration, the SSD is invisible to Finder, Disk Utility and Terminal. Is this SSD toasted? The OS on the suspect Samsung SSD is High Sierra, and the OS on the working 13” MBP is Mojave. Update (01/03/2019) Also, I got no prompts from any of the folowing OS’s stating that the drive could not be read and needed to be initialized or formatted when connected as an external drive in a USB enclosure: Mac OS El Capitan, macOS Mojave, mac OS Sierra, Window 8, Windows 10 (yes, I tried it on 5 different machines). Not even a nudge to indicate that the computer recognized a device hooked up to USB.
I don’t think your drive is dead! Both the 13” & 15” unibody systems have issues with the HD SATA cables. The first generations did not support SATA III (6.0 Gb/s) I/O. The original Apple drives where SATA II (3.0 Gb/s) so they never pushed the limits of the cable. Even some SATA III drives 5200 RPM drives still didn’t push the limits of the cable, but SSD’s do! In addition, the thin foil wires within the cable can breakdown. This is when people over bend the cable trying to crease them instead of making even smooth arcs. So the first thing is to replace the HD SATA cable with the newer version. For the 15” MacBook Pro 15" Unibody (Mid 2012) Hard Drive Cable and for the 13” MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable And yes! These are for the 2012 models and are fully workable in the 2011 models. In addition to the new cable you’ll want to place a strip of electricians tape on the uppercase where the cable crosses over as the rough surface can also wear the cable. On the 15” models you need to make sure the plastic bottom lid mid plane clip near the drive is not broken as the pressure of the bottom case can cut into the cable where it crosses over the optical drive. Once you have replace the cable we now have the second issue: When you upgraded to High Sierra the OS installer updated the drive from HFS+ to APFS and the systems firmware was also updated. On your 13” system which you’ve already upgraded to Mojave it too would have upgraded the SSD to APFS but the 2nd version and as far as I’ve found the system won’t read High Sierra APFS SATA drives. As for fixing things: I would put the drive back into your 15” and using the recovery partition run Disk Utility to see if you can at least get the drive running so you can recovery anything important. Once you’ve done that reformat the drive and re-install the OS. You might want to redo the full drive using an external bootable USB OS installer drive How to create a bootable macOS Sierra installer drive Frankly, I don’t recommend running High Sierra or Mojave on SATA based systems as Apple has not addressed the queuing issues which could have been the root issue in your case.
I have the same problem after a short cut the SSD wont boot, The SSD lights up as an external HD but wont boot in other macs or recovery mode. I think it also has something to do with Mojavo and the security mode. I read somewhere that sometimes Mojavo /macos can activate the disk as unreadable as a security measure when it is not proper ejected without a password etc. Dont have enough inside knowledge in this matter but since my SSD disk wont show up properly after one restart it seems more and more unlikely that it is a cable issue but more and more a Mojavo/Macos security precaution.
