Released June 2012, Model A1278. Intel processor with Turbo Boost, Up to 512 MB DDR5 Video RAM

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Prohibit sign at start-up. No command works. Happens 4 / 5 of the time

Hi guys,

(English isn't my first language so sorry for any grammatical error)

Three days ago my Macbook Pro freezed and when I start it up again I got a grey screen with a prohibit sign on it. I turn it off and the next morning when I turned it on It seems like nothing happen. Then 20 min running-in, it freezed again and got the same problem..

I did my research and found out a lot of things so at this point i've tried almost everything (apart from reinstalling os Sierra). When I reboot the option+command+R does not work (just get a grey screen that last forever). I've reset the PRAM several time it doesn't change anything. Recovery mode doesn't work either. When I hold down the option key It shows my SSD but when I select it, same sh*** happens :-(

Every now and then (about 1 time on 5) I'm able to access my desktop and back-up important stuff. Today I even got the chance to work "all day long" on it with Illustrator and stuff so I thought I'd be gone but nope about 30 min ago it freezed again and here I am on another computer.

I change my old HDD to a new Crucial SSD 1TB about 6 months ago plus the RAM and the ventilator (all by myself). Also took off the Superdrive and put the old HDD there (which I formatted to a simple internal back-up drive)

I'm about to erase and reinstall Sierra on it (the SSD) but as the repair mode doesn't work I don't really know how to do so. I do have several Mac at my disposition but yeah.. what am I supposed to do ?

  • Do you think my "brand new" SSD could be broken ?
  • Any cables (SATA for ex) could be malfunctioning ?
  • Is the heat of something inside could lead to the problem ? (I don't think so as I was able to work today on "big" apps (that obviously increase the temperature))

Anyway, any type help is welcome !

Really appreciated any feedback.

Cheers !

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Well you likely have two different issues here ;-{

The first is a common issue in this series which is the HD SATA cable degrades from rubbing on the upper case. I would start off by replacing the cable and placing some tape just under it were it rubs the case. HEre's the IFIXIT guide you'll need to follow: MacBook Pro 13" Unibody Mid 2012 Hard Drive Cable Replacement and the part you'll need: MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable - Apple P/N 923-0104. You'll want to wait until you get the cable replaced before attempting a backup and once you've backed up you'll want to redo the drive, format it and install a fresh copy of OS in it and then recover your stuff back on.

The second issue you maybe facing is the optical drive carrier. Sadly, Apple didn't do a great job in the logic board circuitry so using SATA III (6.0 Gb/s) drives can encounter corruption issues. Here's a bit more: OWC Data Doubler It makes no difference who's carrier you get its Apples failing. Auto sense drive also don't work well here either as they can't decide which speed to run at. You'll need to make sure the drive you use is a fixed speed drive, one that only runs at SATA II (3.0 Gb/s).

Here's the guide to create an OS installer: How to create a bootable macOS Sierra installer drive

MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable Image


MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable


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Hi Dan,

Thank you for your answer ! Really appreciate it.

I did think about the SATA cable so i'll start with that... ! Then we'll see about the Optical Drive. Hopefully that's not it otherwise I must say I dunno what i'll have to do.. take out my drive and RAM and put it into a new laptop :'-(

Your answer clearly help me out !

Cheers to that !


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