04-04-2018 10:14 AM
I've got a mid 2012 15 inch macbook pro, with 16gb of RAM bought from crucial that has been working fine since then. the 512gb hard drive is the one that came with the laptop.
The other day it wouldn't boot up. I took it to the genius bar and they said it might be to do with the logic board, which would cost around £500 to replace.
I managed to run the hardware test and it came up with the code 4mem/62/40000000 which is apparently a memory problem. I replaced the memory with a different 16gb of crucial matched RAM to no avail.
I've taken the laptop to an independently run apple repair shop, and they've said the RAM is faulty, and the laptop should only take 8gb of RAM (which I know is not true). They also said the hard drive is faulty, but not completely broken, just running slowly and needs to be replaced.
Do you think it's possible that the RAM is fine and it's just the hard drive which needs replacing?
Thanks, sorry this is such a complicated and possibly unanswerable question.
04-05-2018 12:03 AM
The error reported by the diagnostic appears to be either a memory or Logic Boad error. It is not uncommon to have memory related issues with these laptops. Apple uses a plastic locking mechanism to hold the RAM in place and sometimes they don't fully engage or sometimes the "lower" RAM unlocks when inserting the "top" module.
On the memory latches, there are very small triangular protrusions which hold/lock the memory in place. If they have been damaged/worn there may not be enough plastic to lock the memory in place. Installing & removing memory can tend to slice some of this plastic away.
Disconnect the battery & take a non-metalic stick like a toothpick and press on the outer edge of the "lower" module. Be careful not to push on any of the very small components on the module as they can be easily damaged. Then press on the "upper" module to make sure it is latched.
Sometimes pressure on the center of the Bottom Case can push against the memory modules or Logic Board causing the laptop to freeze. Sometimes this is due to a loose memory module, cracked solder joint on the Logic Board or perhaps even a dented Bottom Case.
You may also want to blow some compressed air in the memory slots in case some dust or dirt got in there.
You can also try running Memtest86 for testing the memory. No errors doesn't neccessarily mean everything is good. It just means it hasn't triggered a failure. Running mprime in Torture Test mode using option #3 may also help locate a failure or make it more reproducable. It will stress your CPU as well. If you get errors, then try the tests again with only a single module installed. Try testing each module by itself to see if you can identify which one is bad (hopefully only one is bad).
If neither one appears bad or both modules produce errors, then try testing a single module in the other memory slot in case you have a slot issue. Between these two tools and the Apple Hardware Test hopefully they will make the error reproducable so you know when it is fixed. If your drive is bad, then Memtest 86 and the AHT are your best options.
BTW, Apple only officially supports 8GB (2x4GB) in this laptop, but Crucial and others have discovered in most cases it will work with 16GB (2x8GB). Apple Authorized Repair Centers are supposed to follow Apple's guidelines or risk losing their authorization and access to official parts & diagnostics. Sometimes the techs only know what Apple provides them, but others tend to investigate unofficial options.
To verify your hard drive is Ok, you can check its SMART Attributes using SMARTReporter or DriveDx. Using these apps you can initiate an internal Extended Self Test which will likely take a couple of hours to run. Feel free to post a screenshot of the SMART Attributes if you want me to check them for you.