A1502 820-4924-A Won't Mount Boot Partition

[MexicoTV]

Hello all,

Am trying to repair this formerly damaged macbook pro. The original board was so bad that I decided to replace it with one from a cracked screen MBP. This new board seems all fine but boots into a folder icon. The mac passes the hardware test with no isssues. When booting into recovery the SSD shows up along with one partition in gray that will not mount. Any ideas what this is about? Below is a picture.

 

[dukefawks]

SSD has APFS file system and the replacement board has not had the EFI update for APFS yet. Install Mojave on another SSD and it will update, then put back the original SSD.

 

[MexicoTV]

Thank you. Does it have to be mojave specifically? How does the update work, does it happen automatically when mojave is installed?

 

[2informaticos]

Try High Sierra, if you have it.
Remember, MUST be installed on the internal SSD.
In the process, BIOS is automatically updated.