Answer to "Will a M.2 SSD work in my MacBook Pro?"Near the coloured buttons on the top left of Disk Utility is a drop down menu (View), make sure you've got 'Show all devices' selected. If you have 'Volumes' selected your new SSD will NOT show up as there is, as yet, no volume to show. Once you see it, you can format it and install the OS.
Answer to "Apple diagnostics Ppt004 code"I have this error too after replacing the battery in my 2015 MacBook Pro 15” Retina. The battery is behaving normally and Coconut Battery App gives it a clean bill of health. I suspect too, protectionism by Apple who always seem resistant to any third party being involved in their machines as evidenced by the fact the latest machines cannot change RAM or SSD. I love this machine, but if I need to replace it, it will be with a Linux one. Apple have lost the plot to me, they’re far too arrogant for me.