Gigabyte X370 debug error codes. No boot

[Rammster]

Hi. I have a gigabyte auros x370 gaming k5 rev1.0 and everything was working fine then the other day turned it on and got error code 48. I have tried to mess about with ram grabbed a new psu and on one bios I get error code 48 and the other error code 15. I'm struggling to know what to do here.

 

I have also reset cmos tried a new cmos battery. As above I've swapped the psu and still nothing. I don't know if this is cpu/board/ram or gpu related please can anyone help or guide me. 

[GhostRoadieBL]

error code 15 comes from windows registry errors or improper shutdown, 48 is sometimes related to graphics configuration but not listed in my manual as a used code. 
typically I would start this with swap boot drive plugs (swap Sata to another header) to reset the boot drive location, then if you can boot to a USB drive run a windows startup repair scan. If you are stuck pre bios, it's unplug and reseat everything on the board then reset cmos and try to boot.