Mac Pro 2013 not booting

Hello everyone.

Hoping someone with some experience can share some insight.

Firstly, this was a free Mac so it’s worth me reviving it despite its age, if I can get the right parts for a good price.

I’ve got a late 2013 trashcan Mac Pro. It’s not booting, and holding the diag led button nets me 11v, 12v and S5 LEDs (the S5 led starts blinking when the power button is pushed)

Additionally, when pushing the power button the outside IO turns on and then seemingly the Mac stops again after 15s or so.

I am gathering that this is a logic board fault, but which board?

Thanks