(1) Check the board for any Physical or liquid damage. (I have seen similar damage due to a part getting knocked off the board. (2) Check the screens flex cables for any damage. (3) Attempt disconnecting the fingerprint scanner. (4) Attempt Changing the Battery. (5) Attempt changing the screen. (6) Attempt putting your device in DFU mode and connect it to iTunes.(you should attempt to back up the phone before this step) (7) Note: These are the steps I use to diagnose any boot looping iPhone. #

I am not sure what you are asking, but if you are wondering what part you should replace should be easy, use an amp reader to see if the motherboard is pulling any power from the charge port if it's not then its a port replacement if it is then its a battery replacement.