stock.v33, does it work sufficiently to show any codes? As far as how to get it to show codes should the car be working sufficiently for it to do so, I don't have first hand knowledge as I haven't as of yet had to have my G37 blink codes off to me, but here's what I found via a quick internet search:
https://www.infinitihelp.com/diy/com...des_read_2.php

But to re-echo what's been posted earlier in this thread, if you have water down there, the issue is almost surely the sunroof drain. There's a lot of videos on youtube on how to address this issue, but here's a starting point as posted above.
https://www.myg37.com/forums/body-in...ml#post4268890