Liquid Damaged MBP - Battery or MLB?

I have a 13" MBP 2015 that had some minor water damage. The liquid damage sensors on the MLB are all still white but the sensors on the battery board, the I/O board, and the wireless card were red and clearly damaged.

I started easy and cheap and replaced the I/O, airport, and D/C boards... but that doesnt seem to have changed anything. I can't get it to boot at all.

I might try to clean the components next but am looking for advice where to start my next phase of diagnostics?

Do I replace the battery? Should it turn on with the battery disconnected and Magsafe attached? The MagSafe doesnt turn colors or even acknowledge attachment when connected.

Please advise! Thanks!!