Flood-damaged Explorer: Starts on old BCM but no OBD communication / No screens or accessories. Need help!

[majsterkov]

Hi everyone,
I’m struggling with a flood-damaged Explorer and could really use some expert advice. Here is the exact breakdown of what's happening:
What works (on the old, dried-out BCM):

• The car starts and runs (power steering works too).
• The car detects the keyless fob and starts when the key is inside/nearby.
• The rear power windows work perfectly.
• The onboard power inverter (110V/230V) is working.

What does NOT work:

• Zero OBD Communication: This is the biggest hurdle. No software (including FORScan) can "see" or detect the car, whether the old or new BCM is plugged in. There is power/voltage at the OBD port, but absolutely no data communication.
• The remote keyless entry (buttons on the key fob) does not respond at all.
• The screens (infotainment/APIM and instrument cluster) are completely dead.
• The steering wheel buttons/controls do not work.
• Hazard lights do not respond.
• The new BCM: If I plug in the new (identical) BCM, nothing works at all, likely because I cannot program it due to the lack of OBD communication.

What I've done so far: I have replaced several other damaged modules and thoroughly cleaned all the wiring plugs and connectors. Surprisingly, there wasn't much corrosion or green residue on them; they look clean.
Since the engine starts, the PCM and key transponder system are communicating on some level, but the lack of OBD access and dead screens points to a major network issue.
Could a single shorted module (like the Gateway Module/GWM, APIM, or a door module) be pulling down the entire CAN bus network and blocking OBD communication? Where should I start probing with a multimeter to diagnose this?
Thanks in advance for any schematics, pinouts, or advice!