CAN Communication and Immobilizer Failure?

I'm working on the car listed above Sport 1.5T that I purchased from auction as a flood vehicle. I've replaced several major electrical components including the BCM, fuse boxes, spark plugs, and CAN Gateway Module. The ECM was sealed well, so I did not replace it.

Before replacing the CAN Gateway, the immobilizer system and BCM were functioning normally — I was able to scan all systems, and the immobilizer light was off.

After installing a different CAN Gateway module, the U0056-00 code disappeared, but now I’m getting immobilizer issues — specifically a red immobilizer light flashing on the cluster, and the car cranks but will not start.

Currently, the car has multiple U-codes across key modules:

ECM:
U1029 – Communication problem on CAN

U0151 – Lost Communication with BCM

TCM:
U0155 – Lost Comm with Instrument Cluster

U0100 – Lost Comm with ECM

U0038 – CAN Bus A Off

U0146 – Lost Comm with GCM

U0129 – Lost Comm with ABS

ABS:
U0126-00 – Lost Comm with Steering Angle Sensor

U0123-00 – Lost Comm with Yaw Rate Sensor

U0402-68 – Invalid Data from TCM

U0151-00 – Lost Comm with BCM

U0129-00 – Lost Comm with ABS

ESP:
U0151-00 – Lost Comm with BCM

U0416-68 – Invalid Data from VSA/ABS

U3000-49 – Internal Module Error

Instrument Cluster (GCM):
U0151-00 – Lost Comm with BCM

IDAS (ADAS Module):
U0420-68, U0418-68, U0402-68, U0416-68 – Invalid data from multiple sources

I’ve confirmed:

Fuel pump is working

Spark plugs were changed

Injectors have power, but no pulsing

CAN voltages at the OBD2 port are both 2.49V (normal idle voltage)

CAN High and Low resistance is 120Ω, which suggests only one terminating resistor is active

I also verified:

Injectors and ignition coils show voltage but behave like both wires are grounded (no pulsing from ECM)

BCM was programmed and functional before the CAN Gateway swap

All modules are now throwing U-codes that suggest a communication breakdown, possibly blocking immobilizer sync

My main concern now is that after replacing the CAN Gateway module, the immobilizer light came on and now the scanner shows an immobilizer system fault, even though that wasn’t the case before. This raises the question of whether:

The new CAN Gateway is incompatible

There's a VIN mismatch or network map conflict

Or possibly ECM-to-BCM-to-GCM handshake is failing, blocking fuel/spark delivery

If you have experience with the 2018+ Accord platform and immobilizer logic (especially in post-flood conditions), I’d appreciate any insights into:

Whether the new CAN Gateway may need to be reprogrammed or is VIN-locked

Whether one mismatched module could explain the communication collapse across the whole bus

What your recommended next diagnostic steps would be

ALSOOOO please if anyone wher I can get a complete can bus wiring diagram please let me know


*** the car still crank and no start and all the the F can moduals have issues ****