Gauges, power windows and locks not working, also intermittent service lights on

I have the SUV listed above which I had driven daily with no issues and I drove it 400 miles the day before it presented with the following problems. Codes U0109, U0102, and P1682 no run or start, intermittent dash lights, ABS, traction control, airbag and security light also no power locks or windows. I checked all of the ground and power connections. I also took the fuse boxes and relays apart and cleaned them and checked for corrosion. I replaced the battery, ignition switch and lock cylinder. Still the same problem. I towed it to the closest dealership which was 100 miles away, they had it for a week and then called me and said they couldn't figure it out. I went to they're shop in hopes of asking the mechanic what tests they had done and they said it was a wiring problem and they inspected all the wiring and they didn't know what was wrong. So $400.00 and I had to tow it back home. I replaced the ECM and the BCM with aftermarket replacements preprogrammed to the VIN. Now it will start and run, but it still doesn't have any gauges no power windows or locks and has the same intermittent service lights on. It has no codes which I expected being as the computers were replaced. I was dumbfounded when the dealership said they couldn't fix it! I have only lit driven it because I am afraid it is going to quit running again and I really don't trust it without the gauges working. Any suggestions will be greatly appreciated. Thank you