are you sure you don't have any more codes for us. lol  wow am going to play the lottery with a few of those codes, I think i will hit the play 4  for sure.  first make 100% sure that this vehicle is a 2003 and not an 04, complete different data bus line. the b-codes are for the bcm not been able to read passlock, keys. now you got a bunch of u-codes, communication codes, high voltage on the data line. the serial data line goes from the dlc to the fuse box inside the car, junction connector then spreads to all modules, except the ipc, which comes from the bcm. you also have a low voltage code which could be very well a bad ignition switch, which are defective on this vehicles. you never mentioned which modules showed up on the auto scan, since they are all connected to the same serial bus line, except the ipc like i said cuz it comes out of the bcm.  disconnect the bcm, erase all codes and do an auto scan again of all modules, you should see all of them except bcm and ipc. report back for part2. good luck.

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 pull splice pack sp102. bring each branch back online with jumpers till you get to the branch that brings the buss down. Recently I dealt with a similar situation where a water bottle was driping water under that passenger seat on a connector for the passenger seat presence module which brought the whole buss down freaking the whole truck out