backstory: so i bought this g37 a few months ago and while driving it home the front differential blew up which i found out later was due to not having any fluid. i pulled the engine and transmission and replaced the diff, drove great for a few weeks after engine was reinstalled but one day while i was driving (dry outside, no rain prior to this) a bunch of lights popped up on the dash (awd, tc, abs, brake, tpms, no key, and master caution, only abs light was on prior to this) i then stopped and tried to turn off the engine to see if the dash lights would go away but the ignition button wouldn't respond at all, i then used my laptop to individually turn off spark to 3 cylinders to get the engine to die using nisscan NDS 3 software, after disconnecting and reconnecting the battery to get the ignition to turn off i attempted to start the car again but the ignition went to "accessory" then to "on" but the ignition would not turn back off after that and the car would not recognize my key even with it in its slot, i've had to disconnect the battery since then to get the ignition to turn off, i scanned the codes and i had u1000 codes (from tcm and av unit. the abs, ipdm, and hvac modules failed to wake up), u1001, p1721, u0415, b2557, b2601, b2607, b2612, c1729, p0500, p0555, p0113, p0037, p0057

diagnosis done so far: i have replaced the ipdm, and abs module with used units off ebay which neither changed anything and i ordered a AC amp module that's not been delivered yet, i have also measured the resistance of the CAN-H and CAN-L network at mutiple different points with mutiple different module configurations
messurements taken:

• obd2 port: 66ohm
• bcm wiring harness: 66ohm
• ipdm wiring harness: 29ohm
• ac amp & unified meter wiring harness: 57ohm
• av control unit wiring harness: 57.5ohmp
• awd control unit wiring harness: 59.9ohm
• abs wiring harness: 112ohm
• actual abs module pins: 34.3ohm
• abs wiring harness, module disconnected: 69.8ohm
• ipdm wiring harness, abs and ipdm disconnected: 32.9ohm
• ipdm wiring harness, ipdm harness connected abs disconnected: 120.2ohm
• obd2 port measurements with ipdm disconnected and abs disconnected: 66.2ohm
• obd2 port measurement with abs connected, ipdm disconnected: 65.9 ohm
• obd2 port measurement with ipdm and abs connected: 65.9ohms
• obd2 port, ac amp disconnected: 65.9ohm
• obd2 port, bcm disconnected: 65.9ohm
• obd2 port, av unit disconnected: 50.1 ohm
• av unit wiring harness: O.L
• ac amp module pins: 19.20 ohm
• ac amp wiring harness: 122.2 ohm

extra info: when ignition is in the "on" position the radiator fans stay on, highlights are always on(unable to turn off) and i am unable to use high beams and i'm sure there's many other issues i just can't think of at the moment. i will attach photos of all codes i got using a obdlink device and the nisscan NDS III software and of the vehicles on board CAN bus diagnostics screen, ill also attach a photo of my dashboard when the issues first occurred before i turned the car off.


im not very good with wiring or electrical work so i would greatly appreciate if anyone could give me any advice for what may be wrong based off of the measurements i’ve taken so far or any recommendations for what measurements i should take next, or just any advice in general. i'm very desperate at this point, i’ve been trying to figure out the issue for months and don't want to have to pull the entire interior apart to replace the wiring harness so i want to rule everything else out first, any advice whatsoever would be greatly appreciated, thank you in advance everyone!