i just bought a g37 and had to pull the engine cause the front differential exploded on the drive home and i replaced it and the car drove fine for a couple weeks but i was just driving it and suddenly a bunch of lights popped up on dash (awd, tc, abs, brake, tpms, key) and my high beams stopped working, i stopped and tried to turn the engine off and it wouldn't so i pulled the negative terminal, and when i connected it back the car was off like normal but key light was still on and when i press the ignition it switches to acc and on but won't start and ignition won't turn back off, and as i was typing this dash lights started to flicker and slowly fade away and gauge cluster lights turned off and key showed up and after a few seconds it started flicking and fading so i got out and disconnected the negative terminal again. i attached photos of all the codes that popped up, anyone know what's going on? i’ve tried disconnecting wiring harness cables and reconnecting and it did nothing

 

The lights flickering on the dash and the headlights not coming on lead me to believe it may be your battery or alternator going out. If you were to take out your battery and/or alternator and bring them to to AutoZone, they'll be able to test it for free.