[jack10685]

So, I have been having an issue with my n54 535i (figured here would be the best place to post) in which everything works fine in accessory mode, but when you turn the car on, everything starts shutting down (codes below), and the dme says its getting 17 volts or whatever. The shop I took it to told me that the alternator is fine, and that the issue appears to be somewhere between the voltage regulator inside the dme and the rest of the system (idek that this car has one inside the dme, I only knew about the one on the alternator). First started happening with an oem bmw battery, then I bought an autozone battery (that said it was a direct replacement), that one died completely and I warrantied it for another autozone battery (which is now also dead, unsure if it can be recharged or not). So far I have replaced the DME+EWS as well as removed my jb4 unit, to no avail. I have ordered a new voltage regulator for the alternator just in case that is the issue, but I am not sure if that is. Does anyone know what it might be?

Codes:
2AAD Fuel pump, emergency off
2E83 Electrical cooling pump, low-power mode
2E98 generator, communication
2F9A outside temperature sensor, communication
CDA1 no description found
CD95 no description found
2DEB power management, vehicle wiring system control
2E82 electrical cooling pump: switch off
2DE4 fuel fill level sensor, right: signal
2DE5 fuel fill level sensor, left: signal
29CD Misfirings, cylinder 1 (most likely unrelated)
00F1 no description found
2304 no description found

Symptoms:
Car seems to be fine when in accessory mode with engine off
all the vehicle's systems seem to shut off when the engine turns on
battery dies overnight, even after full charge

what I have done so far:
replaced battery
replaced dme+ews
removed jb4

waiting on/to be done:
replace alternator voltage regulator

any ideas? Sound like the correct course of action?