Originally Posted by nick325xit 5spd

I've noticed that with the engine off, even with a charger connected, that my E90 will frequently fail to communicate with a lot of modules.

Is it practical to hook up another running car with a set of really good (2 gauge or better) jumper cables and re-run the tests? The kinds of power supplies that, say, a dealer would have are unlikely to exist in a residential context. No guarantees, but this is a cheap and easy thing to try.