OK i just pulled C43 BM US, I believe it was radio module in trunk, i checked 7.5 Amp fuse and it was good for continuity, i looked @ radio, this was not the black module in the same location, it was silver, the plugs did not look good, looked kind of correded. I sprayed with electrical contact cleaner and still nothing. Just from my expiernce with this stuff this unit may have been underwater. the car i bought from insurance co and they whored it up but good. Swapped out a bunch of stuff and made a real mess of IHKA, mirrors, tail lights, etc. They swapped out all the good stuff as it had only 61k miles on it. No disclosure on flood and i would say it was not a flood car, way too clean, but that is not saying they could not have swapped the radio module out fo a flood vehicle......

If i take my radio our of my 540 that is sitting right next to it will that screw up the coding in my 540? Will i have to code it to the M5 for it to work?

I have read a frew places that there are better radio modules out there OEM, C53 i believe had sirus capabilities, the next one has traffic controll capabilities. I do not car about traffic stuff as not much congestion up here in the frozen tundra.