A quick update on the resolution of this issue with my car. My mechanic spent many hours working on the car, including speaking with two very senior BMW technicians, and eventually found the issue in the passenger footwell wiring. He's a bit pissed at himself for not finding the issue quicker, but many of the modules were sending signals that contradicted each other. A very long story short, he ran new wiring and solved the issue. It sounds like nobody ever tries to repair these 2004-2005 elecrical K-CAN issues, with most throwing their hands in the air and replacing modules until nothing is left except for the wiring, and then replacing that as well.

I am so glad I have a reliable, trustworthy and honest mechanic who really knows his stuff!

Thanks for the update.

Where is this indie mechanic located? Southern California?

No, in BC, Canada. Your question has made me realize I need to update my profile!

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I am dying over here with similar issues please be more specific about the cause and the fix

From what I understood, there was faulty wiring in the passenger side foot well. This was causing the modules to malfunction and replacing the wiring solved the issue, but not after my mechanic spent hours trying to figure out why so many modules were reporting faults. Apparently on the earlier model E60's when one module malfunctions it sends inputs to all the other modules causing them to malfunction causing a constant feedback loop. Makes me think of string lights where one bulb going out causing the entire line to stop working. In my case it was the wiring, but if one module fails it could cause all the other modules to send faulty readings. I think they fixed this in the later model E60's so that one faulty module didn't cause haywire readings on all the others.

The testing of the modules is way outside my pay grade but hope that helps.