BMW 5 Series Electronics Nightmare: FlexRay Bus Failures

Hi there! I've got some experience working on BMWs, not an expert but I've dealt with similar issues with my 2004 BMW 3 Series. Had almost identical symptoms on my car, unusual electrical failures, stereo cutting out, and dashboard lighting up like a Christmas tree. Turned out it was just a loose connection in the main wiring harness. My mechanic found it during diagnostics and fixed the cable connection. Cost me around 95 Euro, which wasn't too bad considering I was worried it might be something major. Before suggesting anything specific though, could you share: Current mileage on your 5 Series? Did these issues start suddenly or gradually? Are the problems constant or do they come and go? By the way, have you checked if there's any correlation with wet weather? This could help narrow down if it's a moisture-related connection issue.

Thanks for your detailed response! I'm at 85674 KM and just noticed these issues last week. They seem to come and go out of nowhere, which is super frustrating. Sometimes everything works perfectly fine for a few hours, then suddenly all sorts of warnings pop up. Interesting point about the wiring harness, that's actually a relief to hear it might be something relatively simple. The issues don't seem to be related to weather, they happen even on completely dry days. I'll definitely mention the wiring harness possibility to my mechanic when I take it in. Did your cable connection fix solve the problem completely, or did you have any lingering issues afterward?

Hey again! Thanks for asking about the follow-up, and yes, I can totally relate to that unusual nature of the problems you're describing. After my mechanic fixed that cable connection in my BMW 3 Series, everything worked perfectly for about a month, but then I started noticing some minor glitches again. Not as bad as before, but still annoying. Turned out there was actually a second issue, a corroded ground connection near the battery. Once that was cleaned up and properly secured, all the electrical gremlins finally disappeared for good. I've had zero problems for the past 8 months now. Since your mileage is pretty similar to what mine was when I had these issues, I'd definitely suggest having your mechanic check all the ground points too, not just the main wiring harness. These BMWs from that era seem to be a bit sensitive when it comes to ground connections. The fact that it's not weather-related in your case actually makes me more confident it's probably a similar issue to what I had. The unusual nature of the problems is such a typical sign of a bad connection somewhere in the system. Quick tip from my experience, while you're waiting to get it to the mechanic, try gently wiggling some of the main wire bundles when the problems occur. If the symptoms change when you do this, it can help point your mechanic in the right direction. Just be careful not to disconnect anything!

Thanks for such thorough advice! You've really helped ease my mind about this. The tip about checking the ground connections is particularly helpful, I hadn't even considered that could be causing these issues. I'll definitely get my mechanic to look at both the wiring harness and ground points. I tried your suggestion about wiggling the wire bundles when my stereo cut out yesterday, and interestingly, the problems did seem to change when I moved some wires behind the glove compartment. Looks like you might be onto something with the connection theory! I'm feeling much more optimistic now that this won't be some massive repair bill. I'll make sure to take detailed notes of when and how the problems occur before I take it to the shop. Really appreciate you sharing your experience, it's given me a much better idea of what to expect and what to ask the mechanic to check. I'll update you once I get it sorted!