BMW X6 ECU No-Start: Ignition Switch Mystery

I had a similar issue with my 2012 BMW X5 35i last month. The ECU error with no voltage supply turned out to be a faulty wiring harness connection near the ignition module. The symptoms were identical, car wouldn't start, and the diagnostic showed power supply problems. My trusted mechanic found corroded pins in the main connector block that links the ignition switch to the ECU. It wasn't too serious, but definitely needed immediate attention. The fix involved cleaning the connector pins and replacing a section of the wiring harness that had moisture damage. Based on your symptoms, I'd suggest checking the wiring connections first before replacing the ignition switch. Sometimes it's just a loose or corroded connection rather than a component failure. Get someone to check the voltage at different points to trace where the power drop is happening.

Thanks for sharing your experience, that's super helpful! I'm really interested in knowing how much you ended up paying for the wiring harness repair? Also, has everything been working smoothly since then? I'm hoping my issue is similar to yours because it sounds less complicated than a full ignition switch replacement. Just trying to figure out if I should budget for something major or if it might be a simpler fix like yours.

Hey again! Just wanted to follow up, after seeing my mechanic, turns out it was indeed similar to what I experienced before. They found the Terminal 15 ignition positive was interrupted, basically a connection issue that was causing all those headaches with starting the car. The repair was pretty straightforward and cost me 95 € to fix the faulty cable connection. Since getting it fixed, my X5 has been running perfectly, no more starting issues or ECU errors. It's such a relief when these things turn out to be simpler fixes rather than major repairs! You're right in thinking it might not be something super complicated. Honestly, if your symptoms are anything like what I dealt with, you might be looking at a similar solution. Just make sure whoever looks at it checks those connections thoroughly. Sometimes these electrical gremlins can be tricky to diagnose, but once you find the actual problem, the fix isn't usually too bad. Let me know how it goes with yours!

Just wanted to update everyone, got my car fixed today and it was such a relief! After all the worrying about major repairs, it turned out to be pretty straightforward. My mechanic spotted the issue right away, a damaged wire connection near the ignition module. The whole thing cost me about 120 bucks, way less than what I was preparing for. The best part? The car fired up instantly after the repair. Had a nice chat with the mechanic who explained everything clearly (much better than my last experience). He even showed me what caused the problem, some moisture had gotten in and corroded the connection over time. Really glad I asked here first instead of jumping straight to replacing the ignition switch. Thanks again for the advice, definitely saved me from an unnecessary expensive repair. Car's running smoothly now, and I've learned a bit more about these pesky electrical issues!