BMW X7 ECU Issues, Multiple System Failures & Power Loss

Hi there! I had a similar issue with my 2019 BMW X5. Boy, do I feel your pain! I have some experience working on cars, but electrical issues always make me nervous. The symptoms you're describing sound exactly like what I dealt with, sluggish start-up, reduced power, unusual system failures. My trusted mechanic diagnosed it as a faulty main relay. Got it replaced and it fixed everything. The whole thing cost me around 120 Euro, parts and labor included. Before jumping to conclusions about the ECU (which would be way more expensive), I'd suggest getting the relay checked first. It's a much simpler fix. Could you share more details about when these issues started and if you notice any pattern? Like does it happen more when the engine is hot or cold? Also, are you getting any specific error codes? This would help narrow things down. Hope this helps!

Hey, thanks for sharing your experience! I just had my service done last week at 137044 KM, and these issues started popping up right after. The problems seem more frequent when the engine is cold, especially during morning starts. The error codes are mainly pointing to electrical system faults, but they're inconsistent, sometimes showing up, sometimes not. You might be onto something with the relay suggestion. That's definitely a more wallet-friendly fix than replacing the ECU! I'll have my mechanic check that first. It's interesting that your X5 had such similar symptoms. After reading your reply, I'm feeling a bit more optimistic about this whole situation. Quick question, did you notice any warning lights on your dashboard before the relay completely failed?

Hey again! Yes, actually! With my X5, I did notice the battery warning light flickering occasionally before things got worse. Sometimes the check engine light would also come on and off out of nowhere, which was really annoying. Looking at your situation, the timing with the recent service is interesting. My issues also started after routine maintenance, makes me wonder if something got disturbed during the service. When they worked on my car, I remember they had to disconnect the battery, and I think that might have stressed the already weak relay. In my case, the symptoms got progressively worse over about two weeks before I finally took it in. The cold start issues you're experiencing are exactly what I dealt with too. It would take forever for all systems to boot up properly in the morning, but seemed a bit better after the car had been running for a while. The inconsistent error codes you're getting sound really familiar. Mine were all over the place too, which is what initially made my mechanic suspect the relay rather than the ECU. A bad relay can cause all sorts of weird electrical gremlins. Let me know what your mechanic finds. I'm curious if it turns out to be the same issue!

Thanks so much for all this detailed info! It's actually a huge relief to hear that your symptoms were so similar to mine, especially the part about the warning lights and cold starts. The fact that your issues also started after maintenance makes me feel better, I was worried I'd gotten some major damage during the service. You've convinced me about getting the relay checked first. I've already called my mechanic and scheduled an appointment for tomorrow morning. Going to specifically ask them to inspect the relay before jumping into more expensive diagnostics. The way you described the progressive worsening over two weeks matches what I'm experiencing too, so I definitely don't want to wait too long. I'll update this thread once I get it checked out. Really appreciate you taking the time to share your experience, it's saved me a lot of worry about potentially needing a new ECU. When car problems pop up, it's always helpful to hear from someone who's been through the same thing! Thanks again for all your help!