BMW Z4 ECU Failure? Strange System Issues & Shutdowns

Hey! I had very similar issues with my 2016 BMW M2 a while back (some experience with car maintenance here). The symptoms you're describing sound exactly like what I went through, sluggish start-up, power loss, and unusual electrical gremlins. My mechanic diagnosed it as a faulty main relay, which was causing inconsistent power supply to the ECU. Got it replaced and everything went back to normal. The whole thing, including diagnostic and parts, cost me around 120 Euro. The symptoms can be tricky though, as they might point to different issues depending on your specific model and conditions. What's your mileage? And have you noticed if these issues happen more during hot or cold weather? This could help narrow things down. Just a quick tip: if you're experiencing these issues, try to avoid driving the car too much until it's fixed, as unstable power supply to the ECU could potentially cause more problems.

Last time I had my service was about 2 months ago at 22587 KM, and these issues started showing up recently. Thanks for sharing your experience! It's really helpful to know about the main relay, that's definitely something I'll have checked out. The problems seem to happen regardless of the weather, which made me think it was something more systemic. I'll get it to a mechanic soon to have it properly diagnosed. Better safe than sorry with these electrical issues!

Hey again! Glad I could help point you in the right direction. After reading about your mileage and the timing of these issues, it really does sound similar to what I experienced. You know, it's interesting you mention it happens regardless of weather, mine was the same way, which is actually what helped my mechanic rule out some temperature-sensitive components. Just thought I'd add, after I got my main relay replaced, I learned these kinds of electrical gremlins can sometimes be related to the battery health too. When my mechanic was diagnosing my M2, he actually tested the battery as well. Turned out it was fine in my case, but apparently, a weak battery can cause similar symptoms because it affects how the electrical systems power up. Since you had service just 2 months ago, did they mention anything about the battery health during that check? If not, might be worth having them look at that too while they're checking the relay. These BMWs can be pretty sensitive to electrical issues, and sometimes one problem can mask another. Keep us posted on what you find out! Always good to know what these symptoms end up being, helps all of us learn more about these cars.

Thanks everyone, especially for the follow-up about the battery! Actually, they didn't specifically mention anything about the battery during my last service. You've given me a really solid starting point with both the main relay and battery check. Makes total sense about one electrical issue potentially hiding another, these modern BMWs are pretty complex machines after all! I've already called my mechanic and booked it in for next week. Asked them specifically to check both the relay and battery, along with a full electrical diagnostic. Will definitely keep you all updated once I get to the bottom of this. Really appreciate all the help and detailed advice, it's so much better walking into the mechanic with some knowledge rather than being completely in the dark!