BMW M2 ECU Issues: Warning Signs and Solutions

Hey there! I had a pretty similar issue with my 2015 BMW M4 last year (I'd say I have some experience working on BMWs, as I also owned an M3 before). Those symptoms sound exactly like what I dealt with, super frustrating! Turned out the main relay was defective, causing all those electrical gremlins. Had it diagnosed and fixed at my regular workshop. Total bill came to 120 Euro, parts and labor included. Since then, everything's been running smooth as butter. Before you make a workshop visit, could you share what specific error codes you're getting? Also, does this happen more often when the engine's hot or cold? This info would help determine if you're dealing with the same problem I had.

Thanks for sharing that experience! Mine's got 151367 KM on the clock and had its last service two months back. The errors mostly pop up when the engine's hot, especially after longer drives. Getting P0685 and P0687 codes consistently. Was thinking it might be something more serious like the ECU, but your relay situation has me thinking. That's way better than shelling out for a full ECU replacement! Did you notice any warning lights on the dash before the complete shutdowns? Just trying to compare symptoms before I take it in.

Hey again! Yeah, those error codes you're getting (P0685 and P0687) are exactly what I saw with my M4, they're related to the main relay circuit. And the hot engine correlation? Spot on with what I experienced too. Before my relay completely gave up, I definitely had warning lights popping up on the dash. The battery light would flicker occasionally, and I'd get unusual check engine warnings. The most annoying part was how the car would sometimes hesitate to start back up after being driven for a while, exactly what you're describing. Given your mileage (mine was around 140k when this happened) and those specific codes, I'm even more convinced you're dealing with the same relay issue I had. The fact that it's happening after the engine's warm is another telltale sign. I initially freaked out thinking it was the ECU too, which would've cost a small fortune to replace. Really glad I got it checked out before jumping to conclusions. Just make sure your mechanic tests the relay circuit thoroughly, sometimes they can miss it if they're too quick to blame the ECU. Let me know how it goes when you get it checked out. I'm curious if it turns out to be the same problem!

Thanks so much for the detailed info! You've honestly made me feel a lot better about this whole situation. The symptoms match up perfectly, especially that part about the battery light flickering and the startup issues when hot. I was seriously stressing about potentially dropping a huge amount on an ECU replacement, so hearing about your relay fix is such a relief! I've actually just booked an appointment with my mechanic for tomorrow morning. I'm going to show them your relay experience and make sure they check that first before looking at more expensive options. Definitely won't let them jump straight to ECU conclusions without properly testing the relay circuit. Will update you once I get the diagnosis. Really appreciate you taking the time to share your experience, it's saved me a lot of worry and potentially a lot of money too! I'll let you know if it turns out to be the same relay issue as yours.