BMW M3 Starting Issues: Dead Battery or System Fault?

Hey there! I have some experience working on cars, and this reminds me of an issue I had with my 2020 BMW M4. After having the transmission serviced, I experienced similar symptoms, weak lights and starting problems. Turned out the mechanic had accidentally damaged a crucial wiring connection during the previous repair. Since it was a consequential error from their work, they fixed it at no cost. The issue was resolved by rewiring and properly securing the connections to the starting system. To help you better, could you share: When did these symptoms first appear? Did this happen after any recent maintenance work? Are there any other warning lights on the dash? Does the engine crank at all? Let me know these details and I'll try to point you in the right direction!

Thanks for the detailed response! The symptoms appeared right after my latest service about a week ago. The engine cranks weakly and I've noticed the battery warning light flashing occasionally. I've put 15362 KM on my M3 so far and it's been running great until now. Interesting that you mentioned the wiring issue, I'll definitely have them check the connections, especially since this started post-service. Really appreciate the insights about your M4 experience, it gives me a good starting point to discuss with my mechanic.

Hey again! Yeah, this definitely sounds very similar to what I experienced with my M4. Given that it started right after your service and you're seeing that battery warning light, I'm even more convinced it's related to the recent work they did. In my case, during the transmission service, they had to remove some components to access certain areas, and in the process, they nicked one of the main power supply cables. It wasn't immediately obvious, but it caused those exact same symptoms, weak cranking and flickering lights. The battery warning light was kind of the smoking gun. Since you've only got 15K on the clock, and this started right after service, I'd strongly recommend taking it back to them. They should definitely check all the wiring connections they touched during the service. These M cars have pretty complex electrical systems, and it's surprisingly easy to disturb something during routine maintenance. In my situation, once they found and fixed the damaged wiring, the car was back to normal immediately. Make sure to mention that the issues started right after their service, they should be willing to at least check it out without charging you. Keep me posted on what they find!

Thanks so much for the follow-up! Your experience is really helpful, especially since our situations seem so similar. I've already called the service center and they agreed to take a look tomorrow morning, particularly focusing on the wiring connections since I mentioned the timing with the recent service. They seemed pretty concerned when I brought up the battery warning light and weak cranking issues. I actually feel a lot better about the situation now. Initially, I was worried it might be something major with the electrical system or even the battery itself, but hearing about your M4's wiring issue makes me think this could be a straightforward fix. I'll definitely update the thread once they've checked it out. Really appreciate you taking the time to share your experience, it's given me a much clearer direction to pursue with the mechanics!