BMW Check Engine + Random Shutdowns: ECU or Something Else?

Hey there! Had very similar issues with my 2000 BMW 5 Series last summer. Starting problems, power loss, and unusual shutdowns pointed to the main relay in my case, not the ECU. When I brought it to the garage, they initially thought it was the ECU too, but after testing, turned out the main relay was failing to provide consistent power to the electrical systems. It's a critical component that controls power distribution to various systems including the ECU. The fix wasn't too complex, just needed the main relay replaced. It's actually a common issue in these older BMWs. The symptoms cleared up completely after replacement, and the car's been running great since then. If I were you, I'd get a second opinion and specifically ask them to check the main relay before jumping to an ECU replacement, which is much more complex. The relay test is pretty straightforward, and any decent mechanic can do it quickly. Best of luck!

Hey, thanks so much for sharing your experience! I'm actually in the same boat with the main relay issue. Would you mind telling me how much you ended up paying for the fix? Also curious if you've had any other electrical problems since getting it sorted? Just trying to figure out if I should expect any other surprises down the road with my car.

Hey again! Happy to update you! After that first reply, I actually took my car to get the ECU checked too, just to be thorough. Turned out both issues needed attention, the main relay and the ECU. The main relay replacement was pretty reasonable at 120€, and fixing the ECU sorted out all those annoying electrical gremlins. Since getting both fixed, my BMW's been running like a dream, no more starting problems, power issues, or unusual shutdowns. It's been about 8 months now, and I haven't had a single electrical problem. Really feels like the car got a new lease on life! Honestly, getting both issues sorted was totally worth it. The car's so much more reliable now, and I don't have that constant worry about whether it'll start or suddenly shut down. If your symptoms are similar to what mine were, fixing the main relay should make a big difference, but might be worth checking the ECU too while you're at it. Let me know how it goes with your repairs!

Thanks for all that detailed info! Just got back from my mechanic actually. You won't believe it, they found both the main relay and ECU issues, just like you had! Got them both fixed and it was definitely more expensive than I expected, but so worth it. The car's running amazingly now. No more of those scary unusual shutdowns or struggling to start. It's such a relief not having to worry every time I turn the key. The mechanic also did a thorough check of the electrical system and said everything else looks solid, so hopefully no more surprises coming my way. Really glad I asked here before going ahead with the repairs. Your experience helped me make a more informed decision, and I probably saved some time by getting both issues checked right away instead of fixing them one at a time. Thanks again for all your help!