BMW i8 ECU Failures: Hybrid System Warning Signs

I experienced similar symptoms with my 2011 BMW i3 hybrid last year. Initially, the mechanics suspected the ECU, but after thorough diagnostics, they found it was actually a defective main relay causing those issues. The symptoms matched yours perfectly, delayed starts, power loss, and unusual system shutdowns. The main relay controls the power distribution to various electronic components, including the ECU. When it starts failing, it can mimic ECU problems. In my case, the repair involved replacing the main relay and recalibrating the system. It wasn't a major repair in terms of complexity, but it was crucial to get it fixed quickly to prevent potential damage to other electronic components. Before you spend money on ECU repairs, have them check the main relay. Also, get the battery connections inspected, corroded terminals can cause similar symptoms. A reputable BMW specialist should be able to diagnose this accurately. Hope this helps with your decision.

Hey Steve! Thanks a lot for sharing your experience with the main relay issue. That's actually super helpful and could save me from an unnecessary ECU replacement. If you don't mind me asking, what did the repair end up costing you? And have you noticed any other electrical quirks since getting it fixed? Really appreciate the tip about checking the battery connections too. Think I'll get those looked at first.

Happy to give you an update! After seeing the mechanic, it turned out you were spot on, it was indeed the main relay causing all that trouble, just like with your i8. Got it fixed for 120 € and I'm telling you, it was money well spent! The best part? All those annoying problems completely disappeared. The car starts like a dream now, no more power issues, and those unusual system shutdowns are history. The ECU was actually fine, just needed that relay sorted out. Haven't had a single electrical problem since the repair, which was about 8 months ago now. I was actually pretty relieved it wasn't the ECU, as that would've been a much pricier fix. Sometimes the simplest solution is the right one, right? Just make sure you get a proper diagnosis before letting anyone touch your ECU. Hope this helps with your decision-making!

Hey Steve! Just wanted to give you a quick update on my i8 situation. You were absolutely right about getting a proper diagnosis first! Took it to a specialist mechanic yesterday. Turns out it was actually a combination of a faulty main relay and some corroded battery terminals, exactly what you mentioned! The repair wasn't too bad on the wallet either. Paid about 150 € for the relay replacement and terminal cleaning. The mechanic was really thorough and even showed me what was wrong. Can't believe how much better the car runs now! No more startup issues or unusual shutdowns. Really grateful for your advice, saved me from an expensive and unnecessary ECU replacement. The car's running like new again. Sometimes the best advice comes from fellow car owners who've been there before. Thanks again for all your help!