BMW 7 Hybrid Start-Stop Failure Causing Random Shutdowns

Had the same problem with my 2014 BMW 5 Series Hybrid last year. The symptoms were identical, start-stop failure, unusual engine shutoffs, and warning lights. Turned out the main hybrid battery was severely degraded and wasn't holding charge properly, which caused the system to malfunction. Took it to a certified shop that specializes in hybrid systems. They ran diagnostics and found the battery cells were unbalanced and several had failed. This isn't a quick fix, they had to replace the entire hybrid battery pack. It was quite serious since driving with a failing hybrid battery can damage other electrical components. Would strongly suggest getting it checked by a hybrid-certified technician. The symptoms you're describing match a failing hybrid battery, but only proper diagnostics can confirm this. Don't wait too long, continuing to drive with these issues could lead to more expensive repairs down the line. Since you have similar mileage to what mine had, it's likely the same issue. These batteries typically start showing problems around the 140,000-160,000 km mark.

Thanks for sharing your experience! Really helpful since I'm dealing with exactly what you described. I had a gut feeling it might be the hybrid battery. Do you remember roughly how much the replacement ended up costing you? Also, have you had any other issues pop up since getting it fixed?

Hey there! Happy to give you an update. I actually just got my car back from the mechanic last week. They found that the battery was indeed heavily discharged and faulty, just as I suspected when I first replied to you. The total bill came to 290 € to get it sorted out. The best news is that the start-stop system is working perfectly now, no more unusual shutdowns or warning lights! Such a relief. The car feels like new again. Really glad I got it fixed when I did, as the mechanic mentioned it could've led to more serious issues if left unchecked. Since the repair, everything's been running smoothly. No other problems have cropped up at all. I've put about 500 km on it since the fix, and it's performing exactly as it should. The start-stop system engages and disengages properly at traffic lights now, which is great for fuel efficiency. If you're experiencing the same symptoms, I'd definitely recommend getting it checked out sooner rather than later. The repair cost was actually less than I initially feared it might be, and it's totally worth it for the peace of mind.

UPDATE FROM: Just wanted to update everyone. Finally got my car checked and fixed last week. Called several places and found a certified hybrid specialist. I'm so glad I did! They diagnosed it right away, turned out was spot on about the battery issue. The whole process was pretty smooth. They had the parts in stock and got it done in two days. Cost me around 300 €, pretty close to what paid. The mechanic was really thorough and showed me exactly what was wrong with the old battery. Drove about 200 km since the fix, and what a difference! No more unusual shutdowns, warning lights are gone, and the start-stop system works like a charm. Feels like I got my confidence back in the car. Really happy I didn't put this off any longer. Thanks again for all the advice, especially. Your experience helped me make the right decision instead of trying cheaper fixes that probably wouldn't have worked. Definitely worth every penny to have it properly sorted!