BMW M3 Water Sensor Issues, CEL On, Engine Running Rough

I have some experience working on BMWs. Had a similar issue with my 2005 BMW M5, and previously owned a 330i too. The water sensor problem you're describing sounds exactly like what I dealt with. My engine was running rough and throwing the same code. Turned out it was just a loose connection at the sensor plug. My mechanic cleaned the connector, secured it properly, and replaced a damaged wire section. Total bill was 95 Euro, and the car was ready the same day. The rough running disappeared completely after the fix. Could you share more details about when this started happening? Does it get worse when the engine is cold or warm? This would help narrow down if you're facing the same issue I had.

Thanks for sharing your experience! My issue actually started about two weeks ago, mainly when the engine is cold. I just had my service done at 186884 KM, and everything else was running perfectly until this showed up. It does settle a bit once the engine warms up, but that check engine light is still stubborn and won't go away. I'll definitely have my mechanic check the sensor connections first before jumping into any major repairs. Did you notice any other symptoms before getting yours fixed?

Hey there again! Glad I can help with more info about my experience. Yeah, with my M5, I actually noticed a few other things before getting it fixed that I didn't mention in my first reply. The cold start symptoms you're describing are exactly like what I experienced, my car would run pretty rough for the first few minutes, especially on cold mornings. I also noticed slight hesitation during acceleration, and sometimes the idle would be a bit unstable until the engine warmed up. The interesting thing is, my issues also started right after a regular service (around 190000 KM). Initially, I thought it might have been related to the service work, but it turned out to be just a coincidence. One thing I'd suggest checking, when my mechanic was working on it, he found that some water had gotten into the connector, causing minor corrosion. That's why just cleaning and securing it properly solved the issue. Since you mentioned your car behaves better when warm, it's very likely you're dealing with the same problem. Just keep in mind, even after fixing it, my check engine light stayed on for about 3-4 start cycles before finally clearing itself. So don't worry if yours doesn't go away immediately after the repair. Let me know how it goes after you get it checked out!

Thanks so much for all that detailed info! It's really helpful to know about the corrosion possibility and that the CEL might take a few cycles to clear. You've actually made me feel a lot better about this whole situation, sounds like I might be looking at a simple fix rather than something major. The hesitation during acceleration you mentioned is exactly what I'm experiencing too, so I'm even more convinced we had the same issue. I've got an appointment with my mechanic tomorrow morning. I'll definitely have them check for water damage and loose connections first. Really appreciate you taking the time to share your experience in such detail. I'll probably check back in once it's fixed to let you know how it turned out. Fingers crossed it's just a connection issue like yours was!