BMW Check Engine Warning Signals Water Sensor Failure

Had the same issue with my 2008 BMW 3 Series last month. The rough running and check engine light turned out to be more than just a sensor problem. In my case, it was a faulty wiring harness connection to the coolant temperature sensor, the cables were corroded and making poor contact. The repair wasn't terribly complex, but it needed proper diagnostic equipment to pinpoint the exact issue. Initially thought it was just the sensor, but the mechanic found the wiring problem during testing. The corrosion had spread a bit, so they had to replace a section of the harness along with the sensor. Not a huge repair job, but definitely needed professional attention, DIY could've led to more problems. The car's running smooth now with no check engine light. Based on your symptoms, could be similar, but best to get it checked properly to be sure.

Hey, thanks for sharing your experience! That's really helpful since I've been worried about my car. By the way, do you remember roughly how much you ended up paying for the whole repair? And has everything been running smoothly since, or have you noticed any other issues popping up? Just want to get an idea of what I might be looking at cost-wise and if I should be watching out for anything else.

Hey again! Yes, I can definitely update you on that. I went to the mechanic last week and got it all sorted, turned out to be exactly what I suspected with the water sensor. The total bill came to 95 € which covered fixing the cable connection that was causing the malfunction. They found a faulty plug connection that was causing all the trouble. I'm happy to report the car's been running perfectly since the repair, no more check engine light and the rough running is completely gone. No other issues have shown up either, which is a relief! Honestly, I was preparing myself for a much bigger bill based on past experiences, so I was pretty pleased with the outcome. If your symptoms are similar to what I had, you might be looking at the same kind of repair. Just make sure to get a proper diagnosis first, but don't worry too much, it might not be as expensive as you're fearing. My mechanic mentioned these sensor connection issues are fairly common on these BMWs.

Thanks so much for the detailed follow-up! I finally got my car checked out yesterday. You were right about getting a proper diagnosis first. Went to a new mechanic who took the time to properly check everything. Turns out my issue was also sensor-related, but it was the crankshaft position sensor that was acting up. The repair cost me about 150 bucks including labor, which wasn't nearly as bad as I'd feared. Way better than the last place that tried to sell me on replacing a bunch of unnecessary parts! The mechanic was really honest, showed me the old sensor and explained everything. Car's running like a dream now, no more check engine light and that rough running is completely gone. Such a relief! Really glad I asked here first and got your advice. Sometimes these BMW issues sound scarier than they actually are. Thanks again for helping me avoid another overcharging situation!