BMW M4 Coolant & CEL Issues: Common Causes Revealed

Hey there! I have some experience working on BMWs. Actually, had a similar issue with my 2013 BMW M3 last summer, and I've also worked a bit on my 's M5. Had the same warning lights pop up, and like you, I initially thought it was just low coolant. Turned out it was a faulty connector on the coolant temperature sensor. The cable connection had gotten corroded over time, causing weird readings. My regular workshop fixed it by replacing the connector and checking the wiring, cost me about 95 Euro for the whole job. Before I share more specific details: can you tell me if you've noticed any other symptoms? Like, does your engine temp gauge show normal readings? And have you scanned for the specific error code? That would really help narrow things down. I know BMWs can be tricky with these symptoms, but with more info, I might be able to point you in the right direction.

Thanks for sharing! I've got 39053 KM on mine and just had it serviced last month. Haven't noticed any unusual temp gauge readings, but I'll definitely get it scanned. Good to know about the sensor connector issue, that's actually a relief since I was worried it might be something more serious with the cooling system. Will check with my mechanic about the connectors, hoping it's a similar easy fix like yours. Did you notice any performance changes when your sensor was acting up?

Hey again! Glad to help further with this. Yeah, about those performance changes, when my M3 had that sensor connector issue, I didn't notice any major performance drops actually. The car ran pretty much the same as always, which is partly why it took me a bit to take it seriously. But it's definitely good you're getting it checked out early, I waited longer than I should have! Just to add to my previous experience, after they fixed the connector issue, I did have them do a full cooling system check just to be on the safe side. With these M models, it's always better to be thorough, you know? The fact that you've just had it serviced and your mileage is pretty reasonable makes me even more confident it's probably just a sensor or connector thing like mine was. One thing I learned from my situation, keep an eye on the temp gauge for the next few days even after it's fixed. In my case, it took a couple of drives for all the warning lights to settle completely, but everything's been perfect since then. Let me know what your mechanic finds, I'm really curious if it turns out to be the same issue as mine!

Thanks so much for all the detailed follow-up info! That's super helpful to know about the performance staying normal and the warning lights taking a few drives to settle. Just called my mechanic and booked it in for tomorrow morning, mentioned the connector issue you had, and he said it's actually quite common with these models. You're right about being thorough, I'll definitely ask for a complete cooling system check while it's there. Really appreciate you taking the time to share your experience! Will update you once I know what's actually causing it. Thanks again for helping ease my mind about this!