BMW Z4 Coolant Warning & CEL: Trustworthy Help Needed

I had a similar issue with my 2020 BMW M440i last month. The coolant sensor was acting up due to a faulty wiring connection at the temperature sensor plug. The warning lights came on exactly like yours, coolant temp and check engine together. Took it to the dealership where they diagnosed a corroded connector at the sensor. They had to replace both the wiring harness and the sensor itself since corrosion had spread. It wasn't a major repair, but definitely needed professional attention since it involved electrical components. If you're seeing low coolant, have them pressure test the system too. In my case, there wasn't an actual coolant leak, it was just the sensor giving false readings because of the bad connection. Don't put this off though. A malfunctioning temp sensor can't properly monitor your engine temperature, which could lead to overheating if there's a real issue being masked by the faulty sensor.

Thanks for sharing your experience! This really helps since it sounds exactly like what I'm dealing with. I'll definitely get it checked out asap and have them run that pressure test you mentioned. Just curious, can you remember roughly how much the repair set you back? And has everything been running smoothly since they fixed it, or have you noticed any other quirks pop up?

Hey there! Happy to give you an update. After getting it fixed, my M440i has been running like a dream, no more warning lights or any other issues. The repair was pretty straightforward and cost me 95€ for fixing the cable connection problem. They also topped up my coolant while they were at it, which solved the low coolant warning. I actually feel a bit silly now for being so worried about it, but better safe than sorry with these things, right? The car's been perfect for the past few weeks, no quirks, no warnings, nothing. Just smooth sailing. Definitely worth getting it sorted quickly though, I wouldn't want to risk any engine damage from temperature issues. Just make sure they check all the connections properly when you take yours in. Sometimes these things can be really simple fixes, but you definitely want someone who knows what they're doing with the electronics. Let me know how it goes when you get yours checked out!

Just got back from the mechanic and wanted to update you all! Took your advice and had them check everything out. Turns out it was pretty similar to what you experienced, faulty sensor connection plus a tiny coolant leak. The repair was quick and cost me about 120€ total, including the new sensor and labor. What a relief it wasn't anything major! The mechanic I found was actually great, super thorough and explained everything clearly. They even showed me the corroded parts they replaced. Car's running perfectly now, no warning lights, and the temperature gauge is steady. Really appreciate everyone's help on this. Sometimes these BMW quirks can be scary, but it's good to know there are others who've dealt with similar issues. Time to enjoy my Z4 again without stressing about every little dashboard light!