BMW X3 Temperature Chaos: Cooling Grille or Something More?

I had nearly identical symptoms with my 2015 BMW X5 35i last winter. Initially thought it was just the thermostat, but turned out more complex. When diagnosed, the main culprit was a faulty DME control module, it was sending incorrect signals to the cooling system. Also found a blown fuse that was affecting the electronic coolant control valve. The repair wasn't just a quick fix. They had to replace the DME module and reprogram it, plus fix some corroded wiring to the temperature sensors. Those temp fluctuations you're seeing could definitely be similar to what I experienced. Based on my case, I'd suggest getting a second opinion. A blocked cooling grille alone typically doesn't cause such erratic temperature readings. This was definitely a serious electrical issue that needed proper diagnosis and repair to prevent potential engine damage.

Thanks for sharing your experience, that's really helpful! I'm actually dealing with pretty much the exact same symptoms right now. Would you mind telling me what the total damage was to your wallet? Also curious if you've had any other issues pop up since getting it fixed? I'm trying to budget for this repair and want to make sure I'm prepared if it turns out to be something similar to what you dealt with.

Hey there! Just wanted to follow up about my X5 repair situation. Actually, after seeing the mechanic, they found and fixed that cooling grille restriction I mentioned, it was definitely blocked up pretty bad. About those other issues, my total bill came to 52 € for replacing that blown fuse that was messing with the coolant control valve. I'm really glad you asked about any problems since the repair, honestly, everything's been running perfectly smooth. The temperature gauge stays steady now, and the engine warms up just like it should. No more check engine light either, which is a huge relief! The best part? That second opinion really paid off because it ended up being a much simpler fix than what I initially went through with the DME module drama. Guess sometimes the simplest explanation is the right one, huh? Let me know if you need any other details about the repair, happy to help!

Just got back from my mechanic and wow, what a relief! Turns out my issue was pretty different from what I originally feared. Had my car checked by another shop and they found a cracked radiator hose and a failing water pump. The weird temp readings were happening because coolant was leaking out slowly. Fixed both issues and my car's running like new again, no more crazy temperature swings or slow warm-ups. Bill came to around 400 bucks including parts and labor, which wasn't as bad as I was expecting. Much better than dealing with electrical problems or computer modules! Thanks for sharing your experience earlier, it really helped me push for a proper diagnosis instead of just accepting the first answer. Sometimes getting that second opinion makes all the difference. Really glad I asked here before moving forward with any repairs.