BMW 7 Series Coolant Warning: Check Engine Light Alert

Hey there! I had a similar situation with my 2001 BMW 5 series last summer. The symptoms were exactly like yours, coolant temp warning and check engine light combo. Turned out the coolant temperature sensor had a faulty connector. The wiring harness was corroded and wasn't sending proper signals to the ECU. The repair wasn't too complex, but finding the actual issue required proper diagnostic tools. My previous sensor replacements didn't solve it because the root cause was the connection, not the sensor itself. It wasn't a serious problem, but ignoring it could've led to wrong temperature readings and potential engine damage. I know BMWs well since I've owned several. These symptoms often point to either sensor issues or wiring problems rather than actual coolant levels. Still, worth checking the coolant level first as it's the easiest thing to verify. Make sure whoever looks at it knows BMW electrical systems and has the right diagnostic equipment. Generic OBD readers don't always pick up the specific BMW codes properly.

Thanks for sharing your experience! I had the exact same issue, and your description matches what happened to mine. Finally found a good mechanic who knew what he was doing and fixed it. Just curious, do you remember roughly how much you ended up paying for the repair? And has everything been running smoothly since then? Would love to know if any other related issues popped up afterward.

Hey again! Glad to hear you got it sorted! Yeah, in my case it cost me 95 € to fix that pesky cable connection issue. The mechanic found the corroded wiring harness at the coolant temp sensor and replaced it. They also topped up the coolant while they were at it, which was actually running a bit low. Everything's been running like a charm since then, no warning lights, no temperature issues, nothing. It's been about 8 months now and the car's performing perfectly. Haven't had any related problems pop up afterward, which is a relief. These BMWs can be finicky with their electronics, but once you get the right fix, they're solid. Just goes to show how important it is to find someone who really knows these cars. A lot of shops might've just replaced the sensor and called it a day, but getting to the root cause, that damaged connector, was key. Money well spent in my opinion! Hope your fix holds up as well as mine did!

Thanks so much for the follow-up! Funny enough, my repair bill was pretty close to yours, around 100 bucks. The mechanic I found was actually great, super thorough and explained everything clearly. He fixed the corroded wiring and did a full coolant system check too. It's been about three months since the repair, and I haven't had a single issue. The temperature gauge stays steady, and those annoying warning lights haven't come back. You're absolutely right about finding someone who knows these cars, I got lucky with this mechanic after my previous bad experience. He actually showed me the damaged connector and explained why it was causing all those problems. Really appreciate your help with this. You basically described my problem exactly, which made me feel a lot better about getting it fixed. I'll definitely stick with this mechanic for future work on my BMW!