BMW i8 Limp Mode: Temperature Sensor Fault Solutions

Hey there! I've got some experience with hybrids, not an expert but I've dealt with my fair share of issues. I actually had a similar problem with my 2017 BMW i3. My car also went into limp mode and showed similar symptoms. Turned out there was a leak in the exhaust system that was messing with the sensor readings. Had it fixed at my local workshop for about 265 Euro, they had to replace a gasket and recalibrate the sensor. But before jumping to conclusions, could you tell us if you've noticed any unusual smells or sounds from the exhaust? Also, what's the mileage on your i8? These details would help me understand if you're dealing with the same issue I had. The i8 is quite different from my i3, so it'd be good to get more specifics about when this started happening. Did it come on suddenly or gradually get worse?

Thanks for sharing your experience! Actually, my i8 just had its latest service two months ago, and I'm sitting at 64362 KM. I haven't noticed any weird smells, but there is a slight rattling noise when accelerating. The issue started quite suddenly, was driving normally one day and boom, limp mode. It's super frustrating because the car was running perfectly fine before this. Really interesting about your i3 exhaust leak, I'm hoping my fix will be as straightforward as yours was. Did your car also show increased fuel consumption when you had the problem? I'm burning through fuel like crazy right now, which seems weird for a hybrid that's supposed to be efficient. Definitely planning to get it checked out this week, but wanted to gather some insights first. These sensor issues can be tricky to diagnose!

Hey again! Yeah, I totally get your frustration, sensor issues can be super annoying. When I had my i3 problem, the fuel consumption went through the roof just like yours. It was burning almost twice as much as usual, which was a real pain given that efficiency is why we got these cars in the first place! That rattling noise you mentioned during acceleration, that's interesting. Mine didn't have that specific sound, but given you're mentioning it, it could point to something a bit different than what I dealt with. Since your car just had service two months ago, maybe something wasn't properly secured? In my case, the increased fuel consumption was because the car wasn't able to optimize the engine performance with faulty sensor readings. The computer basically goes into a "safe mode" where it's not running at peak efficiency. The sudden onset of your problem does sound similar to what I experienced though, these sensor issues tend to show up out of nowhere rather than gradually. One thing I learned from my experience, make sure they do a complete sensor diagnostic, not just the exhaust temp sensor. Sometimes these symptoms can be caused by multiple sensors acting up. Keep us posted on what they find, really curious to know if it's similar to what I dealt with!

Thanks for the detailed follow-up! That's really helpful info about the sensor diagnostics, I definitely wouldn't have thought to ask them to check multiple sensors. The similarity between our fuel consumption issues is making me feel a bit better about this whole situation. Just called my mechanic and got an appointment for tomorrow morning. Going to mention everything we've discussed, especially about checking all the sensors and making sure nothing got loose during the last service. The rattling noise does make me think something might have come loose, now that you mention it. Really appreciate you taking the time to share your experience. It's been super helpful having some real-world insight before heading to the shop. I'll update this thread once I find out what's actually causing the problem, might help someone else down the line with similar issues!