BMW i8 Hybrid Cabin Filled with Exhaust, AUC Sensor Issue?

Hey there! I had similar issues with my 2021 BMW i4 (have also owned an iX). I've got some experience working on cars, but nothing too advanced. My blower completely stopped, and I was getting those nasty fumes in the cabin too. After taking it to my trusted workshop, they found it was just a loose connection in the wiring harness connected to the auto-recirc sensor. Total fix was 95 Euro, mostly labor costs for tracking down and fixing the connection issue. Before you head to the shop, could you share: Does the issue happen more when you're idling? Have you noticed any unusual sounds from the ventilation system? Does the AC still work normally? This might help pinpoint if you're dealing with the same problem I had or something else. These newer BMW hybrids can be tricky with their sensor systems, but usually it's something fairly straightforward once diagnosed properly.

Hey, thanks for sharing your experience! My i8 has 165192 KM on it, and was just serviced last month. I'm experiencing exactly what you described, it's definitely worse when idling. The AC seems to work fine, but I've noticed a faint clicking noise from behind the dash when switching between fresh air and recirc. Your wiring harness tip might be the answer I'm looking for. Was a bit worried it might be something more serious, but hearing your experience gives me hope it's just a connection issue. Did they have to remove much of the dash to access the wiring? I'm trying to get an idea of what I'm in for when I take it in. Thanks again for the help!

Hey again! Glad to help out a fellow BMW owner. After fixing my wiring issue, I can tell you that clicking sound you're hearing is exactly what I experienced before getting it sorted. For the dash removal, they actually didn't need to take apart as much as I initially feared. The access point was mainly through the glove box area. My mechanic just had to remove the glove box and a few trim pieces to reach the wiring harness. Took about an hour and a half total. Since you mentioned your recent service, it's possible they might have accidentally disturbed some connections while doing other work. These sensors are pretty sensitive to any wiring changes. The high mileage on your i8 could also mean some of the connectors have worked themselves loose over time. Just a heads up though, my clicking noise did get worse before I got it fixed, and the fumes started getting really noticeable in stop-and-go traffic. Don't wait too long to get it checked out. These cabin air quality issues can get pretty uncomfortable, especially in heavy traffic. Let me know how it goes when you get it sorted. Always interested to hear if it's the same fix across different BMW models!

Thanks for all that detailed info! I really appreciate you taking the time to explain everything, especially about the dash access and repair time. It's super helpful knowing it's likely not a major teardown job. You're probably right about the service possibly disturbing something, the timing does line up. I'll get it into the shop this week before it gets worse like you mentioned. The clicking is already getting more frequent, and with all this traffic lately, I definitely don't want to deal with more fumes in the cabin. I'll make sure to let everyone know what the fix turns out to be. Would be interesting to see if it's just a loose connection like yours. These BMWs are amazing cars but they sure can be finicky with their sensors and electronics! Thanks again for all your help, it's made me feel a lot more confident about getting this sorted out!