Strange seatbelt chime malfunction

Seat belt chime came on after driving 1/2 mile, though buckle was properly clipped. Dealer couldn't find anything in the system showing the problem, and suggested maybe a purse on the seat caused the alarm to go off. Having driven an i3 for 3 years, I knew this wasn't the problem, especially since my husband also had same issue when he picked up my car from work to take to the dealership for me.

The dealer ordered new parts and repaired it, but the alarm started again after I was a half mile off the lot.

Turns out a new lightweight and empty insulated bag (kind bought at grocery to keep items cold) that I had left on the front seat caused the problem. The foil interior was interfering with the seat belt sensor somehow. Took over a week during Xmas and NY holidays to find this ghost in the machine. Glad to have BMW customer service and loaner car available.

This would suggest that the sensor is capacitive, and that would explain why my heavy backpack wouldn't do anything, but then my ThinkPad laptop (which has a magnesium internal structure), did set it off when I had it sitting on the chair while playing around with ISTA.


It's actually kind of nice to know it's smarter than just a dumb pressure sensor.