I had the intermittent passenger seat chime problem on my X5 for a while. Drove around with the seatbelt connected for a while until a buddy who owns a shop told me to bring it to him. His tech hooked up the laptop GT1 software, found some codes (he didn't write them down and I was jabbering with my buddy at the time so neither did I), and then cleared the codes. Magically, the random seat occupancy sensor fault went away. I don't think the mechanic disabled the chime only, as the seatbelt warning light doesn't come on randomly anymore, but does come on at startup or when I don't have mine on as the driver (backing out of the garage).

BTW: these were codes that my Peake code reader did not report, but were reported by the GT1 software.

Worth a try...

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Kirk
Las Vegas
2016 X5 40e Mineral White/Black Dakota Leather, ZLL, ZCW, ZDA, ZDB, ZPP, multi contour seats, rear side window shades, HK stereo
2011 E90M3, 6-speed manual