los angeles county is a big area....not knowing where you are,
in terms of dealers that are open sunday (maybe they'll be able to help in some way even if their service dept is closed):
new century bmw in south pasadena/alhambra area
in the hollyweird area
the other area dealerships are closed on sundays/mondays usually (irv seaver, brown bmw, long beach bmw).
2016 Aprilia Tuono Factory | 2012 Vespa 300 Super
past: Ducatis, Aprilias, Moto Guzzis, a Husky, KTM 1290 SDR, and some BMWs as well