BMW M3 2015–2017 — technical service bulletin
Bulletin B520217 · NHTSA communication 10136728 · issued Dec 1, 2017
Technical service bulletin
communication type
Seats
component
2015–2017
model years
6
vehicle entries
Official summary
SERVICE ACTION: CHECK PUMP FOR BACKREST WIDTH ADJUSTMENT: The backrest width adjustment and, the lumbar support adjustment of the front seats are accomplished by a common air pump.
What a TSB means. Technical service bulletins are repair guidance manufacturers send to dealers — they are not recalls, and repairs are not automatically free (warranty extensions are an exception worth checking). The full document is available via NHTSA’s vehicle lookup.