Buick Rainier 2002–2005 — technical service bulletin
Bulletin 040421004 · NHTSA communication 10017442 · issued Dec 1, 2004
Technical service bulletin
communication type
Power Train
component
2002–2005
model years
13
vehicle entries
Official summary
4wd switch indicator lights flashing, 4wd inoperative, diagnostic trouble codes c0327, p0550 set. *tt
Vehicles covered
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.