- 1990–1991 Single-source
the Reatta Owners Journal prints CO5 (letter O) without a year; GM's service lists print C05 with the same wording; Wikipedia gives the convertible for 1990 and 1991
C05 Single-source
Also documented for Chevrolet
Documented applications
This page aggregates every documented appearance of C05 in the Buick reference. Confidence and citations are shown per application — the same code can be better documented in one year than another.