Convenience package, decor level #1

Years 1983–90, 2004–08 Models 3 Factory citations 14

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Also described as Trim package, SierraTrim package, High Sierra

Also documented for Chevrolet

Documented applications

Canyon — GMT355 (2004–2012)

2004–2008 Factory-verified

GM factory document — 2004 gmc canyon pickup 2wd rpo code list, p.1.
GM factory document — 2005 gmc canyon pickup 2wd rpo code list, p.1.
GM factory document — 2006 gmc canyon pickup 2wd rpo code list, p.1.
GM factory document — 2007 gmc canyon pickup 2wd rpo code list, p.1.
GM factory document — 2008 gmc canyon pickup 2wd rpo code list, p.1.

Jimmy — first generation (1983–1994)

1989 Factory-verified

the base trim level; the joint data book prints it as S-10/T-10/Sierra, the Chevrolet and GMC names; the 1989 page prints YCI; shared S/T platform code; cited from the joint S-10/15 Blazer/Jimmy pages of the S-10 Blazer kit

GM Heritage factory kit — 1989 Chevrolet Blazer, p.5.

Sonoma — first generation (1982–1993)

1983–1990 Factory-verified

the 1984, 1989 pages print YCI; the joint pages print it as Durango/High Sierra, the Chevrolet and GMC names; shared S-series code; cited from the joint S-10/S-15 pages of the S-10 kits

GM Heritage factory kit — 1983 Chevrolet S 10, p.24.
GM Heritage factory kit — 1984 Chevrolet S 10, p.25.
GM Heritage factory kit — 1985 Chevrolet S 10, p.31.
GM Heritage factory kit — 1986 Chevrolet S 10, p.23.
GM Heritage factory kit — 1987 Chevrolet S 10, p.31.
GM Heritage factory kit — 1988 Chevrolet S 10, p.95.
GM Heritage factory kit — 1989 Chevrolet S 10, p.10.
GM Heritage factory kit — 1990 Chevrolet S 10, p.20.

This page aggregates every documented appearance of YC1 in the GMC reference. Confidence and citations are shown per application — the same code can be better documented in one year than another.