  For a sequence $S=(s_1, \ldots, s_k)$ of non-decreasing integers, a packing
$S$-coloring of a graph $G$ is a partition of its vertex set $V(G)$ into $V_1,
\ldots, V_k$ such that for every pair of distinct vertices $u,v \in V_i$, where
$1 \le i \le k$, the distance between $u$ and $v$ is at least $s_i+1$. The
packing chromatic number, $\chi_p(G)$, of a graph $G$ is the smallest integer
$k$ such that $G$ has a packing $(1,2, \ldots, k)$-coloring. Gastineau and
Togni asked an open question ``Is it true that the $1$-subdivision ($D(G)$) of
any subcubic graph $G$ has packing chromatic number at most $5$?'' and later
Bre\v{s}ar, Klav\v{z}ar, Rall, and Wash conjectured that it is true.
  In this paper, we prove that every subcubic graph has a packing
$(1,1,2,2,3)$-coloring and it is sharp due to the existence of subcubic graphs
that are not packing $(1,1,2,2)$-colorable. As a corollary of our result,
$\chi_p(D(G)) \le 6$ for every subcubic graph $G$, improving a previous bound
($8$) due to Balogh, Kostochka, and Liu in 2019, and we are now just one step
away from fully solving the conjecture.
