  From a diabatic bound state approach to $J^{PC}=1^{--}$ and $(0,1,2)^{++}$
charmoniumlike resonances below $4.1$ GeV, formulated in terms of
${c\overline{c}}$ and closed meson-meson channels, we calculate mass shifts and
widths due to open meson-meson channels. This calculation does not involve any
new free parameter, so comparison of our predictions with existing data
provides a direct test of our approach. Further mass corrections are also
estimated and good agreement with the measured masses comes out. As for the
calculated widths, overall reasonable, they point out to the need of some
refinement of our current bound state approximation for an accurate description
of data. These results give additional support to the diabatic approach in QCD
as an adequate framework for a complete unified description of conventional and
unconventional charmoniumlike resonances. In this respect, the experimental
discovery of a predicted $2^{++}$ resonance with a mass around $4$ GeV would be
of special relevance.
