The charge state composition of heavy ions, primarily the carbon-nitrogen-oxygen (CNO) group, has been determined for 12 diffuse particle events in the energy-per-charge range ~33 to 132 keV/e observed upstream of the earth's bow shock. The measurements were made with the University of Maryland/Max-Planck-Institut ultra low energy charge analyzer (ULECA) sensor on ISEE 1. The relative charge state distributions found for Q≥3 ions at ~33, 66, and 132 keV/e are consistent with a charge state composition that is consistent as a function of energy per charge. It is suggested that the charge state composition of these locally accelerated heavy ions can be used to estimate the charge state composition in the solar wind and hence to estimate the equilibrium coronal temperatures associated with a variety of solar wind flows. In particular, we obtain average CNO ionization temperatures of (1.5¿0.2)¿105 K for diffuse particle events occurring during interstream solar wind conditions, (1.3¿0.2)¿106 K for events occurring during coronal-hole-associated high-speed streams, and (2.2¿0.3)¿106 K for events occurring during transient-related flows. The diffuse particle event ionization temperatures corresponding to coronal-hole-associated high-speed streams are particularly interesting, since reported solar wind charge state measurements for high-speed streams are presently very limited. The temperature values we infer for coronal-hole-associated solar wind are approximately constant over the range of solar wind speeds covered (420--680 km s-1) and are consistent with equilibrium temperatures predicted for coronal holes.