The Pin Took a Walk
While performing a front-wheel alignment on a 2008-2012 Chevy Colorado, you may notice that the upper control arm bracket alignment pin is missing. This pin serves as a pilot for the alignment cam when adjusting camber and caster. It’s unlikely that someone stole it. The factory simply made an oops.
If the pin is missing, simply make-do by inserting a ¼-inch dowel rod or ¼-inch punch or drift as a temporary aid to properly center the cam to the bracket, while making adjustments and while torquing the control arm nuts.