Search both this site and the Portal site with "Pinnacle Pass", yes, with the quotes. You will find discussion both places.

I've crossed from above Mirror Lake to the north fork drainage twice, but not in the last 30 years. There was a duck at the pass that led you to a brief constructed section starting down. From below I have never been able to spot that part of the route looking up from the north side.

R J Secor
The High Sierra Peaks, Passes, and Trails, 1992
and
Harvey H Voge
A Climber's Guide to the High Sierra, 1954
both describe the pass and it's approaches.

Dale B. Dalrymple