OBD1 vehicle with OBD2 plug in

I was helping a bud the other day with a problem. I rolled up to a 95 S10 4.3 TBI with my Snap ON MT2500 with a OBD1 adapter and a power cord to the battery figuring I had this licked.
As Ron White said I WAS WRONG.
I already knew that 95 was a bastard year but this was the first time I've run into this setup. The truck had a OBD2 plastic connector but very few pins. For grins and giggles I pined the 3rd and 4th pin from the right in the upper row and shazaam started getting flashes from the check engine light for codes.
Yes this was an S10 but I have seen reports of B bodies like this so I hope it can help somebody.