data log port issue on GM OBD1

Have a 88 GM project that I am working on and having trouble getting a data log. I have confirmed that the cable and PC setup is good using TunerProRT by testing on another vehicle of same type (90 chevy pickup). It connects fine on this truck and I am able to retrieve data. My question is anyone familiar with the wiring on these trucks as it relates to this OBD1 port. When I look a Haynes repair manual it only shows 3 connections with 2 of them going straight to the PCM.

Cable is a BoostedNW ALDL unit.