Pin 4 is the ground. Without that, it won't work. Check it with both the key on and off. If there is no continuity to ground, try running a new ground wire to see if that makes things work.
I just ran through the wiring schematics. The DLC ground is referred to as G300. It is located at the left B pillar. There are a number of components that use G300 for a ground location. Most of the things you mentioned as working ground at G300. So, if you have no continuity to ground at pin 4, then chances are the wire is broken at some point. It doesn't go through the PCM. It goes straight to ground.
If you look at pic 1 below, I simply showed the DLC ground. There are several pages of schematics with different components all grounding at this point.
I added pic 2 to help you locate the "B" pillar. I wasn't sure if you knew what it was. Most people don't.
Let me know. Again, recheck continuity. If there is none, try running a separate ground for the DLC to see if it works.
I will watch for your reply.
See pics below.
Images (Click to enlarge)
Saturday, April 24th, 2021 AT 8:05 PM