95 Cavalier no DLC communication
 

I have a 95 Cavalier 2.2L with a 5 speed manual showing no communication at the DLC. I cannot talk to any computer; PCM, ABS, Airbag. It has the 16-pin OBD2 connector, though I've read online that it uses what GM calls OBD 1.5.


Pin 2 shouldn't be used by my vehicle, according to every diagram I've found
Pin 4 has been verified a good ground
Pin 5 has been verified a good ground
Pin 9 is the UART Data line
Pin 16 has been verified to have full power


I've tried using a SnapOn Modis with the K-9 key (as instructed by the tool)
I've tried using an Autel scanner, but that won't connect


There are no loose or broken wires at the DLC, and no broken or bent pins.
All lights on the dash perform a proper self-test with key cycle, and MIL light is not on with engine running.


Any tips on how to restore communication or what to check?