Installed new PCM, diagnostic link still says unable to communicate?

Does the scanner work in another car? If so, let's check the AUX fuse #7 in the interior fuse panel, here are the wiring diagrams for the ALDL connector and the PCM so you can check the grounds and power leads, they will show you how the system works as well.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.