So for the car to run and toggle the injectors, you need a couple of things.
The PCM needs to see that the car is running. This is done with signals from the coil pack getting back to the PCM. Otherwise the PCM turns off the injectors. The injectors are then toggled on/off via the ground wires that go to them from the PCM. I have also seen a bad maf turn off fuel with the pcm thinking it had no airflow, so no fuel.
There's not much that can do it though. I'm trying to load the up GM manuals to see the diagnostic aid.