1990 Chevy Truck Electrical

Truck will not start. There is no electrical spark at the plugs. The ignition coil and pick up coil seem to be within the specifications of the manual. I have replaced the ignition module with no improvement. The next thing that I see in the electrical schematic is the Power train Control Module (PCM). Is this the trucks computer behind the glove box? How do I check it? Or have I missed something else that I should be looking at?

Thanks,
Richard