knowak, If you have acess to a computer unit, go ahead and give it a try. The way I test my electronic problems though is not through ohms unless power and grounds are not available, I do all of my testing through voltage drop, it is a more definite way of testing automotive electronics than ohm testing, and also for this vintage Ford, I use a Breakout Box for this style PCM component, wiring, power and ground testing. You can also backprobe using pins into the back of the components instead of pinching into the wiring. As for the grounds, I just tested a Ford 60 pin computer on the bench, pins 40 and 60 are connected to pin 46 in the pcm, pull your computer out of your vehicle, set your meter on low ohm scale, probe pin 40 with one probe and pin 46 with the other probe, should be "0". Next probe pin 40 to 60 and 46 to 60, all should be "0". I don't think you have to mess with pin 20 at all. I believe from what I am reading from your replys, this is going towards a computer failure. Take the covers off of your computer and look at it under a magnifying lens, look for a burned spot, you may be able to thread and solder a small piece of copper wire across a burned area, (if that is what it is). Been there, done that. Broken Wire

 

Sure enough, it was the computer. Many thanks to everyone here who added their much appreciated input!