I attempted to do the jumper wire to get a diagnostic reading from my ECM and only got the "Check Engine" Light which is constantly on....(84 Fiero-4 cyl.) If the ECM was defective, would it not have other electrical problems?

A solid check engine light is what you would get if the wire didn't make connections.

Make sure the wire is in the correct holes. If nothing else try just grounding the B terminal.

Yes..I made sure the connection of the two terminals were solid but I will try just grounding B terminal..Thx.

Ok..I just connected the B terminal to a straight ground....turned ignition to on position and Service Light came on with no codes....Just solid light....Any other thoughts? Thanks for input.