ECM ? or Data Port ? or Diagnosis ?

I have a 1995 Riviera Supercharged. I missed with diagnosis of the radiator fan control and screwed up the computer. I can live with that but I just want to be sure it is the computer. Biggest symptom is the tranny will not auto shift.

I was hopping to get an error code out but the little tester I bought for 89-95 or whatever GM cars does not plug in. Mine is an 18 pin data port. I do know that the code is triggered by crossing only two connectors, any idea which ones they are?

Can the computer be repaired if I put 12 vdc into the 5vdc control side?

Thanks for any help and I know that this can be answered as a generic ECM data question.

Thanks Lee