ECU PROBLEM

Hey guys!!
I am in need of help and direction about my ecu.
My original one pictured (89661-17380) was working fine, showing only having a speedometer fault due my dash not showing the speed, stop working completely and had no engine light come on at all. After a little would then work and then stall out. I then replaced the ecu with another pictured (89661-17321) but did not work as was displaying fault 12 - PRM Signal - but did not fire at all.
I then checked my capacitors on the original ecu and had a 2 x 10uf 50v looking pretty tired. Replaced them and had no luck at all.
So I am stuck not knowing what I can do??
Any help or direction would be appreciated beyond belief.
Either my ecu can be saved or I can use the new one some how