96 ka ecu won't start my 96 240, but a 95 obd2 ecu will. Why?

[Zombie Killer]

Like the title says, I have a 96 240sx that died on my one day. I tested everything and boiled it down to my ecu. My friend with a obd2 95 240 let me try his ecu in my car. My car started right up, and my ecu worked in his car. So I ordered a ecu from a 96 off some kid and my car still won't start. btw the ecu is telling the the car not to turn the fuel pump on and not to produce spark. I just want to know is their a difference between a 95 and 96 ecu, or why is a 96 ecu in a 96 240 making my car all pissed off at me. Thanks for the help.