So I am a newbie and this is my first time dealing with ecu's. Basically I threw a rod in a 96 civic ex and have a 99 ex motor to replace it. Everything looked exactly the same so I swapped them. I currently have the 99 wiring harness on the 99 motor in the 96 civic. Now that its in and I'm done with everything, I see the ECU's are different I started searching the web and am unclear as to what to do. I am sure you all know this, the 96 has obd-2a and the 99 has obd-2b. Can someone please tell me what to do, I am so close to having a running car again. Not sure, but I read somewhere that putting the 96 harness and ecu on the 99 motor would cause me to fail emmisions? I see they sell conversion harnesses for 100 bucks or so, but I am confused because the 96 has 3 plugs on the engine harness. And the 99 has to plugs on the engine harness and 1 on the old 99 chasis harness. You guys could really help me out by shedding some light on this for me as to what I should do.