2005 S40 - Replacement ECU Needs Reprogrammed?

[jtgray540]

So here's my situation. I have a 2005 S40 2.4i. Just rebuilt the motor. After the rebuild, it started and ran but cylinders 1 and 5 were not firing (P0300 code). In the process of figuring out why, I messed with the ECU a little bit to see if it was loose or something, and then suddenly none of the cylinders were firing and the car would not start. So I bought another ECU from a salvage yard to see if that would do the trick. Plugged it in, and the car would not even crank at that point due to the "immobilizer". To test, I bypassed the starter relay and the engine cranked but still no fire. So I did some research, tried all the tricks to reset the immobilizer (locking/unlocking 5 times, tapping on the key in the ignition, waiting 3 seconds between clicks, etc.) with no success. Plugged the old ECU back in, and the immobilizer was disarmed, the engine cranked, but the cylinders are still not firing. I'm now wondering if the new ECU needs to be reprogrammed for my car, but I hate the thought of going to a dealership after all this. So my question is, does the ECU need to be reprogrammed, and if so, is there a way to do it myself or somewhere besides a dealership that can do it?