Do I need a new PCM when swapping 2.4l dohc engine into a 2.0l song straus?

Are they both the same year engine? Changing engines not identical can be a nightmare due to ON Board Computer Algorithms (Processor chip) not recognizing the newer/older components. IMO a no spark can be the result of the security system .. although if the original OBC is still being used it should recognize the key. The No-Crank is defiantly due to the relay wiring interface from the computer not seeing either neutral or proper transmission position. You may get lucky and find that once you correct that then the engine may crank and start . If all the original wiring is intact and only the engine was changed than a good technician can get it going. However if your not skilled at reading schematics you are not going to trial and error without making some "Krispy Critters"