Not sure why you need a PCM as you did not say what the problem is you are having with your truck. First thing is to remove the chip and see if your PCM is good by installing back in the truck. Until you get your truck running correctly I'd leave the chip out.

The IDM (as I know it) take the 12 volt power and turns it into something like 120 volt power to drive the injectors. The PCM sends a signal to the IDM to open the injector. There are other things that happen but that is the basic explanation. The guys here know more.