I had to replace my motor in my 2005 GMC envoy XL due to a valve going into my number one piston. I replaced it with a 2004 trailblazer 4.2 6 l with less miles. I changed out the fuel rail like I needed to and everything hooked up the way it's supposed to. But now I have a no crank no start and I also have no check engine light when I turn my key to the accessory position. My starter is not making any sound at all now and it was working fine before. I did replace the starter relay still got nothing. I'm getting 12.6 off my battery with a multimeter. I checked every fuse that I could think of. When trying to jump the starter with the solenoid it does make a tapping noise and the purple wire on my starter is showing current 12.2. brand new battery bought last year and new alternator. I don't know if it would be the ignition switch but I don't think that that would control my check engine light. The ECM or PCM that's located on the manifold is the original one that's to my truck the only thing I did was remove the wires and remove the housing when we put the new engine in and then I put everything right back the way it was. I could really use some help on trying to figure this out. I'm trying to find out the best way to fix this problem without spending a bunch more money and I'm having to do this myself.