2002 GMC Duramax No Start

Hey guys, my buddy has a 2002 GMC Sierra 2500 6.6L Diesel with the Allison transmission. He disconnected and removed the shift control module from the side of the transmission, then when he put it back in the truck wont start. You turn the key, all the dash lights come on but when you turn to start it, it seems like the truck is in a gear. We tried it in park and neutral but still the same thing. Does anyone have any suggestions? Because we're lost...

Thanks all, Deven.

the problem is the PNP switch that your buddy removed was not reinstalled correctly,(This switch denies current to the starter circuit when the transmission is in any gear but park or neutral ) so thefore it will not start. it needs to be adjusted. loosen the bolts securing the switch to the trans.
rotate the switch ever so slightly and have someone in the vehicle attempting to start the truck, keep moving it in small incruments and turning the key until it starts. you have found the proper position, tighten bolts.