One of my work trucks is a 2005 GMC Sierra 2500. The transmission took a crap on it and we went ahead and threw one in from a junk yard while the other one is getting rebuilt just to get it back on the road and working again. The junk yard one came out of a cube van. While the boys were under there, they found a bad starter cable (or something-- I am trying to find out the details right now) and got that fixed.
Here is the deal... the truck starts and idles. On the dash, it says "engine running fast" or something like that (again, trying to find out the details on that0. The throttle doesn't work, and turning the key off doesn't shut off the truck. Either does disconnecting the battery. To shut it off, you actually have to turn the key back to "run" again.
Any clue what is going on? It is a 2WD with the 6.0L gas engine and the 4L80-E transmission.