problem with my 4WD on 2004 Chevrolet Colorado

My car was sitting for awhile and when I went to switch into either 4H or 4L it would not engage at all. I checked the fuses and nothing to indicate a problem. I am getting power to the solenoid and switch. Can someone direct me to a schematic?

Asked by for the 2004 Chevrolet Colorado
I don't have a schematic, but you can look at this article for some info about 4WD issues on GM vehicles:
For a possible schematic, check with