1998 GMC Suburban 4X4 not engaugeing

I have replaced the front axle mounted acuator, the transfer case motor and the dash push button assm. And still nothing. When I turn the truck on all the lights will blink on the push button and then go off for a few seconds then the red nuetral light and 2wd and 4wd low lights will stay on? Does this truck have a " Transfer case control module"? And if so could that be the problem and where is it loacated. I also noticed that when I was put up the elec. Windows the lights on the 4x4 push buttons would dim down.