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.