Help. How do i test ecu for 4wd

[dust8888]

I have a 97 limited 3.4 4wd that will not engage into 4wd. I have done several tests with the actuators, but i need to know if there is a simple way to test my ecu for the 4wd to see if it is working? Also if i do need another one of these, does it have to be programmed?
Thanks
dusty