GM-GMC: 4x4 question, gm tech2, tccm

Question
I have a 97 S10 4wd. The 4wd does not work. When I push the button nothing happens. The switch I have been told is in good condition. What can I check next?

Answer
The four wheel drive system is no longer a system that can be diagnosed without a scan tool, unfortunatly.  The days of mechanical transfer cases and mechanical front axles are long gone, again unfortunately.  The shifting of the transfer case is performed by a motor/encoder that receives drive signals from the transfer case control module (TCCM). When the driver selects one of the transfer case shift select buttons, request signals are sent to the TCCM. If the correct input signals exists, the TCCM will send drive voltages to the motor/encoder. The motor/encoder will position the transfer case to the ordered shift position.  In order to observe the inputs and outputs of the TCCM/Encoder/Switch you require a GM Tech2.
Probably doesn't help you much, but that is how the system works, sorry.