My Service 4WD light came on, and I do not have any lights on the 4 button selector. I do not have the ability to read transmission codes.
I checked the fuse for the 4WD System and it is good. Is there a way to check the switch out?

The 20 Amp fuse for ATC was blown, I replaced the fuse and the 4WD worked normally for a little bit and blew the fuse again. Yesterday I replaced the Transfer case shift motor and all is working well. I never did have the system scanned.

This mornings drive to work had no issues. The fuse did not blow.

 

Check under truck, see if any plugs are hanging, follow the lines back, and then pull the switch to make sure its connected, other then that, bring it to napa or auto parts store, they can connect and tell you the codes for free

 

Check the threads in the Tech Article (DIY) Index. There are schematics for the 4-button system that will give you some things to check. The most common issue is corrosion at the TCCM connections. The TCCM is located behind the passenger front kick panel just ahead of the door.