my service 4wd light came on replaced the push button switch and now nothing

Need a different scan tool, generic tools only scan emission codes. Need a more professional scan tool to read the separate modules, like the 4wd module. Just a quick idea had one that the cigarette lighter fuse in the under hood fuse box was blown, of course it didn't power the DLC connector. I use a Tech2 on GM vehicles. Probably need encoder checked.

have its scanned with a tech 11 scanner to get codes

I just did one last week and you really do need the TechII for diagnostics on that system. On the one that I had the module itself had failed and it wasn't communicating on the data bus with the other modules and having the factory tool allowed me to see that right away on the class2 message monitor and really made the diagnostics much easier.