I have a 2005 silverado 1500 Z-71 with 201,000 miles on it which i have been having a problem with concerning the 4wd. I have found others with sort of the same problem but there are always different details. MY problem is that intermittently, service 4wd will come on the message center and my 4wd buttons will not work. They are still lit, but wont do anything. Other times i will have the same message but the buttons will not be lit. And still other times, the buttons will be lit but the truck will be in 4 LO. I have some mechanical ability so I have started checking things out. I read on one forum that sometimes the soldered connections in the shift button cluster will be bad, so I carefully re-soldered all of those with no result. I have not yet taken it anywhere to get the codes pulled because my dealership wants $200 just to read the codes. I read that 90% of the time it is the encoder ring in the transfer case so I have also removed the shifting mechanism from the transfer case to get a look at the encoder ring. No luck there. I dont know how to "check it" to see if it is good or bad. I am thinking my only avenue is to buy a new encoder ring and replace my old one to see if that is the problem or not but i have read that they need to be "flashed". Would a dealership need to do this? Or is there a way that I can? Any thoughts or suggestions will be greatly appreciated!! If you see that I have done something wrong, please point it out.