Hey having the same issue as the rest of you, but I replaced the Switch first, everything went well. It switched into 4wd, hi/low, switched out np's, then I drove it a few blocks in 4wd to get the fluids moving. The on-screen code came back on Service 4wd. Now I went to the dealership prior to changing the switch and they told me that these two parts needed to be changed: Encoder Ring and the Switch console itself, Both both parts for $185. After Switch was replaced as I said in the previous sentences, the error came back shortly after. Now I crawled under my Tahoe change the encoder ring, Great tutorial on youtube btw!!!, and then I get the message Se4rvice 4wd, then Stability Control... System Disabled, now I took it back to the dealership and they found 2 more codes after the change that the encoder ring is the issue... I'll get those codes to ya in a few... I also read somewhere else that you cannot move/start the vehicle until you launch the programmer to show that the encoder ring has been changed?? I wasn't going to pay $400+ in labor to fix something that took me less than an hour to do, and I wasn't told that I need to immediately program it neither.