Greetings to everyone. I have a 2005 tahoe z71 with 39,000 miles. About a year ago i started having trouble with the service 4x4 and stability sys dis. It would rear its ugly head right after using the 4x4, the disappear after awhile. The other day the lights came on again and never went off. Anyway, after reading these posts and found them very helpful, especially the posts from jcat i started my troubleshooting process. I removed the encoder/transfer shift motor and plugged it into my 2003 yukon which also has the nv246 xnsfer case. The problem was duplicated on my yukon which verified the problem. I found on amazon a replacement encoder ac delco part#88962315 for $45. I realized that i could replace just the encoder as the motor worked fine. Here's the iceing on the cake, I disassembled the encoder, cleaned the contacts and re-aligned the brushes and viola! The shift motor works! Reassembled everything and test drive reveals the 4x4 is operating properly. I hope this can help many of you out of a bind. If you dont want to rebuild the motor Doorman has an aftermarket motor for $179.00 on Amazon part #600-910. Many thanks again for everyones input especially jcat. Btw this is my first post here.