Thanks for the reply j cat, My tahoe has the NP8 system I just checked all the 4wd system fuses and found them all good. I did notice when I pulled the #2 fuse on the side of the dash waited 5 min then pluged it back in I heard a click under the dash so that must be the 4wd module I'm not sure if that is good or not. The first owner of the truck for the first 10 years only used the 4wd a total of 4 times. He did get a the fluids changed as required. I'm going to change the switch first since that is the cheapest part to start and the lights on the switch go on and off like it has a bad connection. I would think if the encoder motor was bad it would blow fuses in the system. I would like to know if the front drive shaft should be turning all the time or not. On my suburban when its in 2wd it does not turn but that does not have the auto 4wd feature it just has the 2wd 4HI 4Lo push button.