ive got a 03 z71. the service 4wd light has came on twice. turn the truck off and wait, turn it back on and all is good. well last night i was sitting in a drive through and started to run the 4wd through the gears. well at first it wouldnt switch into 4hi or low. the light would jst sit there and blink. so i pushed the 2wd button and it stopped blinking. so after a min i pushed it again and after a min or so of blinking it went into 4lo. well when i tried to put it back into 2wd it wouldnt go. so i decided to take it easy home in 4lo. after bout 5 min i pulled over put it in neutral push 2wd button and bout 15-30 later it went back into 2wd. do yall think its my switch or is the encoder motor goin out?

 

IMO being its a 2003.....if this was year 2004 or so and the truck was only a couple of years old....I would jump on switch for that year model. But because your truck has seem some life now I would be more guarded on jumping on an undiagnosed problem. I suggest one you check for any thrown codes. Second, you get an electrical diagram and check the signal coming from the switch and over to the trans. with a multi-meter. Results will not be a conclusive answer but at least you will know which 50% of the problematic areas to chase the fix in. The encoder motor sensor has been a frequent issue in the 2004 to 2006 models that I know of....I replaced one in a 2006 model. Through 2003 the switch was a frequent problem....I replaced one in a 2000 model.

Good Luck.

 

I have a similar issue and i've got it pegged as encoder motor. If i key off/on i am able to switch from 4hi to 2 hi no problem but it does fail again after a time.

check for thrown codes as Chavette advised, you should see it.