4X4 shifting after Service Trans message

[bconnel1965]

I have a 2017 Sierra Z71. I had a Service the 4x4 message on my truck several months ago. I took it to my dealer and they had my truck for a week. The dealer could not reproduce the message. They said I need to put the truck into 4x4 and drive it for a few minute every once in a while. This will stop the SERVICE 4x4 message. I middle of Aug I got the same message, but this time it showed the truck shifting into 4H on the information screen. Now I don't know if the truck actually shifted at all. I pulled into a parking lot and turned the 4x4 selector switch several times. the truck was not shifting to anything. I finally got the truck to go back in to 2wd per the info screen.  I called the dealer and he did not have any loaner to put me in. I continued to drive the truck. Last week the same thing happened as the second time. I video taped the selector switch not working etc. I called the dealer and made the appointment for this issue. I was called today and the shop said they can not again reproduce the problem or the truck is not showing and codes.

I going to talk to the shop foreman tomorrow about this and the video I emailed the Service Writer.

What can this problem be so I can talk with some knowledge on this problem?

The truck only has 33,000 miles on it and never has been taken off-road. I have a lifted Jeep for that. This is my first GM product ever. I never have had this problem with any FORD truck I've owned.

Thank you

b. Connel Army ret.