Need Advice 2003 Silverado 4x4 acting up
 

Hello, I need some advice on how to fix 4x4 issue.
When I start the truck up it doesn't remember where the 4x4 was left when it shut off, normally 2wd is used but when I start it up it could go to 4wd low or 4wd high or auto or neutral, anything could happen you never know, also the service 4x4 prompts when this happens. I don't want to keep switching it out of 4x4 all the time, extra wear and tare not necessary. So I've tested the switch out and according to the website I was referencing it was functioning normally. So what is controlling the memory ?
Thanks for any help!
Chev Silverado 1500 Z71