Problem w/ 4wd engaging automatically

We have a 2005 GMC Sierra with approx. 45,000miles. The 4wd sensor has been replaced twice and now we are having a problem with the 4wd engaging on its own when the vehicle is turned on. It has gone into Auto 4wd, 4hi and 4lo all on separate occasions. It does not happen every time the vehicle is turned on, but usually 2-4 times a week. Our dealership and GM does not know what the problem is, as there are no error codes being sent to the computer. We love the truck and would rather not get rid of it - we're hoping someone else has heard of this problem and can help/give advice/ anything!! THanks!

Welcome to the forum, exactly what sensor are they changing? It would either have to be something in the switch on the dash or something in the bcm.