GM-GMC: 2001 GMC Sonoma Transfer cases.. shifting, gmc sonoma, 4lo

Question
I recently had my truck in to fix a problem with the 4wheel not shifting into 4HI. It would shift into 4LO But not 4HI. So he said it was the electric motor. and replaced it. Did a service on the transmission. Then while I was there he started the truck. Shifted it into 4HI and it shifted.. Shifted it to 4LO it shifted. But would not go back to 2HI.  What would cause this.. Truck is at the shop now and need some help. Thanks

Answer
Marcus ,

These GMC are goffy !! The intention of the electric transfer case was suppose to be easier, then lock outs . Try getting in the truck and driving in reverse approx 40' ,listen close .

When you are going foward switch from 4 HI to 2HI . Then come to a stop put vehicle in reverse and try this .
If this works , there is a clip on the transmission that comes loose and it is internal . When this clip breaks ,it causes this problem . instead of holding the gear to go to 2HI , you fool it by placing in reverse and going approx 40' you can try less .25' or so . Everything has to sync ... The more you use it the easier it will get . Try pushing button from 4HI to 2HI back and forth 20times or so ,,,