Originally Posted by collega

I had the same problem several years ago. And when I came to very knowledgeable mechanic so he fixed it for me for free and he told me how to fix it by myself in future if problem will come back: Try to play with your 4Hi and 4HI LOCK buttons, pressing them one after another one to let your transfer case motor to switch mode of transfer case from one to another one. You should do it when your track is not moving( you can do it even during long red light waiting on intersections!) and you should do it at least 20-30 times pressing buttons back and forth letting TC Motor to change mode for transmission. That mechanic-guy told me that it's a "Rule of 30 switches". When you do this procedure your TC motor start to work again and clean some residue this way, that could stay on the rotor and electric brushes of TC Motor after it didn't work for long period of time. So when your TC Motor do it for about 20-30 time, changing modes from 4HI to 4HI LOCK and back it could fix your problem! But be sure that your truck is STATIC and it's not moving during that procedure!
After one or two years this problem with DIC message:"Service 4WD"came back and I fixed it right away with this procedure!
I hope that it could help you for free! By the way, that mechanic guy was former GM specialist and employee!
Try it! And good luck!

Originally Posted by Mars0429

I was hoping this would work. For some reason My H3T is still giving tue SERV 4WD message. 4x4 still works and my scanner does not produce a code. I'm not sure if the issue.