Code P1621, Service 4wd

[03Duramax]

Lights do not light up on dash. My Bullydog shows code P1621. Can any of the techs help out with what is wrong and what needs to be replaced. Truck has 112k on it, it has done this for years randomly and with a cycle of the key it works fine for months. Now it doesn't.

03 Sierra Duramax 4wd.

Thanks guys.

[More Power]

You could search (http://www.thedieselpageforums.com/tdpforum/search.php?searchid=65805) this forum for the keywords "4WD Switch".

I suspect you may have a bad pushbutton transfer case switch....

Jim