What does it mean when the light comes on service 4wd

Illumination of the Lamp indicates a problem with the 4wd system. There will probably be trouble codes set in transfer case controller. These codes are needed to aid diagnosis. The codes should not be cleared before testing is performed, and cannot be cleared without proper test equipment. You should have your regular technician test it for you before the problem gets worse. Good luck!

I have a 2005 silverado 4WD and i had to have a switch replaced twice it wasn't serious just a faulty switch on the transmission