Four-wheel drive light flickers in the dash intermittently.

What is your question?

Four-wheel drive light in dash flickers intermittently and goes out for several minutes at a time while driving. It appears four-wheel drive remains engaged. This is an on the floor shifter. Often four-wheel drive indicator light does not come on for several minutes when truck is cold. My old chevy truck had a faulty ground that made the light flicker, but the four-wheel drive remained engaged. What can cause this in my newly purchase 2006 2500HD? Vacuum leak, fuse, burning out bulb, or ? I'd like to avoid a trip to the shop this month. But, where I live we leave it in four-wheel drive from October until May. I can't make it home from work without four-wheel drive and studded tires. If the four-wheel is on the fritz I'll need it fixed.