Light not on switch or gauge for 4wd on 2002 Trailblazer What is the problem 4wd not working?

I had the same problem on my 2002 Trailblazer back in summer of 2004. I noticed that my light wasn't lit up either. I took it in to the dealer and was told that my four wheel drive hadn't been working probably since the day I purchased the car (new). This alarmed me since I had just returned from a trip out Westdriving the car to the top of Pike's Peak with out four wheel drive. GM covered the cost of the repair.