2003 Chevy Avalanche "Service 4WD" Message?

Okay: So I really really suck at cars. But I was driving my truck today (2003 Chevy Avalanche...) and I noticed this "Service 4WD" message. If I tell my dad, he WILL blame it on me even though I did nothing wrong, and I'll probably get it taken away. Can I still drive with the message on? Is it just a sensor and will it go off eventually? Help!