That's funny, mine went off yesterday. Using my handy dandy Android app called Torque I went in to see what fault code it was. I wish I could remember the exact one, but is was a P0500 (or one close to that), rough idle cold start. I cleared the code and the Service AWD System went out on restarting the Jeep. I'll keep an eye on it, but I don't think it was anything serious. We had snow yesterday and the roads were very slippery and I have a feeling that had a lot to do with it.
Bernie