A friend who used to work for a local Jeep dealer (he was a mechanic) told me that when mine stopped working (years ago) that it was because I drove a crappy friggin' Jeep.
He hated working on valley girl Jeeps, and is somewhat jaded. Anyway, whey I got him to give me a real answer he said it could be a vacuum sending thingie on the t-case.
As was mentioned above, it's a indicator light. Big deal. So mine's still out too.
I don't know if any of that helps, but there it is. :)