won't shift into 4wheel high

I had this problem with mine. For me, it was the electric relay switch that actualy engages the 4 wheel drive, simple $90 fix at the dealer. Dealer said the problem is actually bases off of NOT using the 4 wheel drive. So every once in a while, even in decent weather, I use the 4X to run to the store. Haven't had the problem in 2 years.