Jimm 2/3/2013Usually if it flashes when you start the vehicle - the low range motor on the back of the transfer case is jameed. Easly repaired by loosening the 3 bolts that hold it on. Take it off and tap it gently with a hammer to release the brushes. Put it back on then see if it works. If it does work keep engaging low range once a week to avoid the brushes getting stuck again.
It sounds like the low range engagement motor is bad, it should have left a code in the transfer case control module, you need to get the codes read just to make sure. The only thing left is the transfer case control module itself. It is possible that it just needs to have the codes cleared out or needs to have a program update, which can only be done at the dealer. It is the last thing that there is.