4x4 not working properly 2001 Isuzu Rodeo Sport V6
 

The 4x4 light just flashes, sometimes stuck on off, sometimes stuck on on. When I turn on the 4x4 and then turn off the car and turn it on again it stays on (for now). When I turn off the 4x4 and then turn off the car and turn it on again it stays off (for now). I wish I could get it to work the way it used to work. 100k miles on it, original owner.