I have had many problems with my '99 Explorer's 4x4 not working. It seemed to be simple fixes at first - the actuator switch needing cleaned, the switch itself being replaced, the actuator motor was taken apart and cleaned. Each time the 4x4 quit working, one of these seemed to fix it. Recently, our mechanic tried one of these remedies and it didn't work. We took it to a Ford dealer and they determined that it was the GEM module. Along with that, they discovered that the rear ABS speed sensors were faulty and shorted out the module. So, with new sensors and module, the 4x4 worked for a couple weeks. I took it in to have some unrelated repair work done last week, and now the 4x4 lights don't come on when I turn the ****. At least, before when it didn't work, the lights would flash.

Any ideas?

(Sorry for the long post)

 

I would say the 4x4 shift motor needs replaced.