Got a buddy with an '02. The 4x4 on the dash won't engage. No 4x4 light comes on and nothing engages. Anything in particular I should check? Thanx!
this post seemed helpful to me once.I'm not arguing with you but I don't see how it was a bad vacumn hose. When the light illuminates on the dash that means the transfer case has shifted to 4X4 High or Low. There is nothing that runs off of vacumn on this side of 4X4. Vacumn is only used to locked the hubs on the ESOF system.
Without ruling out a bad relay, wire harness, etc. I would check for codes in the GEM module. The GEM module is what controls the 4X4 functions. I am having the same problem right now except might light will not come on whatsoever and therefore the transfer case will not shift into 4X4. I've ruled out everything else it could be, checked for stored codes with my AE software, and finally had to end up calling a friend of mine who is a Ford tech and he brought his scanner home to look at the PID for the GEM module. When he looked at the 4X4 side it came back as "Unavailable". Currently, I am waiting on a used module to see if this fixes my problem. I apologize for the book, just wanted to explain it in detail. Hope this helps.
How have you checked for leaks? I have a little pump tester deal with different fittings and hoses that you stick in you lines or on the nipples of the hubs and you can watch if the gauge holds steady or bleeds off. Best way I have found to test. The lines get weak and brittle, and the o-rings in the hubs get to where they don't seal, if you have a light and with the vacuum issues I would assume it has to be the o-rings or lines.i have the same issue, but the light comes on...believe my hubs are fubar anyways but I also cant switch the vents from defrost. Heard its all vaccum related so I replaced the vacuum pump (it was shot) and its still not working. Cant seem to find any leaks anywheres.