So I have a 2002 Explorer. As you may have guessed my 4wd doesn't work. I have almost drove myself insane trying to troubleshoot the problem. OK so when I first turn my key to the on position I get just the 4Lo light but when I start the engine the 4Hi and 4Lo light come on but almost instantly the 4Hi light goes off. This part focuses me. I can press the 4Hi button the dash light comes on but I get nothing. I can then go through the 4Lo cycle and can hear the control module click twice and lock into 4Lo but front wheels aren't engaged. Another thing that confuses me is with the engine off I can cycle through the 4wd and hear the TCM engage in and out of only 4 Lo. What is my problem. I've almost pulled my hair out trying to troubleshoot this problem. Can anyone help me?

When I was having issues with my 4x4, I changed out the control module and that didn't do it. It turned out to be a bad ground on the transfer case motor.

Worth a look.

I've checked the grounds and everything its driving me insane

It sounds like your module is good and the relay is working so I'm thinking like bigrondo. My advice is to go back under the truck and double check that ground. There is a pigtail connector coming off the shift motor assembly. There is a short black ground wire coming out of that connector. Tug on it to make sure it's secure in the connector and that it's uncorroded and secure on the lug end. Here's a picture from rockauto:
https://www.rockauto.com/catalog/mor...768&cc=1377671

Ill check it again. Weird part is whenever the engine isn't running and you cycle through the 4wd you can hear the motor turning but only when you put it in low. Its beyond me at this point why its not working

OK so I checked the ground again. Still no 4wd. Is there any thing in the transfer case itself or a vacumm line that is messed up that could cause it to not work?

Did you ever figure this out. i am too now victim of this same thing. Tried a new 4x4 controller and that didn't do it. Ground seems fine. Tried tapping it with a mallet and that didn't do it either. I get no 4x4 hi or low lights when I turn the vehicle on. They used to flash but don't do this anymore either. Now it's almost as if nothing happens at all. No clicks or lights when I press the 4x4 buttons. I am all out of ideas.

2002 ford explorer 4.6 4 by 4 control module help please
 

the explorer i puchased, the previous owner removed the control module with plans on replacing it,never did. does anyone know how i can find one or at least the part number?