Like the title says, my 01 has ESOF and I've done a bunch of research both on here and other sites.
The hubs are locked in turn the switch and nothing happens, no clicking on the hood, no lights on the dash. First off my mechanic told me it was the GEM, his computer was not communicating with it, and happened to working on the same truck and took that GEM out and put it in my truck everything started working... So I bought a brand new one installed it and Nothing so then I took the switch out and put it in a truck with working ESOF and it worked fine in it. So I moved onto the relays, put two brand new relays in still nothing also checked all the fuse, TWICE, after that I replaced the motor on the bottom of the transfer case, once again NOTHING. I have someone coming to buy the truck this weekend and it would be really swell to get it working before they come and possibly not want it bc of the 4x4 issue.
I read that its an electrical issue bc nothing happens on the dash, if it was the vacuum I would still get a light.
My Uncle seems to think its in the hubs and wants to take it apart tomorrow. Is that worth it?
Also I read that there should be a constant power and a key power to Both relays, Tue or false? B/c the relay closest to the dash has no power when the key turns on. So could my whole problem be a broken wire? Is there a way I can "jump" that relay point instead of tracing wires all over the truck?

Any help would be great.
Thanks

 

Turn your air on, if it goes straight to blowing defrost its a vacuum leak (in 4wd).

 

I am also having that same issue. I have put manual hubs on, changed the relays, checked the wiring replaced the GEM module and the shift motor. I have power to both the pins on both relays. Just no signal from the GEM. What else is there, anyone? Thanks.

 

Just a thought but could the 4x4 indicator light be burned out, I don't have a wiring diagram, but if that light is burned out it might be needed to complete the circuit?

 

I just experienced this same problem on my 02 F-250. Once i found the right wire to look for it wasn't that hard to find the problem. The wire that supplies power to the relays is a dark green with light green tracer. I comes from the fuse box from fuse position #111 and goes through the main harness to the top plug under the AUX #3 Relay box and then supplies power to the relays. My wire was broke between the plug and the relay box. It was obvious where the break was as the wire had swollen from corrosion around the break. I have a picture of the area with captions but can't attach it yet. so if you would like a copy if it pm me and i will send it.

Todd

 

Not the dash light bc it comes on when you start the truck and it does its self checks.

 

yes please. I'll pm you as well. I'm having same issues. replaced relays, fuses no light on dash except when i start it and all the lights on dash light up. lifted rear end to see if when in 4x4 hi or low the front shaft moves. it doesn't so it's not my hubs.(CHECK THAT OUT OP BEFORE YOU REBUILD HUBS) .

 

im having an issue as well where my 4x4 will engage but not always ive been trying to figure it out through process of elimination but i dont know anything electrical about the 4x4 system only the mechanical parts, my hubs should be good they were checked out not too long ago but when i hear and feel the 4x4 engage and turn the wheel as far as it can go i notice it doesnt tug on the wheel like it usually does anyone have any ideas? could it be electrical or is there any way i can make sure i know its working?

 

Here's what I found out. There should be a constant power and a key on power to both relays under the hood. Quick check with a test light I found the constant power on both, then turned the truck on and found the key on power on the first relay, no key on power to the second one. tried to jump the power over, this didn't work bc the GEM does not know there is power going to the relay. There for wire has to be broke somewhere between the Relay and the GEM, Its not at the relay so it has to be somewhere near the GEM.
I told the guy that was checking the truck out what was going on with it and that I work constantly and haven't had time to trace the wire. He said he'll buy the truck anyways. He got a loan and everything for it just needs to wait a week to get the money for taxes. So I haven't been concerned about getting it to work. I also bought the Powerstroke I was looking at and the only reason i was selling my truck. So there is also the reason for no motivation to fix it.

 

thats good to know, would it be a broken wire or something electrical if it inconsoistently works however? like i hear and feel it engage while driving but if i take a tight turn i dont feel any resistance while turning.

 

From what I've heard that sounds like it would be something with the vacuum system

 

Ok, I'm going to try and diagnose it today at some point.

 

does your drive shaft move when your in 4hi and drive?

 

I wasn't able to check but if I lock my hubs and turn onthe 4x4 it works fine so Im assuming so

 

I am having the exact same issue as you are...did you happen to figure this one out? My dash light works and all, just really weak 4WD without manually locking the hubs...