Have a 2005 Ford Ex 52k miles, 6.0l diesel, with 4x4 system working intermittently. It works about 1 in 20 times with no rhyme or reason to when it will or will not work. When it works the dash light will come on. It is not a problem with the hubs as the 4x4 light is not coming on when it does not work. Testing as follows. Start vehicle and the 4x4 switch lights on momentarily and then off - normal. Turn the 4x4 switch and nothing - no light on dash, transfer case motor is not operating. I have a wiring diagram and have went through a lot of the wiring. Pulled all fuses and metered them - ok. Pulled relays and tested by applying voltage and metering contacts - ok. Pulled the 4x4 mode switch and checked the resistance in all positions - metered ok. With key on tested for voltage at the 2-wire transfer case relay as someone turned the 4x4 switch - nothing - problem. Applied 12v to the transfer case motor and it operates correctly - normal. Tested for ground signal on the relays when the 4x4 mode switch is turned - nothing - problem - the relays will never try to operate. Is it the 4wd control module that has failed as it should send the signal to the relays? Anyone know how to troubleshoot the 4wd control module or have other suggestions? The 4wd control module is $300 so I hate to just try one and have that not be the problem. Any other ideas or suggestions would be appreciated. Thanks in advance.

 

Man...not to pile on, but my 4x4 stopped working after I had the arp studs put in...it DID require body pulled off frame? What fuses influence the 4x4 not working? Any one for us?

Ad mine has only gone 10,000 miles after a hub replacement. They were working for 5K until this!

 

The fuses per my wiring diagram are 19, 27, 33, 34, 45, 111.

 

Well I finally fixed the 4x4 system and thought I would post what I found in case it will help anyone. I do have the full shop manual and went through most of the wiring diagram and could not pin point the problem. I took it to a diesel performance shop to plug into the computer and pull the codes - codes a normal code reader like my insight and SCT can not read. The codes were leaning toward a bad transfer case motor. The mechanic had a spare and put it on and it was then working (turned out to be a coincedence). Since he did not want to sell it he put mine back on and it was working on the way home. I went to NAPA and bought a rebuilt transfer case motor. Installed it and nothing was working. Took it out and put mine back in and nothing is working. Took it to Ford and they diagnose that it is the transfer case motor. I explained I had already replaced it with a rebuilt but they could try that as long as I am not stuck with the part if it did not fix the problem. They put a new transfer case motor on and nothing. They then called the Ford service hotline they have to discover the test procedures written in the manual are not correct and were sent new test procedures (this means I had been using the wrong test procedures as well). They did some pin point tests and came to the conclusion that it is a bad wire between the transer case motor and the engine bay. I needed to get home so I picked it up and nothing on the way home. I figured before bringing it back to them and having them remove the entire harness I would inspect the wire harness and play with the 6 pin connector. I jiggle it around and all of a sudden 4x4 is working. I put it in 4x4 as we were in the middle of a ice/snow storm and could leave it in 4x4 until a new connector arrives. Ordered the connector and was going to install. The wire harness to the 6 pin connector is about a foot long before joining a large harness. I remove the tape and then remove the split loom wire protector to find a cut wire about 8" from the harness end. Not sure how it could break inside the plastic wire loom protector - very strange. I soldered in a new piece of wire with heat shrink tubing, wrapped it all up, put the split loom on and added a 2nd larger split loom for added protection. It is working great now. The wire being confined inside the split loom was making contact sometimes and not others. Very hard to troubleshoot as any time the wire harness was moved it could all of a sudden make contact again.

 

Intermittents are always tough to find ! Good job though.....you will likely save some poor soul on here some headaches when their does it !