Searched and read most threads on my problem and I began troubleshooting. 2003 6.0 w/ESOF

I get nothing when 4x4 is switched on to either hi or lo. I had my wife sit in the truck with engine running, while I checked voltage at the 2-wire connection to the transfer case motor. There is no power going to the motor.

I tested the switch, it is good.

I believe I have the right box with the relays. There are 2 boxes on the driver's side between battery and firewall, one holding only 2 relays and the other holding 2 relays, a couple fuses and a couple larger, plug-in modules. This bigger box is located closeer to the master cylinder on the firewall and this is the one I believe controls the ESOF. Is that correct for a 2003?

I tried switching the 2 relays, no help. Thinking they might BOTH be bad, I replaced each one with a known good relay, no help. I tested the relay slots. They both have power and good grounds, however nothing happens when the dash switch is turned on. There are also 2 fuses and a couple other bigger modules in there. Both fuses are good, don't know about those 2 plugin modules or what they do.

With those parts eliminated, I am now assuming my trouble is most likely with the "GEM"? Is this the same animal as the 4x4 control module? Where is this located on an '03? I have an SCT that can check DTC's, however it is clean and I don't think it's able to read anything from the GEM anyway. Will the test function on the dash be able to provide me with a code? Is this "dealer only" to diagnose?

Oh, also, when I turn my key to ignition, some lights illuminate on the dash panel, but not 4x4....however, that light does momentarily light up as well as the lo range light once the engine starts. I think that's the way it works correctly?

Have I missed anything to get me to this point? I have no other electrical gremlins, it all works as it should. I would be surprised it's the GEM.

Thanks, any help is much appreciated! I am now getting in over my head!


Howard

 

I saw a thread where there was both a 4x4 module and GEM and he said he replaced both but at this point I would have the dealer check it. It was a recent post in here and it turned out neither one was needed because he broke a gear (or something) inside the TC motor which he replaced also. You might "just" need a new TC motor.......none of it is cheap.

 

I did read that post. While his motor was turning and everything was functioning as it should, but his solenoid gear was stripped and not doing anything when the motor turned. My motor doesn't even get that far, it gets no power to begin with. I wish the motor were bad and that was the problem at this point!

But yeah, I tend to agree that I am getting to the point of letting the dealer work it out. I know they have the code readers that get info from the GEM too. It's just the whole dealer thing, lol.

Thanks for the reply!

 

Yep, going to the stealer is like going to the dentist.

 

No. The correct box is the one with only two relays and nothing else in it.

 

+ 1 on the above.......

 

OH!!! Well, D'oh!!

Thanks! Maybe all is not lost, I'll check on this first thing this morning and report back!

Thanks again, that could turn out to be some very important info! lol


Howard

 

Well, tested both relays and they are good. So I removed the relays and did some testing with the voltmeter.

Pin 87a is apparently ground and it's a good ground on both.
Pins 85 and 87 are both always hot on both, engine on or off.
Pins 86 and 30 are both dead with engine running, however I did note that I am getting a reading of 2.2v on pin 86 on one of the relay slots with ignition off?

While truck running, I had a helper switch from 2-hi to 4x4 hi and nothing changes at any of the pins. Same with going from 4x4 hi to 4x4 lo.

I thought it was strange I am getting a 2.2v reading on pin 86 on the relay closest to the firewall....when it is dead on the other relay?

I tested the transfer case motor and it works fine, of course I get no power there at all when someone switches it to 4x4.

In summary, my switch appears to work when I read it, both relays are good and they are getting a good ground too.....and the transfer case motor works as well. Getting no change in voltage on the pins at the relay block when the switch is turned.

I guess that leaves me with a trip to the dealer?

 

It sounds like it but hang in there, someone with expertise in that area might chime in. The cover on the module comes off and sometimes has signs of corrosion.

 

Thanks, I'm in no rush as it's been this way for at least 10 months now! I have avoided situations needing 4x4 for a long while now.

I did see a thread with a photo of someone's corroded module....almost looked water stained but it was pretty obvious. Is this module the one located above and to the right of the glovebox? I know something is located there.

Thanks for hanging with me here, maybe a tech will read this thread and give some advice.

 

I think that is where the module is.

 

That is what my truck did. It was the relays even if you hear them click. My relays were clicking but not transfering the electric to the transfercase the testing you did was the test i did if there is power going in and no power going out it is the relay the switch on your dash just gives ground to the relay witch activates the relays. the always hot wires supply the relays with power the ground makes the relay click when the switch is activated. it has to be the relays. I hope this helps. try taking some relays out from you dash in side the cab some that you know work for sure. you don't have to have your truck running just the key on. some will tell you that the actuater on the passenger fire wall can cause it. It has nothing to do with the transfercase going into gear. only your hubs I have mine disconected all together and manualy engage my hubs.

 

Oh also there are only two wires to the motor on the transfercase that turn the motor on they just reverse one when it is the power and the other is the ground it makes the motor go one way when the polarity is reversed it makes the motor go the other disconnect the motor from the transfercase all together test it on a battery if it make a loud noise but moves it is bad and will not work. if it works and is quiet just a normal noise it is fine. i flipped the box over and pulled the bottom of it apart where the relays are the same color wires that you see down on the tc motor are the two you need to check to see if they are getting power at the relays them self if you go power to the relays and no power going out of them it is them you can also find the activation ground wire for the relays and activate the relays manualy and listen to see if the motor turns.while the tc motor is off the transfercase if they click and still have no power coming out to the tc motor it is the relays. I wish i was there to help you because i just did all this on mine. I got it figured out after a few days of testing. good luck if i can help just send me a message back.

 

Thanks for all that info, Scott!

I don't hear the relays click at all....nothing happens when I turn the switch. I'll tell you why I think it's not the relays, although I didn't really test the originals that are in there now. I have a relay setup for a light I put in the shell. I used a relay for that light so I could switch it on from either inside the cab or inside the shell. Anyway, I know this relay does work and I switched each of the 4x4 relays with this one, one by one, and tried it with no luck. I just might buy new relays and replace the originals anyway just to be sure.....they're cheap enough and I can always use an extra relay for something I suppose.

Also, yesterday I went under the truck with my battery charger and unhooked that 2-wire plug. Touched the pins with my battery charger, the motor cycled and I then reversed the polarity and it cycled back again. I am thinking the motor is okay. I still don't know about the top wires, I know that's where the position indicator is.

I am going to go through it again like you suggested though, can't hurt and if I run across something it'll sure save me some dough!

 

Checking that relay box is what I am going to try next.....makes sense.