4x4 no longer works
<HR style="BACKGROUND-COLOR: #d1d1e1; COLOR: #d1d1e1" SIZE=1 itxtvisited="1"><!-- / icon and title --><!-- message -->posted this in the wrong forum previously.
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I was searching for threads regarding troubleshooting <NOBR style="COLOR: darkgreen; FONT-SIZE: 100%; FONT-WEIGHT: normal" id=itxt_nobr_0_0>4x4</NOBR> issues. my 4x4 just stopped working and I can't figure out why.
I've had the selector switch replaced, turned out it was just the LED that was out so it didn't help the issue.
I've had the solenoid replaced, still no joy.
now they are saying that i need to replace the 'GEM module' under the glove box. i feel like they are reaching at this point.

does anyone know if there's any relays or anything that may be causing this? the fuses under the steering wheel look ok, but i don't know if there are other places with fuses that I can check.

this is a 2005 <NOBR style="COLOR: darkgreen; FONT-SIZE: 100%; FONT-WEIGHT: normal" id=itxt_nobr_4_0>ford</NOBR> f250, v10 king ranch edition. i found a thread with a bunch of good troubleshooting steps, but it was for an older model because the fuse locations didn't jive under the steering wheel.

if i do replace the GEM module, what else is there to replace?

the truck is throwing out no error codes and the only time i see the 4x4 light on my dash is when the engine starts and goes through the little diag it does.

i hear no noises from the solenoid when i engage the 4x4 on the dash either.

thnx in advance.
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go to the power distribution box under the hood. There are fuses there as well. Refer to the owners manual for your truck here: https://www.fleet.ford.com/maintenan...ls/default.asp.

You should be able to find the fuses for the 4x4 solinoids there.

Do you have defrost only? That is a common problem, that can indicated a vacumn leak somewhere in the system.

So if you turn the hubs manually does your front engage?

 

nah, no defrost issues. ac works as it should.

thanks, i will check the manual out. my search skills on these forums SUCK. there is soooo much info.

 

You need to find a better mechanic. The 2006 doesn't have a GEM module to replace. 4WD is controlled by the 4WD control module.

Knowing how it's supposed to work ought to help you troubleshoot it.

When you turn the switch on the dash to 4WD, the first thing that happens is the 4WD control module activates one of two relays under the hood. That relay powers the shift motor at the transfer case to shift it into 4WD. Along with the shift motor at the transfer case is a set of switches that provides feedback to the 4WD control module, indicating whether the transfer case is in 2WD, 4HI or 4LOW. That entire unit is called the gear motor encoder assembly.

When the 4WD control module gets the signal back from the gear motor encoder assembly, it knows the transfer case is in 4HI and turns on the 4x4 dash light. Then it sends a signal the the Pulse Vacuum Hublock (PVH) solenoid, causing the solenoid to apply vacuum to the hub locks, causing them to lock.

When you turn the switch back to 2HI, the reverse happens. The 4WD control module activates the OTHER of the two relays, causing the shift motor to turn the other way shifting the transfer case out of 4WD. The encoder indicates this back to the 4WD module, which turns off the 4x4 light and eventually sends a different signal to the PVH solenoid causing it to send a smaller vacuum pulse to the hubs, causing them to unlock.

Now, in your case you're not getting a 4x4 indicator light. You know the light works cause you see it when the dash initializes and tests the indicator lights. This typically means one of three things. One, the 2WD to 4WD relay is bad or has a bad connection, the shift motor is bad, of has a bad connection, or the 4WD control module is bad.

Most of the time, the problem is the relay. Occasionally the problem seems to be the shift motor and rarely it seems the problem is the module. I base this on my own experience and from what I have read here over the last few years.

The relays are in a relay box under the hood, on the drivers side firewall up close to the back. It is the only relay box with just two identical relays in it and nothing else. A common diagnostic procedure is to swap the two relay's position. Since one relay turns the motor one way, and the other turns the motor the other way, and it's likely that only one of them has gone bad, swapping the positions should cause the truck to go into 4WD and not come back out. If this happens, then replace the bad relay and you're good to go.

If this doesn't help, then you are left with the slim possibility that both relays are bad, or the shift motor is bad. A good way to test this is to unplug the shift motor wiring harness from the shift motor at the transfer case. It's the plug on the transfer case with just two wires. Put a test light between the two pins of the connector and have someone turn the switch to 4HI with the key on. The test light should light momentarily, as the control module tries to turn the shift motor to 4HI. If the light lights, then most likely your shift motor is bad and needs replaced. If the light doesn't light, then you're back to the possibility of one of both relays being bad, or the 4WD control module being bad.

Another thing that happens occasionally is the windshield leaks water down onto the control module, causing corrosion in the wiring plugs of the module itself. The control module is behind the glove box. Open the glove box and push in on the sides. This will allow it to open further and allow access behind it. Inspect the control module and connectors and wiring for evidence of corrosion.

 

Hey guys great information. I am new at this but that really breaks it down for me. I have a 2003 F 250 Diesel and it has been in 3 different shops over the last two weeks and nobody can fix it. The light does not come on in the dash when you turn the switch on the dash. It does come on when you first start the truck. I hear nothing when I flip the switch. I have been told that it was the switch then it was the GEM module? I have no other symptoms. Is the GEM module same as the 4X4 module? I did put manual wern hubs on it due to the factories been beat up. Anything else I should look at? Thanks in advance

 

Please let me know what you find out about your 4X4

The dealer told me mine was caused by the GEM going bad and it was on back order from Ford for sevaral months. I have called everywhere and cannot find one. But I had the truck hooked up to the rotunda and the GEM did not flash a code?

 

I'm not sure exactly which year it happened but sometime prior to 2004 the GEM module went away and was replaced by other modules. When it existed the GEM module controlled the 4x4, vehicle security stuff like remote keyless entry and any number of other things. I wouldn't be surprised to find that the 2003 did have the GEM.

Before I spent a lot of money finding a new GEM, I'd be really sure I checked the two relays, those are pretty common failure items. I've also read about the wires going into the relay box corroding, or getting pushed out, etc. Also the GEM module getting wet and corroding. I'd check all this stuff out very carefully.

 

Great info I will check it out. As you know it I am in Ohio getting slammed with snow as I had to fill the truck up with snow. Will get back with you thanks again

 

thanks for all of the good info.
I may have been calling the module under the dash by the wrong name. it's a black case with a circuit board in it. it's got two plugs going into either end. that's the 4x4 control module i suppose.

so, i bought one of those and replaced it..it didn't fix my problem.
i also replaced the relay under the hood and that did not work either (even tho the original relay looked fine). *not sure where there is another relay for the 4x4.

i have a new transfer case shift motor on my desk, i've just not had time to install it. kinda worried about installing it because it said it installs in 4x4 high, and i can't currently move my truck into 4x4 unless i do it with a ratchet or whatnot.

so yes, i'm replacing everything possible and it's probably extreme overkill.

i've taken the truck to the local ford dealership and a firestone, fyi. i think the fact that there are no error codes has really confused both sets of mechanics.

i opted to buy the parts myself after seeing that both of them wanted to charge me for all of these parts with installation at a substantial markup. their quote for just replacing 1 of these parts (the 4x4 switch, the transfer case shift motor, or the 4x4 control module) cost more than what it would cost me to purchase all 3 and install them myself. and that was after I had already been suckered into spending nearly $300 on the solenoid replacement, even though it looked to be quite simple to do on my own.

the troubleshooting steps are very, very appreciated. can someone tell me where another relay might be though? i only know of the two fuses under the steering wheel and the 1 relay under the hood.

 

I was mistaken, it actually says 'GEM' on it.

here's some pics of it for anyone who may be following this. this goes above the glove box on the passenger side.

it opens up and inside is a circuit board

 

Do these steps work for a 2001 250 with v 10. today my 4x4 light wouldn't come on.After I got home it started to come on and I could hear the 4x4 click on. When I put it in 4x4 low I would hear a whistling noise for a little while on the drivers side then it would stop. Never heard the noise when I put it in 4x4 hi. I turned it on several times in the drive and it came on everytime. I too am in Ohio

 

There are two relays. One turns the shift motor from 2HI to 4HI to 4LOW. The other turns the shift motor in the opposite direction from 4LOW to 4HI to 2HI.

They are both in a relay box under the hood, near the drivers side firewall towards the back. They are the only two relays in the box. It is the only relay box with 2 identical relays in it and nothing more.

 

thanks for that information. i found them, they both were ok, but i replaced them just for the heck of it just because they are only $6 USD each. that did not fix my problem.

i can actually hear them clicking like 'tick-tock' a few times when i engage 4x4 high. but nothing happens after about 5 clicks. i didn't realize that was there the clicking noise was coming from until you pointed the location out..so thanks.

does the fact that those are clicking help narrow down anything?

 

that almost sounds like a vacuum leak. i think your 4x4 is very dependant on good vacuum lines and seals. someone mentioned the defrost coming on when you engage 4wd if you have vac issues. not sure if that applies to 2001 models though.

 

would also like to mention that those two relays for 'low to high' and 'high to low' are part number 19273 at autozone.

so it appears ford part number f0ab-14b192-aa = autozone part number 19273