4x4 not engaging

[BluIsBlue]

Hi again y’all, I’m still driving my 2001 Ford Explorer Sport 2dr. I’ve got an automatic with the electronic 4wd switch. When starting the vehicle, 4hi and 4low lights do not illuminate. I’ve tested voltage and ground on the 4x4 module’s harnesses. I’ve visually inspected the 4x4 module’s circuit board and cleaned it. I believe I’ve gotten all fuses checked but I may have missed one or two as some that relate to it aren’t labeled as 4x4 related fuses. If there’s any other ways to troubleshoot, please let me know and give me some ideas.

I’m trying to do this without spending a couple hundred on a new 4x4 module.

Thanks,
Blu

 

[J_C]

I would first see if 12V is making it to the transfer case connector on the brown wire. If it is, and the wire connector is not excessively corroded, then you may have a problem with the electromechanical clutch in the transfer case.

If 12V is not making it to it, then I'd check whether 12V is coming out of the 4WD module (aka torque on demand relay (solid state relay module)), and so on, probing further and further towards the battery. A wiring diagram for it is attached below.

 

[BluIsBlue]

I would first see if 12V is making it to the transfer case connector on the brown wire. If it is, and the wire connector is not excessively corroded, then you may have a problem with the electromechanical clutch in the transfer case.

If 12V is not making it to it, then I'd check whether 12V is coming out of the 4WD module (aka torque on demand relay (solid state relay module)), and so on, probing further and further towards the battery. A wiring diagram for it is attached below.

That connector, where would I find that? I assume under the vehicle? I understand it should be seemingly self explanatory but I wanna make sure I don’t go hunting for a connector without having an idea of where it is.

 

[J_C]

It's on the transfer case, under the vehicle. You'll know you have the right wire because it's brown. Same wire terminates at the other end at the TOD (torque on demand) relay in the dash behind the radio.

 

[BluIsBlue]

Could this fault in the connection cause the 4x4 module to not be recognized by a scanner? I’m taking a look at a special scanner on my rig and it simply just does not recognize the 4x4 module. I wonder if the module is bad or if I didn’t do a good enough job checking the harness?

 

[J_C]

There is no scanner recognizing the module, factor. It's not on a data network. Certain Ford-specifc errors seen by the GEM might show up, but failure of the transfer case to energize 4WD is not one of them. See the wiring diagram I posted previously, no data or sensor lines coming from it... well there's the speed sensors in the transfer case, but manually activating 4WD doesn't depend on them.

 

[BluIsBlue]

Was looking around, probed some wires on the transfer case and they look alright. I went to a salvage yard to check out getting a new 4x4CM and found one in a 2002 AWD Explorer. Plugged it in and the 4hi light came on and was blinking. Haven’t bought it yet as I don’t have the spare cash but I think that reasonably narrows it down to my current module being busted. My main worry is that I’ve seen things that say 2001-2005 versions of this module should be interchangeable. I’m worried that because my Explorer is based off the 2nd gen Explorer and not the 3rd that one of these newer modules won’t work? Does it make a difference that the module out of the 02’ came from an AWD vehicle and mine is a 2WD vehicle? Should it work the same? Part numbers differ slightly too but I still see things claiming they work on 2001-2005 explorers and rangers.

 

[J_C]

How far off are the part #'s? Sometimes you can look up the part # on a ford parts site, per model year, and see if there's any crossover.

However I never noticed the 4WD lights blinking in operation so are you certain that's how it is supposed to be and there isn't another fault too or instead?

Personally I wouldn't focus on the light for the moment, but whether 12V is getting to the transfer case on the brown wire. If it is, your control circuit is fine and the problem is at the connector or in the transfer case. If 12V is not getting there, I'd check for 12V at the brown wire at the shift control module and/or at the TOD solid state relay, check for good ground on the shift control model connector #1 pin, and whether 12V is making it to the shift control module over the dark green/lt. green wire pin #3 from the engine bay pwr. distribution box fuse #6. That should be 12V at all times, not just when 4WD is selected.

 

[dvdswan]

Same sort thing was going on with my 02 ST when I bought it. I ended up disconnecting the selector switch and reconnecting it and it worked fine. Fat electron theory was at fault. In other words, the connection was corroded.

 

[J_C]

What I neglected to ask was, your topic is titled "4x4 not engaging" but then so far what was mentioned is the lights.

It is for certain that 4WD is not engaging by no significant (it's a live axle so more than a tiny bit) torque to front wheels?

If you were to run 12V straight from the battery or wherever else, circuit capable of the few amps it needs, over the brown wire to the transfer case, that should activate 4WD (high). Same for jumpering between the lt blue/black and brown wire, corresponding contacts on the TOD relay, assuming your Accessory Delay relay works so that lt blue/black wire is live with vehicle on.

 

[410Fortune]

The 4x4 control module needs to be from a similar model
If your t case is control trac then you need a control trac 4x4cm

Usually it is the shift motor that fails not the control module just fyi
Does your 4wd switch say 2wd 4hi and 4lo or does it say “auto4”

If you have a control trac case (auto4) then I would suggest draining the fluid and look at its condition. Any small white nylon bits in the fluid? Near the drain plug? This would indicate a failed control trac t case

 

[BluIsBlue]

The 4x4 control module needs to be from a similar model
If your t case is control trac then you need a control trac 4x4cm

Usually it is the shift motor that fails not the control module just fyi
Does your 4wd switch say 2wd 4hi and 4lo or does it say “auto4”

If you have a control trac case (auto4) then I would suggest draining the fluid and look at its condition. Any small white nylon bits in the fluid? Near the drain plug? This would indicate a failed control trac t case

Mine is with the switch that says 2wd, 4hi, 4lo

 

[BluIsBlue]

Hey all! I did some digging and it looks like the schematics provided by JC weren’t quite accurate to my Explorer. After further research, my 4x4 control module does in fact have data lines coming off it. I found further trouble shooting (that I believe come from ford directly) on charm.li (freaking wonder of a website)

 

[BluIsBlue]

Hey all! I did some digging and it looks like the schematics provided by JC weren’t quite accurate to my Explorer. After further research, my 4x4 control module does in fact have data lines coming off it. I found further trouble shooting (that I believe come from ford directly) on charm.li (freaking wonder of a website)

This showing that because it wasn’t recognized by my more advanced scanner, there could be an issue in the data line that could further point to the overall issue of 4x4 not working at all

 

[410Fortune]

Okay let me chime in here

The 4x4 control module has one wire that goes to the obd2 sensor it is called the iso wire. Some scanners maybe able to talk to it, I have never had such luck

Your sport is a non control trac, so basically your 1354 t case is same as 02-05 ranger, sport and sport trac. A 4x4cm from any and will not work properly.

You should remove the shift motor from the back of the t case for testing. You may even consider taking the motor apart and servicing it
With the vehicles battery disconnected and Once you have the shift motor back together the system should be in 2wd, the shift motor and dash switch. Now hookup battery and see if she shifts from 2wd to 4wd. Then with foot on brake and shifter in neutral you can get the low range shift

Un hooking the battery gives the control module a reset. Often this is all that is needed to get things working again.
I like to hold the control module in my hand while testing because you can hear it click as it attempts to engage the shift motor.

I’ve said it a few times now, the shift motors fail about 10 times more often than the control module. Consider trying a different shift motor from a 02-05 as
Listed Above or at least clean and lube yours on a bench

 

[BluIsBlue]

Okay let me chime in here

The 4x4 control module has one wire that goes to the obd2 sensor it is called the iso wire. Some scanners maybe able to talk to it, I have never had such luck

Your sport is a non control trac, so basically your 1354 t case is same as 02-05 ranger, sport and sport trac. A 4x4cm from any and will not work properly.

You should remove the shift motor from the back of the t case for testing. You may even consider taking the motor apart and servicing it
With the vehicles battery disconnected and Once you have the shift motor back together the system should be in 2wd, the shift motor and dash switch. Now hookup battery and see if she shifts from 2wd to 4wd. Then with foot on brake and shifter in neutral you can get the low range shift

Un hooking the battery gives the control module a reset. Often this is all that is needed to get things working again.
I like to hold the control module in my hand while testing because you can hear it click as it attempts to engage the shift motor.

I’ve said it a few times now, the shift motors fail about 10 times more often than the control module. Consider trying a different shift motor from a 02-05 as
Listed Above or at least clean and lube yours on a bench

View attachment 452270

My issue is i get absolutely nothing from the control module. No clicking no nothing. Not a single thing happens when flipping that switch on my radio bezel. That’s why I’m so focused on it. Otherwise if I was getting codes flashed through dash lights or some sort of other response from that module especially when attempting to shift into 4wd I’d look closer to the shift motor. Once I’ve finished troubleshooting data lines and the module (I have an OBDII sensor that is adamant that it can communicate with the module cause it tries every time and tells me it’s entirely unresponsive) I will then look at the motor. I understand that 9 times out of 10 that motor will be out not the control module but I’ve had a few things with this car that I’ve had to fix that were in that 1 out of 10 probability. For example my passenger window doesn’t work, normally that happens to be the window motor or regulator. Not mine one of the switches doesn’t work leading to the window not rolling down with the master or passenger door switch. This truck has basically been babied it’s whole life. I’m not even sure 4wd has ever been engaged outside of systems testing. And my biggest reason behind looking at the control module, as I’ve said before, was that in the past I had indication it was being communicated with by the vehicle on startup via my dash lights. 4hi and 4lo are supposed to turn on and hold for a second when the car starts and it hasn’t done that since I had to set my car aside for like 4 months while I had to wait and fix my thermostat housing as it was spraying coolant all over my engine bay.

 

[BluIsBlue]

Okay let me chime in here

The 4x4 control module has one wire that goes to the obd2 sensor it is called the iso wire. Some scanners maybe able to talk to it, I have never had such luck

Your sport is a non control trac, so basically your 1354 t case is same as 02-05 ranger, sport and sport trac. A 4x4cm from any and will not work properly.

You should remove the shift motor from the back of the t case for testing. You may even consider taking the motor apart and servicing it
With the vehicles battery disconnected and Once you have the shift motor back together the system should be in 2wd, the shift motor and dash switch. Now hookup battery and see if she shifts from 2wd to 4wd. Then with foot on brake and shifter in neutral you can get the low range shift

Un hooking the battery gives the control module a reset. Often this is all that is needed to get things working again.
I like to hold the control module in my hand while testing because you can hear it click as it attempts to engage the shift motor.

I’ve said it a few times now, the shift motors fail about 10 times more often than the control module. Consider trying a different shift motor from a 02-05 as
Listed Above or at least clean and lube yours on a bench

View attachment 452270

But even if the only issue is my CM I think I will follow your advice and take this out anyways and inspect it to ensure it is in good shape and properly taken care of. Poor old thing could always use a little extra care. Is there any lubricants you would suggest for one of these?