Hello folks,
It's that time of the month, yes time for another "My 4WD won't engage" thread. Now, before you tell me to search the forums (I did) or check if the 4WD dash lights turn on (they do), please hear me out.
I have a 2003 FX4 with the electronic transfer case. This is the one with the live front axle (no vacuum in the 4WD system). Unlike every other thread on every forum I've checked, I am seeing the following:
- 4WD + 4WD Lo dash lights turn on at start, then turn off. Normal behavior.
- When switching to 4WD (hi or lo), there is no relay sound from anywhere. I have tried with the engine on and off. I have replaced every fuse and all relays. I also have a 97 where the 4x4 works, and I can clearly hear the relays on that truck.
- When in 2WD, the front driveshaft spins along with the front wheels, however it is disconnected from the TC (I believe this is normal, however extensive Googling has only lead to a solid "nobody is really sure")
- When in 4WD, the front driveshaft behaves exactly the same way
Also please note that I have tested the 4WD switch on the dash with a meter, and it behaves as expected. I have also swapped it out for the one in the working truck without any change.
Every thread I have read thus far has indicated that if the 4x4 module goes bad, the lights won't appear on start. My lights do come on, however the switch doesn't make the 4x4 relays "click".
Any ideas before I start dumping money into it? I've spent all summer rebuilding this truck, so I have no qualms about getting underneath and messing with stuff. Just need an idea of what direction to go with it.
Thanks.

 

Yes, there is a "Bulb test" when you turn on the key, all dash light bulbs should come on and go off, some of course stay on, lol, but it is just a test so driver can see if a bulb has burned out, nothing to do with the system the bulb is used for, just FYI.

Ford has used a few different Electric transfer case control modules over the years.

But the electric transfer cases(BW1350 and 1354) all work the same way.
The Electric shift motor turns a shaft(shift rod) that moves a shift fork inside the transfer case, this can engage the chain driven front drive line yolk to main rear shaft giving you 4WD, if shift fork is moved farther it then engages a reduction gear for 4low, which changes the ratio of both front and rear shafts.
When front hubs are locked, the axles and drive line turn with the tires, as does the chain inside transfer case, but in 2WD it is just spinning on the output shaft, not connected to the output shaft, same as any transmission, everything is spinning when moving, but only one "gear" is selected.

The 4WD control module operates the shift motor, in 2003 Ford used 4x4 shift module, it looks like this: https://www.ebay.ca/itm/NEW-OEM-4X4-...-/283063572101
Previously they used GEM module with separate Relay Box(your 1997), and before that(1994 and earlier) a larger Control Module like this: Ford Ranger 4WD Control Module

The point of these "controllers" is to run the shift motor and monitor its position, i.e. 2WD, 4high or 4low were the 3 position the shift controller used
Shift motor is a 12volt motor that can turn in either direction by reversing polarity, same as power window motor.
The Controller used two relays to do the Polarity, one relay for each of the TWO "power wires" going to the motor
When these relays are unpowered(open) they GROUND their wire, so Controller only has to Close 1 relay which then connects that 1 wire to 12volts, since the other wire is already a ground the motor turns.

There are 5 other wires on the shift motor, these are the Position wires, they tell the controller what position the shift motor's contact wheel is in, 2WD, 4high or 4low

Good pictures here of the shift motor, contact wheel and transfer case shift rod and its 3 positions: https://www.explorerforum.com/forums...-motor.123542/

When you are in 2WD and select 4high, for example, the controller will check its current position via the contact wheel, it will then activate the relay that will turn the shift motor counter clockwise, it will wait until motor has moved and Contact Wheel is in the correct position(4high) and then open that relay to stop the motor, it will THEN turn on the 4WD light

A Flashing 4WD light means either motor didn't turn or contact wheel didn't move, possibly a blown fuse or failed shift motor

No 4WD and no flashing 4WD light would mean controller itself may be without power or dead
The shift controllers from 2001 and up Ranger/Explorers did fail more often than the older ones, so yours is probably bad, but armed with the above information eliminate other possibilities first

Here is the wiring diagram for 2003 4WD system, it shows the fuses to check

 

Hi Ron, and thanks for all of that information. Good to know that the "bulb test" is essentially useless. That's the #1 advice I've seen given in other threads, so I wanted to get that out of the way as soon as possible. And a bit of clarification: aside from the initial "test", those two lights never light up whatsoever.
Regarding your comments on the different variations of shift module: if I'm understanding you correctly, there are still relays involved that should be engaging. Are these located in the engine bay relay box, or inside the shift module itself? If they're external, that is just more evidence for a bad module, as the relay box isn't making a sound.
Appreciate your input. In the meantime I'll start shopping around for a new module. Last question: on the 97 the shift module is located on the passenger kick panel (door-side). Does that remain true for the 03? Don't want to remove trim pieces of I don't have to.
Thanks again.

 

Quick update, I went to the junkyard today and picked up a "new to me" 4x4 control module, and installed it. So far the only change is that the 4WD dash switch is now lighting up, which never did before.
I am still not getting any relay clicking or seeing any flashing lights, so something else is clearly wrong.
I have a few other things I need to replace tomorrow before the inspection Wednesday, so this will have to be back-burnered until later this week, unfortunately.

 

The Relays are IN the 4x4 Module from 2001 and up, no separate systems involved.

There are only 3 parts to the system
Switch on dash
4x4 Module
Shift Motor

And of course the fuses

If 4WD lights are not flashing when you change to 4WD, then the problem is NOT the shift motor
Problem is that the 4x4 Module isn't getting the "command" to change, or 4x4 module or wiring is bad

You can test switch at the 4x4 module wiring connector with OHM meter,
There are two wires from 4x4 module to the switch, Yellow/blue and White/blue, hook up OHM meter and test that OHMs change when switch is moved to its 3 positions
KEY OFF

Then test for Voltage at the 4x4 Module see diagram for which wires to test, the Fused wires

 

Thanks for the additional info. Depending on how far I get with the doors today I may be able to test the switch and wiring. Will follow up.

 

Alright, I had a chance to play around with this again.
I tested the resistance across the two wires you mentioned, and got 3 separate values. With key off, I measured across those same wires behind the 4x4 module and got the same values.
I also (again) swapped the switch entirely for the one in my other truck, where there are no issues with 4wd. It behaved exactly the same.
One thing I did notice is that, with key off, if I plug in the black connector to the 4x4 module, there is a clear relay sound coming from behind the dash. I think it is coming from the GEM (part 1l5t-14b205-af), but I can't be 100% sure. Do you know what this relay does for the system? Could the GEM need to be replaced? Are there any other tests I can perform?

 

You have the wiring diagram

No connection between 4x4 Module and GEM except for VSS(speed signal), which comes FROM the Computer(PCM) and goes TO both GEM and 4x4 module, no relays involved

GEM will activate and deactivate Battery Saver relay depending on power draw in the whole system
Shouldn't be any GEM issues that would effect 2003 4x4 system that I can see

 

Hmm, I'll ignore the relay sounds then. At this point I think I need to check for voltage going across the yellow and orange lines, as well as checking the gray wire to see if the 4x4 module is outputting anything (my guess is no). I'm also curious to see what the transfer case position sensor is reading, if anything. If there's no position reading the 4x4 module might not know which polarity to apply power.
Anyway I have work now, I'll test later tonight.
Thanks again.

 

If 4x4 module is working and you change the switch setting, the 4WD dash lights will flash if contact wheel or motor is not working.
Its a simple process
4x4 module gets a voltage change from the switch, there are 3 resistors, so 3 voltages, each voltage is a selection
4x4 module checks contact positions, so it knows which way to turn motor
No contacts and it flashes the lights
If there is contacts then it sends 12v/ground to motor, and watches contacts
If contacts don't change instantly it stops sending 12v to motor and lights start to flash

 

 

Yes, 2001 and up Rangers got a 4x4 control module(4x4CM)

Also go here: https://www.ranger-forums.com/genera...1-models-3747/

Download your owners manual there are a couple of fuses you need to check, the one in the engine fuse box powers the Shift motor
I don't have 2009 fuse numbers, but in 2010 engine fuse box #27, and cab fuse box #10 and #28 were for 4WD system


Picture of 4x4CM here: https://www.ranger-forums.com/4-0l-o...module-140263/

 

 

 

So after last night's snow, I decided I need 4WD again. I just finished playing with my meter, and found a clue.
When I measured the shift motor position sensors, every one of them appeared closed. In other words, voltage is being passed through every sensor, making the module think the motor is in every position at once. Additionally, all of these test positive for continuity with each other - even with the connectors unplugged.
I'm going to pick up a new shift motor and get that installed, and will update here with result.

 

1994 and earlier Rangers used separate 4WD module no programming needed

1995 to 2000 Rangers used a GEM(generic electric module) to control interior electrics AND 4WD system, so yes these need to match the vehicle options, and may need to be programmed for use in another vehicle.

2001 and up Rangers used separate 4WD module, different from 1994 and earlier, it also needs no programming, but wiring needs to match, there were 2 different 4x4 modules, 2001-2005 and 2006 to 2012

Used is fine for 1994 and earlier and 2001 and up

 

I threw a junkyard 4x4 motor in today, and now the 4WD is working exactly as it should.
Thanks for all your help on this, RonD

 

Good work

Thanks for the update and what FIXED it