Hello, I just joined the Ranger club a couple days ago when I bought a used 2002 ford ranger XLT 4.0L and have not been able to engage any 4x4 mode. The 4x4 lights come on for a bit when i turn the vehicle on and the module is connected, meaning the bulbs are functional. The module does not click when a 4x4 mode is selected, but the wires connecting the module and the switch are functioning properly. I checked all the hot wires and grounds of the control module and they are all functioning as well. I also checked the wiring to the instrument cluster and those seem fine as well. The sensors on the transfer case motor are working just fine, but i don't get any power to the wires that power the actual motor (orange and yellow). They are still some wires I haven't checked on the control module because i couldnt find the diagrams for their operation. I went to the junk yard and found 2 control modules that looked a bit corroded on the connector, but those didn't power the transfer case motor either nor did I hear any clicking. I ordered another control module brand new so it should be here in a couple of days. But yesterday I found a control module at the junk yard that looked almost new and that didnt work either. Any thoughts?

 

Welcome to the forum

Some good testing there

There are two relays in the 4x4CM(control module), you should hear 1 click closed when you change selection on the switch if Key is on
If you don't hear the click the module is most likely bad
The 2001-2005 modules were a common failure point and there is no upgrade for them

There is a fuse in the engine bay fuse box, #13, 20amp, its for powering the shift motor, but the relay in the 4x4CM should still "click"

The system is pretty simple
The switch is sent 5volt from the 4x4CM, if 4x4cm gets back 4v that means switch is in 2WD, 3volt is 4high, 2volt is 4low
If the voltage changes the 4x4cm will "see" what contact on the shift motor is closed, there are 4 contacts, 2wd, 4high, neutral, 4low
This is so 4x4cm can determine which way to turn the shift motor, clockwise or counter clockwise

The two relays in the 4x4cm are 5 pins relays, and GROUND both shift motor wires when they are OFF
You can test for this, both motor wires should show as grounded, if not then there is a problem in the 4x4cm or wiring harness

So the 4x4cm only needs to activate ONE relay to send 12volts to the shift motor, because the other wire is already a ground, which wire gets the 12volts depends on which way the shift motor needs to spin, same as power window motors work
When the 4x4cm sends the 12volt it watches to make sure the contact changes, if not 4x4cm will stop sending the 12volts and start to Flash the 4WD lights on the dash, this means 4x4cm is "lost", its not seeing contacts changing so won't move shift motor

If shift motor fuse blows or shift motor dies you would get Flashing 4wd lights
If 4x4 CM dies you won't

2002 4WD Wiring diagram below

 

Thank You so much for the quick response! The new control module just came in and when I installed it, I still didnt hear the relays click. I tested the two wires that power the motor and both are grounded. I decided to turn the truck on and test the voltages of all the wires running through the control module. I noticed the signal return (yellow/light blue) from the switch wasn't receiving a voltage but the 4wd switch (white/light blue) was, Is there a chance those wires are reversed? I also didn't get any voltage from motor 1 (yellow/white). Any thoughts?

 

Well the 4v, 3v, and 2v on the white/blue wire is correct, depending on switch position, and voltage has to be coming from the yellow/blue wire and traveling thru one of the resistors in the switch to get the 3 different voltages

Try reversing polarity on your volt meter probes, to see if you get the 5v on the yellow/blue wire, Ford uses a lot of "Pullup and Pulldown" circuits, these are basically Ground circuits, so can read as 0volts on some volt meters


But it is odd that all 4 of the "motor" tcontact wires(2 to 5) are showing voltage, one should be "nothing" same as yellow/white, the ground, which is how 4x4cm determines shift motors position

 

Hey Ron i'm completely stumped. I tried what you said and I am getting the correct voltage from the sig retrun wire (yellow/lght blue). Everything seems to be working. What would prevent the 4x4 from enagaging? i know 4x4 low wont enagage if not in neutral and brake pedal depressed, is there any chance one of those signals may be preventing the 4x4 module relay from clicking?
Any chance you know how the sensor wires from the motor connect to the wires from the module? Maybe the sensors are wired wrong?

Is there anything else i should try?

 

Have you pulled off the shift motor and tried applying 12v and ground to the 2 motor wires, the yellow and orange wires

Try it, motor should turn BOTH ways, just reverse 12v and ground wires
Long shot but maybe the motor is turned too far one way and past a contact point so 4x4CM won't activate either relay, because it doesn't "know" the position of the transfercase

After you have moved the motor manually using 12v/grd, leave it at a center point between stops, like at 4h position
Then just plug it back into the harness, don't bolt it in, turn on the key and in a few seconds you should hear the "click" and motor should move to correct contact position to match dash switch selection, 2WD
Then try shifting it to 4high and 4low, you should hear the Click each time it moves

Shifting between 2wd and 4high can be done anytime so no, brake or neutral input wouldn't effect those two

Possible but very unlikely any wires are incorrect

 

Hey Ron, i took your advice and investigated the shift motor sensors and finally fixed the 4x4. The problem was a discontinuity on the motor 1 wire (yellow/white). Now I have two working spare modules I've gotta sell on ebay.

 

Good stuff

Thank for posting the FIX

Never ran into that one before, 99.9% of the time if there is no "click" the 4x4CM is the issue

You shouldn't have a hard time selling them, the 2001-2005 did fail, and you can sell them as "confirmed working", with wrecking yard or used you never know

 

Old thread but I have the exact same issue. Replaced the dash switch, TC motor and control module. I tried this fix and it made my system work again, however when I go back to 2wd the motor goes too far and the 4x4CM loses its location and the 4wd doesn't work. Is there a way to fine tune the stop point on the TC motor?
Thanks

 

 

Red line to red line is where is stops on its own and this makes the computer lose its location and stop working. If it can stop on Red/black line then it keeps track of its location and will work. Can this be adjusted?

 

Yes, note the 3 screws holding the LimitSwitch on outer back end of the 4x4ShiftMotor gear box;
loosen\retighten those just enough to slightly rotate the LimitSwitch to "fine tune" the stop positions.

 

+1 ^^^^

Picture here: https://m.media-amazon.com/images/I/..._AC_SY355_.jpg

You can see 2 of the 3 "adjustment" screws on the contact wheel plate(5 wires), these screws allow you to fine tune the stop points of shift motor by rotating the plate