2011 4wd isn't engaging.


Wheelwright

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2011
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Ford
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I have a clean 5s 2011, with ~90k on it. I've put about 20k on it in the last year, almost all highway driving.
I noticed after I got it, that the 4wd didn't really want to engage. It did when I test drove it, but changed its mind after I got it home.
The switch made the 'click' that it should, but it would take several tries to get the 4wd light to come on, and sometimes it would get the light, but not be enagaged. Along with this comes a sound behind the dash that I can only describe as a 'crackling'. it happens a heartbeat or so after I move the switch, almost every time. it's exactly the sound that a wire makes when it's coming apart and has a lot of little tiny arcs at the joint. It's very audible, and my '08 didn't do anything similar.
It's now reached the point where the 4wd doesn't engage at all, crackling or not, 4H or 4L.
I pulled the fuses for a bit to clear any cache memory that might exist, and the system worked as it should for about an hour. It worked when I tested it, and next day it didn't.
The lights don't flash, and a code pull shows nothing.

Is there any way to diagnose this without crawling on the ground? I read that the transfer case motor is a possibility, but there's snow on the ground, and my garage is full of motorcycles.

My inclination is to throw a used transfer controller at it, and maybe a switch, just to se what changes. I know that those are ridiculously specific, but I found one with exactly the same part number and vendor code.

-HR
 


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RonD

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There are 3 parts to 4WD control system in 2001 and up Rangers
Dash switch
4x4 module
Shift motor

Dash switches rarely fail, they have 3 resistors inside, the 4x4 module sends the switch a steady voltage with key on, module then gets back a reduced voltage depending on which of the 3 resistors the steady voltage is passing thru, so pretty simple set up.

4x4 module from 2001 to 2005 were a known issue, 2006 and up were better but could fail

The shift motor is the most common issue because of disuse, its an electric motor with two brushes and a rotor that need to stay clean and in contact or the motor can't start/move when needed
There is also a worm gear and reduction gear that needs to stay lubed
Sitting in the driveway and shifting from 2WD to 4low and then back to 2WD once a month helps keep brushes working a lube spread out
Just a heads up, "use it or lose it", :)

Pictures of shift motor disassembled here: https://www.explorerforum.com/forums/index.php?threads/how-to-rebuild-4x4-shift-motor.123542/

In the shift motor are 5 contacts, they detect the position of the transfer case shift rod
The 4x4 module sends 12v to the motor using 2 internal relays, both relays are Grounds when off
The 4x4 module activates one relay to turn the motor clockwise, and the other relay to turn the motor counter clockwise, so works just like power windows.
The relays are the only "moving parts" in the 4x4 module

The 4x4 module moves the motor until the 5 contacts are in correct position for selection made by driver, 2WD, 4high, or 4low.
If the module sends power to shift motor and contacts do not start to change immediately it will start to Flash the 4WD light on the dash, indicating a problem in the system.

You didn't mention any Flashing 4WD lights which would indicate an issue with the 4x4 module.
But just a guess, if shift motor was not responding/moving then 4WD light should Flash

Its possible the dash switch is shorted and voltage is not changing when you turn the knob, odd way to fail but is possible, if connection was broken inside 4WD lights would Flash
 
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