The 4X4 is not working on this expdition the.

Good afternoon,

I attached a wiring diagram of the system for you.

https://www.2carpros.com/articles/how-to-check-wiring

You need to test for power to the motor on the transfer case to be sure it has power when you command 2 and 4 wheel drive. Check the fuses I circled for power on both sides to be sure available power is available.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

The motor is common for failing for this issue.

I attached the flow chart for the issue below with some pictures.

Roy

Pinpoint Test C: The Vehicle Does Not Shift Between 2WD And 4WD Modes Correctly
Normal Operation
The mode select switch communicates the operator's choice to the 4x4 module (PCM). The 4x4 module (PCM) then controls the transfer case clutch, transfer case motor and integrated wheel ends (IWE's) as necessary. If the vehicle is not responding to the operator's intentions, systematically check the necessary inputs and outputs of the 4x4 module (PCM), components of the transfer case, IWE components and halfshafts. Check all circuits for opens and shorts to power or ground.

Possible Causes
Transfer case
Integrated wheel ends (IWE)
IWE solenoid
4x4 module (PCM)
Front axle assembly
Mode select switch (MSS)
Circuit 682 DB/WH)
Circuit 780 (DB)
Circuit 704 (DG/LG)
CJ13 Fuse 115 (30A)

Hey EEJACKSON,

Does the 4H light on the dash come on?

If so and you are not getting any drive to the front wheels you may have a vacuum issue as you suspect.

Have you got access to a Mityvac or vacuum pump?

What you will need to do here is to check the system for leaks in the lines, reservoir and the hubs themselves. Also there are check valves and vacuum switches that can cause problems.

Regards, Joe

Hello,

It could be the Integrated Wheel End Solenoid Valve is stuck not releasing vacuum. Disconnect the vacuum lines and the front hubs will should engage. The IWE system uses vacuum hubs that engage the front wheel hubs to the front half-shafts or disengage the front wheel hubs from the front half-shafts.
The IWE solenoid receives engine vacuum from the vacuum reservoir.
When the 4-wheel drive system is in 2WD mode, the 4x4 module (PCM) supplies a ground path to the IWE solenoid to apply vacuum to the integrated wheel ends (disengaging the front hubs from the front half-shafts). In 4WD mode, the 4x4 module (PCM) does not supply the ground path to the IWE solenoid, vacuum is not applied to the integrated wheel ends and an internal spring keeps the front hubs engaged to the front half-shafts. I'm attaching repair guides, wiring diagram and vacuum diagram below. Please let us know if this was helpful or if you need more information to help with this repair.

https://www.2carpros.com/articles/how-to-check-wiring

Thank you
Joe T.

There are many things that can cause this, but the best way to begin diagnosis and have an accurate diagnostic path is to retrieve codes from the four wheel drive module. The integrated wheel ends and the integrated wheel ends solenoid are the most common points of failure but we would need to begin with retrieving the codes then we can go from there. I have attached a location of the IWE solenoid with a brief summary of how it operates.

Some scan tools do not have the capability to retrieve codes from the 4wd module. Sometimes the body control module will store codes related to the 4wd module but will not be specific, unfortunately. At my dealership we use the factory scan tool that will retrieve the codes of course but at home I have an Autel Maxidas that does a majority of the tasks other than programming and a handful of other things that the factory tool will do.

Hello,

there are a set of forks that will shift the gears inside the transfer case, what happens is the plastic ends of these forks wear out so it cant shift the 4x4 completely, here is a diagram for what I'm talking about.

Please let us know what you find so it will help others.

Best, Ken