Hey fellas,
started diagnosing the 4x4 issue on my wifes truck.

Problem: wouldnt engage the front end and 4x4 light wouldnt come on.

So i thumbed around here, and googled issues. I watched ford tech makuluco's video on youtube and that got me started.

-So i changed out both of the solenoids for the 4x4 vacuum and 2x4 vacuum because there was no vacuum on top line in either 2wd or 4wd but there was vacuum coming to both from the reservoir.
-I now have 4x4 and the light, but the actuator still does not go back to
2wd position on its own. I had to push it out by hand.
-I then pulled the vacuum line off of the 2wd again and found that there is still no vacuum coming through the solenoid to pull the actuator back....
-I inserted a jumper wire then into the drivers side port of the connector
that attaches to the solenoid and put a volt meter on it. I held the
positive side of the meter to the battery + and connected the jumper
wire to the meters ground and I got a 12+ volt reading. Apparently
there is power... Sooooooooo.....

Does all of this mean that I just have a bad ground going to that solenoid? Are there any particular places that are prone to going bad or am I going to need to go on a scavenger hunt?

Thank you for any input and help.

 

Sorry, forgot to tell what kind of truck...
2003 f150 xlt/lariat 4 door short wb 4x4 (kinda) with 140,000 miles

 

The grounds are supplied by the GEM module.

IIRC, one of the solenoids is supposed to always be energized so there's always vacuum applied to one side of the actuator down on the front differential.

 

So the GEM module is likely my culprit? I'd hate to change it out just for this... everything else works fine...
Just out of curiosity, could a person jimmy rig it and ground it directly to the truck and bypass the GEM?... Seems like a lot of work and hassle just for a ground.

 

The grounds to energize the solenoids are applied according to the logic of the selector switch and the feedback of the motor switch plate. If you want to attempt duplicate that logic manually, be my guest.

 

So ill take that as a no.
Is there any other possible solutions to my problem? or was that the end of the rainbow?

 

Probably need to step through the diagnostic procedure in the service manual. I don't have any silver bullets.