4wd nonexistent

[Dryer Dave]

My. 2003 expy seems to have no 4wd whatsoever...no dashlights, no activity when buttons pushed, nothing. Where would you start? 175,000 on vehicle.

 

[SafariGoneWrong]

Mine is an '06, it may be a bit different than yours. I'd start by checking mini-fuse #30, it's a 25 amp fuse. Might as well verify the voltage at the fuse. If it's not the fuse, the Pinpoint Tests in the service manual get lengthy and you'll probably want to have Forscan or a good scanner to verify certain functionality. I'm wondering if you did an IWE halfshaft rotation test it might provide some clues as to what may be going on. In 2H, rotating a front wheel with the engine running, the halfshaft shouldn't turn. In 4H/4L, the halfshaft will rotate as the IWE has been starved of vacuum by the solenoid. If you get those results something is working right... What I'm not sure of though is if the 4WD module's signal to the IWE vacuum solenoid is dependent upon what position the transfer case sense plate is in or the mode selector switch position. Might be time to see if the transfer case motor works. I've never had to dive into my system that far. Any my 4WD module is integrated into the PCM. Not sure about earlier years.

 

[whtbronco]

The 4WD module on my 2004 is a separate module behind the B pillar trim panel.

The shift motors do go bad, mine was even providing bad feedback causing other modules to have issues.

This thread has some transfer case troubleshooting info and lots of pics of a rebuild that will show how it works. https://www.expeditionforum.com/threads/not-so-good-vibrations.55319/