Ok so my 4wd suddenly stopped working, 2005 excursion 6.0, my dash lights come on when I turn the key, but my switch doesn't do anything.
I have power to my 4wd selector switch. I checked I believe it's fuse 11 and 31 both fuses are fine (both say they are for 4x4 according to manual) but I don't have have power to the #31 fuse.
I tested for power at both wires on the transfer case actuator with the truck running in neutral and a friend turning the 4wd selector.
I pulled out every square normal sized relay under the hood (i didn't test the small rectangle ones, pins are too small) and tried to find continuity between the two wire plug at the transfer case actuator and every pin. none have continuity. all the relays click when I apply power and ground to activate them.

I did have a recent issue with the driver side transfer case plug the lock had broken and it vibrates loose, losing 4x4. so several weeks ago I used shoe goo to hold it securely in place and it seems to still be well connected.

 

Neither F11 (radio) nor F31 (starter) are involved with the ESOF system.

Check F19, F27, F33, F34, F45, & F111.

 

According to my owners Manual they are. just for fun I will verify every fuse tomorrow, dinner has left me bed ridden for at least ten hours!

 

Wouldn't be the first time that that I've seen the owner's manual to have incomplete or incorrect information.

Check the specific fuses I identified, they're all involved in the ESOF system. The ones you cited are not. There is no need to expend unproductive time checking ALL of the fuses.

The relays for the shift motor are in Aux Relay Box #3, tucked back up under the corner of the hood near the hood hinge.

 

That is really peculiar, but ok I will try those fuses!
I will also test for power to those relays, I already confirmed the relays themselves click and supply continuity when powered. I tried testing continuity between the two wire plug at the transfer case and the relay pins under the hood and didn't find continuity, do those relays power something else before the actuator?

what would happen if I supplied power to the actuator or proper relay pins, could I get 4x4 to engage? I have an off-road adventure tomorrow up to the beautiful cheam mountain and I can't go if I cannot fix my 4wd so even a temporary forced shift will help greatly!