99 Excursion 4x4 help

I need some help with the 4x4 in a 99 ford excursion. In short, 4x4 will no longer engage. The switch, GEM module and relays in the dash have been replaced. The solenoids under the hood are not receiving ground (positive is always available, grounded when activated from what I have read), and the 4x4 light never comes on no matter where you place the switch. The wires are all OK. I'm out of ideas where to look next. Does anyone have any good trouble shooting ideas? Can I just jump the solenoids under the hood with a toggle switch to get 4x4 when it's needed? (Don't need auto 4x4) is there any other way to activate the 4x4 or find out what's wrong without throwing more parts at it?

I think these had vacuum diagram things that can fail as well as the solenoids. I know the 99 f150s have these.

If it has auto locking hubs, thats true.

dean1484 wrote: I think these had vacuum diagram things that can fail as well as the solenoids. I know the 99 f150s have these.

From my understanding the solenoids are what actuate the vacuum to the transfer case and hubs. They seem to be fine, somewhere prior they are not being switched on.

The lines go bad