2002 F150 5.4L 4x4, light on dash indicates it is in 4H or 4L, but it is not actually in 4WD, still only in 2H, could it be a vacuum line or the 4x4 actuator?

 

Maybe this will help.

 

Hey Thanks, I'll watch the video, not sure how I missed that video, I subscribe to his channel.

 

One mistake in description.
'Vacuum coming out'.
Vacuum never comes out. It's air being sucked in by the Vacuum generated from a running motor..
An important point for the first time do it your selfer that takes things literally.
A point not covered is the solenoids have the small cap on top.
That is an air port with a filter.
The solenoid has a plastic piston to control the vacuum ports.
The piston can stick from dirt or the filter has come apart and
and froze the piston movement.

 

I just went through this on my 97 XLT. I had 4H light on the dash but was in 2WD. The transfer case motor was defective. The motor turned ok on the bench, but inside there are switches that work with the GEM module to control the 4x4 functions. After replacing, I HAD TO DISCONNECT the battery to reset the GEM module and all good.