I routinely run in 4wd just to exercise it. Yesterday I shifted into high 4 and heard what sounded like a relay opening and closing in the dash, the 4x4 light came on and then went off, no 4x4. I stopped and shifted into low 4x4 and it worked fine, then from there to high 4x4 and it worked fine. I shifted back to 2wd and then high four and got the same result. It is a 2006 Ranger with I believe the 3.0, automatic. Any reasonable suggestions or thoughts would be appreciated.

 

2006 is a pretty simple 4WD setup
Most common failure point is the "4x4CM", 4x4 control module, in 2006 its behind the radio

But your symptoms seem a little different from a failing 4x4CM, reads more like a shift motor contact wheel issue

Read/look here: https://www.explorerforum.com/forums...-motor.123542/

The shift motor has a contact wheel that "tells" the 4x4CM when transfer case shift rod is in 2WD, 4H, Neutral, or 4L, yes there is a neutral you just can't select it
The 4x4CM powers the shift motor until 4H contact is connected, then powers off the motor
The contact wheel is what turns on the 4WD light
You light is coming on and then going off in 4H

When going from 4L to 4H, did the 4H light come on and stay on?
You don't mention that, just that 4WD worked

It could be it just needs an adjustment or cleaning since you use 4H often there may be some corrosion on those contacts, so 4x4CM is moving it too far or too little for 4H from 2WD???
Could also be shift rod itself, inside the transfer case

When you pull off the shift motor, BLOCK A TIRE, then manually shift the transfer case to its 4 position and see how shift rod "feels", no looseness

 

Hi Ron and thanks for the response,



Read/look here: https://www.explorerforum.com/forums...-motor.123542/



When going from 4L to 4H, did the 4H light come on and stay on?
Yes it stayed on

 

So most likely just the contact wheel and contacts need to be cleaned

If you look at the link, picture 5 shows the contact wheel that turns when shift motor and shift rod turns
And picture 6 shows the cover with its 6 contacts connected to the 5 wires

You can pull that cover off without pulling off the shift motor, and clean off any dirt and/or corrosion, although pulling off the shift motor and cleaning it up on a table might be easier