2015 2500 Cummins HD no 4X4

[Trox]

New to this forum I hope to make some sense to you. I have approximately 267K miles on the truck and mostly use it to tow a 29 foot camper. It’s deleted and tuned with EXLynk. Recently installed a Revmax valve body. It now has about 3000 miles on it.
The truck has been running fine with normal driving but I pulled out into 6 inches of snow, selected the manual shifter down to 4hi, 4X4 light on the dash (not flashing), and my front wheels don’t engage. I tried going back to 2wd, neutral and back and still have no 4wd. Any suggestions or more information needed, please let me know. I’m not stuck or anything, just like having 4wd when I want it.

 

[14DieselPW]

If its a manual shifter on the transfer case then only thing it could be it a FAD actuator not engaging. Or a broken axle shaft but I'm assuming you would have heard a snap and some noise associated with that. Could be the FAD actuator itself or the wiring/fuse/connecter to the actuator. You could get a power probe and give the actuator 12V to see if its the actuator or wiring/fuse/connecter that has the issue. Seems like this would set a Service 4WD light though.

Are you sure the linkage on the shifter is good? I'd verify that first and make sure the front driveshaft is spinning when in 4x4. Then move to the FAD.

 

[Great White North Eh]

Starting point. If manual shift lever then get underneath as someone cycles the lever.