In an '05 Durango 5.7 with the standard AWD--4 Lock--4 Lo transfer case selector switch, the truck runs & drives fine in AWD, but the "service 4WD" light is on and it will not engage 4 Lock or 4 Lo. You can't hear the usual switching noises from underneath when trying to do so. Just an electrical problem with the solenoid or motor, or is there actually some servicing that needs to be done? Who else has been here?!

 

Could be an issue with the shift motor. When was the last time you had it serviced? The T case should get a drain/refill with fresh ATF+4 every 30k or so.

How many miles on your D? If you are under 70k and the Power train warranty is in your name, your local dealer will fix it for $100.

Don