Ok I picked up a 2003. When you go from 4 to 4lock or 4low it just blinks then goes back to 4. I replaced the switch, motor and transfer case control module. Yes I am putting it in neutral before trying to shift. I’ve gone forward and back and still nothing. I’m guessing with all major components swapped out that it’s something wiring related or even some safety features that are stopping the shift. Anyone have ideas?

 

does the transfercase have enough oil? or maybe the shift fork inside the transfercase that connects to the selector motor is wore out

 

If you remove the motor you can turn the shifter with a pair of pliers. It’s definitely electrical

 

Scan all modules & post the codes.