Hi there,

I have a 2008 ford ranger. I have changed the 4x4cm and the transfer case module like I was told to do. With both parts changed out the 4x4 still won't engage. I've checked all the fuses and relays and they are all good.

 

4x4CM is the control module

Transfer case shift motor is the other part

With key on all the dash lights should come on, including BOTH 4WD lights, do they come on?
If not bulbs are burnt out which makes trouble shooting harder
This is a bulb test not a 4WD test, just FYI

4x4CM will flash the 4WD lights on the dash if the shift motor is the problem, i.e. not moving when "told" to do so
If no flashing lights the its usually a 4x4CM issue
The 4x4CM has 2 relays inside, you should hear one of them "click" when you change the dash 4x4 switch to a different position, key on of course

There are 4 fuses, 1 in engine bay(for shift motor) and 3 in cab fuse box(SJB)

Wiring diagrams below


Pull out the radio and 4x4CM and test the wiring with OHM and Volt meter
4x4 switch on dash rarely breaks but test it with OHM meter, its just 3 resistors of different values, so see if valves change in the 3 positions
Then check that you are getting 12volts on each wire that should have 12v with key on
The SJB in 2004 and up Rangers was known for corroded connections, so fuse can be "good" but the 12v is not making to the device because of a corroded wire in the SJB

The shift motor can be removed and tested using the 12v battery in vehicle, you will see its two MOTOR wires, when one is 12v and the other Ground motor will move ONE-WAY, it you reverse the 12v and ground MOTOR will move the OTHER WAY, works the same as a power window motor
There is a mechanical stop in the gear drive so motor will only move so far in one direction, so try moving it in both directions before deciding it doesn't work

The other 5 wires on the shift motor are "sensors" they tell the 4x4CM when shift motor is in 2wd, 4high and 4low positions
4WD lights on dash will flash if these are not working

The 4x4CM was by far the most common failure on 2001-2011 Ranger 4x4s
Shift motors next, but failed from disuse not overuse, lol
Transfer case shift rod would be next, with wheels BLOCKED and shift motor off, use pliers to turn the shift rod to 4high and back to 2wd, making sure its free to move
4x4 dash switch, really never even read about one failing unless if was physically damaged, broken during dash work