Like others before, my 4wd is not engaging. paid ford 125.00 to troubleshoot... they said vacuum actuator, transfer case motor ... and transfer case...

This seemed fishy, so decided to work it out myself.

1. Motor tests good (and replaced without change
2. Switch on dash test good
3. Vacuum actuator I replaced, but no change... and I did not expect one

When the motor is not installed on the transfer case... going from 2 to 4hi to 4 lo does not move the motor

Swapped relays... no change.

Only thing left is control module... anyone now how to test it?

 

we have no Vacuum and no power to the transfer case solenoid, I have checked most the fuses and changed the relays.

I have power to the center wire of the vacuum solenoid.

I will check the other fuses. 19,27,31,33,34,45 and 111

Ford in Canada wants $422.14 before taxes for the 4x4 shift module and I want to make sure I need it before we go there.

I found 3.5v on the blue wire on the dash switch which I believe is low voltage used to switch the relays to send 12v to the correct applications.

Can I put 12v to the transfer case motor? there was water in the connection in the transfer case motor connector.

Looking for direction,

 

Dchamberlain, I read your post on diagnosing the electronic side of the 4wd and I'd like to pick you brain if you have a few minutes. I can get mine to work if i jump the wires at the relay. However with new working relays installed i get nothing. I bought a new 4wd GEM and installed it and still nothing. Installed a new switch and nothing. Losing my mind here...

 

Not knowing the 4x4 systems for these trucks myself but you said " I can get mine to work if i jump the wires at the relay". So are you tapping a hot line somewhere to power the relays? Also if you are, did you check for power on the relay harness before jumping the relays?

 

I am using the always hot side of the relay harness to get actuate the transfer case motor. I would have thought the GEM would have cleared up the issue but i installed the new one and nothing changed. not sure if I needed to "reset" anything to get the truck to recognize the new GEM.