on the fly 4x4 not working

Hey gang,
Anyone had the problem with the 4x4 not going in with the knob on dash?
I have to get out and engage 4x4 at the hubs.
works fine when i lock it in at the hubs.

I looked at the fuse, looked good. More than one??
what else can i do?

Never been in the mud or deep water not an off road truck, just jobsites.
Any help would be great, Thanks, Kenny

do your dash controls work ok for the air/heat? Maybe the HVAC vacuum unit is going

there is vaccum lines that connect to engage them. mine are gone i have to manually do them also. thats all i got check those. thats how it is on my 00 not sure on the 06

i have this problem too but my lights on the switch on the fly dont work and even if i manually lock them in they still dont engage, i dont have any idea where to start with that problem? its almost like there is no power to any of it

first check your vacuum pump make sure its working. next check your vacuum hoses to make sure there connected to the spindle. if that doesnt fix it one of your seals are out behind your wheel bearing. causeing a leak and cant create a vacuum and that will cause your hubs not to auto lock in

My 06 has the same problem right now. I plugged my lines, and the defroster still comes on, so I know it's a a leak somewhere.

pump works i will check the other stuff in the morning but the lights on the switch dont even light up orange like they should

I have power to all controls on dash
The heat / ac works fine.
were are the vacum hoses located that i need to look at??
Thanks for the help gang, Ken

The vaccum pump is on the passenger side fender. With the key on engine off. Turn on the a/c system. Then turn on 4x4 high or low dosent really matter. If the a/c goes to defrost it is a vaccum problem that can be worked around by using the manual locks. This problem should either be a bad pump, loss of power to pump, leak in either the hoses or the hubs them self. For the other guy having a different problem where his light is not comming on and locking the hubs does not work. First verify power to the electronic motor on the t case. If there is power and it does not shift I would start with a new motor. You can probably manually engauge it to check to see if the mechanism is binding but I would assume the motor as my first action.

thanks for the info

Hey gang,
I did the turn on key, turn on ac, turn on auto 4x4 switch,
Light comes on on dash that reads 4x4
The ac does not change to the defrost vent.
all the different vents work no problem on the ac
Checked all the vac. lines from pump to were you can see them going into spindles, gave them a slight tug down at spindle area to see if they were loose or busted off and they seem tight.
I did not remove wheel and such as of yet.

Were abouts is this elec. motor on the t-case??
I can check that next.
Thanks again, Ken

my 04 would work intermittenly. when i would want to use it it wouldnt work. when i would go to check it the stupid thing would work. a pita

I checked the pump and it is running and shutting off.
What is the piece monted on the pass. fender that the pump is plumbed into??
It looks like a valve of some type, It has a white rectangular cap on top and under the cap it has a foam filter like an intake for air.
This also has power going to it with one vacuum line in and one line out.
Is this part of the auto 4x4 or somethingelse??
Thanks again, Ken

I checked the pump and it is running and shutting off.
What is the piece monted on the pass. fender that the pump is plumbed into??
It looks like a valve of some type, It has a white rectangular cap on top and under the cap it has a foam filter like an intake for air.
This also has power going to it with one vacuum line in and one line out.
Is this part of the auto 4x4 or somethingelse??
Thanks again, Ken
This is the PVH (Pulse Vacuum Hub) solenoid. Disconnect the three wire connector to it. Turn the ignition key to the RUN position. Get out your DVOM and set it to DC-VOLTS. Check the middle wire (light blue with pinkstripe), by probing it with the red lead and connecting the black lead to your passenger side battery ground. You should see 12 volts approximately. If you're not getting 12 volts there, you'll need to check fuse #27 (15A) on the fuse panel inside the truck under the steering column, for an open circuit. If the above checks out good, reconnect the three wire connector back onto the solenoid. With the ignition key in the RUN position, connect a jumper wire or paper clip into the back side of the red wire and jump it to the passenger side battery ground terminal to test the hub DISENGAGE circuit. You should hear a click from the solenoid as you do this. Now repeat this same test on the grey with black stripe coloured wire to test the ENGAGE circuit. If you don't hear clicks from the solenoid while testing either, or both circuits, replace the PVH solenoid. The part number for the PVH solenoid is 7C3Z-9H465-A. The price of this part is as follows:

https://www.tituswillfordparts.com/cart/?pn=7C3Z9H465A&submit=Search

If you are getting 12 volts to the PVH solenoid, and the above test checks out good, you'll need to look elsewhere into your problem.

HOPE THIS HELPS.

Beautifully said.