How do I check the vacuum system for 4x4 on F150 2006

Do you have vacuum to the front actuators?

Engage the 4x4 and using a vacuum gage check for approx. 14-15" of vacuum at the lines to the actuators.

On these issue, there are few solved help links for troubleshooting the issue easily.-------

Click the link below: ---

No 4x4 light on dash?

http://repairhelpcenter.blogspot.com/2011/12/no-4x4-light-on-dash.html

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4X4 Truck makes roaring noise in the front end?

http://schematicsdiagram.blogspot.com/2012/01/4x4-truck-makes-roaring-noise-in-front.html

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Car will not go into 4WD high or 4WD low?

http://schematicsdiagram.blogspot.com/2011/12/car-will-not-go-into-4wd-high-or-4wd.html

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No 4x4 light on dash?

http://repairhelpcenter.blogspot.com/2011/12/no-4x4-light-on-dash.html

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4 wheel drive system will not disengage?

http://technoanswers.blogspot.com/2012/01/4-wheel-drive-system-will-not-disengage.html

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4WD light is flashing and beeping? NO 4WD high?

http://schematicsdiagram.blogspot.in/2012/02/4wd-light-is-flashing-and-beeping-no.html

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2002 Jeep Wrangler: 4WD Idiot Light is ON?

http://technoanswers.blogspot.in/2012/06/2002-jeep-wrangler-4wd-idiot-light-is.html

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Traction control switch will not engage on 4WD High or Low

http://whoisbyme.blogspot.com/2012/10/traction-control-switch-will-not-engage.html

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4WD light flashing and 4WD will engage after few minutes

http://repairhelpcenter.blogspot.com/2012/10/4wd-light-flashing-and-4wd-will-engage.html

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2008 Toyota Tundra: 4x4 Wheel Drive Light is Flashing?

http://technoanswers.blogspot.in/2012/05/2008-toyota-tundra-4x4-wheel-drive.html

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4x4 front differential will not engage the axle on ford?

http://technoanswers.blogspot.in/2012/02/4x4-front-differential-will-not-engage.html

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4x4 will not engage on Ford F150?

http://technoanswers.blogspot.in/2012/02/4x4-will-not-engage-on-ford-f150.html

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Dodge Ram 4x4 light keeps flashing

4X4 LOW LIGHT IS FLASHING ON DASH

http://technoanswers.blogspot.in/2012/09/dodge-ram-4x4-light-keeps-flashing.html

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Ford 4x4 front wheels will not engage?

http://technoanswers.blogspot.in/2012/02/ford-4x4-front-wheels-will-not-engage.html

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These details will help.

Thanks.

have also had same problem, green light flashing on my isuzu trooper 3.0
check to see if drive prop shaft is engaged firstly, first step for front wheels engaging, then 2 more solenoids are under engine front of jeep, one coloured blue one grey, these work with vacuum, if i remember blue for engaging drive grey for disengaging, inside solinoids small tiny piston, could be stuck as mine was, can be taken apart & cleaned, reason sticking is moist in vacuum system, & not being used as 4 wheel drive until winter months, hope this helps

Check out F150OwnersBlog.com or 4x4Owners Blog. It sounds like the actuator inside the transfer case is stuck.

If this is the Vacuum shift setup, the plunger inside the 4x4 box is sticking. You also could have low vacuum pressure from a bad Vacuum pump on the engine.

The Electric setups worked differently. The voltage running to the underside wires to the shift solenoid had set values to extend and retract the solenoid plunger. Often, a burned out light in the inside Selector switch on the dash would affect the Voltage sent to the solenoid. A silly thing like changing the indicator bulb would restore the proper voltage underneath the truck.

Remember to sequence the trans to neutral before engaging some of the transfer cases.

I hope my solution is helpful.

First, You said you DID NOT check for voltage at the solenoid connector...I think that would be a real good idea.

Did you check to see if the vacuum lines actually had vacuum? Did you check to see if vacuum was present at the solenoid? Does the solenoid "click" when changes are made to the 4X4 controls? Did you check for Did you check that the vacuum from the solenoid to the axle actuator was being applied to the actuator?

Operationally vacuum shifts the front axle between 2WD and 4WD mode. The GEM ( Generic Electronics Module ) applies ground to the solenoid needed for the mode selected on the switch ( for ESOF ) or when the transfer case shift lever is moved ( MSOF ).The contact plates in the transfer case signal the GEM that the transfer case is engaged, and the Vacuum solenoids need to be activated ( either 2WD to 4WD or 4WD to 2WD ).

Lift and support the front of the truck so the front wheels are off the ground ( take safety precautions, chock wheels, jack stands, etc )
Key on, engage 4x4 and try to turn the front drive shaft.
- If it turns it is a problem with the transfer case.
- If it doesn't it is a front axle engagement problem ( this is what you seem to have, the transfer case is engaged and will drive the front shaft mine was a key on engine off test ).

- If the front drive shaft does not turn :
•With the truck running ( with front wheel back on the ground ), switch from 2WD to 4WD and back again, the vacuum shift motor should move the lever on the front axle.

-- If the vacuum shift motor does not move:
1.Check for vacuum on the lines while shifting between modes. Pink vacuum line is 2WD mode, Light Blue vacuum line is 4WD.
2.Check the fuses for the 4WD system and the solenoids.
3.Check the vacuum lines from the vacuum shift motor to the solenoids on the firewall.

4.Check the vacuum lines from the solenoids to the vacuum reservoir box behind the battery.
5.Check the vacuum reservoir box for cracks.
6.Typical solution is the vacuum lines ( to the solenoids or to the vacuum shift motor ) are cracked or the vacuum shift motor has a cracked diaphragm and has water in it.
7.Could be the shift plate contacts in the transfer case are corroded / not making good contact, and not activating the solenoids.


Usually the case is cracked vacuum lines from the solenoids, the next common is a cracked vacuum reservoir box, and 1 time I have seen the mount for the vacuum disconnect motor broken ( motor floating free so it could not push against the axle )

Today and over the weekend .I too had the same problem. Took it to the dealer and they tested everything and could not find the problem. Did vac test on the lines, Test drove it with code tester to see if there was any problems . Checked the hubs... They replaced the IWE solenold. Just hope that is the fix and it didn;t damage anything else... Thanks for the above info!

I am not sure about Ford, but several of the 4x4 models use a vacuum hose connected to engine vaccum to switch the 4x4 functions. If you have a push button engage system then you may want to check the rubber hoses around the front drive shaft. This only applies for the push button models.

change the 2 solenoids on the firewall on the passenger side. they contol the vacum to the acuator.