4 wheel drive does not engage when turning knob

It is your 4 x 4 electronic shifter at fault. Located on your transfer case it is mostly black/brown plastic electronic switch that engages and disengages your transfer case from low, high 4 x 4 or 2 wheel drive.
Check connections for electric continuity and replace it if there is no power...

Test the electric motor that engages the transfer case.

ford ranger 1990
If you have trouble in fixing your vehicles, try this link. Very helpful

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

-----------

4X4 Truck makes roaring noise in the front end?

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

-------------

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

--------------

No 4x4 light on dash?

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

------------

4 wheel drive system will not disengage?

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

----------

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

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

----------

2002 Jeep Wrangler: 4WD Idiot Light is ON?

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

----------

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

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

-----------

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

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

------------

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

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

----------

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

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

-------

4x4 will not engage on Ford F150?

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

-------------

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

----------

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.

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

-----------

4X4 Truck makes roaring noise in the front end?

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

-------------

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

--------------

No 4x4 light on dash?

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

------------

4 wheel drive system will not disengage?

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

----------

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

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

----------

2002 Jeep Wrangler: 4WD Idiot Light is ON?

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

----------

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

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

-----------

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

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

------------

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

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

----------

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

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

-------

4x4 will not engage on Ford F150?

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

-------------

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

----------

Ford 4x4 front wheels will not engage?

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

-------------

These details will help.

Thanks.

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

-----------
4X4 Truck makes roaring noise in the front end?

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

-------------
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

--------------
No 4x4 light on dash?

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

------------
4 wheel drive system will not disengage?

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

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

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

----------
2002 Jeep Wrangler: 4WD Idiot Light is ON?

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

----------

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

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

-----------

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

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

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

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

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

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

-------
4x4 will not engage on Ford F150? http://technoanswers.blogspot.in/2012/02/4x4-will-not-engage-on-ford-f150.html

-------------
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

----------
Ford 4x4 front wheels will not engage?

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

-------------

These details will help.

Thanks.

Does dash indicate whether it's in 2 wheel, 4 hi,or 4 low?It sounds like it might be in 4 wheel low.With the car running in Park, try turning dash knob from 2 wheel to 4 wheel low and then back to 2 wheel..now depress the brake pedal. Instructions to to do this are usually on the driver's side sun visor.

Since this is done electrically today with no light on dash I would check the switch that you move to engage the 4X4 action.

It depends, look at the hubs on your front wheels? Is there a knob in the center of the wheels? If so, then turn this knob to the right and you will have engaged the 4 wheel drive? If you do this, however, make sure you engage the 4 wheel drive inside the truck (if your truck has a 4 wheel drive gear shifter).
Oh other Rangers you have a knob on the inside of the cab it should be somewhere on the dash. You can turn it to the right and this will engage the 4 wheel drive.
Finally, when you engage the 4WD make sure the engine is cut off so it doesn't mess up your transfer case.

you will need to let the durango sit in the nuetral position without moving, then turn the knob from 2WD to 4WD. if that doesnt work, try putting the durango in reverse and then back to drive a couple times. you may have some mud/dirt/oil caked up under there interfering with the 4WD moving parts.