Part-time 4wheel drive

check the actuator is working to select 4wd. even if the lights say so doesn't mean that the action is occurring If vacuum operation check hoses and if electric check all wires,fuses and solenoids for operation

Could be the switch/valve in the front differential.

There are a few things that would cause this problem.
The first and most common would be the switch itself is bad. the next would be a bad 4wheel drive encoder motor, this is the motor on the transfer case that is used to operate the 4wheel drive. The last would be the 4 wheel drive module.
You will need to do some testing, if the four wheel drive is working and goes in and out of 4 wheel drive then i would say it the switch. if it does not work correctly it may still be the switch or one of the components i listed above.I have enclosed a wiring diagram, you will need to do some testing to check system, first make sure all fuses are good. the fuses that operate the 4wd are listed on diagram, it will also tell you the location of each part. you will need to test front axle actuator and selector motor and switch, you will need a test light and a meter. hope this is helpful, good day.

It will eventually. most likely the electrical connections under truck got wet and stops the operation your explaining. My 03 yukon xl does this all the time. when i shut it off next day i start and it works. sometimes the 4 lo light comes on yet it is still in 2 hi. other days they all flash. somedays the red nuetral light is on yet i'm driving. Damn electronics. My ford explorer is the same way. I never get the underbody wash either as this leads to two days of flashing.

Make sure you have activated your hubs.

- sent by jglaubitz via email -

The solution to the problem of the 1998 ford explorer was shutting the vehicle off in neutral tapping on swith a couple of times to get the 4wheel drive to disingage. eventually a new swith will have to be purchased.

there is NO '4wheel drive emergency' light on a 2006 Tucson.

If there is no switch present then it is full time 4X4, it does not disengage, good for travel bad for fuel mileage.

The transfer case shift soleniod that engages the transfer case is sticking .
I would take it to the shop and have it checked out.

I have a 2005 Tahoe that recently had a similar problem. To resolve, I did the following.

1. Change the transfer case fluid (Which you already did)
2. Change Gears to 4L while in neutral, change back to drive, and drive slowly 50 yards or so.
3. Change Gears to 4H while in neutral, change back to drive, and drive slowly 50 yards or so.
4. Change Gears to 2H while in neutral, change back to drive, and drive normally for a couple of miles.

This will cycle the fluid within your transfer case, and hopefully clean out the sensor. I did this, and my Service 4WD light went away after one day of normal driving. Hope this helps. Note: When I went into 4L the first go around, it had a hard time shifting due to non use. I changed between 4H and 4L a few times until it got smoother.