Stuck in 4WD High 1999

[6stringsandapick]

I see that this post has come up a few times, but I wanted to ask anyways.

I have a 1999 Explorer XLS 4.0L Electronically switching 4WD.
4WD high and low work fine, but when swiched to Auto it does not disengage the front wheels. Tried switching while in Neutral and park and reversing to disengage the hub, all to no avail. Does someone have a method to diagnose the issue more systematically. I have not purchased a repair manual for this vehicle yet, but plan to do so. Is this repair discussed in Chilton's etc.

on another topic I have the infamous P0171 code coming up, what is the most common fix for this on the Explorer. (my windstar had this and just needed an O2 sensor)

 

[drdoom]

P0171 is often a vacuum leak and/or leaking intake manifold gaskets.

As for the 4x4 issue, perhaps the t-case speed sensors are "telling" the computer to keep the clutch energized. Are all four of your tires an EXACT match in circumference? Are your t-case sensors clean, and is the fluid changed regularly?

 

[drdoom]

Another possibility is a blown t-case clutch pack.

 

[6stringsandapick]

P0171 is often a vacuum leak and/or leaking intake manifold gaskets.

As for the 4x4 issue, perhaps the t-case speed sensors are "telling" the computer to keep the clutch energized. Are all four of your tires an EXACT match in circumference? Are your t-case sensors clean, and is the fluid changed regularly?

Not sure on the service intervals as I just purchased it. Got a great deal and I can put some money in it to get the problem resolved.

Tires are all matching and inflated properly.
Should I start by changing the TC fluid? or TC speed sensors.?

 

[drdoom]

No you shouldn't need to change the sensors, they can be cleaned.

Changing the fluid is always a good idea, and n this case taking a sample of the fluid may give some idea what's going on in there. Also you could clip the brown wire, adding in male/female connectors, and see if that unlocks it. I suppose you could do a run-up on the dash switch to make sure it is not bad. Sorry, I'm kind of guessing here.

 

[drdoom]

Forgot to ask this, but does the dash indicator stay on when you switch to AUTO?

 

[6stringsandapick]

4wd unstuck

first tried disconnecting the battery and resetting the computer. (cheap and easy first, Right?) took a look at the fluid in the TC and strangely it came pouring out of the fill port, not sure how it got that full. Changed the fluid and disconnected the TC shift motor and put it in reverse while in the Grass. after hearing a nice chunky sound it was out.

just hope it doesn't stick again next time.