Been reading these forums for several days now and trying different things. Here is the scenerio: 3-push button 4wd, all lights work correctly flash and then stay on. 4Lo engages fine. 4hi light stays on as it should but does not engage and does not default back over to the 2Hi light until you push 2Hi. With just the ignition in the run position, I can hear the click behind the dash and can hear the encoder motor also turning as I toggle between 4hi and 2hi, but with the engine running the vacuum actuator (under the battery) only pulls in when I push 4Lo. Vacuum actuator does not move when I push 4hi. Any ideas?? This forum is great and very informative. Also, on the port under the steering column, I saw on this forum to jump the 13 pole to the ground pole (4 or 5), and that gave me no codes on the 3 push button switch. So, I'm kind-of at a loss now. Thanks for any help.

PS- I jacked up the passenger front tire and manually pulled the vacuum actuator all the way in. The right front continued to spin freely. Did I check this correctly, or was I supposed to push the 4hi button with the truck running to perform this test. Thanks again, guys for any help you can provide!!

 

Chances are it has to do with the Encoder Motor located on the transfer case. This is what tells everything which position the case is in. If you have2Hi and 4Lo, it can't tell what positiont he case is in, so it reverts to the 2 extremes...i.e 2Hi and 4lo. Check the connections for corrosian/clean the connections then go from there.

As for the actuator part in 4Hi, this goes along with the encoder motor. there is a vacuum switch located on the transfer case and when you select what you want, there is a small lever like that pushes on the switch which allows vaccum to the actuator, thus engaging it. So if your encoder motor can't tell where the case is, it won't open up the vacuum switch for it to pull the actuator in 4Hi.

Hope that made since and helps

 

Ok, I replaced the encoder motor this weekend and still have the same problem. 2wd Hi and 4wd Low, but no 4wd Hi. The push button lights all act just like they should and stay on until I push 2wd hi again, but when I push 4wd hi the light stays on 4wd hi, but the truck stays in 2 hi. I can here the encoder motor moving when just the key is turned on when I push any of the buttons, just as it did before I changed the ecoder motor. Am I down to the TCCM? I took the passenger kick plate off and there are two boxes there, one silver one attached to the kick plate and one small black box/plug that is fitted in a slot in the sheet metal side of the panel behind the kick plate. This black box/plug is covered on the end you can see with clear epoxy around the wires to seal it up. Looks like factory done. I don't think either one of these are the TCCM. Do I need to look farther up in the dash behind the glovebox or is one of these behind the kick plate the TCCM? Thanks for all the help, I really appreciate it.

 

So we know the transfer case is engaging, the next place we need to look is to see if the front axle is engaging. There is a black actuator under the battery. It needs to contract about a half to 3/4in to pull the cable enough to engage the front axle. If you've already done this, let us know then we'll go from there haha

 

The vacuum actuator does pull in on 4Lo but not 4Hi.

PS - I think I've done enough reading now to say that my TCCM must be behind the ash tray. I've seen many other postings say that ultimately was where they found it after it wasn't behind the passenger kick plate.

 

The little silver box that u described behind the kick panel sounds like the TCCM to me.

Did your little silver box look like this:
http://kylestubbins.com/files/images...r_tccm_01c.jpg

There was a year where they did move them from somewhere to behind the kick panel. Whenever you do find it, check the connections for corrosian

 

No, it doesn't look like that. The box that is behind my kickplate is attached to the plastic kickplate, is almost square, with sharp edges. I unplugged it, pushed the 4wd buttons, lights still came on and I could here the encoder motor move each time. There was definitely a clicking sound coming from elsewhere behind the dash. I found several posts elsewhere that made reference to the tccm (in some of these 96's) being behind the ash try. I'm pretty sure that's where it will be. What I'm confused about is why are the 4wd lights acting properly, I can certainly here a clicking coming from behind the dash TCCM or switch (don't know if difinitively that means its doing what it is supposed to or not), the encoder motor (before and after it was replaced) is certainly moving the transaxle, and the vacuum actuator is pulling in and engaging in 4Lo.

 

I'm not sure if the 96 is the same way, but when i had my faulty encoder motor on my 95 after reaplcement you needed to clear the codes out of the TCCM to reset it in order for it to start working properly again.

When my encoder motor went bad it wouldn't go into 4-hi like yours does though. The 4hi light would blink and you could hear clicking and then it would revert back to 2hi after about 10 seconds. It would switch from 2hi to 4lo with no problem thuogh.

 

The TCCM is located near the center of the dash accessible from below once the hush panel is removed.

Check out this thread and see if it helps:
NV233 No Mode Switch (ie. 2HI to 4HI)