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Discussion Starter · #1 ·
First off, I did search and came up with a few things. I am a little confused on what is actually happening though.

My 92 has push button 4wd. When I bought the truck a month ago the 4wd worked and engaged in 4hi and 4lo just fine. The lights illuminated and everything.

Today my Dad and I were out pheasant hunting and we drove through a field to park the truck. I put it in 4hi as a precautionary measure, or what I thought was 4hi. I just hit the button, it blinked a couple of times and I took my eyes off of it. It seemed to be in 4hi but I don't think it was. So we got back in the truck after walking a little, and the I noticed the 4hi light wasn't lit. I hit the button, heard the relay click and that was it. I hit the button again and the light lit for a second and went off. Now it will only light up for a brief moment and then it goes off. Sometimes it wont light at all though. The relay clicks every time though so I don't think the switch is bad. Also, the 4wd lights illuminate when the key is turned to the on position just like they always did.

I am going to check the actuator under the battery and looked for cracked vacuum lines. What I don't understand is why the lights on the 4wd switch stopped working now. Any other suggestions?

Thanks
 

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could be a fuse or the TCCM or the TC motor.....
 

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Discussion Starter · #3 ·
A little update. I unhooked the positive terminal of the battery and let it sit for a couple of mins. Hooked it back up, started the truck up, hit the switch and now it blinked like normal but then went out. Tried it again, same thing. Eventually the light stopped coming on again when I pushed the 4hi or 4lo button. Relay still clicks and everything.

What does this indicate? If the actuator was not working or there was a vacuum leak would the 4wd light still stay on? I did some more searching and could not come up with an explanation for what it happening.

What does it mean when the 4wd light does not stay on? Just trying to get a clear picture of what to look for before I start tearing things apart and replacing things. Thanks all.
 

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So now it was my turn to lose my 4x4 hi and lo and only have rear. Did you find any help Im new to this too.
There must be some sticky tread here somewere about this.
Or some simple plan to show were how vacum lines goes or electric to this prob.
I did check under Transmission & Rearend But I must be blind not too find help there.
 

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Discussion Starter · #6 ·
I did some more trouble shooting last night man but still nothing.

I tried unplugging the TCCM like I found in another thread. Tried resetting it again, unplugged the battery, all that stuff. Looked at the actuator and there is a small hole in it but when I press the 4wd button I hear the TCCM relay click still but nothing happens down by the T-case or actuator. My question for you gurus is this...if there is a vacuum leak will the actuator still try to pull and can you visibly see this?

Lastly, I did the OBD1 jump from pins A and J and it showed codes 1 and 3. One I read was normal but 3 is something with the TCCM. Is it possible the TCCM just quit working? I also found another thread that said a code 3 means the encoder motor needs to be replaced. I am at a loss here and it is starting to get colder. Any help is greatly appreciated.

MV70 let me know what you find out and I will do the same.
 

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MV70 let me know what you find out and I will do the same.
Mine was simple fix http://www.s10forum.com/forum/f13/lost-front-drive-4x4-vacuum-hoes-lose-pics-455591/


But there was some good info in "vacuum thread" before.

"how to help narrow it down a bit. take a set of vice grips and manually pull the cable at the actuator and take the vacuum completely out of the loop. if the 4wd system does not work after this, then your problem is in the electronics, not the vacuum. it it works, then your problem is vacuum. to start diagnosing the vacuum system, i would make sure the lines going back to the t-case are intact and plugged in. if they are, then start the engine and make sure one of the lines will pull a vaccum. if it does, make sure its plugged into the valve properly. if that is correct then put it in 4wd (still with the motor running), and see if the line at the actuator is pulling a vacuum. this will narrow down which of the two lines may have a fault in it. the open air line does not matter, it could be un-plugged at the t-case for all it cares."
 

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Discussion Starter · #8 ·
Thanks for the heads up man. I am thinking that mine is the encoder motor. I tried pulling the cable last night and nothing happened. The only sound I get is from the TCCM under the dash. I get nothing from the T-case at all.
 

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Discussion Starter · #9 ·
Alright, checked the voltage at the encoder and all were 4.95 Volts which is obviously close to the 5 that is needed. Changed the encoder with one from a scrap yard, that didn't work either.

Now when I reset the TCCM and press the 4HI switch the light will blink and TCCM makes several clicks then the truck kicks back into 2HI. After pressing the switch a few more times it will stop blinking altogether and I only get one click from the TCCM.

Is it possible for the TCCM to be bad and still be "clicking"?
 

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Discussion Starter · #11 ·
Nismo, from what I have read and researced it sounds like your encoder is likely to be the culprit. Hope you get it figured out.

Anyone have any ideas on my situation? Should I try another TCCM or should I get a brand new encoder and give that a go?
 

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When this happened to me last spring I was sure it was the tccm from everything I read until I bought a new switch and voila fixed. I did however. unplug the tccm, clean the contacts and plug it all back together.
 

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Discussion Starter · #13 ·
When this happened to me last spring I was sure it was the tccm from everything I read until I bought a new switch and voila fixed. I did however. unplug the tccm, clean the contacts and plug it all back together.
What was yours doing exactly?
 

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Discussion Starter · #14 ·
Tried replacing the TCCM and the encoder. No dice. Still throwing a code 3. All connections are good, no wires are burnt or anything. What else could it possibly be? I am getting power at the encoder as well but it wont do anything when the switch is pressed.

Dumb question, but does the car need to be running to engage the encoder? I figured I would at least hear it turning correct? I thought it just needed to be running to create vacuum to engage the front wheels.

Any other things I can try before I blow this thing up? Also, I was able to take back all the parts so I'm not out any money yet. Thanks guys.
 

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same with me. Where did you get your stuff to try and then return ? where is the tccm at ? does that run just the 4x4 ? is there a way to hook up a toggle switch to get the hi side on the 4x4 case and then go with the posi lock cable? thanks
 

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ok put it in neutral and the light flashed and it click under the dash look under the batterry and it is pulling on the cable jacked up the back and it moved forward !! if got the posi lock and put that in i could just keep it in hi and use it to put in the front ????? mileage would be down for sure but aleast it would have the transfer in ???? and would not walk with the front being out ?? Thanks
 
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