4x4 issues

1997 Blazer 4x4, 108k miles

My 4x4 lights randomly change. I am allways in 2-hi but sometimes the 4hi light flases, sometimes 4hi stays on, sometimes 2hi and 4hi strobe, sometimes no lights at all.


While this is an amusing light show, it is frustrating to not be able to use my 4x4 when I need it. It will never switch to anything except 2-hi, doesn't even try. Reseting the electronics (remove battery for 20 mins) does nothing. Vacuum switch is new, and if I pull on the cable from it i can feel the transfer case "notch".

All fuses are good, and all lights work when i turn the key on.



I tried replacing the transfer case control unit, and it does exactly the same thing.
:banghead:
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Can anyone help me?
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What transfer case does it have?
The Auto 4W mode or regular?
Have you checked for codes?
Will it shift to 4W and 2W and to low range?

What transfer case does it have?
The Auto 4W mode or regular?
Have you checked for codes?
Will it shift to 4W and 2W and to low range?

How do I tell which transfer case it is? (there is a plate on the end of it that says its model 233, that sound right?)
There is no auto-4wd, just 3 buttons
I checked the codes, and i get 2 flashes, so I guess that means I have code 2
It will not shift out of 2-hi (even though the indicator lights strobe around)

Tag on back will ID transfer case.
If a 3 button shift it is a 233.

To check for codes ground pin 13 on diagnostic connector.
Count shift light flashes.
Post back light flashes /codes.

Check all fuses and in IP panel check fuse 13-4-16 for 12 volts on both sides key on.
This link may help.
http://www.automotiveforums.com/vbulletin/showthread.php?t=572914

While poking around under the car I found the encoder motor. I removed the bolt holding it in, and removed/reseated the connector. I then discnnected the power for 30 mins, and turned the key on and off 5 times (just to on, not actually starting the truck). After the 5th time i started the truck and then I had 4wd again.

I will post the artical I found to help anyone else that may have the same problem.


MT, thanks for taking the time to help with my problem.




All this info helps as well that I wrote on another forum:

Well, through everything I have gone through with this electronic 4x4, I figured I would share my knowledge as best as I can. If anyone thinks something should be added, feel free to. This is also from gathered information on other posts.

***HOW TO CHECK WHAT IS WRONG***

You will probably know when your 4x4 has failed when you needed it in the mud pit. Mine, for instance, failed by not doing anything when I hit the 4HI button. However, it would go into 4LO.

To read the codes for the 4x4 with electric shift transfer case, install a jumper wire from terminals "J" and "A" on the ALDL (12 pin connector under the driver's side dash)

The lights on the 4x4 indicator (switch) will flash in a pattern, there are only 4 codes, one flash is code one, 2 flashes is a code 2, and so on...

Code "1" is "RAM standby power" and is considered normal, may be caused by clearing the codes.
Code "2" is "Encoder fault"
Code "3" is "TCCM motor circuit"
Code "4" is "RAM/ROM failure"

If you have the codes 2 or 3 check all the encoder motor connections at the transfer case, if OK it will need a new encoder motor assembly.
If you have code 4, replace the TCCM.

Make sure all connections are good and no corrosion, and then it's either an encoder or TCCM.

***TO FIX THE TCCM***

The TCCM is located behind the glove box, and is accessed from underneath the dash. To remove, the kick panel and black cover come off. Then a 1/4" screw holds the "brains" in the dash. The middle computer is the Truck's brain, the one on the backside is the TCCM, and on the front is the small ABS computer. Simply loosen the 2 10mm nuts on each side, and they will separate.


***WAYS TO FIX THE ENCODER MOTOR PROBLEM.***

This is the most common problem, and was my problem.

Cheap way - To clear the codes and reset the computer, pull the 5 amp TCCM fuse, located at the bottom of the fuse box. Wait at least a half hour, and then replace the fuse. Turn the ignition key to run, wait for the 4x4 lights to blink, and then turn off. Repeat 5 times, and then start the truck.

Decent price way - I just went and bought a rebuilt encoder motor from a company off of Ebay. Their company is www.northernautoparts.com (http://www.northernautoparts.com/) The part cost me around $140 with a 1 year warranty and $38 core refund when I send the old one back.

Expensive way - buy a brand new one from GM for over $300.

***HOW TO INSTALL THE NEW ENCODER MOTOR***

Lucky way - Only thing that needs to be removed is the encoder motor itself. Tools needed are a 10mm hand wrench and a 8mm and 10mm socket wrench. The 10mm socket will work on the upper and lower bolts, while the regular wrench is needed for the middle bolt. (Tight squeeze). The 8mm socket is for the electric plug.
Then, just pull out, and wiggle it out of the truck. Install in reverse order.

Unlucky way - This means the encoder motor did not just wiggle out. Now the front drive shaft will have to be removed at the transfer case. Then, a yolk puller is needed in order to remove the yolk from the transfer case. Once this is done, go to the directions in lucky way.

This is as much knowledge as I have at the moment about the beautiful setup called the electronic pushbutton 4x4. Thank you to all that have helped me, and hopefully this will help others in fixing the future.

-=Glenn=-

I wish to Thank Glenn aka gmshades from s-10forum.com


I followed everything and I finally figured out what was wrong.
Thanks Glenn