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  #1  
Old 02-16-2010, 06:20 AM
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First off, I'd like to say this is my first post and I am new to the board. Secondly, you guys have a wealth of information posted amongst these topics and I've researched the best that I can from within.

So off to my problem...I have a 1999 Chevy Blazer 4dr, 4wd, LT model. I just bought it used and they told me the 4wd wasn't working. Here is what I've done and what I hear.

I turn the ignition key to the on position or start car and a get a series of clicks coming from the passenger side kick panel. These are roughly 6-8 fast clicks (almost like your hazards are on). The blazer starts and initially none of the 4wd lights would come on (Back light or the red lights) Car runs fine and seems to be in 2wd hi.

I check the ATC fuse under hood, swap with a new one same issue.
Checked the 4wd fuse on interior dash/driver's side, swap with new one, same issue.
Note: When I plug the ATC fuse back in, I can hear the clicking inside the blazer again from the area of the passenger kick panel.

I check power to the fuse, leaving the fuse. I pulled the battery, tray, and visibly inspected the actuator under the tray and the hoses back to the actuator solenoid. Disconnected the upper/lower vacuum hoses. I feel vacuum coming from the bottom hose, no vacuum to the top hose. Put the two hose ends together and I hear an audible click by the transfer case and see the actuator pull to the out position. When I remove the hoses from each other, the actuator goes all the way to the in position.

I have swapped out the 4 button 4wd switch in the dash and check connections. So I pull the kick panel off and visually inspect the connections of the TCCM. This is where the clicking is coming from. Soon as I plug in the large 32 pin?? connection it clicks when the key is on, pull connection and the clicking stops.

Initially I thought I might have an issue with the switch itself or the solenoid valve actuator that is near the firewall. Now I am not so sure. None of the red lights would flash quickly when turning the ignition over...that now works but still have the issue with none of the red lights staying on or displaying the mode it's in.

The blazer will not go into 4lo when in neutral, and none of the buttons change modes. I am at a loss and really don't want to drop $2-300 on a TCCM module or the the encoder motor underneath.

Any suggestions, I am banging my head over here....Thank you.



Edit to add: Also note that I had my bro-in-law (gm/ase certified) run diags from the port. No codes, also no trouble codes in the instrument cluster. Only thing that flashes initially is security, when starting car and then everything clears out.



Forgot to tell you that when I had the battery and tray out, if I pushed the actuator valve in by hand I could hear air coming out of the solenoid where the two vacuum hoses connect by the firewall. Is that normal?

Edit to add: I also have the 4 button switch. Auto/wd, 2hi, neutral light, 4hi, 4lo.

Last edited by swartlkk; 03-08-2010 at 06:10 AM. Reason: *Combining Consecutive Posts* - Please use the EDIT function to add additional information to your post if another member has yet to reply.
  #2  
Old 02-16-2010, 12:03 PM
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Ok, you need to be patient and actually wait instead of violating the rules of the forum repeatedly and being unreasonably insistent... If you want instant results, open your wallet and go to a shop. If you want free advice, be patient and wait for responses.

In the mean time, you could do some leg work yourself and read through the vast number of posts concerning troubleshooting the NV236 transfer case. If you had done so, you would know that it is quite difficult to properly diagnose the system without the use of a full feature scan tool. You could throw a TCCM and encoder motor at it and likely fix the problem, but you really wouldn't know what was wrong to begin with.

If the solenoid is not energized, it should vent the line from the actuator so it releases, disengaging the front axle.
  #3  
Old 02-16-2010, 12:32 PM
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swartlkk,
Sorry I don't believe that I was being "unreasonably insistent." Not sure how I came across that way. Sorry about that. I also am unaware of what forum rule I violated (as I read the entire thing.)

I will be more patient, I was, still am slightly frustrated at this issue. I know that isn't an excuse. Your right, I don't want to just throw parts at it and say wow, it's fixed. I want to know why it did what it's doing..so I can learn from it. So thank you for your reply.

So I take it that the solenoid is working as it's supposed to based upon my description of troubleshooting. Does the full feature scan tool plug into the TCCM? My father has a buddy who owns his own transmission shop and he told him that the two most common failures he sees are the switch and the encoder motor. I guess I'll have to run it out to him today and get it diagnosed.

Thank you.
  #4  
Old 02-16-2010, 02:44 PM
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The front axle engagement system is the most common problem when it comes to an inoperative 4wd system, but that will not prohibit a shift. As far as blinking lights go, the most common issue is the encoder motor.

The 4-button switch can be diagnosed rather easily with a multimeter set to read resistance. I have posted that in the past, search for "nv236+resistance" and you should turn up the relevant threads.

The TCCM and encoder motor for the NV236 transfer case are quite a bit more difficult to diagnose. This is where a full feature scan tool comes in. It is required to watch what is going on when you push the button.

About the rules, don't sweat it, just making you aware of the consecutive posting tidbit.
  #5  
Old 02-16-2010, 02:49 PM
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The weird thing is the TCCM clicking 6-8 times rapidly when I turn the ignition key to the on position or start the engine. If I pull the 20A fuse under the hood for the ACT, then put it back in...the TCCM does the clicking sound again.
  #6  
Old 02-16-2010, 02:59 PM
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Sounds like the TCCM is the culprit, but that is just a guess without proper diagnosis with a scan tool. If the scan tool is not able to communicate, the next step is the replacement of the TCCM. If it is able to communicate, then there are some tests that you can run.

Have you tested for proper power and ground at the TCCM?
  #7  
Old 02-16-2010, 07:06 PM
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Ok just got back from getting it diagnosed..cost me a case of beer.

Here are the codes I am throwing.

C0310-Motor A/B Circuit Open
C0323-Transfer case lock circuit low
C0327-Encoder circuit malfunction


Old code on history:

B2725-active transfer case mode switch malfunction

We cleared the codes and the top three come right back. He said I can try to clean the connections/area around the encoder motor and if it still doesn't work to replace the encoder.
  #8  
Old 02-17-2010, 01:14 PM
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Anybody had any luck troubleshooting those codes without a part replacement? The reason he said to swap out the encoder motor was because he could communicate with the TCCM.
  #9  
Old 02-17-2010, 01:49 PM
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Did he try to diagnose the codes? The sheets for most of them are listed in the OBD2 Code Index post located in the Tech Article (DIY) section.

*EDIT* Actually, all of them are there...
B2725 - Active Transfer Case Mode Switch Malfunction
C0310 - Motor A/B Circuit Open
C0323 - Transfer Case Lock Circuit Low
C0327 - Encoder Circuit

Sounds like you need to find a new mechanic if he needs this much hand holding.
  #10  
Old 02-17-2010, 09:31 PM
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This was a stop by the shop, on his off time, he was doing a bunch of stuff with the code reader/computer and told me that everything was pointing to the encoder motor. This wasn't on the clock work or was he expecting payment. The case of beer was for him spending an hour looking at my blazer.

Every single one of those codes ends up in either replacing the encoder motor or the TCCM. The first code is for the switch itself.

Last edited by SureShooter29; 02-17-2010 at 09:38 PM.
Old 02-17-2010, 09:31 PM
 
 
 
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4wd, 97, actuator, atc, blazer, chevrolet, chevy, driver, information, problem, repairing, series, system, tutorial, vacuum, work, working


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