Hello everyone. Long time reader, first time poster here. First of all I'd like to say that this is an excellent forum with a lot of knowledgeable users. I hope someone can help me out with my issue.

This may be a little long, but I'll try to give as much info as I have come up with thus far.

I have a 1999 Blazer with a 233 transfer case with the 3-button electronic shifter in the dash.

The problem started a while back when I shifted to 4Hi. It did not like to go back to 2Hi. Usually after some driving and pushing the 2Hi button several times, I could get it to go back. A couple months ago in some snow/ice, I used 4Hi, and ever since, no matter what I do, it would not go back to 2Hi. The TCCM would click, I could hear the motor engaging, 2Hi light would flash for a while, then back to 4Hi. However, it would shift to 4Lo and back to 4Hi just fine.

So, TCCM seems to be working, and the front axel was locked in, so the vaccum switch, hoses, and accutator all seemed to be OK.

After investigating as much as possible, and some tips from a fellow general mechanic, I decided that it was probably the encoder motor that was not strong enough to shift back to 2Hi. Got the old motor off. Was able to manually shift the transfer case to 2Hi with a wrench without any problems. I then connected the encoder motor to the harness but not to the TC and used the botton to shift to 2Hi. The motor moved to that position but sounded "weak". Ordered a remanned encoder motor from Advanced Auto Parts. It comes in 2Hi for installation. After battery disconnected overnight, I installed the new motor. Connected everything back up and 4wd light shows 2Hi. Shifted to 4Hi. Then 4Lo (yes in neutral). Back to 4Hi. Then I tried to go back to 2Hi and it acted the same way. Didn't want to shift back to 2wd. I finally got it after hitting the button enough times.

This starts a new problem. Now, then I try to shift back to 4Hi, I do not hear the encoder motor engaging. I still hear the relays in the TCCM, and the 4Hi light flashes, but never tries to engage. Stays in 2Hi (front driveshaft free). After trying that a few times, I guess it's throwing a code and stops trying. The code is 3 flashes, which points back to the motor. I can clear the code by pulling the fuse and cycling the ignition 5 times, and it will go through the same actions, resulting in no response and code 3 again. But why would have cycled to 4, and back to 2, then just stop working? Bad remanned motor? I never had the "no response from encoder motor" or a code until installing the new one. It would always try to shift back to 2Hi, just never sucessfully get it there.

I'm getting another encoder motor shipped overnight at the store's cost, so I'll have that to try tomorrow. Until then, I'm going to try the following tonight:

1. Battery has been disconnected since last night to clear TCCM.
2. Unmount new encoder motor and try shifting it with the button but not connected to the TC (I don't expect it to respond) .
3. Reconnect my old encoder motor and see if it will shift the TC (I doubt it, but if the new motor doesn't respond and the old one does, I would say bad new motor and wait for the new(est) one to show up.

I have not yet replaced the 3-button switch, nor the TCCM. Seems the switch is probably OK. I'm still not sure about the TCCM at this point, but don't have another one to try, and would rather not spend the $$ on one if I don't need to.

So now that you know my story, does anyone have any suggestions? I've scoured the net for any information and have not found a single instance that matches mine exactly. So please, any help would be greatly appreciated. This thing is driving me nuts. This blazer has been nothing but a problem since I bought it (used).

Thanks again,
Kevin

 

New updates from tonight's test. After leaving the battery unhooked overnight, the first thing I did was connect it and test the "new" encoder motor. Same results. Light flashes, tccm clicks for a while, then back to 2Hi. I then removed the new motor and connected, but did not mount the old motor. Tried the test with it and same results. So the motor may not be the problem at all. I'm going to swap the new motor out for a newer one tomorrow and see what it does. Although, I expect the same result at this point.

So, my question is now, is my TCCM bad? Does anyone know the possible causes of it throwing code 3 when trying to switch to 4Hi? It didn't do this before I put the new motor in and shifted it into 4Hi, 4Lo, 4Hi, 2Hi with it.

Any ideas guys? I'm about done with this POS.

Thanks,
Kevin

 

Push Button 4wd Operation, Problems, Troubleshooting and Diagnostic Codes [Archive] - S10PLANET.COM

dunno if that link helps it has alot of information though. maybe your vacuum switch

 

Thanks for replying. Yea, I've looked through the post before. Good info. I just wish there was more detailed info on what causes the code 3.

I'm at the point of just replacing everything one part at a time to see what works. I found a 3-button 4wd switch for $10 and a used TCCM online for $30. I didn't think that was too bad since new (remanned) they are over $200 togehter.

I forgot to mention about the vacuum switch. I bought a new one with the encoder motor since I figured I had that out of the way, I might as well replace it. Well, I don't have a stubby wrench to get up in there, so I tried a short cresent wrench but could not get it to fit tight enough, and was not able to get enough leverage to break it free (I'm laying on the ground working upwards). Any tips on that? I assume it uncrews counter-clockwise just like anything else, right?

Also, I think that is probably working fine (but who really knows), as before I made the encoder swap, stuck in 4Hi, the actuator was engaged and locking the front axel. After manually shift TC back to 2Hi for encoder motor swap, and with engine running, the front axel is no longer locked. But I'd still like to replace it while I'm in there now.

 

I would take a closer look at the DTC 003 section of the GM service guide, starting on page 8 in the PDF link. I copied this from the original guide and put it in PDF format so I could search for things easier. Go step by step through the whole troubleshooting process (can probably skip step 1, since I believe you've confirmed that the t-case does work properly when you manually shift it). The DTC 003 has a little more to do with the TCCM, versus a 002 which is probably more common when it's just the encoder motor which decides to crap out. In the end, you may have to get a new TCCM, but at least you've got a shot at figuring it out for sure. Let us know how it goes.

 

Thanks for the post. I haven't seen this before. I'll give it a shot.

 

Well, I finally got it working, at least better than it was.

After replacing the encoder motor, I also put a used TCCM in. The combination seems to have worked. I was able to switch from 2-Hi to both 4's and back. Towards the end of my testing, it was starting to get a little harder to get it from 4Hi back to 2Hi, but did finally go, and I left it at that. I can at least rely on being able to use 4wd if needed.

The "new" problem I started having after replacing the first encoder motor (just clicks in the tccm, no motor movement) turned out to be a blown ATC fuce under the hood. Replaced that and it started shifting again.

Thanks for all your help guys!