I have a 2002 S-10 Blazer with intermittent problems shifting from 2 to 4WD and back. Three buttons are on dash. Here's my scenario:

---About 2wks ago went to shift from 2 to 4WD and dash light just flashed.

---Tried what manual said about shifting to neutral/park, but never worked

---Problem is intermittent with no apparent rhyme or reason. May work 20 times in a row, perfectly, and few minutes later, not work at all. Can be dry/rainy/hot/cold....makes no difference.

---Sometimes, push dash button once and it works. Sometimes, when button pushed it flashes on/off for about 10 seconds. Sometimes, when button pushed, it flashes once. I'm usually going from 2 to 4 WD although a couple times it took a while until it would shift back to 2 WD. I can push the button 20 times and it won't change. Then 5 minutes later it may or may not....i just wait and try it "later". Eventually it will work. I always hear clicking from module when I push button.

---Pulled off passenger side panel and visually checked connections at module. all looked fine/no corrosion.

--Replaced transfer case switch...no difference. Did find small amount of what looked like tranny fluid at vacuum connection on switch. Replaced vacuum actuator,(old one seemed to work fine. Held diaphragm in when 4WD engaged)...no difference. Vacuum lines at transfer case switch and actuator seem tight.

---Took vent fitting apart at radiator making sure it's clear. That is just a vent, right, not a check valve or one way valve? There's no rubber seat/ball like a check valve would have, so I figure it's just a vent opening.

---For what it's worth, in case there's a tie in. Several weeks ago I had a small leak at heater core as I could smell antifreeze. Water level never dropped enough to notice. Never had liquid visible anywhere or wet floor. Used Bar's Stop Leak. I only mention it as I thought it possible anti-freeze corroded a vacuum line. But then it would be a continuous problem.

---Cable to vacuum actautor seems free, no binding.

---I'm guessing only things left are transfer case motor assy. or the control module behind passenger foot panel. I'm leaning towards encoder motor assy. since I hear module clicking when shift buttons pushed. Or am I totally missing something here? How much work is involved in transfer case encoder replacement? I have a solid mechanical background....it's just the 4WD stuff is all new to me.

Any help would be greatly appreciated.

Thanks,
Dave

 

Have you tried holding the button on the dash while it is shifting?

Your problem sounds like the typical encoder motor failed shift. Have you tried reading the codes from the TCCM?

If you have the 3-button switch:
OBD2 Non-Automatic Transfer Case Diagnostics by lastcoupe & swartlkk - has the codes and how to get them
NV233 transfer case / encoding motor switch by error_401 - A good write up on the diagnosis of the NV233 transfer case (don't let the year of the OP's truck dissuade you).

If you have the 4-button switch on the dash, then you need a Tech2 or equivalent scan tool to access the TCCM and pull codes.

 

swartlkk,

Thank you for replying. Yes, I have tried holding the button down while shifting. It makes no difference. No, I have not tried reading the codes from the TCCM. I will follow the instructions you sent. I do have the 3 button switch.

I apologize for the repost. It will not happen again. I was surprised I had not received an answer sooner so I thought maybe my post got overlooked. I was hoping to hear from you as you seem to be the guru of the Blazers from all I've read...lol.

Thanks again,
Dave