I've got a 99 with the 4 button 4wd. All my lights do is blink, and there is no 4x4 engagement. It happened all of the sudden with no signs that is was gonna act up.

I verified that the push buttons work, all vaccum lines are good, and the front axle actuator works, as in it pulls the cable fine. But no 4wd. I checked the tccm connections, tried resetting it- no luck. I thought that I could feel the encoder motor trying to do something when I had someone push the buttons.

Am I missing something? I also noticed that I can't pull the codes myself. The service 4wd light comes on about every 3 tries when i select 4lo.

Thanks!!

 

thanks

Well i just had the truck scanned, and the only code that came up was 0387 failure to shift.....

the mechanic says he's seen this countless times, and his money is on the switch. so I guess i'll order one up.....

When i hold in 2 hi and 4lo to go into neutral on the tc (i think those are the buttons)- should the transfer case stay in neutral?

Thanks

So I think my 4wd will briefly work after i leave the battery disconnected for a bit, but then it fails again. I read on here that means possilby an encoder motor? But that was for the non auto transfer case. I'm not sure if they're the same or not. When my 4wd does work after connecting the batt, my lights still flash. Any suggestions on what to replace first? Encoder or tccm. The tccm does click everytime I hit my buttons.........thanks

 

well, i am guessing if you hear the tccm doing its thing then it probably is.
if the mech says encoder motor and you still question him then i guess a second opinion is in order.
you could take off the encoder motor (which if you ordered part you are going to)
and try to shift it by hand...like so

ZR2 encoder motor instal questions? - S-10 Forum

look at about midway thru thread.

also this will tell you a little about your setup..
https://blazerforum.com/forum/tech-a...rmation-41198/


i hope that helps a little.
you should cruise thru the DIY section...LOTS of goodies in there.

i also read in your first post that you checked everything as well so...i say go with the mechanic.

 

Thanks for the reply!

The mechanic thought it was the push button switch, as apparentley he has seen it many times. The blinking lights, and no engaugement. He even called a friend of his for advice. That tech told him to disconnect the battery, and if the 4x4 worked, then to replace the tccm. That doesn't make sense to me though. Same as the switch theory. With that being said, after I disconnect the battery, and try it, it does engage- but the lights still blink. I have a nice patch of ice on my rd that I was trying it on. Once I put it back in 2wd, it wont go back into 4.

Let's recap everything:

I replaced vaccum lines, I checked the actuator under the battery, and that seems to work fine. Pulls on the cable, and will stay compressed until I push 2wd again. If that plunger works, is it safe to assume that the solenoid on the fire wall is functioning correctly?

I recently swapped my rear end out, and 2 days later we had snow, and that is when I tried my 4wd- and no go. It worked perfect before I changed the rear end. Huge coincidence?

The tech did check the codes, and came up with the failure to shift. One thing he found strange, is on his "data stream screen"- all it showed him was "no data". That he couldn't understand.

I have read through MANY of the posts on this wonderful site, and have gathered this:

-The 4wd activates via switch (obviously lol), tells the tccm what to do, in turn activates the solenoid on the firewall to pull the cable for the front axle. Now the switch mounted in the axle, from what I understand tells the tccm where the axle is. So...all that does is keep the desired 4x4 button lit?

I can hear the tccm, and the encoder motor, and the plunger works and pulls the cable. All this time my lights are blinking except when I select 2wd again, in which case that lights up like it's supposed to. Even while the lights are blinking, and I go to switch back to 2wd, I still can hear the encoder motor and the tccm clicking. I've read sooooooo much info-I'm confused.

Thank you, I'm going out again to hook my battery up to see what happens this time. Oh.. I also checked my ATC fuse, which was good, and my 4wd fuse which was good.

To clean my tccm connections, would rubbing alcohol work fine?

 

i actually just cleaned my tccm connectors...they were acting up.
i just bought some electronics cleaner for 4.00 at the zone.
worked great...no more 4x light.

rubbing alcohol...dont know enough to say.

 

Did you find any solution? have the same problem whit my 99 blazer auto4x4 is blink and so is the 4lo. 4hi does not react. have done the same check that you done and still have the problem.

 

Well I checked and rechecked everything. I unplugged all connections, cleaned where I thought was neccessary. My truck is engaging in 4hi, never did go into lo since I had it so I'm not too concerned with that. However, all my lights still blink, including the auto- so I'm not sure if that works or not. I also went under and unscrewed the axle switch and pushed on the ball to see if that would turn my blinking lights to solid....it didn't.

I'm expecting about 15cm of snow today so I'll let ya know if my auto is working or not.

I guess that if the encoder motor starts pulling too much power to operate that it can destroy the tccm.........

Well, the snow started accumulating on the roads here so I went out to try my auto.....it doesn't work.

 

Just a quick update:

The past 2 weeks or so, my 4 hi was working fine although the button just flashed. To me no big deal, I just want my 4hi to work.

Then the other day I went to put it into 4hi and got nothing. Just the flashing light, but no 4x4. So now when I push 2hi, my truck tries to go into 4lo- or so the lights indicated on the dASH. Also, when I push 2hi I can hear the transfer case solenoid "click" under the hood. It's more like a faint clunk, but it's definitley the solenoid I hear. That makes it's noise, but the tccm does not.

I wont be able to afford a new encoder or tccm for a few days, but- is it possible that my problems all along was the transfer case solenoid?

Thanks!!

 

Well, the lights are flashing, but still not solid. The tccm only clicks when i start the truck, and when i hit 4lo- but of course it doesn't enguage.

In what year did they start using this particular encoder?? Would a 97 work?

Thanks

 

You need an encoder for an NV236, but really it isn't worth it to buy used. The potential for the used one to have the exact same issue costing you time & money is just too great.