ok searched the fourm and found no similar problems lol

1993 Chevy s10 Blazer 4x4 4.3l Vortec. Auto with auto 4x4

bought the blazer a few months ago and 4x4 worked fine. couple days after owning it i went to go into 4x4 and nothing happend. no lights and not engaugement. was told to disconnect battery for 1/2 and hour and reconnect to clear codes. did that and had 4x4 all day till i shut truck off. after restarting truck i had no 4x4 again. now when i start the truck the lights on the switch light up and act normal. no matter what gear im in it wont turn lights on the switch and it wont engauge. i know it works if i disconnect the battery but what can i do i miss my 4x4 and the weather is getting to be **** . its weird but i found if im in drive and i shift to park then into reverse i hit the switch and it lights up as in 4 lo but it wont enguage the 4x4. i have to shift back into park then reverse in order to shut the lights off as well any thoughts and advice as to what to do is greatly appreciated. thanks

Brad

 

I have the same exact problem with my 94 balzer. I have changed the TCCM twice and the switch itself once, to no avail. I finally found the way to check the codes in the Transfer Case Computer and it tells me that the motor on the transfer case is malfonctioning, they call it the "encoder." I have removed the part and I am now looking for the same in a junkyard. If I engage the 4 wheel drive manually on the transfer case it works fine. You may have the same problem.

 

https://blazerforum.com/m_52228/tm.htm

 

Same kind of problem here, some wrinkles though.
I read the above linked post. Very cool info.

I got my '92 truck with no working 4x4. I was told it was the vacuum accuator under the battery.
Finally carved out some time last month, pulled the battery and found the vacuum accuator in perfect order.
I unbolted it and after re-connecting the battery temporarily tested it and found it working. (This was before reading the above linked post explaining what was really happening) I had no idea what I had done to fix it, but not one to brake something working I was happy.
To make future repair easy, I moved the accuator to the fender where the black ball was and put the black ball under the battery. (What is the black ball anyway?)
All back together, 4x4 worked perfectly. Used it several times on muddy mountain roads after thanksgiving. Actually, would never have gotten into or out of some State Forest hunting without it.

Fast forward to last week. I hit the button on the dash and, Nothing. Just like when I got her.

Pause. Here is a possibly related issue. I have determined that the probable cause of my non-functioning reverse lights is a bad neutral position sensor on the shifter/steering column. Have not bought the part yet.

Play. Today, goofing around waiting for someone, I shift into neutral and hit the 4hi 4x4 button. The 4hi and 4lo lights blinked with a clicking from behind the glove box. Here is the weird part. Shift from R into N and - nothing. D into N and I get the blink and clicks.
Had my wife shift and hit the button for me while I felt for the click under the dash. The silver boxes with the big multi-wire plugs were too hot to touch.

I just went out to check for vacuum leaks related to the black ball (wonder what that is) and found that if I shift into N from D and then hit the 4lo button it shifts into 4x4 Low. Confirmed by the major torque change. Hit 4hi button and it just blinks and clicks.

I'm wondering if the bad neutral position sensor is causing my problems. After reading related topics I realized that my initial successfull "repair" where I really did nothing had me disconnecting the battery for more than 30 mnutes. According to others, this would reset some kind of computer. Maybe I'm getting closer to a solution.

Ideas? Thoughts? Solutions to my problem?

 

Yep. Just re-connected the battery and all works perfectly.
With snow in the forecast tonight, I am psyched.

But what caused this to happen?
I vote neutral switch giving the computer bad info.

 

Sounds like a faulty TCCM or encoder motor to me. Pulling the power will work for a bit as it resets the system. If you have Auto4wd, your only way to properly diagnose what is happening is with a Tech2 or equivalent scanner. If you do not have the Auto4wd, then you can run through the diagnostics as posted in the DIY section.

 

Thanks.
I'm not familiar with "Auto4wd". Is that an all wheel drive option?
I would figure if mine was Auto4wd I would know?

 

It is not all wheel drive, but auto 4wd engagement. If you do not have an Auto4wd button, you do not have Auto4wd. I suggest you create a new thread on your problem after consulting the DIY article as I already suggested.

 

Thanks.