HEy guys, I looked but couldn't find any threads with similar symptoms. I went to check my 4WD on my '98 blazer because I was going to go offroading. I pushed the 4 wheel hi button, and i heard the inside servo click, but nothing outside and my lights went off where it points out 2wd or 4wd. the buttons don't do anything right now and my truck is stuck in 2wd. I check some fuses but not really sure to go from there. any help is greatly appreciated. Thanks

 

There are no lights on your 4WD Switch now? If you hit 4WD (4Hi) do you feel it engage?

 

the lights would ignite when i turned the ignition but would go off afterwards. Today though the 2 wheel light went on which is good i think, but i can push any button but nothing works. can anyone give me advice with what i should be looking for? THanks

 

i had a similar issue and it was the vaccum tube under the battery had fallen off, this was on an 01

 

could someone give me a diagrahm or point me in the direction where the tccm is? Thanks again

 

On my 2001, a 4WD vacuum hose, kept slipping off the firewall, RIGHT above the distributor. It was too short(by none of my doing), so I bought a (I can't think of the term right now) "double nipple thing", and extended it.

 

Just an update, i checked all of the vacuum lines, and everything is connected fine, but there is no vacuum reaching the actuator. I believe its something electrical, but how can i tell if its the solenoid or the TCCM. I tried jumping out the system and that did nothing, last week it did the same thing and i resetted something.(I believe the TCCM). I appreciate the help

 

This is an update, and i was wondering if anyone knew any symptoms, if i forgot to mention its a 3 buttom 4wd, set up. as of right now all of my hoses are connected to my actuator, but i see that there is no vacuum reaching it.
There is no check 4wd light on my dashboard, but at the same time I will have no indicator lights next to the buttons, until I drive for about 20-25 minutes, the 2 wheel hi light will go on, but it still wont go into four wheel drive.
I tried jumping out my TCCM and when i started it I heard the TCCM click (or clunk as it sounded that time) as if it wanted to shift into 4wd, but then all of the lights would go out again.
So i bought another "used" TCCM trying to see if it was that working inproperly, but the same symptoms occured. Could it be the vacuum solenoid? if so how do I check it? And also would anything come up on a Gen. 2 scanner even if there is no light on my Dash or would I be wasting my money?

 

You have the NV233 transfer case. The vacuum is controlled by a mechanical switch on the transfer case. This switch can go bad.

First though, you should go through the diagnostic check on the TCCM. It is located behind the passenger side kick panel under the dash. Check it over thoroughly for corrosion on the electrical connections. Do the same on the encoder motor located on the side of the transfer case.

Please have a look at these threads for diagnostic checks/procedures/explanations & wiring diagrams:
NV233 transfer case / encoding motor switch
OBD2 Non-Automatic Transfer Case Diagnostics

You can check it for free!