My 99 blazer is stuck in 4-Low and I have no clue what's wrong with it after trying tons of stuff. I have right now in my possession 5 transfer case control modules (TCCMs) and three 4-button switches. I also bought an ODB-II code reader that hasn't told me anything.

It is stuck in 4-low and the 4-button switch doesn't show any status light to say what it is currently "in", but it drives like it's in 4-low.

I tried and bought more TCCMs because I wasn't sure if I had bad ones etc, and I bought more switches just in-case lol. The 4x4 fuse on the drivers door fuse panel is fine. Are there other fuses to pull somewhere?

What would cause it to have no status lights on the switches??

 

Well, sounds like you are starting off with the shotgun approach to auto repair. This path is a sure fire way to frustrate yourself. I just hope that you picked these parts off of junkyard vehicles instead of buying them new...

You can test the switch (search "nv236+resistance").

The only way to test the TCCM and encoder motor is basically with a full feature scan tool. Your typical over the counter scanners won't be able to communicate.

Check out the thread below from the Tech Article (DIY) section on the NV236 transfer case for some more information:
NV236 Wiring Information

 

I did hunt around to get these parts cheap'ish (ebay, craigslist, junkyard). I'm pretty sure the switch and TCCM are fine just because I've gone through a bunch of them. Are there any other suggestions on what -could- be wrong that'd make the status lights not display a status? The wires are clean and don't appear to be broken to the TCCM.

I was thinking there might be another fuse somewhere I'm missing (I've checked the door panel fuses and the ones under the hood mostly). Also, behind the glovebox I read somewhere (I can't find now) that there might be some fuse or something above the TCCM?

Do you have any suggestions on something I could replace? I'm not really able to read a schematic very well...(I am reading now a "how to" read schematics).

 

Ok so I bought an Ohm meter and according to this thread:
https://blazerforum.com/forum/showthread.php?t=41198

I tried testing pins A & B according to this image:



And 2 of my 3 switches are good. I'm still not seeing any lights on the switch which is perplexing...any ideas?

 

did you try putting your blazer in nuetral and pussinh the 2hi button? thats how you get them out of 4wd lo

 

Yes I did try that. And I can't figure out how to delete post but I screwed with the tester more and pins A & B are in fact the BLUE ones. I had it on 200 which didn't register anything across the other pins, but when I switched it to 20k like I read in another post, the switch tested fine.

I now know my switch(es) are good.

Could a bad encoder motor cause the lights on the switch to not display anything? How many fuses are related to this whole operation? I've only been able to find one.

 

Those are pins A & B. The command for the lights come from the TCCM.

 

That's what I figured. I guess that my TCCM's I have must just be bad. The one that was in it that I think was water damaged is numbered 15154323 and I replaced it with another one that -could- also be water damaged. I took one that I'm pretty sure is working from another 99 blazer numbered 12577412 that doesn't fix the problem, so perhaps it isn't compatible. I have a 98 TCCM that isn't he same, but I just plugged it in anyway and it made all sorts of terrible noises when I tried shifting gears so that was a bad idea.

These are the only fuse blocks I found and I could only see 1 fuse that relates to the 4x4 system...are there any more that are used?




I recall somewhere reading that there was a relay under the glove box that did something...I don't suppose anybody can confirm/deny this perhaps?

 

The fuses listed in the wiring schematics all play into the 4wd system. ATC, 4WD, ILLUM, and CRANK all tie into this system in one way or another. The ILLUM fuse only deals with the back lighting of the switch. The CRANK fuse powers up the TCCM, but also deals with a number of other crucial systems.

The power from any and all fuses can be tested with your multimeter by setting it to the voltage scale and probing the terminals in the connectors listed in the schematics.

 

Al3x I am having a similar problem. When I disconnected my encoder motor there where no lights on the 4wd switch so maybe check the connections on that. Don't even know if that is supposed to happen but on mine it did.