I just bought a 99 blazer (4 button) from the auction to find it's stuck in 4wheel low (I think). It had 3 windows broken out of it and it had some snow in the passenger front, but the windows were taped off, so it makes me think they did that after it got a bunch of snow in there. I've spent the last 2 weeks reading and trying things to no avail.

Symptoms:

• 4-wheel switch has backlights, but the light to show Auto/High/Low/Neutral/Etc isn't on.
• I don't hear a clicking from the TCCM (transfer case control module) when I push the buttons, but they don't seem to do anything.
• Seems to be stuck in 4-low as it roars a bunch and I can drive over big piles of snow near my apartment with ease

What I've tried:

• Pushing the crap out of the 4wd buttons over and over
• Checked 4x4 fuse on DS fuse panel
• Put it in neutral and pushed all the buttons
• Drove like 40yds in reverse and forward etc.
• Disconnected battery and TCCM for 30 min, turned key on/off 5 times then restarting
• Bought a used TCCM from a junkyard vehicle I unhooked myself, so not guaranteed to be working and hooked that in
• Bought stuff from autozone to clean corrosion and blasted the connections and cleaned them pretty well, also checked for broken wires and found none. Cleaned the connections to the TCCM too
• I tried reading the service manual and then I found a pin-out and I tried jumping pins 1 & 4 to see if I could get it to switch into 2wd
• I got under the car and looked at the transfer case for a while to see if I could figure out how to switch it to 2wd but I don't really know what I'm looking at. I saw the electronic switch thing, but that's about it.

Any ideas what could be wrong? The buttons seem basically unresponsive, but the wires in the back look fine and it looks essentially new. There is a chance that I have 2 bad TCCM's I suppose. I don't hear any clicking unless it's soft enough I can't hear it from drivers seat while focusing, but I don't have any lights on the 4wd switch so I'd think they'd be required to click first...any ideas?? It feels like the buttons don't do anything.

 

If none of the lights are lighting up, I would check over the power and ground to the TCCM. Check the Tech Article (DIY) section for wiring diagrams and pin-outs for the NV236 (4-button) transfer case.

 

First check the fuses - under the hood fuse block (i dont think their is any 4X4 related fuses here but check em all while your there) and in the cab fuse block (driver side of dash when you open the driver door) fuse 15 is a 10 amp and is labeled 4WD. than try pushing buttons and see what happens

 

worth a shot, When your trying to get the truck out of 4lo, The gear shifter is in the neutral position before you push the 2wd button right? You probly know that, But well worth the 2 seconds to write it. Hope you figure it out!

 

I got your reply immediately and then I've been staring at the diagrams almost ever since and I've decided I probably need to get with my friend who's an electrician sort of.

I also found your link about "4x4 no worky" and I see "switch failure" as a common problem...could it be as simple as the 4x4 4-button switch being faulty somehow?

The car was in an accident that caused 3 windows to break, the hood to get dented and the DS front fender and DS door to get dented. Also DS seatbelt cut and roof dented towards front. I think it was some sort of mild rollover in a ditch.