4wd push button wonky? Or t-case?

[Aholter90]

New problem in my ‘96 K1500. Went to shift it into 4lo, no lights on the push-button actuator were lit. No biggie, right? Well, I put it in neutral and pressed 4lo, and I hear the case shift, then immediately shift back. Both 4hi and 4lo lights are now blinking, then after 3 seconds they stay solid on til I turn the truck off. Now that I’ve restarted the truck, the same thing is happening. It shifts onto 4lo (does the same for 4hi too), then shifts immediately back to 2wd, followed By blinking lights. I replaced the front axle engagement about 2 years ago with the upgraded electric motor version, and have had no problems shifting into either 4x4 range up to this point.

 

[Aholter90]

I should add, in Park, nothing on the 4wd switch works. Won’t light, won’t attempt to go into 4hi…any t case activity that is happening is only in Neutral.

 

[VIKING_MECHANIC]

Well these 4x4 switch panels were notorious for failing. Try replacing it with a used one from a salvage yard.

 

[Aholter90]

Ok, so quick update. I replaced both the pushbutton and encoder motor. While I had it off, I was able to get a adjustable wrench up in there and manually shift the T-case into 4hi and 4lo without issue. So I think the T-case is ok.

Now, back together, I’m still having issues. When I’m in 2wd, the truck indicates that, so that’s good. It still won’t shift into 4wd at all unless the truck is in Neutral and the brake is pressed. It won’t go into 4Hi, though I hear a whirring sound I think from the front axle actuator that I replaced, so that’s at least working when I press the button. But it won’t shift into 4hi.

4lo it will shift into, but both 4hi and 4lo lights stay lit permanently.

It will go back into 2wd, again only in neutral, and it take me pressing the 2wd button twice for the 4wd lights to turn off.

In the midst of all this button pressing, im hearing clicks from under the dash I don’t remember hearing. It’s possible I’ve never paid attention but I don’t know. So these trucks have an under dash TCCM, or is that later years? If not, I’m wondering if I have a wiring issue.

 

[Aholter90]

Potentially figured it out. I read an old post about unplugging and reinstalling the TCCM, and that appears to have worked. Will update this thread if it fails again.