impossible np243 problem

[camccardell]

Hey guys, been working on a buddy's 98 tahoe. Bringing it back from the dead as it was behind his barn for the last 5 years.
Anyway, I noticed that the damn thing is stuck in 4wd. I took off the driveshaft and the front diff yoke spins freely.
Buddy says he replaced the 4wd fuse, and the lights on the switch came on, but still nothing. Press any button, and nothing happens.
He had it towed to a shop after we replaced all the brake lines and they charged him 2 hours to diag the problem, said it was the t-case shift motor.
Well, we replaced it and also the switch on the dash, and are still right where we started.

I was thinking tccm, but there is no service 4wd light on the dash and no check engine light or codes either.

You must be registered for see images attach

As you can see, the neutral light is on, the damn 4 low light is on and getting a slight glow from the 2hi light.
I've tried putting the truck in neutral and switching it back out into anything. No dice.

Really beating my head into the wall on this one. Ideas?

 

[rosco]

Could be the TCCM, but have you verified it's a 243 tcase? There is a tag on the rear that as the model. Only reason I ask is the switch in the pic is for a 246 tcase. That's what I have in my 98 'burb. Now it needs to be stated that I'm not very educated on the differences between the 2, but I don't think the switches were interchangeable. Hopefully someone will chime in that knows more than me.

 

[1999bigburb]

I just copied this from a past post I mentioned this in....try this I am certain it will work. I have fixed this issue with 3 of these trucks with this very same issue using this method.

I dont know if this will help anyone or has been mentioned before regarding the 4 low not engaging issue with the electronic transfer case but give this a try...
Start the engine and when running place the trans in neutral as though you are going to engage 4 low. At this point shut the vehicle off while leaving the trans in neutral, of course hold your brakes if needed. After a few seconds start the engine again and IMMEDIATELY press your 4 low button. It will engage as it should providing all the parts are in working order. Do the exact same to disengage. I went through everything on my truck trying to get 4 low to engage until I stumbled across this, been working flawlessly since so long as I follow the procedure above. Still won't engage otherwise.
All that I think is happening is that I am sending the command to engage the 4low before the computer/electronics figures out there is some issue somewhere, by the time it does its to late...its engaged. I have helped a buddy with this same concern and he was super happy...he had no 4 low for 4 years lol. I can take a video if someone needs me to show them but really it's super simple.