My 2004 silverado 3/4 ton has autotrac. A while back it would "put itself" in 4wd low. I could stop and push it to 2wd Hi, or auto, and it would be back to normal. That went on for a while, and I replaced the dash button, and it went away completely. A while after that, the message came back on, and the dash buttons quit working all together. Stealership said that it was the actuator in the transfer case. So that was replaced yesterday after all of the winter ice crap. . . . Still no action on the dash buttons for the transfer case.
I checked the power wires at the t-case, and I have 1.8v. This is while using the ground on the harness or grounding off of the frame.
I checked the 4wd fuse on the door panel and it's also good with 12v.

What else is there to check or reset? New dash button, and new t-case actuator.

 

Actuator fixed mine. Similar issuses.

 

A neighbor said there was Gm bulliten on this, ( master machinic for them) made mention that the front diff fluid needed to be changed out to a synthetic....

I had that message come on but it would go away- I changed those fluids and haven't seen the message since-

Good luck hope it's a easy fix for ya this time around

 

fluids were all changed out when the truck was recently recovered . . . so they're all good.

Found out that there's some kind of controller that might need to be read at the stealer ship

 

You really need access to a tech 2 or equivalent to get into the TCCM and see what codes it has stored and then see if you can actuate the front axle lock and shift the case and look at what the data is saying when buttons are pushed etc.

 

ok I'm over a year and not having this fixed yet.


So there's a new Dash switch, and a new tcase actuator. The dash buttons never light up, and the tcase is in neutral.

Need a little help here. What am i missing now?

 

This is exactly why I went to the AWD NP149 case. For you I'd look at a 241 and have a manual case. They're easier to fit on a 4l80. Autotrac sucks.

 

wishing that mine was a manual . . ..

I found some testing procedures, I'll try them out tomorrow

transmission/transfer case issues

 

Did you Read the post above yours?

Did you get access to the codes or see if the actuator could be controlled with a scan tool.

Likely you have a broken wire or a loose connection if you have replaced the switch and the actuator with no success.

A friend of mine had a loose connection at the fuse box under the hood.

Verify all the grounds are good as well.

 

Just chased mine in my 3/4 Burb. Ended up being a ground on the front diff. There's so many sensors and wires on this system just go one by one through fuses, grounds, and sensors until you find the issue. It's a bitch but cheaper and easier than a t-case swap...