I engaged my 4wd a few days ago, and after leaving the beach, I dialed it back to 2WD mode. I noticed a few minutes later that the "service 4wd" message was on. I stopped, and turned off the vehicle, restarted and, the code was gone. A few blocks later, the 4wd engaged and, ( I noticed it turning at a light, pulling hard). The dial was still on "2wd", but, the light over the "automatic" selection was lite up.
I turned the dial back and forth, restarted, and backed up, but, the 4wd would not disengage. I then traveld 10 miles down the highway, and then the 4wd disengaged, and the light over the 2wd mode lite up.
This is my first chevy in over 20 years, and I have never had any problem with my Ford 4wd system. I am familiar with the Ford 4WD system. I called the dealer, andtold them about what happened, and they said to bring it in and they could check it out. (I know that todays mechanics do not know anything except to plug it into their computer and hope it show them the problem).
I got under the truck, and with it in neutral, 2wd mode, the front drive axles could not be turned. I asked the dealer if the truck had "Hubs" that engaged when 4WD was selected, and he said it was all electronic. So, I again asked him if the front hubs engaged "electronically". He said the trucks do not have hubs anymore, and the front drive shaft axle was connected to the front hub, and should always turn, even in 2WD mode. This would result in the front differential turning all the time. It does not sound right, and I am guessing he really did not know that he was talking about.
Should the front axles disengage when the truck is in 2WD, and free the front differential from turning?
The truck milage went down from around 16MPG average to 14MPG average after a few thousand miles, and I suspect that my front hubs are not disengaging and causing the poor milage.
FYI, the 4WD system is used often, and the truck has not shown a malfunction until this week. The truck has 10,500 miles on it.

 

it really needs to be checked...either the switch or encoder motor probably

 

So, you are saying it is normal for the front drive axles to turn when the vehicle is moving in 2WD?

I know on Jeep, Ford, and Dodge, when it is 2WD, the front axles are disengaged and the wheels are rolling free.

 

I agree with Argon as I hd the encoder motor go bad on mine. As far as the front differential it should disengage and the wheels should spin freely in 2wd.

 

you say its used a lot then id imagine its that motor...