2005 Z71 4WD not working

[KJCA3]

I have a 2005 GMC Z71 SLE with the 5.3 flexfuel engine, it has 92000 miles on it.

The Service 4WD message came on and the light for the push button 4WD either does not come on at all or the red neutral light is lit. Occasionally it will start out normally when i start my truck with the yellow light lit up on 2wd but most of the time the problem is as stated above.

I have never been in an accident in the truck or abused the truck in the mud so i do not think anything is mechanically wrong.

Thanks for any help!
KJCA3

[lefty1120]

Can't help solve your problem..just want to share my experience. I have the same vehicle as yours (only 48,000 miles) and don't get to use the 4wd very much here in the south. On a recent 300 mile road trip (back in Sep 08) the "Service 4WD" message came on at a stop light. Once I got to my destination, I cycled the 4wd thru the ranges in a field. Since then it has not come back.........and I hope it don't. I occasionally now run it thru the ranges just to exercise the system.

Once you do figure out what is wrong..please post it for us all. Good luck.

Lefty

[Citi]

I have a 2004 GMC Sierra with the 5.3 that had the same problem a week ago. I was told by 2 mechanics that it was either the switch on the dash, module on the encoder, or the encoder itself. After putting it on the computer and testing all 3 it turned out to be the encoder. They changed it and it has been great ever since. That was about 300 miles ago. One mechanic also told me that if they don't get used for a while, the switch will stick so cycling it through the options every once in awhile is a good idea, just be careful putting it in 4 low in case it stays there. Make sure you are close to your mechanic if you do.

[lefty1120]

How much was the encoder? Do you have a part number? How easy was it to change out?

Thanks for the tip. May come in handy in the future.

Lefty

[Citi]

I do not know how much it cost. I bought the truck from a dealership with 45,000 miles on it and the warning came on just as I got home with the truck. I called my mechanic to see what I was dealing with. I started to tell him what I bought and before I could finish he said "and the Check 4 wheel drive" warning came on didn't it. He said this is common and he told me the three things that it could be. I called the dealership and the maintenance manager told me the exact same three things. They had me bring it back and they would take care of it for me. It ended up being the encoder. The one thing I do know is of the three things, the encoder was the most expensive. So I am not sure what it costs or how hard it was to swap out but once it was diagnosed, it didn't take too long to fix it.