I have a 06 GMC and the display shows "service 4WD" when you start it. The manaul says to kill the truck and start it back up and if it stays off not to worry about it but if it comes back on see the dealer. Well it comes back on every time. Does anyone know what needs to be done so I don't have to take it to the dealer?

 

I did a quick search and found this thread.
https://www.performancetrucks.net/fo...ht=service+4wd

Good luck getting it fixed.

 

Is it under warranty? Id take it to the dealer. Theres quite a few things it could be.

 

I would say its prolly the switch? Have you done anything to the bcm in the truck? High 6 or 4 conversion? If you bend a pin in the grey connector you can get that light. Also check the grounds on the cab mount on the drivers side. That will do it too.

 

Its most likely the encoder motor sensor. Its a common problem with the autotrac transfer case. Or it could just need a reprogram. Those are the most common problems with those trucks.

 

The only thing I have to read codes is my superchips programmer that came with the radix and it doesn't show anything.

Truck does not have warrenty.

What is the bcm and 6 or 4 conversion?

The truck is stock with the radix and I have the torsion bars cranked. I found out today you have to put over 30miles on the truck before the light comes on. Yesterday I was on the road all day and every time I'd make a stop and get back on the road the light would come on. Today running around town it didn't come on.

 

Were you driving in rain or snow yesterday when the light was on?

 

No. Just normal highway driving. After I posted yesterday I took off shortly after and the light came immediately but then today it stayed off. I haven't checked anything yet but thanks for the info.

 

I pulled the switch and everything looked fine, when I put it back on the dash light for the 4hi and 4lo buttons went out. The switch works fine but the service 4WD light wasn't on when I was trying it. Everything I read about the encoder motor sensor says you will have a code "C0327" and my programmer isn't picking up any. Would that mean it's not the switch or the encoder?