Hey all, I have a 2012 Suburban 1500 LT. I'm getting a service 4WD message since this spring when I switch to 4WD Auto from 2H and it would not shift into 4wd at all.. I just left it alone during the summer, but as we're moving into the winter months, I need to get this figured out. My first step was to replace the actuator on the front differential. It's an easy swap and I figured that was the issue. After the swapout, when I move the switch to auto, it take a minute or so, then gives the error, but if I put it into 4H, it will switch into 4WD. It makes a pretty loud sound when driving down the road in 4WD. I'm figuring that it's not electrical at this point because it IS switching. I plan on servicing the transfer case as it's overdue for a fluid change. What else do I need to look at?

 

That light came on a few months ago. At the same moment I smelled something burning under the dash. I went to the local pick your part and got a 4WD control module from a wreck. I found out later that I had a ground wire issue and that's what fried the 4WD module. Nevertheless, it wasn't a difficult job. On my burb it was a little tricky to get to but, I learned the trick on the wreck so, the replacement on my burb was easy.

Probably best to not start throwing money at it though. Based on the burning solder smell I had a strong idea that my problem was the module. But for that it would have been harder to diagnose. And, I had Chevrolet look at it and they said it was the servo on the transfer case thingamabob. I didn't trust their diagnosis since they missed the grounding issue that a local shop found and fixed in 20 minutes. So, I went with what I thought and fixed it.