Mr.GGMMCC

2014 GMC was stuck in 4WD (High) with message "Service 4WD" As with several other comments....not 100% what caused it but....transfer case was stuck in 4WD (high) and the light on the selector dial would only come on when the selector dial was on "AUTO". But it was not in "Auto" it was in 4WD (High). To test if it was the electrical or mechanical, with the truck off, I first removed the fuse #6 (FWD) in fuse panel in the engine comp (without DC power it shifts to 2wd) I did a short test drive to see if the 4WD had disengaged and it had. When I put the fuse back in, it reengaged the FWD and the actuator was still stuck, turning the dial on the dash still did nothing. To resolve or get it to reset. I left the truck engine running and again removed the fuse. With the engine still running, I turned the dial to 4WD (hi) and put the fuse back in. This time is cycled and the light on the dial was now on when it was in 4WD hi, to match what the transfer case was positioned in. Now when I rotated the dial it shifted to Auto, 2WD, etc. with the light blinking during shift just like it is supposed to. It has been working fine since then. I sort of viewed it as forcing it to reboot. I may have been able to get this same result with the ignition switch simply turned (without the engine running), but that isn't how I did it.