I'm having a problem with my 2003 GMC envoy. The car appeared to be slipping when driving in the snow, so I went to change it into 4WD. Then instead of the light blinking on 4WD and then going solid, it just kept blinking and went out eventually. The same thing happened when I tried to switch the knob back to 2WD. I also noticed that by the selector knob there was a little red "N" light that was on. There are no other warning lights on.
