Sorry if I should already know this, but I'm not finding my exact symptoms via search. I'm new to 4wd. Just bought my 2000 Sierra a week ago. It seems sometimes it wants to go into the 4wd mode that I say, and sometimes it doesn't do anything, sometimes the lights go out, at one point yesterday I got the "Service 4WD" light, then last night I hit 4H and it went to 4wd auto. Then when I got home it wouldn't change at all. Does this sound like the infamous 4WD switch gone bad issue?
Thanks in advance.

 

Nevermind. Opened the switch and the solder was broken. 15min fixed it (10min for soldering iron to heat up).