Well, I may have typed too soon...
I've had a problem with the 4wd not engaging, to the point of not having it the last time I needed it, and I replaced the $12 switch, hoping that would fix the problem. Wrong! Looks like the module is bad, as the 4wd wouldn't work again today when I needed it! Now it's a $90 part, and no 4wd on a 4wd truck is no bueno!