Chevrolet Repair: 99 Silverado Z71, wheel sensors, z71

Question
If you can answer for this year Thanks!
System display shows "service 4WD" in 2WD after about 1/2hr highway driving.Has happened twice in 10 days.

Answer
Hi Gus,
Sorry this answer is so late...I signed out on vacation, but the site doesn't seem to update all the areas I am in, even though it says it will.
As for your question, I haven't had that, but some things that come to mind that may apply, are wheel sensors, and more likely, tires worn to different circumferrences, although I don't know for sure if they would send that message.
Van