My Blazer did this when I first bought it back in 2014. It was the first thing that I repaired on it. I just removed the front sensors, cleaned up the rust, and installed them back in using an anti-rust gun grease made by Birchwood-Casey named RIG. Never had a problem since, and the cost was zero.

If you remove the sensors (careful they are plastic and have an o-ring), make sure to plug the holes with something clean, fairly tight, and removable. Be careful to not push anything into the hub when installing the plug, and make sure anything that goes down into the hole during your repair comes back out with the plug when you are done. I used packed paper towel in the hole, did my rust removal, and then used a dental pick to drag the plug back out with the rust and other junk that fell down on top of the plug.