2005 Chevrolet Venture Getting Moaning Sound Front End Apply Brakes Sometimes

I am getting a moaning sound from front end when I apply brakes and sometimes it feels as if the abs is being activated with the switching from one wheel to the other. Also, periodically, the abs light comes on. When the light is on I have never had the moaning or the switching. I have had it to Mieneke two times and they can find nothing wrong. But, it will not act up when it is there nor will the abs light come on so they cannot put it on the computer.