ABS Switch to Manual w/o warning

My abs light and track off lights come on when they feel like it. I've had the left front sensor replaced and that works for about 6,000 miles. Now my car has decided to switch from Anti-Lock to Manual at a whim. This generally happen as I am stopping. P.S. I live in Michigan so I'm a little nervous with the snow and all. Also the low traction light comes on when I am at a complete stop. I have a 1999 Grand Am SE.

Same car, same problem. Once every week or two the ABS light and Trac light come on. Turn car off, start it back up, everything's fine.

The ABS can be affected by the cheap piston in the calipers. The Computer once in a while detects a malfunction and automaticaly turns the abs off.
Usually caused by the piston getting stuck or not returning properly. Ive talked to at least 40 GA owners and thats what they discovered too. Check into it some more if you have warranty , it wont be covered if your pads are worn out though.