2002 Chevy Impala Service Traction System Light comes on with ABS light; What's the problem?

My Service Traction System light comes on sometimes and I hear what sounds like the car adjusting something. It does not come on all of the time but the ABS light is on all of the time. I had the brakes serviced about a month ago so I have new brakes. What is causing this and how much should I estimate the cost to repair the problem?