[Jared Russell]

It sounds to me like one or more of your sensors has become unplugged. Under such a condition, a closed loop system like your steering control would try to move to a new position, but because the sensor is not giving readings, it never thinks that it gets there so it keeps going.

I would follow Al's suggestion, but you can also try printing out your sensor readings in your code so you can verify that you are getting sensible numbers out of them (in my experience this is generally quicker than tracing wires for a large number of sensors, especially if they are buried in your chassis).