Is there a mechanic in the house?

My 2000 Plymouth Neon keeps coming up with code P 0551. I found that this is the power steering sensor. My issue is that it only happens at highway speeds (over 55). The light then stays on for a week or so. I have not had a chance to replace the sensor yet. I wondered if my car has a few loose plugs (pun intended) and it is the O2 sensor or something else that would react to high speed. Any suggestions would be appreciated!