Okay here it goes. The front O2 sensor does it's job by notifying the ecu that either the exhaust is too rich or too lean correct? The exhaust continues on to the cat and assuming everything goes according to plan the final product is cleaner air. If the O2 sensor however does NOT pick up the fact that the air is rich/lean then the ecu makes no adjustments and the cat works even harder and ultimitley fails. Am I on the right track? Now since I'm not getting an indication from the ecu that there is indeed a problem with the O2 sensor, would it be safe to assume that the sensor MAY be "stuck" in an open state indicating that all's well and that there is most probably a failure within the cat as well.