How can I fix the P0420 trouble code on my Ford Taurus?

The Ford Taurus commonly experiences the P0420 trouble code, which is often due to a faulty oxygen sensor, although there could be other reasons behind it as well. The code signifies that the catalytic system's efficiency is below the required level. Your Taurus is equipped with two oxygen sensors - one located before and the other after the catalytic converter. One of the key roles of these oxygen sensors is to monitor the emissions levels entering and exiting the converter. If the readings from both sensors are similar, the car will illuminate the service engine soon light with the P0420 code, usually triggered by the sensor before the converter. Drivers typically won't notice any performance issues related to P0420, as the first indication of a problem is usually the illumination of the service engine soon light.