Replace cat converter? Worth it?

Hello, has there been a diagnosis that says your catalytic converter has failed? There is a sensor before the catalytic converter and a sensor after it that measure exhaust gases and oxygen in the exhaust flow. Each sensor should show a different reading, indicating that exhaust gases are cleaner after flowing through the catalytic converter. There is no change in the reading then it indicates that the catalytic converter is not doing its job. As a result, not only are you polluting the atmosphere by not properly processing the output of your engine, but you can also cause poor engine efficiency that can result in poor engine performance. The information from those sensors goes back to the engine's processor -- which then looks at the information and adjusts fuel, spark and air mixture ratios desired for the engine. These adjustments, when based off of erroneous engine processor information, can cause performance issues and damage to engine components. So yes, when you have a failed catalytic converter - replacement is necessary on multiple levels.