I have a 2003 Disco 2 and I have a P0430 code showing. Im getting some mixed search results. I need to know if I need to replace the O2 sensors or the whole catalytic converter assembly? Thanks.

 

Run a bottle of Cataclean through the tank. Follow the instructions closely. That took care of mine, though I know that I have to replace the sensors anyway at some point.

To answer your question, if the catalytic converter and sensors have never been replaced, when you do it you will probably have to replace both. If yours is like my LR2 the sensors are on the catalytic converter segment of the exhaust.