roastbeefalo

Hey all- I have a 96 Subaru Legacy Outback Wagon 2.5 L with 185k miles. I just got some CEL codes that read 0420 which is "Catalyst System Efficiency Below Threshold." I was wondering if this is definitely the Catalytic Converter or if it could possibly be the oxygen sensor going out on me. I just repaired 2 burnt exhaust valves at 180k. They warned me that too much driving on the three cylinders before it was repaired could burn out the converter, or really muck up the oxygen sensor. I was wondering which of the two is likely and/or possible. Thanks. ps - I believe the car is ok to drive like this, it just will not pass emmissions. Is that the wrong line of thinking, and if so how long do I have before I need to repair it?

I have a 96 2.5L Legacy Outback Wagon with 185k miles. No head gaskets blew. I did burn two exhaust valves at 180k, at which point the head gaskets were obviously replaced and new timing belt and water pump for $1700. Other than that, no problems.