Catalytic converters are in the exhaust system so replacing them is a job similar to replacing a muffler. Difference is that the converters are bolted in and have gaskets that must be replaced at the same time.
The new catalytic converter and gasket for my 2005 outback wagon was $830 installed at an independent Subaru specialist. Are you sure that yours is not covered under warranty (80,000 miles, I think)
A Catalytic Converter reduces unburned exhaust gasses.
Two.
there are two. both along the exhaust under the car. one just before the catalytic converter and one just after.
Oxygen sensors on all cars built in the last 20 years or so are located in the exhaust system. Subaru has them before and after the front catalytic converter.
Remove both converters, install the new ones. Don't forget the "donut" gaskets.
Yes.
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There is only one catalytic converter in the exhaust system.
Federal government says 8 years or 80,000 miles, whichever comes first for all vehicles built since 1995.
Subaru Outback "woodriff key" is good for the life of the vehicle.