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Subaru 2005 Catalytic Converter

I just took my car to a mechanic and he said that i had mis-fires in two of my cylinders and that he was also getting an error indicating that i have a bad catalytic converter. Would the mis-firing be the cause of the second error message? Should i have the spark plugs/air filter replaced before replacing the entire converter?

I would fix the misfire condition first and then see if the catalyst code remained.
Can you please provide more info about your car? What model, miles, engine size, etc.

Also, please post the error codes you are seeing.

One of the killers of a catalytic converter is prolonged engine misfires. These misfires can break up the cataylist substrate requiring the catalytic converter to be replaced.

The catalytic converter in your vehicle is warranted for 8 years/80,000 miles by the auto manufacturer. Unfortunatly, when the catalyst is found to be destroyed due to engine misfires, that warranty is null and void.


Its a 2005 Subaru Legacy with 48000 miles, boxer engine. The error messages are P0420, P0303, P0301. The check engine light would come on for a few days and then off for a few. This process has occured for about a week so i finally took it in. The error messages that the mechanic reported were P0420, P0303, P0301. I am having him change the spark plugs and i am going to see what happens. He said to replace the converter with labor would be around 1000$…is that reasonable?

You need to visit the dealer and forgot your mechanic and their estimate.

Your powertrain (if issue lies there) is still under warranty 5yrs/60k and converter if the problem is covered 8yrs/80k parts & labor under federal emissions warranty.