My wife’s cousin check engine light came on along with Stability Control and Cruise Control lights. He mechanic stated P0420 code was for catalytic converter. Repair will be very expensive. This Subaru has first converter welded to exhaust manifold (parts price from Auto Store was $1700 and second converter with pipe is no longer available). This car is running fine, no drop in miles per galling, no stalling, no rotten egg smell, no exhaust leaks around exhaust manifold and no rattle from first or second converter. Connected BlueDriver and it appears downstream O2 sensor has fluctuating readings in LiveData. Will replacing both O2 sensors clean a P0420 code? What do you think?
He mechanic stated P0420 code was for catalytic converter.
That isn't necessarily the case. Did the mechanic diagnose and rule out the several other possible causes for that code? Is there an underlying engine condition such as oil burning that might have poisoned the catalyst?
Will replacing both O2 sensors clean a P0420 code?
If they test bad that might help. (There are many videos on youtube showing how to test O2 sensors.) It is the downstream sensor that is responsible for monitoring catalyst operation.
If replacement is needed only OEM sensors should be used.
Engine is not burning any oil and runs very smooth!