Ok the car has 90,000 miles, Is this code for the drivers side or passenger side cat?

I replaced the Cat on the drivers side at 80,000 miles with an aftermarket one. I know that this was not the ideal option but that said, no cat should go so quickly.

Could this be the 02 sensor. How would I best test this before I spend a bunch of cash on parts?

Any advise would be appreciated.

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With best regards

Al