The O2 sensor screws into the exhaust system and the wire goes through a floor pan grommet to the connector under the front passenger carpet insert. You need a special offset socket tool to remove the O2 sensor ... available at Pep Boys or other auto stores for around $12. I'd call the dealer and question why they didn't analyze the cause of the rich fuel mixture instead of merely replacing some parts and leaving you with a poorly tuned engine.

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Fred Hoelzle