There are two emission systems on this year Camry. The PZEV model has one air fuel ratio sensor and two heated oxygen sensors. The non PZEV has one air fuel ratio sensor and one heated oxygen sensor.
The air fuel ratio sensor is a newer style sensor which operates in place of an oxygen sensor. The AF sensor provides a more accurate measurement and correction of the fuel mixture as the engine runs.
I see no reason to replace the AF or oxygen sensors as a maintenance procedure. The Toyota sensors can be rather pricey and aftermarket sensors can (at times) cause more harm than good. In addition to the expense, the complex on board diagnostic system monitors the performance of these sensors closely and will turn on the check engine light as soon as one of the sensors begins to fail.
If you have concerns whether or not your engine is running as efficiently as possible you could have the long term and short term fuel trims checked with a scantool. Anything below 10% correction is considered a well running engine. A positive long term fuel trim over 10% may indicate a dirty mass air flow sensor. This is a more likely cause of poor fuel mileage and or performance. The MAF sensor can be cleaned with brake or electrical contact cleaner to restore its accuracy.
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