Toyota Repair: Air Fuel Ratio Sensor, air fuel ratio, toyota avalon

Question
QUESTION: I have a 2000 toyota avalon which has recently had issues with the check engine light coming on. We had the car checked by a mechanic and they told us it was the O2 sensor which turned the light off for two weeks and then it came on again. We once again had the car checked and found out it should have been the Air Fuel Ratio Sensor, which looks identical to an O2 sensor. Where is this located on the car? Can the part be purchased from someone other than toyota?

ANSWER: Each cylinder bank has an a/f ratio sensor, I need to know the diagnostic trouble code in order to help.

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QUESTION: They did not give us a code they just said that the sensor was not responding. We replaced the one near the Catalytic Converter.

Answer
Air/fuel ratio sensors are located one in each exhaust manifold, the O2 sensor is located behind the catalityc converter, without knowing the trouble code I can't tell you which one needs to be replaced, can you go to an autozone store they will scan it for free.