O2 Sensor Bank 1 Sensor 1 on 2004 Toyota Avalon

My check engine light came on recently and the code indicates Bank 1 sensor 1 is the problem. It is my understanding that there are 3 or 4 Oxygen sensors on 2004 Avalon, I can see one right on the exhaust manifold another is around the firewall and a third I saw after the catalytic converter. Can you tell me the location of bank 1 sensor 1.

2 answers
may not be the o2 sensor. just because there is a code does not condemn the sensor. did you have the code pulled or get a full diag?? it will be an expensive guess as these are fuel/air ratio sensors that are pricy. bank 1 sensor is the one by the firewall.

Roy
bank 1 sensor 1 is the first sensor off the manifold