Toyota Repair: Location of Bank1 Sen1 O2 Sensor

Question
My 2003 Toyota Camry XLE, 2.4 engine (2AZ-FE) is showing a code of P0031. I'm trying to find the exact location of that O2 sensor so I can fix it myself. I also see that Auto Zone has 2 different parts numbers for this sensor: 1 with CA emissions & 1 without. How do I know which to buy? I'll need some detailed instructions on how to replace the sensor. Will I need a special tool?

Answer
Hello, this engine has four sensors, two at the top of the exhaust manifold before the catalytic converter and two at the bottom, one cat converter for each bank and two sensors for each, the #1 sensors are at the top, the sensor #1 is at the right side if the manifold standing in front. California emission certified engines have air/fuel ratio sensors instead of O2 sensors, to find out which type you have check the label on the inside of the hood, if it says certified for federal and California emission standards it is considered CA certified, if it only says certified for federal emission standards it has O2 sensors, you will need an O2 sensor socket to remove it, the autoparts stores should have this also.
If your exhaust configuration looks different than what I described let me know or if possible attach a photo, Toyota made some changes later and went back to the single converter configuration which has one sensor before the cat, in either case the #1 sensors are always in front of the cat converter.