Catalytic, upstream o2 sensor AF sensor P0420 & P0150 codes 3rz FE

I have a 2.7 manual 3rz fe and live in California . No modifications to 50 state emmisions system done..I got the 0420 code which is catalytic converter efficiency below threshold bank 1. Took it in for a diagnostic and was told that both cats are wore out (yet no restriction or rattle in them and great mileage/power) and o2 sensors should be replaced (I have 214k miles and never have replaced them yet). I question if the cats are really bad - he just said they are taking longer to heat up and he kept mentioning my mileage and well you know things need replacing (sorry buddy, not biting in), but know I probably should replace my upstream o2 sensor as there is also a pending P0150 code which is o2 sensor bank 2 , sensor 1.. Do I even have a bank 2 sensor 1 o2 sensor (which would be upstream drivers)? There is what looks like a sensor just in front of the cat that is really easy to get to (please be the one) or is that the af sensor and one behind towards the exhaust but the cat/exhaust is on the passenger side. Bank 2 is supposed to mean drivers side.?? Can't find a good diagram of this or anything online. There was a lot of mention of a very hard to reach o2 sensor but that may be on 6 cyl. Where is the a/f sensor - I don't want to replace the a/f sensor thinking its the upstream o2 sensor..confused..

 

4 cyl only has 1 bank. The sensor closest to the engine is the only one that measures andcontrols the mix. The post cat keeps an eye on cat efficiency. If the cat goesbad it doesn't heat as high Or if the sensor is aging out you getthe same results. The generic code Is p0420, it shouldn't affect mpg or power at all, just a cel.

Many vehicles can bypass the 2nd entirely. My mustang has no cats, $5 and 20 minutes and the computer thinks the cats are working fine.

 

Thanks, I will definitely be trying a new upstream o2 sensor.