Fault code P0138

I have a 2006 4x2 Double Cap. I got a P0138 which points to Bank 1, Sensor 2 which is the driver side post catalytic convertor sensor. I replaced with an OEM sensor. I also cleaned the MAF sensor. Cleared the fault code and a day later the fault code came back. What else can produce the same code? I look around the exhaust to check for leak but could not find anything that will jump out at me. Any help? Thanks,

 

Bank 1 sensor 1 could be on its way out causing irregular performance on the one you just replaced, sensors work together, that’s why it’s usually recommended to replace all of them.

 

Agree with this. At the bare minimum do Bank 1 sensor 1. If possible do the other 2.

 

Don't you mean Bank 1 and Bank 2 sensor 1s at a minimum?

 

Swap sensors from on side to the other and see if the code follows.

 

I chased the cat inefficiency code for a while and finally solved it with the anti-foulers

https://www.tundras.com/threads/bad-cat-w-02-sensor-obd-data.95762/#post-2489829

Reading elsewhere said the software on these Tundras is way too sensitive. One post said that once cat efficiency drops from 100% to 96% the cel will light and throw a code preventing you from passing emissions. I'm all for clear air but I'm not gonna spend $1,400 on a new cat just to gain 4%.