I get an error code of P2040. How can I fix that?

NOTHING IN ALL DATA REGARDING THIS CODE

...P0420 .....maybe....? Failed converter possibly........Proper diag , not just a code , would be good to avoid wasting money.

The code is for a bad air fuel ratio sensor i have same problem in 2005 Mazda Rx8 Gt Model With 13b-Re Motor if the code comes up you will need to change the sensor about $100-$150 for the sensor if anybody else charges you more for it then there scamming you and you should look online at Rockauto.com hopefully this helps and ps. if you dont change soon you could have bigger problems down the road with the seals blowing or the engine seizing and will lose gas mileage and mpg not by alot no loss in power though