I have a 2001 Millenia 2.5L with 63000 miles on it. I keep getting an intermitent CEL went to Autozone and the code is a P0431. The print out they gave me says this: the pcm has determined that the warm up catalyst efficiency for bank 2 is below threshold for the current engine operating conditions. (bank 1 indentifies the location of cylinder#1, while bank 2 indentifies the cylinders on opposite bank). I was told this was an o2 sensor which one is it the one closest to the firewall or the radiator or is it even an o2 sensor. Any help would be appreciated.[/size][/size]

 

a similar problem is discussed further down:

https://www.mazdaforum.com/m_18915/tm.htm

erase the code, and it will probably stay off for a while. if it keeps coming back, you may have a cat problem, but i think the car is covered under emissions warranty for the cat. on the earlier cars, this code was thrown because of overly sensitive post cat o2 sensor. bank 2 is closest to the radiator.

 

I"mhaving the same problem have to replace the cat converter code P0431 BANK2 below threshold.dealer price 700.00 what web site has a cheaper price?

 

probably every mazda dealer that has a web site