DTC P0421 & P0431: Catalyst Warm-Up Efficiency Below Threshold: Notes
WARNING: This page is about a different car, the 2002 Mazda 626. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
Right front HO2S is identified as O2S11. Right rear HO2S is identified as O2S12. Left front HO2S is identified as O2S21. Left rear HO2S is identified as O2S22.