DTC P0421, P0431:Warm-Up Catalyst System (RH) Efficiency Below Threshold; Warm-Up Catalyst System (LH) Efficiency Below Threshold: Notes

WARNING: This page is about a different car, the 2004 Mazda MPV. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: DTC P0421, P0431 Detection Condition & Possible Causes Chart

Courtesy of MAZDA MOTORS CORP.