Detection Condition

WARNING: This page is about a different car, the 2003 Mazda Tribute. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0420 indicates Bank 1 catalyst system efficiency is below acceptable threshold.
DTC P0430 indicates Bank 2 catalyst system efficiency is below acceptable threshold.

NOTE: Interior deterioration of catalytic converter is usually caused by abnormal engine operation. Events that produce higher than normal temperatures in the catalyst are particularly suspect (misfires).

Incorrect HO2S signal input may cause abnormal temperature increase in catalyst. Engine Coolant Temperature/Cylinder Head Temperature (ECT/CHT) sensor DTCs may indicate an incorrectly operating thermostat or coolant level is not to proper level, producing higher than normal operating temperatures.