DTC P0420:00, P0430:00 [MZI-3.7]: Notes

WARNING: This page is about a different car, the 2009 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

DETECTION CONDITION & POSSIBLE CAUSE

DTC P0420:00 DTC P0430:00	P0420:00: Catalyst system efficiency below threshold (RH) P0430:00: Catalyst system efficiency below threshold (LH)
DETECTION CONDITION	P0420:00 indicates catalyst system efficiency (RH) is below the acceptable threshold P0430:00 indicates catalyst system efficiency (LH) is below the acceptable threshold
POSSIBLE CAUSE	Use of leaded fuel Oil contamination Cylinder misfiring Retarded ignition timing Fuel pressure too high Damaged exhaust system pipe Damaged exhaust manifold. Damaged muffler/tailpipe component Damaged catalytic converter A/F sensor wiring harness malfunction Downstream HO2S wires incorrectly connected. Damaged A/F sensor Damaged HO2S Malfunctioning CHT sensor. Leaking fuel injector PCM malfunction NOTE: Internal deterioration of a catalytic converter is usually caused by abnormal engine operation front of the catalyst Events that can produce higher than normal temperatures in the catalyst are particularly suspect, such as misfiring. Incorrect A/F sensor/HO2S signal input (e.g., rich/lean signal when engine is operating under rich/lean conditions) can cause an abnormal temperature increase in the catalyst CHT sensor DTCs can indicate that the thermostat is not operating correctly or that the engine coolant level is not filled to specification, producing above normal operating temperatures

DTC P0420:00
DTC P0430:00

P0420:00: Catalyst system efficiency below threshold (RH)
P0430:00: Catalyst system efficiency below threshold (LH)

DETECTION CONDITION

P0420:00 indicates catalyst system efficiency (RH) is below the acceptable threshold
P0430:00 indicates catalyst system efficiency (LH) is below the acceptable threshold

POSSIBLE CAUSE

Use of leaded fuel
Oil contamination
Cylinder misfiring
Retarded ignition timing
Fuel pressure too high
Damaged exhaust system pipe
Damaged exhaust manifold.
Damaged muffler/tailpipe component
Damaged catalytic converter
A/F sensor wiring harness malfunction
Downstream HO2S wires incorrectly connected.
Damaged A/F sensor
Damaged HO2S
Malfunctioning CHT sensor.
Leaking fuel injector
PCM malfunction
NOTE:
- Internal deterioration of a catalytic converter is usually caused by abnormal engine operation front of the catalyst Events that can produce higher than normal temperatures in the catalyst are particularly suspect, such as misfiring. Incorrect A/F sensor/HO2S signal input (e.g., rich/lean signal when engine is operating under rich/lean conditions) can cause an abnormal temperature increase in the catalyst CHT sensor DTCs can indicate that the thermostat is not operating correctly or that the engine coolant level is not filled to specification, producing above normal operating temperatures