A failing catalytic converter on bank 2 that has degraded internally or been contaminated.; A faulty downstream oxygen sensor on bank 2 sending inaccurate readings to the computer.; An exhaust leak before or near the bank 2 catalytic converter, allowing outside air to skew sensor readings.; Engine misfires or rich running conditions that have overheated or damaged the converter over time.; Oil or coolant consumption entering the exhaust stream and poisoning the catalyst.; A failing upstream oxygen sensor on bank 2 that is slow to respond and causing incorrect fuel control.; Damage to the converter from road debris or physical impact.

DTC codes / P04xx · Auxiliary emission controls / P0430

P0430Catalyst System Efficiency Below Threshold (Bank 2)

Q: What does code P0430 mean?

Catalyst System Efficiency Below Threshold (Bank 2). P0430 means the powertrain control module has determined that the catalytic converter on bank 2 is not cleaning the exhaust as efficiently as it should, based on oxygen sensor readings before and after the converter. The computer compares the switching activity of the upstream and downstream oxygen sensors and flags the code when the downstream sensor mirrors the upstream sensor too closely, indicating the catalyst has lost its ability to store and release oxygen.

P0430 means the powertrain control module has determined that the catalytic converter on bank 2 is not cleaning the exhaust as efficiently as it should, based on oxygen sensor readings before and after the converter. The computer compares the switching activity of the upstream and downstream oxygen sensors and flags the code when the downstream sensor mirrors the upstream sensor too closely, indicating the catalyst has lost its ability to store and release oxygen.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaAuxiliary emission controls

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms.
A slight decrease in fuel economy as the engine management system adjusts for perceived catalyst inefficiency.
Occasional engine misfire or rough running if the root cause is unburned fuel reaching the converter.
A faint sulfur or rotten egg smell from the exhaust in some cases.
Failure of an emissions inspection due to the stored trouble code.
In rare cases, a noticeable loss of power if the converter is partially clogged.

Common causes, most likely first

A failing catalytic converter on bank 2 that has degraded internally or been contaminated.
A faulty downstream oxygen sensor on bank 2 sending inaccurate readings to the computer.
An exhaust leak before or near the bank 2 catalytic converter, allowing outside air to skew sensor readings.
Engine misfires or rich running conditions that have overheated or damaged the converter over time.
Oil or coolant consumption entering the exhaust stream and poisoning the catalyst.
A failing upstream oxygen sensor on bank 2 that is slow to respond and causing incorrect fuel control.
Damage to the converter from road debris or physical impact.

How to diagnose and fix it

Perform a visual inspection of the bank 2 exhaust system for leaks, loose clamps, or damaged components.
Use a scan tool to check live data for both upstream and downstream oxygen sensors on bank 2, looking for sluggish or stuck readings.
Check for stored misfire codes or fuel trim deviations that could indicate an engine performance issue affecting the converter.
Test the downstream oxygen sensor response with a propane enrichment test or oscilloscope to confirm it is switching as expected.
Verify the catalytic converter inlet and outlet temperatures with an infrared thermometer; a significant drop indicates a failed converter.
Repair any engine misfires, vacuum leaks, or fuel delivery issues before replacing the converter to prevent repeat failure.
Replace the bank 2 catalytic converter only after confirming the sensor and engine management systems are functioning correctly.

Bank 2 checks before you buy a converter

A downstream oxygen sensor that is lazy or contaminated can mimic a failed converter, so always compare its switching pattern to the upstream sensor before condemning the catalyst.
Exhaust leaks upstream of the downstream oxygen sensor pull in outside oxygen and make the converter appear inefficient, so inspect the entire bank 2 exhaust path carefully.
Engine misfires or a rich fuel mixture can overheat and destroy a new converter in a short time, so fix any underlying driveability faults first.
Some vehicles set P0430 due to a software calibration issue or a known sensitivity in the catalyst monitor, and a reflash may be required after confirming hardware is good.
A converter that is only marginally efficient may not set the code until after a specific drive cycle, so clearing the code and hoping it stays off is not a diagnosis.

Can I keep driving with P0430?

You can usually continue driving with P0430, but avoid heavy loads and prolonged idling until it is repaired, and be aware that the vehicle will fail an emissions test. If the check engine light begins flashing or you notice misfiring, stop driving to prevent converter damage.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.