What causes P0430 on a Honda Civic?

Common causes of P0430 on Honda Civic: Deteriorated catalytic converter on Bank 2 (rear catalyst on V6); Downstream O2 sensor failure giving false catalyst readings; Exhaust leak between catalyst and downstream O2 sensor; Engine misfire or rich running condition damaging the catalyst over time.

P0430

P0430 Honda Civic

Q: How much does it cost to fix P0430 on a Honda Civic?

Fixes for P0430 on Honda Civic include: Replace catalytic converter (OE Honda or CARB-compliant aftermarket), Replace downstream O2 sensor before condemning catalyst — retest, Repair exhaust leaks near the catalyst, Address root cause (misfires, rich condition) before replacing converter, On V6 models, verify Bank 2 is the correct bank before replacement.

Catalyst System Efficiency Below Threshold (Bank 2) · Powertrain Code · Medium

What is P0430?

The catalytic converter on bank 2 is not operating efficiently. Same as P0420 but for the opposite bank.

When the Honda Civic triggers code P0430 (catalyst system efficiency below threshold (bank 2)), it typically points to an issue in the powertrain system. Below you'll find the most common causes, symptoms, and repair options specific to the Honda Civic.

Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your Honda Civic.

Common Causes on Honda Civic

Deteriorated catalytic converter on Bank 2 (rear catalyst on V6)
Downstream O2 sensor failure giving false catalyst readings
Exhaust leak between catalyst and downstream O2 sensor
Engine misfire or rich running condition damaging the catalyst over time

Symptoms

Check Engine Light on
Failed emissions test
Sulfur/rotten egg smell from exhaust
Slight reduction in fuel economy
Possible rattling from inside the catalytic converter

Recommended Fixes

Replace catalytic converter (OE Honda or CARB-compliant aftermarket)

Replace downstream O2 sensor before condemning catalyst — retest

Repair exhaust leaks near the catalyst

Address root cause (misfires, rich condition) before replacing converter

On V6 models, verify Bank 2 is the correct bank before replacement

Notes for Honda Civic

Catalytic converter replacement on Honda V6 models is expensive — always confirm with downstream O2 sensor data and verify no underlying misfire is killing the new cat.

P0430 Honda Civic

What is P0430?

Common Causes on Honda Civic

Symptoms

Notes for Honda Civic

Check Honda Civic Specs