$200–$2,400
DIY from $35
Moderate
If you do it yourself
Within a few weeks
Before bigger damage
Common symptoms
- Steady check engine light
- Typically no noticeable change in drivability
- Fails emissions testing
- Possible faint sulfur smell from the exhaust
Common causes, ranked by likelihood
Based on typical diagnoses for P0430. Work from the most likely cause down before replacing expensive parts.
How to diagnose it
- Identify Bank 2 for your engine (the side that does not contain cylinder 1) so you work on the correct converter and sensors.
- Clear any misfire or lean/rich codes first — they can cause P0430.
- Inspect Bank 2 exhaust for leaks ahead of the rear oxygen sensor.
- Compare upstream and downstream O2 sensor data on Bank 2 to judge converter health.
- Check the Bank 2 downstream O2 sensor and wiring.
DIY vs shop cost
$200–$2,400
Parts + labour at an independent shop.
Make-specific notes
P0430 frequently appears alongside or instead of P0420 on V6 Toyota and Lexus models as the original cats age.
Common on higher-mileage V6 Nissans; confirm the rear O2 sensor before replacing the converter.
P0430 questions, answered
What's the difference between P0420 and P0430?
They're the same fault on different sides of the engine. P0420 is Bank 1, P0430 is Bank 2. Diagnosis and repair are identical — just on the opposite cylinder bank.
Can I drive with P0430?
Yes, usually for the short term. It rarely affects how the car drives, but you'll fail emissions and should diagnose it within a few weeks.
How much does P0430 cost to fix?
A downstream O2 sensor is roughly $150–$300 at a shop; a catalytic converter replacement ranges from about $400 aftermarket to $2,000+ for an OEM cat.