P0430 — Catalyst System Efficiency Below Threshold (Bank 2)
Drive with caution — fix soon.
What P0430 means
P0430 means the computer judged the catalytic converter on Bank 2 (the cylinder bank opposite Bank 1) to be working below its required efficiency. As with P0420, the real culprit can be an oxygen sensor, an exhaust leak, or another engine issue rather than the converter itself. This code only appears on engines with two cylinder banks, like many V6 and V8 vehicles.
Common symptoms
- Check engine light is on, usually steady
- Minor drop in fuel economy
- Failed emissions or smog test
- Occasional sulfur or rotten-egg smell
- Engine runs normally otherwise
Common causes
- Aging or contaminated catalytic converter on Bank 2
- Faulty downstream oxygen sensor (Bank 2, Sensor 2)
- Faulty upstream oxygen sensor on Bank 2
- Exhaust leak near the Bank 2 converter
- Misfire or oil/coolant contamination on that bank
- Rich or lean mixture from a separate fault
Typical repair cost
$200 – $2200
Varies by vehicle and root cause.
Frequently asked questions
Can I drive with a P0430 code?
Yes, it's generally safe for short-term driving and the car behaves normally. You'll fail emissions, so have it diagnosed within a few weeks to avoid a bigger repair.
How much does it cost to fix P0430?
Repairing an oxygen sensor or exhaust leak typically costs $200-$500, while a catalytic converter replacement on Bank 2 often runs $900-$2,200 depending on the vehicle.
Is P0430 serious?
It's moderate. The car stays drivable, but the emissions system isn't performing and ignoring a root cause like a misfire can damage the converter.
What's the difference between P0420 and P0430?
They're the same fault on different cylinder banks. P0420 is Bank 1 and P0430 is Bank 2, the side of the engine opposite cylinder number one.