Catalyst System Efficiency Below Threshold (Bank 2)
The catalytic converter monitor for bank 2 reported efficiency below the vehicle calibration threshold. This is a monitor result, not proof that the converter itself must be replaced. Misfires, mixture faults, oxygen sensor behavior and exhaust leakage can affect the result. A shop should inspect companion codes and sensor data before selecting a repair.
Can I keep driving?
A code alone cannot establish that driving is safe. With a flashing warning, shaking, overheating, unusual mechanical noise, smoke or substantial power loss, stop safely and arrange assistance. Otherwise ask a repair shop for vehicle-specific advice before driving further.
What does this code mean for your car?
The same code can need different checks depending on the model and engine. Enter your vehicle details to find relevant sources and checks.
Symptoms
- Check engine light on (often no other symptom)
- Rotten-egg smell from exhaust
- Slight drop in fuel economy
- Failed emissions test
Possible causes
- 1Worn or failed catalytic converter
- 2Faulty downstream/upstream O2 sensor
- 3Exhaust leak before the sensor
- 4Misfires or rich mixture that damaged the cat
These possibilities are not ranked by frequency and do not diagnose your vehicle.
Checks you can safely do yourself
Safe checks only: engine off and cold, car on level ground.
- Record companion misfire (P030X) or fuel-trim codes and ask the shop to diagnose them before selecting a converter repair.
- With the engine off and cool, record companion codes, observed symptoms and service history. Do not disassemble components or clear codes before a shop saves the diagnostic evidence.
When you need a shop
Stop and arrange assistance if the engine shakes or the warning flashes. Ask the shop to evaluate misfire and mixture codes, exhaust integrity and oxygen sensor data before condemning the converter.
How much does it cost?
A US repair estimate needs a diagnosis and a local shop quote.
No verified US repair estimate is available. Ask a local shop to diagnose the vehicle before quoting parts and labor.
Get 2-3 quotes
Investigate this code for my carFAQ
Can I keep driving with P0430?
A code alone cannot establish that driving is safe. With a flashing warning, shaking, overheating, unusual mechanical noise, smoke or substantial power loss, stop safely and arrange assistance. Otherwise ask a repair shop for vehicle-specific advice before driving further.
What can cause P0430?
Possibilities to investigate include Worn or failed catalytic converter; Faulty downstream/upstream O2 sensor. The code does not prove a particular part has failed; diagnose before replacing parts.
If I clear the code, is it fixed?
No. Clearing a code does not repair its cause and may erase diagnostic evidence or reset readiness monitors. It may return when the monitor runs again. An unlit warning does not prove the vehicle is fault-free.
I saw this code on a car I'm thinking of buying - now what?
Don't run, don't shrug it off. Ask the seller for a shop diagnosis before you sign, and use what it finds to negotiate.
How much does fixing P0430 cost?
We do not have a verified US repair quote for your vehicle. Diagnosis, local labor rates and the confirmed repair determine the price. Get 2-3 quotes.