P0430: Catalyst System Efficiency Below Threshold (Bank 2)
On a V6 or V8, the catalytic converter on bank 2 is not cleaning the exhaust as well as required.
What P0430 means
P0430 is the bank 2 version of P0420. RepairPal explains it means the bank 2 converter emissions reducing efficiency has dropped below the minimum allowed, as tracked by the oxygen sensor near the converter outlet. V6 and V8 engines often have one converter per bank, sometimes built into the exhaust manifold. The computer compares upstream and downstream sensor activity on that side, and when the downstream sensor starts copying the upstream one, it decides the converter can no longer store enough oxygen. RepairPal lists a defective converter and internal engine damage such as high oil consumption or a leaking head gasket as the main causes, and warns that both sensors and converters get replaced when the real problem is elsewhere. Shops check for misfires on bank 2, look for oil or coolant burning, test the oxygen sensors and inspect for exhaust leaks. If the converter is truly bad, replacing it without fixing the cause can mean another P0430 a few months later.
Common symptoms
- Check engine light on
- Failed emissions test
- Usually no driveability change
- Lack of power if the converter is clogged
- Sulfur smell in some cases
Most common causes
- Worn out bank 2 catalytic converter
- Faulty bank 2 oxygen sensor
- Misfire on bank 2 that overheated the converter
- Internal engine damage burning oil or coolant
- Exhaust leak near the downstream sensor
What to check yourself first
Check for misfire codes on bank 2 cylinders and fix those first. Watch for blue smoke or oil use, which can poison the converter. Check whether your car is still within the 8 year or 80,000 mile federal emissions warranty, which covers converter defects.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace catalytic converter | $2,280-$2,480 | If testing confirms the bank 2 converter is worn out. |
| Replace oxygen sensor | $440-$523 | RepairPal warns sensors are often replaced when the converter is the real problem, and vice versa. |
| Check engine light diagnosis at a shop | $125-$183 | Finds the root cause, such as oil burning or a head gasket leak. |
| Replace ignition coil | $238-$320 | If a bank 2 misfire from a bad coil caused the damage. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0420 Catalyst System Efficiency Below Threshold (Bank 1)
- P0300 Random/Multiple Cylinder Misfire Detected
- P0157 O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)
- P0175 System Too Rich (Bank 2)
- P0150 O2 Sensor Circuit (Bank 2 Sensor 1)