P0430Moderate severityEmissionsDIY: Moderate
P0430: Catalyst System Efficiency Below Threshold (Bank 2)
Identical to P0420 but on the second cylinder bank (V6/V8 engines). Same diagnostic flow — verify with the downstream O2 sensor before replacing the converter.
Can I keep driving?
Usually yes. It rarely affects how the car drives but it will fail an emissions test.
Symptoms you might notice
- Check engine light, usually with no change in how the car drives
- Failed emissions test
- Sometimes P0420 is stored at the same time
What to check first
- Confirm which side is bank 2. It is the side of a V engine that does not hold cylinder 1.
- If P0420 is stored too, suspect something upstream that affects both sides, such as a misfire or fuel-trim problem, before blaming two converters.
- If only P0430 is set, check for an exhaust leak on that side and compare the bank 2 upstream and downstream oxygen sensors on a scan tool.
- Replace the sensor or converter only after those checks.
Most common causes
- Worn catalytic converter (bank 2)
- Faulty downstream O2 sensor
- Exhaust leak
Check it against your exact vehicle
A code means the same thing on every car, but where the parts are and what to check first depends on your year, make, model and engine. Tell CaliperAI what you are seeing and it will help narrow down the likely causes for your vehicle.
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General information about this code, not a diagnosis of your specific vehicle. Safety-critical work such as brakes, fuel and airbags is best left to a qualified mechanic.