OBD-II · Engine and powertrain (P)
P0430
Catalyst efficiency below threshold bank 2
What it means
The ECU's catalyst monitor reports conversion efficiency below the required threshold on bank 2. The test method depends on the engine and aftertreatment system. Confirm bank 2's location in the engine's service information.
Symptoms
- engine warning light
- usually no change in how the car drives
- fails the emissions part of the roadworthiness test
- sometimes a rotten-egg smell or a rattle from a broken catalyst core
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | aged catalytic converter |
| 02 | exhaust leak |
| 03 | lazy downstream oxygen sensor |
| 04 | misfire damage |
| 05 | oil or coolant contamination |
| 06 | non-type-approved replacement catalyst |
What to check, step by step
- 01Fix any misfire, fuel-trim or lambda sensor codes first: they can damage the catalyst or fake this code
- 02Check for exhaust leaks between the upstream and downstream lambda sensors
- 03Run the OEM catalyst monitor/test under its specified conditions; account for the fitted lambda sensor types rather than treating every upstream sensor as a switching narrowband sensor.
- 04Check for oil burning or coolant loss that poisons the catalyst
- 05Replace with a type-approved catalyst for that car (ECE R103 marking in the EU), not a cheap universal unit