P0430
Catalyst System Efficiency Below Threshold (Bank 2)
- Severity
- Medium
- Driving
- Drivable — book it in
The catalytic converter on bank 2 is not cleaning the exhaust as effectively as the module expects. It works this out by comparing the oxygen sensor before the converter with the one after it: on a healthy converter the two readings look very different. When they start to look alike, the module concludes the converter has lost efficiency. Note that this is an inference, not a direct measurement - a faulty rear oxygen sensor produces the same code.
Possible causes
- CommonFaulty rear (downstream) oxygen sensor
- CommonExhaust leak between the engine and the rear oxygen sensor
- CommonGenuinely worn-out catalytic converter
- PossibleAn unfixed misfire or rich-running fault that has damaged the converter
- PossibleEngine burning oil or coolant, contaminating the converter
- PossibleAftermarket converter that does not meet the original specification
What you might notice
- Often no symptom at all beyond the warning light
- Sometimes a sulphur or rotten-egg smell from the exhaust
- Failed emissions test
- Slight loss of power if the converter is physically blocked
What to check, in order
- Do not replace the converter first. It is the most expensive part in this list and frequently not the fault.
- Check for exhaust leaks between the engine and the rear oxygen sensor. A leak lets fresh air in and makes a healthy converter look ineffective.
- Compare the front and rear oxygen sensor readings on the live data screen. The rear sensor should be relatively steady while the front one oscillates. A rear sensor that swings like the front is either faulty or reporting a genuinely dead converter.
- Check for other stored codes. If there is a misfire or rich-mixture code as well, fix that first - it is very likely the cause of the converter damage, and a new converter will fail again if you do not.
- Ask whether the car burns oil or has lost coolant. Either will poison a converter.
- Only after ruling out the sensor, exhaust leaks and upstream faults is replacing the converter the right call.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Auxiliary emission controls
P0400P0401P0402P0403P0404P0405P0406P0407P0408P0409P0410P0411P0412P0413P0414P0415P0416P0417P0418P0419P0420P0421P0422P0423P0424P0425P0426P0427P0428P0429P0430P0431P0432P0433P0434P0435P0436P0437P0438P0439P0440P0441P0442P0443P0444P0445P0446P0447P0448P0449P0450P0451P0452P0453P0454P0455P0456P0457P0458P0459P0460P0461P0462P0463P0464P0465P0466P0467P0468P0469P0470P0471P0472P0473P0474P0475P0476P0477P0478P0479P0480P0481P0482P0483P0484P0485P0486P0487P0488P0489P0490P0491P0492P0493P0494P0495P0496P0497P0498P0499