P0431: Warm up catalyst efficiency below threshold (bank 2)
The small warm up catalytic converter on bank 2 is no longer cleaning the exhaust well. It may be worn out, or an oxygen sensor may be misreading.
| Code | P0431 |
|---|---|
| System | Engine and transmission |
| Group | P04xx, Emissions control |
| Type | Generic: it means the same on every make |
| Can you keep driving? | With care |
What P0431 means
Some cars have a warm up catalyst close to the exhaust manifold so it starts working quickly from cold. The ECU compares the oxygen sensors before and after it and has found that it is no longer storing and converting gases well. Bank 2 is the side of the engine opposite cylinder 1; it only exists on V and flat engines.
Most common causes
- Exhaust leak near the oxygen sensors (gasket or pipe)
- Slow or faulty downstream oxygen sensor (sensor 2)
- Corroded oxygen sensor connector
- Worn out or damaged catalytic converter
- Misfires or oil burning that have damaged the converter
Symptoms
- Engine warning light on
- Failing an emissions test
- Rotten egg smell from the exhaust
- Sometimes loss of power if the converter is blocked
Can you drive with P0431?
With care You can drive, but if there are misfires or the converter becomes blocked, it can get worse. Take it to a garage soon and before the next inspection.
Open the bonnetthe in-depth explanation
How to check it
With the engine warm, watch the oxygen sensor voltages on your reader: the upstream one (sensor 1) should switch quickly and the downstream one (sensor 2) should stay fairly steady. If both switch the same way, the converter is worn.
How to read and clear P0431 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0431 with its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- P042D The catalytic converter temperature sensor (bank 1
- P042E The exhaust gas recirculation A control has got stuck
- P042F The exhaust gas recirculation A control has got stuck
- P0430 Catalytic converter efficiency below threshold (bank 2)
- P0432 The main catalytic converter on bank 2 works below the required efficiency
- P0433 The heated catalyst on bank 2 is working below the minimum efficiency threshold
- P0434 The heated catalyst temperature on bank 2 is below its minimum threshold
- P0435 The catalytic converter temperature sensor (bank 2
- P0400 Exhaust gas recirculation (EGR) flow malfunction
- P0401 Exhaust gas recirculation (EGR) flow insufficient
- P0402 Exhaust gas recirculation (EGR) flow excessive
- P0403 EGR control circuit malfunction
What does code P0431 mean?
Some cars have a warm up catalyst close to the exhaust manifold so it starts working quickly from cold. The ECU compares the oxygen sensors before and after it and has found that it is no longer storing and converting gases well. Bank 2 is the side of the engine opposite cylinder 1; it only exists on V and flat engines.
Can you drive with P0431?
You can drive, but if there are misfires or the converter becomes blocked, it can get worse. Take it to a garage soon and before the next inspection.
How do you clear P0431?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0431 comes back.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
