P0156: Oxygen sensor (bank 2, sensor 2): circuit fault
The bank 2 oxygen sensor after the catalytic converter is sending a signal the ECU rejects. Usually a connector, a wire or the sensor itself.
| Code | P0156 |
|---|---|
| System | Engine and transmission |
| Group | P01xx, Air and fuel metering |
| Type | Generic: it means the same on every make |
| Can you keep driving? | Yes, no rush |
What P0156 means
The oxygen sensor after the catalytic converter is mainly there to check that the converter is cleaning the exhaust properly; it has little effect on how the engine runs. This code means its signal makes no sense to the ECU, either because of an electrical problem or because of the sensor itself. Bank 2 is the side of the engine opposite cylinder 1, and it only exists on V-shaped or boxer engines.
Most common causes
- Sensor connector loose, damp or corroded
- Sensor wires burnt or chafed against the exhaust
- Exhaust leak close to the sensor
- Ageing or faulty oxygen sensor
- Faulty engine ECU (uncommon)
Symptoms
- Engine warning light on
- The car usually drives exactly as before
- A catalytic converter efficiency code may also appear
Can you drive with P0156?
Yes, no rush You can keep using the car normally, as this sensor has almost no effect on the engine. With the warning light on, though, it will not pass its inspection.
Open the bonnetthe in-depth explanation
How to check it
With the engine warm, the sensor after the converter normally gives a fairly steady voltage. If live data shows zero or an impossible fixed value, check its connector first: it sits under the car, exposed to water and dirt.
How to read and clear P0156 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 P0156 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
- P0152 The lambda sensor (bank 2, sensor 1) gives a higher signal than normal
- P0153 Oxygen sensor (bank 2, sensor 1): slow response
- P0154 Heated lambda sensor 1 on bank 2 shows no activity
- P0155 Oxygen sensor heater (bank 2, sensor 1): circuit fault
- P0157 Oxygen sensor (bank 2, sensor 2): voltage too low
- P0158 Oxygen sensor (bank 2, sensor 2): voltage too high
- P0159 The lambda sensor circuit (bank 2, sensor 2) responds slowly
- P015A Heated lambda sensor 1 on bank 1 is late switching from rich to lean
- P0100 Mass or volume air flow sensor circuit fault
- P0101 Air flow sensor range or performance problem
- P0102 Air flow sensor circuit low input
- P0103 Air flow sensor circuit high input
What does code P0156 mean?
The oxygen sensor after the catalytic converter is mainly there to check that the converter is cleaning the exhaust properly; it has little effect on how the engine runs. This code means its signal makes no sense to the ECU, either because of an electrical problem or because of the sensor itself. Bank 2 is the side of the engine opposite cylinder 1, and it only exists on V-shaped or boxer engines.
Can you drive with P0156?
You can keep using the car normally, as this sensor has almost no effect on the engine. With the warning light on, though, it will not pass its inspection.
How do you clear P0156?
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, P0156 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.
