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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 at a glance
CodeP0156
SystemEngine and transmission
GroupP01xx, Air and fuel metering
TypeGeneric: 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.

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 this same explanation and whether it’s confirmed, pending or permanent.

With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.

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 the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.

Similar codes

P0156 is a generic code, so it means the same on any make, for example on Alfa Romeo, Dacia, Kia, Nissan, Opel / Vauxhall, Škoda. See what Final OBD does on your car in makes and models.

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.