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P0056: Oxygen sensor heater circuit fault (bank 2, sensor 2)

The circuit that heats the rear oxygen sensor on bank 2 has a fault; usually the fuse, the connector or the sensor’s own heater.

Code P0056 at a glance
CodeP0056
SystemEngine and transmission
GroupP00xx, Air, fuel and emissions
TypeGeneric: it means the same on every make
Can you keep driving?Yes, no rush

What P0056 means

An oxygen sensor (lambda sensor) only reads accurately when very hot, so it has a built-in heater that warms it up as soon as the engine starts. The ECU monitors that circuit and has found it is not working as it should. This sensor sits after the catalytic converter on bank 2 (bank 2 is the side of the engine opposite cylinder 1) and is used to check that the catalytic converter is working.

Most common causes

  • Blown oxygen sensor heater fuse
  • Sensor connector loose, burnt or damp
  • Broken heater element inside the sensor (most common)
  • Wire cut or chafed against the exhaust
  • Faulty heater relay or power supply

Symptoms

  • Engine warning light on
  • Usually no change in how the car drives
  • Possible inspection failure because of the warning light

Can you drive with P0056?

Yes, no rush You can drive normally, as this sensor plays no part in the fuel mixture. Just get it fixed before the next inspection.

How to check it

Start by checking the oxygen sensor heater fuse in the fuse box. With the engine cold and the sensor unplugged, a multimeter across the two heater terminals should show a low resistance; if it reads nothing, the sensor has failed.

How to read and clear P0056 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 P0056 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

P0056 is a generic code, so it means the same on any make, for example on Citroën, Ford, Hyundai, Mercedes-Benz, Renault, Volvo. See what Final OBD does on your car in makes and models.

What does code P0056 mean?

An oxygen sensor (lambda sensor) only reads accurately when very hot, so it has a built-in heater that warms it up as soon as the engine starts. The ECU monitors that circuit and has found it is not working as it should. This sensor sits after the catalytic converter on bank 2 (bank 2 is the side of the engine opposite cylinder 1) and is used to check that the catalytic converter is working.

Can you drive with P0056?

You can drive normally, as this sensor plays no part in the fuel mixture. Just get it fixed before the next inspection.

How do you clear P0056?

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, P0056 comes back.