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P0051: Oxygen sensor heater circuit low (bank 2, sensor 1)

The ECU sees too low a voltage in the heater of the front oxygen sensor on bank 2; usually the sensor, a wire or the fuse.

Code P0051 at a glance
CodeP0051
SystemEngine and transmission
GroupP00xx, Air, fuel and emissions
TypeGeneric: it means the same on every make
Can you keep driving?Yes, no rush

What P0051 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 sees a lower voltage than normal in that circuit, nearly always from an electrical fault: a broken heater element, a wire, the connector or the fuse. This sensor sits before the catalytic converter on bank 2 (bank 2 is the side of the engine opposite cylinder 1) and measures the mixture so the ECU can adjust fuelling.

Most common causes

  • Blown heater fuse
  • Loose or corroded sensor connector
  • Open heater element in the sensor
  • Wire cut or shorted to earth by rubbing on the exhaust
  • Fault in the ECU’s control circuit (uncommon)

Symptoms

  • Engine warning light on
  • Slightly higher fuel consumption, especially on short trips
  • Higher emissions that can fail an inspection

Can you drive with P0051?

Yes, no rush You can drive normally; the engine runs fine, although it may use a little more fuel when cold. 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 P0051 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 P0051 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

P0051 is a generic code, so it means the same on any make, for example on Audi, Fiat, Kia, Mazda, Opel / Vauxhall, Toyota. See what Final OBD does on your car in makes and models.

What does code P0051 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 sees a lower voltage than normal in that circuit, nearly always from an electrical fault: a broken heater element, a wire, the connector or the fuse. This sensor sits before the catalytic converter on bank 2 (bank 2 is the side of the engine opposite cylinder 1) and measures the mixture so the ECU can adjust fuelling.

Can you drive with P0051?

You can drive normally; the engine runs fine, although it may use a little more fuel when cold. Get it fixed before the next inspection.

How do you clear P0051?

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, P0051 comes back.