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P0151: Oxygen sensor (bank 2, sensor 1): voltage too low

The bank 2 oxygen sensor before the catalytic converter reads a voltage that is too low. Often a damaged wire, the connector or a worn sensor.

Code P0151 at a glance
CodeP0151
SystemEngine and transmission
GroupP01xx, Air and fuel metering
TypeGeneric: it means the same on every make
Can you keep driving?With care

What P0151 means

The oxygen sensor before the catalytic converter measures how much oxygen is left in the exhaust, and the ECU uses that to fine-tune the air and fuel mixture. This code means the ECU sees a voltage below what the sensor should produce, nearly always due to a wiring problem or a worn-out sensor. 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 or corroded
  • Signal wire with worn insulation touching earth
  • Exhaust leak ahead of the sensor letting air in
  • Intake air leak making the mixture lean
  • Worn-out or faulty oxygen sensor

Symptoms

  • Engine warning light on
  • Higher fuel consumption than usual
  • Slightly rough idle or small hesitations
  • High emissions that can fail the inspection

Can you drive with P0151?

With care You can drive, but the mixture may not be controlled properly: fuel use goes up and, left too long, it can end up damaging the catalytic converter. Get it looked at soon.

How to check it

With the engine warm and idling, watch this sensor’s voltage in live data: a conventional sensor swings quickly between roughly 0.1 and 0.9 V. If it stays fixed, the problem is the sensor or its wiring (some cars use a wideband sensor, which shows different values).

How to read and clear P0151 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 P0151 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

P0151 is a generic code, so it means the same on any make, for example on Abarth, Citroën, Cupra, Hyundai, Mini, Seat. See what Final OBD does on your car in makes and models.

What does code P0151 mean?

The oxygen sensor before the catalytic converter measures how much oxygen is left in the exhaust, and the ECU uses that to fine-tune the air and fuel mixture. This code means the ECU sees a voltage below what the sensor should produce, nearly always due to a wiring problem or a worn-out sensor. 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 P0151?

You can drive, but the mixture may not be controlled properly: fuel use goes up and, left too long, it can end up damaging the catalytic converter. Get it looked at soon.

How do you clear P0151?

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, P0151 comes back.