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P0151 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


P0151 is an OBD-II Code that refers to O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)


A P0151 code is caused by an ECM (Engine Control Module) receiving a signal indicating the O2 sensor for bank 2 sensor 1 has failed to increase the voltage output above .21 volts, indicating excessive oxygen in the exhaust.


Common causes for this code include:

  • Exhaust leak near the sensor.
  • Loose electrical connections.
  • Bad O2 sensor.
  • Short to ground on circuit of the Oxygen Sensor.
  • Open circuit in Oxygen Sensor wiring.
  • Faulty ECM (Engine Control Module).


The symptoms of a P0151 code are:

  • Check Engine Light on.
  • Poor fuel economy.
  • A hard start when cold.
  • Engine running lean in the lower RPMs.
  • Engine may hesitate upon acceleration or stall under hard acceleration.


To diagnose a P0151 DTC code, a technician would:

  1. Verify that the O2 sensors are electrically sound, replace if necessary.
  2. Check for any exhaust leaks around the sensor.
  3. Check for loose wiring connections.
  4. Replace faulty Oxygen Sensor if any problems are found.
  5. If no problems are found, inspect and test ECM (Engine Control Module.

Common mistakes

The following are common mistakes when diagnosing the trouble code P0151:

Replacing Oxygen Sensor before electrical tests of the sensor.

No faults found during testing, therefore, no repairs made and the vehicle is left with code present.

ECM (Engine Control Module) not tested for faults after it has been diagnosed as faulty.

How serious is this?

A P0151 code is by no means an end-of-the-world repair. It is mainly an inconvenience, but it can run up the cost of the repair because of what it causes; a lean running engine that could potentially cause overheating and identify other problems with the vehicle.

If the O2 sensor is faulty, the ECM can’t adjust the fuel-to-air ratio of the engine. This will result in a poor fuel consumption and clogged spark plugs over time as a result of the excessive gasoline.

What repairs can fix the code?

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The following are solutions that may fix this problem:

  • Replacing the faulty Oxygen Sensor.
  • Repairing or replacing any exhaust leaks present.
  • Repairing or replacing any loose wiring connections present.
  • Replace ECM (Engine Control Module) if all else fails.

Related codes

A P0151 is related to and may be accompanied by the following codes:

How much does it cost to fix the P0151 code?

The repair cost of a P0151 code varies from company to company. The more common repairs will be between $120 and $250 if the Oxygen Sensor is being replaced alone. If a problem with the exhaust or wiring of the sensor is found, it could cost up to $600 for those repairs. If a new ECM (Engine Control Module) is needed, prices may vary from as low as $100 to as high as a few thousand dollars.


In conclusion, the P0151 code is not that bad at all. If the vehicle is running fine it may not need urgent attention. However, if there are any other problems with the vehicle or noticeable performance issues (i.e., hesitation in acceleration), definitely get it checked out sooner rather than later. The more serious consequence of a malfunctioning O2 sensor is the effect it has on the fuel economy and spark plugs as mentioned earlier.

P0151 Code – What Does It Mean & How To Fix It