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P0151 - OBD-II Trouble Code

Oxygen Sensor Circuit Low Voltage (Bank 2, Sensor 1)

Our emissions expert has put together the following information about the P0151 fault code. We have also included diagnostic procedures you can take to your repair shop if the mechanic is having difficulty analyzing the code.

OBD II Fault Code

  • OBD II P0151

Fault Code Definition

The purpose of code P0151 is to track the amount of time that the Oxygen Sensor or Air Fuel Ratio Sensor takes to go from indicating that the fuel control system is in open loop to rapidly switching above and below the 450-millivolt set point, thus indicating that the fuel control system is in closed loop. P0151 is set when there is a sustained low voltage signal from the Oxygen Sensor for a specified amount of time.

front oxygen sensor Symptoms

  • Check Engine Light will illuminate
  • In many cases, no abnormal symptoms may be noticed
  • In many cases, the emissions will be elevated
  • Poor fuel economy

Common Problems That Trigger the P0151 Code

  • Defective Oxygen Sensor
  • Faulty Oxygen Sensor wiring or connections
  • Defective Powertrain Component operation

Common Misdiagnoses

  • Oxygen Sensor is replaced when the problem is faulty Oxygen Sensor wiring or connections
  • Oxygen Sensor is replaced when the problem is a vacuum leak or defective Mass Air Flow Sensor

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