How To Fix a P0171 OBDII Error Code

By | April 20, 2020

How To Fix a P0171 OBDII Error Code

  • System Too Lean (Bank 1)
    Below is the basic causes and common fixes for a P0171 OBDII error code.

    What Is a P0171 Error Code?
    A P0171 code indicates there is a fuel/air mixture problem on bank 1 of the engine.

    The term Lean means the cylinder is receiving too much or too little air creating a bad fuel mixture.

    What Causes a P0171?

  • Mass Air Flow Sensor
  • Vacuum Leak
  • Bad Oxygen Sensor
  • Bad Fuel Pressure Regulator
  • A Weak or Failing Fuel Pump
  • Fuel Filter
  • Bad Injector
    Several things can cause a P0171 with the most common failures being the Mass Air Flow Sensor or Vacuum Leak.

    Vehicle Symptoms

  • Loss of Power
  • Engine Hesitation
  • Engine Difficult to Start
  • Engine Dies Easily
  • Black Smoke from The Tailpipe

    P0171 Error Code Fixes

  • Replace or Clean Mass Air Flow Sensor
  • Find and Fix any Vacuum Leak
  • Replace the Oxygen Sensor
  • Replace Injector
  • Replace Fuel filter
  • Replace Fuel Pump
  • Replace Fuel Pressure Regulator
    There are several components that must work together to get the right air and fuel pressure mix.

    A vehicle computer uses the mass air flow sensor to adjust the air mix into the engine.

    For this reason the mass air flow sensor is commonly replaced to fix a a P0171 error code but may not be the problem.

    A vacuum leak can cause the mass air flow sensor to get a bad reading.

    The first step would be to clean the mass air flow sensor to see if the problem goes away or the vehicle runs better.

    Next look for a vacuum leak using one of the many vacuum troubleshooting techniques.

    Once a vacuum leak or mass air flow sensor is ruled out next step is to look at the fuel pressure.

    A weak or failing fuel pump can case the pressure to be off messing up the mixture.

    A clogged up fuel filter or pressure regulator can also cause this problem.

    The fuel injector may also be failing causing a bad mixture to go into the cylinder.

    Do you have a P0171 story? Let us know in the comments below.

    P0171 Fix Videos



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