Menu

Error “System too lean bank 1 and 2” meaning

The error “system too lean bank 1 and 2” is an issue with the air/fuel ratio in your engine being too lean. If you’re using an OBD scanner, this shows up as code P0171 for bank 1, and code P0174 for bank 2. There are several possible causes:

  • There is a leak between the MAF or MAP sensor and the rest of the intake, giving the ECU a false air reading. This is usually caused by a loose clamp or a disconnected hose to the intake.
  • The injectors aren’t spraying enough fuel. This could be caused by clogged injectors or low fuel pressure caused by a bad fuel pump or clogged fuel filter.
  • The O2 sensors are bad, giving the ECU a false reading.

Helpful Resources

Advice, how-to guides, and car care information featured on AutoZone.com and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

FREE Loan-A-Tool® program requires returnable deposit. Please note that the tool that you receive after placing an online order may be in a used but operable condition due to the nature of the Loan-A-Tool® program.

Related Posts