Question 1

What are P0171 and P0174 codes?

Accepted Answer

P0171 means system too lean bank 1. P0174 means system too lean bank 2.

Question 2

What Does P0171 and P0174 Mean?

Accepted Answer

DTCs P0171 and P0174 are generic codes that set when the feedback on the engine's air/fuel mixture becomes too lean for the Engine Control Module (ECM) to correct within its normal operating range. A lean mixture is a mixture that has too much air or not enough fuel. The ECM sets a target air/fuel ratio and monitors it using oxygen sensors and on newer vehicles air/fuel ratio sensors. When the ECM sees the engine running lean, it will add fuel and display the correction as a positive fuel trim percentage. If the correction goes past the ECMs predetermined range in the positive (add fuel) direction, the ECM will set a lean DTC P0171, P0174, or both.

Question 3

What Causes P0171 and P0174 to Set?

Accepted Answer

Vacuum leaks, intake air leaks, incorrect air metering, faulty Mass Air Flow (MAF) sensor, malfunctioning oxygen (O2) sensor or air fuel ratio (A/F) sensor, or low fuel pressure, incorrect fuel flow/delivery

Question 4

How to diagnose P0171 and P0174 DTCs?

Accepted Answer

Inspect for vacuum leaks, check Mass Air Flow sensor, check oxygen sensors and/or air fuel ratio sensors, and check fuel pressure

Question 5

How do I repair a P0171 or P0174 DTC?

Accepted Answer

Execute the appropriate diagnostic checks and repair the appropriate faulty parts. Due to the number of potential issues guessing could be costly. If you need assistance please call the GoTech team.