Ford P0171 Code – System Too Lean Bank 1
Limited
Safe to drive :
Ford vehicles only
Applies only to :
Not applicable to :
This explanation does NOT apply to Toyota, BMW, GM, VW, or other manufacturers.
Medium
Severity level :
When Does This Code Appear on the Vehicles
Ford P0171 appears when the engine runs lean and may cause hesitation, rough idle, or loss of power.
What This Code means on the Vehicles
On Ford vehicles, P0171 indicates the PCM has reached the limit of fuel correction on Bank 1 while attempting to compensate for a lean condition.
Why This is different from a generic OBD2 Code
Ford engines are highly sensitive to unmetered air, making vacuum leaks and MAF errors more common causes than fuel pump failure.
Common Situations That Trigger This Code
Vacuum leaks; Cracked PCV hoses; Dirty MAF sensor; Intake manifold leaks.
What Will NOT Fix This Code
Replacing oxygen sensors alone; Replacing fuel injectors without diagnosis.
How to Clear This Code on Vehicles
Locate vacuum leaks, clean the MAF sensor, verify fuel trims, then clear the code.
Related Manufacturer Specific Codes
Ford P0174; Ford P2195