Causes and Fixes Ford P0171 Code: System Too Lean (Bank 1)

How to fix a Ford P0171 engine code: System Too Lean (Bank 1)

A lean condition exists if the engine is getting more air than fuel in the cylinders. (Air/Fuel Ratio is off)

P0171 Code is problematic code since it can be caused by several things.

Ford vehicles with V6 or V8 engines, Bank-1 is on the Passenger side. A 4 Cylinder has only Bank-1.

Possible Causes of a Ford P0171 Code:
Dirty Air Filter
Mass Air Flow Sensor (Codes P0100, P0101, P0102, P0103, P0104)
Clogged Fuel Filter
Fuel Pressure Regulator
Weak Fuel Pump
Vacuum Leak
Oxygen Sensor (Bank 1 Sensor 1)
Bad Fuel Injector
DPFE (Differential Pressure Feedback Sensor) (P0401 code)

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