7 Causes of a Kia P0171 Code: "Fuel Trim System Too Lean Bank 1"

How to fix a Kia P0171 engine code: "Fuel Trim System Too Lean Bank 1".
Possible Causes of a a Kia P0171 engine code
Mass Air Flow Sensor
Fuel Filter
Fuel Pressure Regulator
Fuel Pump
Vacuum Leak
Oxygen Sensor
Injector

[@embtroop]

Great walk-through for that code. I believe I need a new pump. Occasional shut-off and shuddering while stopped.

[@embtroop]

New pump is in. I'll post results soon.

[@MasrizalMahmud]

Hi. I have a PO171 on my Toyota Wish 2006. The check engine light always comes on in the morning after driving the car for about a mile and goes away by switching the engine off. It comes on again the next morning. If I drive the car in the afternoon, I never see the light. Weird!
The MAF sensor has been cleaned but the light is still there. Recently a mechanic found a crack vacuum hose and it has been replaced, and he also cleaned the throttle body, but the light is still there. Could this be the O2 sensor that needs replacing? Can you help? Many thanks.