Running too lean. Engines create vacuum. You have too much air in yours in comparison to fuel. First check fuel pressure and if ok, check for split hoses especially air intake.
Trouble code P0171 means: Fuel System Too Lean (Cylinder Bank 1)
Trouble code P0171 means: System too lean (Bank 1)
Trouble code P0171 means: System Too Lean (Bank 1)
Trouble code P0171 means: Bank 1 Combustion Too Lean
Trouble code P0171 means: System Too Lean (Bank 1)
Trouble code P0171 means: System Too Lean (Bank 1)
Trouble code P0171 means: System Too Lean (Bank 1)
Trouble code P0171 means: System Too Lean (Bank 1)
Trouble code P0171 means: Fuel System Lean (Bank 1)
Trouble code P0171 means: Fuel Trim System Lean (Bank 1)
Trouble code P0171 means: System Too Lean (Bank 1)
Trouble code P0171 means: System Too Lean (Bank 1)