Is this an RX? If so, replace your mass air flow sensor located on the top of you Air filter housing. Do yourself a favor, and replace it with a Lexus replacement part.
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: 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: Fuel System 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)