P0171 OBD2 5 SECOND FIX.. System Too Lean

The P0171 OBD-II code means that, on the first bank of the engine, the fuel system is running weak or a vacuum leak exists near this side of the engine. A lean condition occurs when the engine either receives too little fuel or too much air.
What are the causes of the P0171 code?
Causes of the P0171 code may include:
A faulty fuel pressure regulator
A weak fuel pump
A clogged fuel filter
A faulty powertrain control module
A vacuum leak
Faulty injector(s)
Faulty oxygen sensor(s)
A faulty mass air flow sensor

[@loganz20939]

I woulda forget to tighten it too

[@survivormary1126]

My issue is dropping the bolt into motor before getting chance to tighten...lol

[@vanpocalypse3529]

Oh haha yep me too... everything that can go wrong goes wrong with this stuff.