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enter image description hereCorolla with intermittent code saying System Too Lean (Bank 1) P0171 after refueling. First i noticed that there is slightly stronger fumes when i refuel then the code will illuminate ( Code not always comes on). It happens with half tank and up and always improves with lower than third of tank. I never top off and i just replaced gas cap but didn't help. I read here a lot and checked Fuel trims and found they go higher positive every time i refuel. I have some data file to share Here Please help.

Thank you in advance.

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    Dec 14, 2020 at 0:13

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Have you checked the fuel tank filler neck? It can deteriorate on the Corollas and cause the issue you describe. See this link for a picture.

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  • I didn't check that. I don't have any gas leaks underneath.The only code i get sometimes is the p0171. Will check it tomorrow and report back. Thanks!
    – Student677
    Dec 14, 2020 at 6:52
  • Hi Carguy! So just to clarify, A bad gas filler neck can cause a lean condition and higher positive trims?
    – Student677
    Dec 14, 2020 at 18:33
  • Yes, a cracked filler neck could be leaking air into your gas tank & evap system, just the way a loose gas cap could. It would explain why you smell raw gas fumes when you fill the tank at the gas station. The leak may be slight, not enough find gas leaks underneath.
    – Carguy
    Dec 15, 2020 at 2:51
  • The fumes are mostly coming when the engine is running not sure if it is all from bad air/ fuel ratio or fuel rail issue?
    – Student677
    Dec 15, 2020 at 18:02

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