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P0171 – System Too Lean (Bank 1)

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P0171 – System Too Lean (Bank 1)
Description:         The adaptive fuel strategy continuously monitors the fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit. Refer to Section 1, Powertrain Control Software Fuel Trim for more information.
Possible Causes:       
Fuel System:
Ethanol content in the fuel
Fuel filter plugged or dirty
Damaged or worn fuel pump
Leaking fuel pump check valve
Leaking or contaminated fuel injectors
Low fuel pressure or running out of fuel
Evaporative emission (EVAP) canister purge valve is leaking when the canister is clean
Fuel supply line restricted
Fuel rail pressure (FRP) sensor bias Exhaust System:
Exhaust leaks in the exhaust manifold gasket or mating gaskets before or near the heated oxygen sensor (HO2S)
EGR System:
Vacuum hose disconnected on exhaust gas recirculation (EGR) system module (ESM) applications
EGR valve tube or gasket leak
EGR vacuum regulator solenoid leak Intake Air System:
Air leaks after the mass air flow (MAF) sensor
Vacuum leaks
Positive crankcase ventilation (PCV) system is leaking or the valve is stuck open
Incorrectly seated engine oil dipstick
Intake air turbulence due to incorrect air filter
Damaged or contaminated MAF sensor
Diagnostic Aids:          View the freeze frame data to determine the operating conditions when the DTC was set. Observe the LONGFT1 and LONGFT2 PIDs. Refer to Section 2, Adaptive Fuel Diagnostic Trouble Code (DTC) Diagnostic Techniques, for more information and the appropriate pinpoint test for specific concern identification.
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