P0171 - System Too Lean (Bank 1)

WARNING: This page is about a different car, the 2007 Mercury Mariner and 2007 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

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 toPOWERTRAIN CONTROL SOFTWARE Fuel Trim for more information.
Possible Causes:	Fuel System: Fuel pressure regulator (leaking or damaged) Fuel filter plugged, dirty Fuel pump (weak, check valve leaking) Leaking/contaminated fuel injectors Low fuel pressure or running out of fuel EVAP canister purge valve leaking (when the canister is clean) Fuel supply line restricted Fuel rail pressure sensor (incorrect reading) Intake Air System: Air leaks after the mass air flow (MAF) sensor Vacuum leaks PCV system (leak or valve stuck open) Improperly seated engine oil dipstick Mass air flow (MAF) sensor Exhaust System: Exhaust leaks before or near the HO2Ss (exhaust manifold gasket, mating gaskets) EGR System: EGR valve tube/gasket leak EGR vacuum regulator solenoid leak
Diagnostic Aids:	View freeze frame data to determine the operating conditions when the DTC was set. Observe the LONGFT1 PID. Refer toADAPTIVE FUEL DIAGNOSTIC TROUBLE CODE (DTCS) DIAGNOSTIC TECHNIQUES for more information.
Application		Key On Engine Off	Key On Engine Running	Continuous Memory
All		-	-	refer to PINPOINT TEST H .