Possible causes

– Intake air leaks
– Faulty front heated oxygen sensor
– Ignition misfiring
– Faulty fuel injectors
– Exhaust gas leaks
– Incorrect fuel pressure
– Lack of fuel
– Faulty Mass Air Flow (MAF) sensor
– Incorrect Positive Crankcase Ventilation (PCV) hose connection

Tech notes

If the P0171 is combined with the P0174 code, it’s very likely that the problem is caused by an intake leak. If there are no intake leaks, the next step is to replaced the air filter and clean the air flow meter. If the problem persist the front oxygen (O2) sensor may need to be replaced.

When is the code detected?

– Fuel injection system does not operate properly.
– The amount of mixture ratio compensation is too small. (The mixture ratio is too lean.)

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Excessive Fuel Consumption

P0171 Description

With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from the heated oxygen sensors 1. The Engine Control Module (ECM) calculates the necessary compensation to correct the offset between the actual and the theoretical ratios.
In case the amount of the compensation value is extremely large (The actual mixture ratio is too lean.), the ECM judges the condition as the fuel injection system malfunction and light up the Malfunction Indicator Light (MIL) (2 trip detection logic).

P0171 Information for specific makes

P0171 1999 FORD WINDSTAR
P0171 2000 FORD WINDSTAR
P0171 2001 FORD WINDSTAR
P0171 2002 FORD WINDSTAR
P0171 2003 FORD WINDSTAR
P0171 FORD
P0171 HONDA
P0171 INFINITI
P0171 KIA
P0171 MAZDA
P0171 MITSUBISHI
P0171 NISSAN
P0171 SUBARU
P0171 TOYOTA
P0171 VOLKSWAGEN
P0171 ACURA
P0171 BMW
P0171 CHRYSLER
P0171 DODGE
P0171 JEEP
P0171 HYUNDAI
P0171 ISUZU
P0171 LEXUS
P0171 SCION
P0171 AUDI
P0171 SAAB
P0171 JAGUAR
P0171 CADILLAC
P0171 CHEVROLET
P0171 GMC
P0171 2003 FORD ESCORT
P0171 BUICK
P0171 PONTIAC
P0171 SATURN
P0171 2006 CHEVROLET TRAIL BLAZER
P0171 2006 TOYOTA COROLLA
P0171 2005 TOYOTA COROLLA
P0171 HUMMER
P0171 OLDSMOBILE