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

P0174 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 MIL (2 trip detection logic).

P0174 Information for specific makes

P0174 1999 FORD WINDSTAR
P0174 2000 FORD WINDSTAR
P0174 2001 FORD WINDSTAR
P0174 2002 FORD WINDSTAR
P0174 2003 FORD WINDSTAR
P0174 FORD
P0174 INFINITI
P0174 NISSAN
P0174 ACURA
P0174 HONDA
P0174 BMW
P0174 CHRYSLER
P0174 JEEP
P0174 DODGE
P0174 HYUNDAI
P0174 KIA
P0174 LEXUS
P0174 TOYOTA
P0174 SCION
P0174 MAZDA
P0174 MITSUBISHI
P0174 SUBARU
P0174 AUDI
P0174 VOLKSWAGEN
P0174 JAGUAR
P0174 GMC
P0174 CHEVROLET
P0174 CADILLAC
P0174 BUICK
P0174 PONTIAC
P0174 SATURN
P0174 OLDSMOBILE
P0174 HUMMER