Possible causes

– Faulty front heated oxygen sensor
– Ignition misfiring
– Faulty fuel injectors
– Exhaust gas leaks
– Incorrect fuel pressure
– Faulty Mass Air Flow (MAF) sensor

When is the code detected?

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

Symptoms

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

P0172 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).

P0172 Information for specific makes

P0172 SAAB
P0172 INFINITI
P0172 NISSAN
P0172 ACURA
P0172 BMW
P0172 CHRYSLER
P0172 JEEP
P0172 DODGE
P0172 FORD
P0172 BUICK
P0172 HONDA
P0172 HYUNDAI
P0172 ISUZU
P0172 KIA
P0172 LEXUS
P0172 TOYOTA
P0172 SCION
P0172 MAZDA
P0172 MITSUBISHI
P0172 SUBARU
P0172 AUDI
P0172 VOLKSWAGEN
P0172 JAGUAR
P0172 CADILLAC
P0172 CHEVROLET
P0172 GMC
P0172 PONTIAC
P0172 SATURN
P0172 HUMMER
P0172 OLDSMOBILE