What the P0172 code means?
P0172 indicates that there is too much gasoline being detected in the exhaust gases exiting the combustion chamber. The ECU uses a number of instruments, such as the mass air flow sensor (MAF), oxygen sensors, and manifold absolute pressure (MAP) to monitor the air-fuel ratio of the engine.
Most routinely, the air-fuel ratio will be measured through the oxygen sensors calculating the amount of oxygen and carbon monoxide present in exhaust gases. This particular ratio was chosen because it was discovered to have the highest power output but lowest fuel consumption rate.
What causes the P0172 code?
1) The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters can cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
2) There could be a vacuum leak.
3) There could be a fuel pressure or delivery problem
What are the symptoms of the P0172 code?
Symptoms include poor acceleration, engine stall under acceleration or at idle, a no start condition, rough engine idle, an engine misfire, or a surge upon acceleration.
Common mistakes when diagnosing the P0172 code?
Oxygen sensors are often replaced in error when this code is exhibited. Many vehicles are successfully repaired by replacing a fuel filter that is long overdue.
What repairs can fix the P0172 code?
1) A repair of a vacuum leak
2) A replacement of a faulty fuel injector, fuel pump, or fuel regulator
3) Replacement of an excessively restricted air filter
4) Replacement of the thermostat or coolant temperature sensor
5) A replacement of the spark plugs
6) A cleaning of the oxygen sensors and mass air flow sensor.