code P0172 may mean that one or more of the following has happened:
The MAF (Mass Air Flow) Sensor is dirty or faulty. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
There could be a vacuum leak
There could be a fuel pressure or delivery problem
Possible solutions include:
Inspect all vacuum and PCV hoses, replace if necessary
Clean the MAF sensor.
Inspect fuel lines for cracks, leaks, or pinches
Check the fuel pressure at the fuel rail
Check the fuel injectors, they may be dirty.
Check for an exhaust leak before the first oxygen sensor (this is unlikely to cause the problem, but it is possible)