DTCs P0172 and P0175 System Too Rich Diagnostic Aids

WARNING: This page does not describe the selected car, but rather 16 other vehicles, including the 2011 Mercury Mariner, 2011 Lincoln Navigator L, 2011 Lincoln Navigator, 2011 Lincoln MKX, and 2011 Lincoln MKT. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: If the system is rich at certain conditions, then the LONGFT PID would be a negative value at that airflow, indicating that decreased fuel is needed.

System rich concerns are caused by fuel system concerns, although the MAF sensor and base engine (for example, engine oil contaminated with fuel) should also be checked.