DTC P0172: System Too Rich (Bank 1)

WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2005 Mercury Sable, 2005 Mercury Mountaineer, 2005 Mercury Monterey, 2005 Mercury Montego, and 2005 Mercury Mariner. However, it is still accessible from the selected car via links, so may be relevant.

P0172 - SYSTEM TOO RICH (BANK 1)

Description:	The adaptive fuel strategy continuously monitors the fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit. Refer to FUEL TRIM for more information.
Possible Causes:	Fuel System: Fuel pressure regulator (vacuum hose off, diaphragm leak) Leaking fuel injectors Fuel return line restricted Fuel rail pressure sensor (incorrect reading) EVAP canister purge valve leak (when canister is full) Base engine. Engine oil contamination Air Measurement System: Mass air flow (MAF) sensor (contaminated, damaged, or corroded connector)
Diagnostic Aids:	View freeze frame data to determine the operating conditions when the DTC was set. Observe the LONGFT1 and LONGFT2 PID(s). Refer to ADAPTIVE FUEL DTC DIAGNOSTIC TECHNIQUES for more information.
Application	Key On Engine Off	Key On Engine Running	Continuous Memory
All	-	-	GO to H: Fuel Control STEP H21.