P0401 - Exhaust Gas RECIRCULATION (EGR) Flow Insufficient Detected

WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2008 Mercury Sable, 2008 Mercury Mountaineer, 2008 Mercury Milan, 2008 Mercury Mariner, and 2008 Mercury Grand Marquis. However, it is still accessible from the selected car via links, so may be relevant.

P0401 - EXHAUST GAS RECIRCULATION (EGR) FLOW INSUFFICIENT DETECTED

Description:	The EGR system is monitored during steady state driving conditions while the EGR is commanded on. The test fails when the signal from the differential pressure feedback EGR sensor indicates that EGR flow is less than the desired minimum.
Possible Causes:	Vacuum supply EGR valve stuck closed EGR valve leaks vacuum EGR flow path restricted EVR circuit short to voltage VREF open to differential pressure feedback EGR sensor Differential pressure feedback EGR sensor downstream hose is off or plugged EVR circuit open VPWR open to EGR vacuum regulator solenoid Differential pressure feedback EGR sensor hoses are both off Differential pressure feedback EGR sensor hoses are reversed Damaged EGR orifice tube Damaged EGR vacuum regulator solenoid
Diagnostic Aids:	Carry out the key on engine running (KOER) self-test and look for DTC P1408 as an indication of a hard fault. If DTC P1408 is not present, look for contamination, restrictions, leaks, and intermittent concerns.
Application		Key On Engine Off	Key On Engine Running	Continuous Memory
Vehicles with an EGR system module (ESM)		-	-	refer to PINPOINT TEST HH .
All others		-	-	refer to PINPOINT TEST HE .