Exhaust Gas Recirculation Flow Insufficient Detected

Possible causes

• CommonCarbon blocking the EGR passage in the intake manifold or cylinder head
• CommonEGR valve stuck shut by carbon on its seat
• CommonFaulty differential pressure sensor (the DPFE sensor on many Ford engines)
• PossibleBlocked or split hoses feeding the differential pressure sensor
• PossibleNo vacuum reaching a vacuum-operated valve - split hose or failed solenoid
• PossibleClogged EGR cooler on a diesel engine
• PossibleFailed EGR valve motor on an electronically actuated valve

What you might notice

• Check engine light on
• Failed emissions test - nitrogen oxide readings high
• Pinging or knocking under load, especially climbing a hill
• Slight loss of power
• Frequently no symptom the driver notices at all

What to check, in order

1. Remove the EGR valve and look at it, and look into the passage behind it. If either is packed with soot, that is the fault - no further diagnosis is needed before cleaning.
2. Clean the valve and the passage with carbon cleaner and a suitable brush. Blocked passages are frequently the whole repair, and a new valve fitted onto a blocked passage will set the same code again within days.
3. Check the small hoses to the differential pressure sensor. They run close to hot components, go brittle and split, and a split hose produces this code with a perfectly good valve.
4. On a vacuum-operated system, apply vacuum to the valve directly with a hand pump and watch it open. If it holds vacuum and moves, the valve is fine and the fault is upstream in the control solenoid or hoses.
5. On an electronically actuated valve, compare commanded against actual position on the live data screen while the engine warms up.
6. On a diesel, consider the EGR cooler. Coolers block with soot in the same way the valve does, and a blocked cooler restricts flow no matter how well the valve works.