Failure mode - Ford Triton gasoline (Super Duty / Excursion / E-Series)

EGR system faults / DPFE sensor failure (gas)

Reliability tier: verified - verify before ordering, see /disclosure/

Symptoms

P0401 (insufficient EGR flow) / P0402 (excessive) with rough idle
non-commanded EGR flow - rough idle that comes and goes
knock under load on an otherwise healthy engine

Root cause

The gas EGR path (valve + DPFE sensor + orifice tubes) clogs and the sensors drift - Ford's bulletins cover both the diagnostic traps and the flow faults. This is the strongest gas VOQ signal (21 complaints). Note: this is the GAS EGR path - valves and sensors, no coolers; do not cross-match diesel EGR-cooler parts.

Diagnosis

scan the EGR DTC family; command the valve with a scan tool and watch flow
inspect the DPFE hoses/orifice tubes for carbon blockage before replacing the sensor
clean-vs-replace the valve: sticking valves often recover; leaking diaphragms do not

Fixes

replace the DPFE sensor (match by year) and clear the orifice tubes (sensor + tubes) - cheap; check tubes first or it recurs

DPFE Sensor (EGR pressure feedback)

clean or replace the EGR valve per its condition (valve) - cleaning is often enough; a leaking diaphragm mandates replacement - contested call, see contested[]

EGR Valve, gas engines

Prevalence

very-common