Trouble code

P0402: excessive EGR flow

The same code points to different failures on different engines. Below, engine by engine, are the documented failures whose records name P0402, with the record's own words, how to tell them apart and the usual fix. The meaning above is taken from the record EGR valve soot clogging / sticking.

6.7 Power Stroke (2011-present)6.7 Cummins 2007-2018 Triton (gas)

6.7 Power Stroke (2011-present)

1 documented failure names this code. All about this engine

1 EGR valve soot clogging / sticking

verified How widespread: Common 8 NHTSA owner complaints match it, out of 1,754 checked

Where its record names the code

check-engine codes P0401 (insufficient EGR flow), P0402 (excessive flow), P0404/P0405 (valve position faults)

Its other signs

rough idle, hesitation, or surging as a sticking valve mismeters exhaust gas
a valve caked in dry soot with sluggish actuation on inspection (vs a wet, steam-cleaned valve - see EGR cooler thermal-fatigue coolant leak)

How to tell it apart

command the valve through its range with a scan tool while watching position feedback for sticking or dead spots
distinguish from cooler failure (EGR cooler thermal-fatigue coolant leak): dry sooted passages = clogging; wet/steam-cleaned passages = coolant intrusion

Usual fix

clean a lightly sooted valve to buy time

Root cause, parts and sources →

6.7 Cummins 2007-2018

1 documented failure names this code. All about this engine

1 EGR valve sooting / failure

verified How widespread: Common 16 NHTSA owner complaints match it, out of 1,355 checked

Where its record names the code

EGR flow DTCs (P0401/P0402/P0404-family), check-engine light

Its other signs

rough idle, smoke, occasional power loss; failed regens
valve found coked with soot on inspection

How to tell it apart

read EGR DTCs and commanded-vs-actual valve position PID
remove and inspect for coke; clean vs replace decision follows condition
check the EGR cooler and CCV filter state at the same time - they share the soot/oil load

Usual fix

clean the valve (if pintle moves freely after cleaning, reinstall); replace when worn/stuck

Root cause, parts and sources →

Triton (gas)

1 documented failure names this code. All about this engine

1 EGR system faults / DPFE sensor failure (gas)

verified How widespread: Very common 23 NHTSA owner complaints match it, out of 7,111 checked

Where its record names the code

P0401 (insufficient EGR flow) / P0402 (excessive) with rough idle

Its other signs

non-commanded EGR flow - rough idle that comes and goes
knock under load on an otherwise healthy engine

How to tell it apart

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

Usual fix

replace the DPFE sensor (match by year) and clear the orifice tubes

Recalls and bulletins

TSB 05-4-17 TSB 05-3-1 TSB 17-5-68

Root cause, parts and sources →

A code tells you which system flagged a fault, not which part failed. Read it with the signs your truck shows: symptoms by engine. For your exact truck: check your VIN.

Order: how widespread each failure is in its record (near-universal, very common, common, occasional, rare), then the number of NHTSA owner complaints that match its keywords. Complaint counts are keyword matches, not a manual review of each complaint. A symptom listed here means the failure is documented with that sign; it is not a diagnosis of your truck. Tiers: verified, aggregated, contested, data-gap. How we tier and source facts.