P0402 on Ford: How to Diagnose & Fix
Exhaust Gas Recirculation Flow Excessive
9 Ford models · 10 documented issues · 6 critical · $50-$3,500 repair
P0402 on Ford by model: symptoms, diagnosis and fix
The EGR (Exhaust Gas Recirculation) cooler on 2011-2019 6.7L Power Stroke diesel engines is prone to clogging with soot and eventually failing, particularly on trucks used for highway driving, light loads, or trucks that idle extensively. The EGR cooler recirculates cooled exhaust gas back into the intake to reduce NOx emissions. Over time, soot accumulates in the cooler's internal passages until coolant flow is restricted, causing the cooler to overheat and fail. When it fails, exhaust gases enter the coolant system, causing overheating and "puking" coolant from the degas bottle. The 2011-2014 models are particularly susceptible due to narrow internal coolant passages. Ford issued TSBs for 2011-2014 trucks covering EGR cooler cleaning/replacement under extended warranty up to 120,000 miles. The EGR cooler for 2011-2016 is OEM part BC3Z-9V425-A; 2017+ is HC3Z-9V425.
Common Symptoms
- Coolant loss with no visible external leak
- Coolant reservoir overflows or "pukes" coolant
- White smoke from exhaust (coolant in combustion)
- Engine overheating warning
- DTC codes P0401 (Insufficient EGR Flow) or P2457 (EGR Cooler Performance)
- Bubbling or foaming in coolant degas bottle
- Loss of power under load (especially towing)
- White deposits around degas bottle cap
How to Fix
Replace EGR cooler (BC3Z-9V425-A for 2011-2016; HC3Z-9V425 for 2017+). Check if truck qualifies for Ford extended service coverage with active DTC P0401 (Insufficient EGR Flow) or P2457 (EGR Cooler Performance). Some 2011-2014 trucks covered to 120,000 miles. Preventive: use a fuel additive (Diesel Kleen, Hot Shots Secret EDT) to reduce soot. Perform regular EGR cleaning at 60,000-mile intervals. Upgrade kits from Sinister Diesel and Dorman (904-405 kit) include both EGR cooler and gaskets.
Sources for this issue (1)
The Crown Victoria's EGR system measures flow with a Differential Pressure Feedback EGR (DPFE) sensor reading pressure drop across an orifice in the EGR supply tube. The early aluminum-body DPFE sensors are heat-sensitive and drift out of calibration; the steel EGR supply tube that runs from the exhaust manifold to the EGR valve rots, crimps or plugs with carbon. Either one sets P0401 (insufficient EGR flow) and, in states with OBD-II emissions testing, fails the car outright. It is not a single-part problem: the community-documented pattern is owners replacing the DPFE, clearing the code and having it return in a day because the actual restriction is a carboned or cracked tube or a stuck EGR valve. The DPFE is also a common cause of rough idle, surge and hesitation that gets misattributed to the transmission.
Common Symptoms
- Check engine light with P0401
- Failed OBD-II emissions or smog test
- Rough idle and surging at light throttle
- Hesitation on acceleration
- Soot-clogged or cracked DPFE hoses
How to Fix
Diagnose in order rather than parts-swapping. Check the two rubber hoses to the DPFE for cracks and soot (they harden and split), then check the DPFE signal voltage at rest (should sit near 0.45-1.0V key-on engine-off) and while the EGR valve is commanded open. Then remove and clear the EGR supply tube and the intake EGR passage - carbon blockage is extremely common at high mileage. Replace the DPFE with the later ceramic-element Motorcraft unit rather than an aluminum reman, and replace the EGR valve only if it is actually stuck or leaking. Parts: DPFE roughly $30-70, EGR valve $60-130, tube $40-90. Shop diagnosis and repair typically $150-400 total. No recall or emissions warranty extension applies at this age, though the EGR system is a federally covered emissions component when the vehicle is within its original emissions warranty term.
Sources for this issue (3)
On the 2004-2010 E-350/E-450 6.0L Power Stroke the factory EGR cooler is a coolant-cooled tube bundle that both clogs with soot and carbon and cracks internally from thermal stress, dumping coolant into the intake. Van duty cycles (ambulance, shuttle, box truck idling) accelerate it. Failure is usually secondary to a restricted oil cooler, so replacing the EGR cooler alone typically leads to a repeat failure. Not applicable to the gasoline E-Series engines, which have a conventional EGR valve rather than a liquid-cooled EGR cooler of this design.
Common Symptoms
- Unexplained coolant loss
- White smoke on start-up or under load
- Sweet smell from exhaust
- Bubbling or pressurized coolant degas bottle
- Loss of power and check engine light
How to Fix
Confirm with a coolant loss with no external leak, white sweet-smelling exhaust and a pressurized degas bottle. The correct repair is to replace the EGR cooler AND the engine oil cooler at the same time, clean the EGR valve and intake, and flush the cooling system. Many operators fit an updated/aftermarket round-tube or bar-plate cooler. Removing or blanking the EGR cooler is common in the field but is an emissions-defeat modification and not legal for on-road use. No recall covers this repair.
Sources for this issue (3)
The 2011-2016 F-350's 6.7L Power Stroke uses a dual EGR cooling arrangement - a primary cooler plus a secondary cooler section - and both are subjected to thermal cycling between roughly 1,200 F exhaust gas and 200 F coolant. Repeated expansion and contraction fatigues the cooler cores and they crack internally, letting coolant into the exhaust stream. Owners see gradual coolant loss with no external leak, white sweet-smelling smoke (most obvious on a warm restart or under acceleration), and eventually overheating. Trucks that idle for long periods or tow heavy - the typical F-350 dually or chassis cab duty cycle - fail earliest. A common repeat-failure trap is replacing only the primary cooler and leaving the second cooler in place, which sends the truck back in within tens of thousands of miles.
Common Symptoms
- Unexplained coolant loss
- White sweet-smelling exhaust smoke on warm restart or under throttle
- Rough cold start
- Overheating while towing
- Low coolant warning with no visible leak
How to Fix
Diagnose with a cooling system pressure test and by checking for exhaust gas in the coolant; do not assume a head gasket before checking the EGR coolers. Replace both cooler sections together, along with the EGR valve if it is fouled, and flush the cooling system. Inspect the passenger-side cylinder head at the same time, as it can be cracked on early 2011-2012 engines presenting with the same coolant loss. There is no recall for the EGR cooler; some trucks were covered under the 5-year/100,000-mile diesel powertrain warranty when new.
Sources for this issue (3)
On the 2003-2007 6.0L Power Stroke used in the F-350 Super Duty, the engine oil cooler is a stacked-plate unit with very small coolant passages that sits in the valley of the block. Casting sand left from block manufacture plus silicate dropout from degraded Ford Gold coolant progressively plug those passages. Once the oil cooler is restricted, coolant flow to the EGR cooler (which is fed downstream of the oil cooler) collapses, the EGR cooler boils its coolant locally and its core splits, dumping coolant into the intake. Industry write-ups and shop teardowns attribute roughly 90 percent of 6.0L EGR cooler failures to a plugged oil cooler upstream, which is why replacing only the EGR cooler produces repeat failures. On F-350s used for heavy fifth-wheel and gooseneck work the sustained high coolant temperatures accelerate the deposit process.
Common Symptoms
- Coolant level dropping with no external leak
- White sweet-smelling smoke from exhaust, especially at startup or under load
- Overheating while towing
- Low coolant warning light
- Oil temperature reading far above coolant temperature on scan tool
- Bubbling or pressurized degas bottle
How to Fix
Diagnose by measuring oil-temperature-to-coolant-temperature split with a scan tool: more than roughly 15 degrees F of spread under load indicates a restricted oil cooler. The correct repair replaces the oil cooler AND the EGR cooler together, flushes the cooling system thoroughly, and refills with the correct coolant. Ford released an updated round-tube stainless EGR cooler that survives far better than the original square-tube design. Many owners add a coolant filtration kit to trap remaining casting sand, or delete/relocate the EGR cooler where legal for off-road use. There is no recall covering this; it is a wear/design issue paid by the owner. Some trucks were covered under Ford's extended 6.0L service plans when new, but those have long expired.
Sources for this issue (3)
The Freestar uses Ford's differential pressure feedback EGR system, and it fails in a well-known pattern. The DPFE (EGR pressure feedback) sensor loses accuracy when its diaphragm weakens or moisture contaminates it, so the PCM commands more vacuum to the EGR valve and the engine runs poorly. Separately, the EGR passages under the plastic upper intake carbon up and physically restrict flow. The original DPFE hoses are a high-temperature type that crack or collapse internally from thermal cycling, which produces the same code. Because there are three independent causes, owners commonly replace one part, clear P0401, and have it return within weeks — this is the single most repeated repair loop on these vans.
Common Symptoms
- Check engine light with P0401
- Rough idle or stumble at light throttle
- Hesitation on acceleration
- Failed state emissions test
- Repeat return of the same code after a sensor replacement
How to Fix
Test DPFE voltage, inspect both high-temperature hoses, test the EVR solenoid and clean the intake EGR passages before ordering. The exact sensor, regulator and hose branches could not all be verified as a current purchasable fitment set, so no partial parts-swap link is approved.
Sources for this issue (3)
P0402 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0402 mean on a Ford?
P0402 stands for "Exhaust Gas Recirculation Flow Excessive." P0402 means the Exhaust Gas Recirculation (EGR) system is flowing too much exhaust back into the intake. The EGR system intentionally routes a small amount of inert exhaust gas into the engine to lower combustion temperatures and reduce nitrogen-oxide emissions, but the flow must be metered precisely. When the PCM determines the flow is excessive — often because the EGR valve is stuck open or letting gas through when it shouldn't — it sets this code. Too much EGR can cause rough idle, stalling, hesitation, and a check engine light. On Ford it is documented across 9 models: F-250 Super Duty, Crown Victoria, E-Series, F-350, Freestar, Escort, Bronco Sport, F-150, Explorer.
What are the most common causes of P0402?
The most common causes of P0402 are: EGR valve stuck open or not closing fully, Failed or sticking EGR valve diaphragm/solenoid, Carbon buildup holding the EGR valve open, Faulty EGR position or differential pressure (DPFE) sensor, Leaking EGR valve gasket or pintle seat, Vacuum control or solenoid fault commanding EGR open, Wiring or connector problems in the EGR control circuit. The specific cause varies by vehicle.
How much does it cost to fix P0402 on a Ford?
Published repair estimates on Ford range from $50 to $3,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0402 on a different make?
View P0402 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.