P0404: How to Diagnose & Fix — Exhaust Gas Recirculation Circuit Range/Performance
19 vehicles · 13 makes · $20-$3,500 repair
How to diagnose and fix P0404: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Ford F-250 Super Duty · 2011–2019
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 and restricts exhaust gas flow through the cooler core, and a cooler that overheats can 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 TSB 13-6-5 (superseding 12-6-14) covers 2011-2012 6.7L trucks with DTC P0401 and P2457, calling for EGR cooler core replacement under normal New Vehicle Limited Warranty coverage. 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+). For 2011-2012 trucks with DTC P0401 (Insufficient EGR Flow) and P2457 (EGR Cooler Performance), Ford TSB 13-6-5 applies; coverage follows the truck's normal warranty, so have a Ford dealer check the VIN. 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 (2)
GMC Sierra 2500HD · 2011–2016
The LML Duramax EGR (exhaust gas recirculation) cooler is prone to coolant leaks internally, allowing coolant to enter the intake manifold and combustion chambers. Coolant in the intake causes white smoke, rough running, and potential hydrolocking of cylinders. The EGR valve also sticks open or closed from carbon buildup, causing rough idle, black smoke, and check engine lights. The EGR cooler failure can occur as early as 60,000 miles on trucks used in stop-and-go driving. GM issued multiple TSBs addressing EGR cooler design improvements.
Common Symptoms
- White smoke from exhaust especially on startup
- Coolant loss with no visible external leak
- Rough idle or engine misfire
- Check engine light with EGR codes (P0401, P0404)
- Coolant smell from exhaust
- Overheating or coolant in oil (severe cases)
- Black smoke and poor fuel economy (EGR valve stuck open)
How to Fix
Replace EGR cooler with updated GM design or aftermarket stainless steel unit (Mishimoto MMEGR-DMAX-LML). Clean or replace EGR valve. Flush cooling system and inspect for coolant contamination in intake. Consider EGR delete kit for off-road/race use only (illegal for street use). Prevent premature failure by maintaining proper coolant pH and avoiding extended idle periods.
Sources for this issue (1)
GMC Sierra 3500HD · 2008–2016
The exhaust gas recirculation cooler on 6.6L Duramax LMM and LML engines is prone to internal cracking, allowing coolant to enter the EGR system and combustion chamber. Owners experience white steam from the exhaust, unexplained coolant loss, and in severe cases hydrolocking. This is a well-documented failure mode covered under extended warranty campaigns and referenced in NHTSA complaint database for 2008–2016 model years.
Common Symptoms
- White or grey smoke from exhaust at idle or under load
- Unexplained coolant loss without visible external leak
- Coolant smell from exhaust or air intake
- Engine overheating or coolant temperature fluctuations
- Milky residue in coolant reservoir or degas bottle
How to Fix
Replace EGR cooler assembly (GM part 98010538 for LML, or ACDelco 12642878 for LMM) and thoroughly flush cooling system. Inspect EGR valve for carbon buildup and replace if necessary. Upgraded aftermarket EGR coolers (Fleece Performance, BorgWarner) offer improved durability. Labor is 4–8 hours; coolant flush and fill required.
Sources for this issue (1)
Chrysler Crossfire · 2004–2008
Ford Escape · 2025–2025
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P0404 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 P0404 mean?
P0404 stands for "Exhaust Gas Recirculation Circuit Range/Performance." This code means the exhaust gas recirculation (EGR) system isn't performing within its expected range. The EGR valve routes a metered amount of exhaust gas back into the intake to lower combustion temperatures and reduce nitrogen-oxide emissions, and the computer monitors the valve's actual position versus what it commanded. When the valve sticks, moves incorrectly, or the feedback doesn't match the command, P0404 sets. This can cause rough idle, hesitation, pinging, and increased emissions.
What are the most common causes of P0404?
The most common causes of P0404 are: Carbon buildup clogging the EGR valve or passages, Sticking or failed EGR valve, Faulty EGR position sensor, Corroded or loose EGR connector, Damaged or shorted EGR wiring, Vacuum leak or failed vacuum control (on vacuum-operated systems), Clogged EGR cooler or tubes, Faulty PCM/ECM (rare). The specific cause varies by vehicle.
How much does it cost to fix P0404?
Repair costs for P0404 range from $20 to $3,500, depending on the vehicle and root cause.
Which vehicles are affected by P0404?
Au7o has documented P0404 across 19 vehicle models from 13 manufacturers: Chevrolet, Chrysler, Ford, GMC, Lincoln, Mercedes-Benz, Mitsubishi, Opel, RAM, SEAT, Saturn, Skoda, Volkswagen.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.