P0404 on Mercedes-Benz: How to Diagnose & Fix
Exhaust Gas Recirculation Circuit Range/Performance
1 Mercedes-Benz model · 1 documented issue · $550-$1,900 repair
P0404 on Mercedes-Benz by model: symptoms, diagnosis and fix
Sprinter diesels (OM642 V6 and OM651 4-cylinder) recirculate soot-laden exhaust through the EGR valve and cooler. Over tens of thousands of miles the valve and the cooler's small passages choke with hard carbon, causing the valve to stick, EGR flow to read out of range, rough running, power loss and limp mode. Short-trip/urban duty cycles accelerate the buildup. The cooler is often more clogged than the valve and frequently cannot be cleaned, requiring replacement.
Common Symptoms
- Reduced power / limp mode
- Rough idle
- Check engine light
- Hesitation under load
- Failed emissions test
How to Fix
Scan for EGR codes, then clean or replace the EGR valve and inspect the EGR cooler. A clogged cooler usually must be replaced rather than cleaned. Clear adaptation/fault codes after the repair. Periodic highway driving and quality low-ash diesel oil help slow recurrence.
Sources for this issue (2)
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 on a Mercedes-Benz?
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. On Mercedes-Benz it is documented across 1 model: Sprinter.
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 on a Mercedes-Benz?
Published repair estimates on Mercedes-Benz range from $550 to $1,900 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.
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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.