2009 Mercedes-Benz P0401: What It Means & Is It Safe to Drive?
P0401 on the 2009 Mercedes-Benz: Exhaust Gas Recirculation Flow Insufficient. Here's what it means, what usually causes it, what repairs typically cost, and whether it's safe to keep driving.
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What this code means
The EGR system is not flowing enough exhaust gas. Usually due to carbon buildup or a stuck valve.
Common causes on the 2009 Mercedes-Benz
- Carbon-clogged EGR valve or passages
- Faulty EGR valve
- Faulty EGR position or differential pressure sensor
Symptoms
- Check Engine Light
- Rough idle, hesitation
- Knock under acceleration
Typical fixes
- Clean or replace EGR valve
- Clean EGR passages in intake
- Replace EGR sensor if applicable
Repair cost range
For a 2009 Mercedes-Benz, repairs for P0401 typically fall between $150 and $600, depending on the root cause and labor rates in your area.
Known issues on Mercedes-Benz
Mercedes diesel OM651 P0401 typically indicates a clogged EGR cooler or stuck EGR valve. The OM651's EGR cooler is prone to cracking and coolant contamination past 100k miles—confirm no coolant loss before just cleaning the EGR valve. On petrol M272/M273, P0401 is uncommon.
Most commonly affected models
C220 CDI OM651 2008–2015E250 CDI OM651 2009–2015GLK250 CDI 2012–2015