What does code P0401 mean on a Mercedes-Benz and is it safe to drive?
P0401: Exhaust Gas Recirculation Flow Insufficient. Here's what it means on your Mercedes-Benz, what usually causes it, what repairs typically cost, and how safe it is to keep driving.
What this code means
The EGR system is not flowing enough exhaust gas. Usually due to carbon buildup or a stuck valve.
Common causes for your 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 Mercedes-Benz, repairs for P0401 often fall between $150 and $600, depending on the cause and whether you use OEM or aftermarket parts. Labor rates vary by location.
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