P0401: insufficient EGR flow
The EGR system is passing less exhaust gas than expected. It is not urgent for safety, but have it checked, because it can affect emissions, performance and fuel consumption.
Can you keep driving?
Yes. It is not urgent for safety, but have it checked.
What the code means
EGR routes a small amount of exhaust back into the engine to reduce emissions. The passages are narrow, and they block with soot over time.
Common causes
- A blocked EGR passage
- An EGR valve stuck with soot deposits
- A faulty valve or its control
What to do now
- Note whether the car is used mostly for short trips. Soot loves them.
- Ask for the valve to be cleaned and assessed before it is replaced.
- Now and then, take a longer run at a steady speed.
What people often get wrong
That P0401 means a faulty valve. Often the valve is fine but stuck in soot, and a clean solves it.
When the car must go to a workshop
Cleaning is often enough, and considerably cheaper than a new valve. Ask for that to be tried first.
Read next
- P2002: the particulate filter is not cleaning properly
- P0455 and P0442: a leak in the EVAP system
- P0128: the thermostat is stuck open
This page is general information and does not replace a professional assessment. Symbols, codes and behaviour vary between makes. Always check the handbook for your own car.
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