Exhaust Gas Recirculation Flow Insufficient
What it means
The EGR system, which routes some exhaust back into the intake to lower combustion temperature, is flowing too little.
Symptoms
Pinging/knock, rough idle, failed emissions test.
Common causes
Clogged EGR passages, stuck EGR valve, or a faulty EGR sensor.
Recommended action
Clean the EGR valve and passages of carbon; replace the valve if it is stuck.
Related codes
FAQ — P0401
What does code P0401 mean?
Exhaust Gas Recirculation Flow Insufficient. The EGR system, which routes some exhaust back into the intake to lower combustion temperature, is flowing too little.
What are the symptoms of P0401?
Pinging/knock, rough idle, failed emissions test.
What causes P0401?
Clogged EGR passages, stuck EGR valve, or a faulty EGR sensor.
What should I do about P0401?
Clean the EGR valve and passages of carbon; replace the valve if it is stuck.
General reference based on the SAE J2012 standard. Exact causes for your vehicle may differ — when in doubt, consult a workshop.
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