P0401 - Exhaust Gas Recirculation (EGR) Flow Insufficient Detected
Plain-English meaning
The engine control module (ECM) has detected that the flow of exhaust gases through the EGR system is less than expected during operation.
What to check first
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What not to replace yet
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Stop driving when
Generally safe to drive with this code, but if engine performance severely degrades or stalling occurs, have the vehicle inspected promptly.
Related symptoms
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Owner steps
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Likely causes
Clogged or blocked EGR valve or passages (medium)
Faulty or stuck EGR valve (medium)
Vacuum leaks affecting EGR operation (for vacuum-controlled systems) (medium)
Faulty EGR solenoid or control circuit (medium)
Malfunctioning EGR position sensor (medium)
Wiring or connector issues in EGR system (medium)
Faulty engine coolant temperature sensor causing incorrect EGR operation (medium)
Shop steps
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Follow-up questions
Has the vehicle experienced any recent performance issues such as rough idle or hesitation?
Is the Check Engine Light steady or flashing?
Have any recent repairs been made to the intake or exhaust system?
Are there any other diagnostic trouble codes present?
Has the vehicle had regular maintenance including air filter and oil changes?