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Common codes
P0420P0300P0171P0455P0442P0128P0401P0113

P0401: Exhaust gas recirculation flow insufficient

Drive carefully. Get it checked within a week or two.

Can I drive with P0401?

Yes, but drive carefully and get it checked soon. Clogged passages prevent exhaust gas recirculation, raising combustion heat and NOx emissions.

What does P0401 mean?

P0401 stands for Exhaust Gas Recirculation Flow Insufficient Detected.

Symptoms you may notice

  • Spark knock (pinging or rattling) when accelerating uphill
  • Rough, stumbling idle if valve is stuck open
  • Slight drop in fuel efficiency

How much does it cost to fix?

Repair costs for code P0401 depend on the specific underlying root cause, ranging from simple DIY checks to component replacement. The table below lists the most common causes and rough price ranges in USD:

  • Carbon buildup clogging the EGR ports or tube
    $30-$100 common
  • Defective EGR valve or vacuum modulator
    $90-$260 common
  • Faulty EGR differential pressure (DPFE) sensor
    $40-$110 possible
  • Cracked or severed rubber vacuum hose
    $15-$40 rare

What to do next

  1. Remove the EGR valve and scrape carbon deposits out of the intake manifold ports.
  2. Check vacuum hoses feeding the EGR solenoid for deterioration.
  3. Test the EGR valve diaphragm or electric stepper motor.
Last updated: October 2026

Related codes

P0402 P0171 P0420
General guidance only, not a professional diagnosis. If the check-engine light is flashing, or the car is running rough, overheating or losing power, stop driving and get help.

About this code

Code P0401 means the engine computer commanded the EGR valve to open but did not detect the expected drop in intake vacuum or temperature change. Exhaust gas recirculation cools peak cylinder temperatures to eliminate harmful nitrogen oxides. Driving with this code is generally safe in the short term, but prolonged pinging under load can stress pistons.