What Does Engine Code P0401 Mean?

If your car is showing the P0401 engine code, you’re dealing with an insufficient exhaust gas recirculation flow.
Written by Rob Shapiro
Reviewed by Melanie Reiff
If a P0401 engine code is showing for your car, then an exhaust gas recirculation flow insufficient has been detected. This can be rather serious and should be diagnosed and repaired immediately.
The role of diagnostic trouble codes (DTC) is to identify specific issues within a car’s engine. It’s good to have an understanding of what these engine codes mean to ensure your car is safe to drive and to avoid costly repairs.
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What does the engine code P0401 mean?

Definition: Exhaust gas recirculation flow insufficient detected
This engine code means that the car’s computer has detected insufficient exhaust gas recirculation (EGR) flow in the system.

How much will it cost to fix?

To diagnose this problem, a mechanic typically needs about one hour of labor. Most auto shops charge between $75 and $150 per hour, so this cost depends on where you take your car to be serviced. 
Total repair costs should fall in the $150 to $750 range, including parts and labor. 

What can cause the P0401 engine code?

Insufficient exhaust gas recirculation flow could be the result of the following issues with your engine:
  • A clogged EGR passage
  • A faulty EGR vacuum modulator valve
  • A faulty EGR valve
  • A faulty EGR solenoid valve harness is open or shorted
  • An EGR solenoid valve circuit with poor electrical connection
  • A dead or weak battery
  • A faulty EGR  temperature sensor and circuit
  • An exhaust gas leak

Common symptoms of the P0401 engine code

This engine code shows when low EGR flow control is detected. Two possible symptoms that can come from it are:
  • Engine light on (or service engine soon warning light)
  • Engine hesitation

How serious is the P0401 engine code?

P0401 engine code is rather serious and should be repaired as soon as possible. A faulty EGR valve can cause ignition pre-ignition in the engine, potentially damaging the valves and pistons.

Can I fix the P0401 engine code myself?

If you are comfortable with auto repair then you can fix this problem yourself. Start by performing a diagnostic to identify the exact problem:
  • Visually inspect the wiring harness and connectors
  • Look for components that may be damaged or if the connector’s pins are broken, bent, pushed out, or corroded
The next step is to repair the P0401 engine code:
  • Replace the clogged or leaking EGR valve
  • Replace the broken vacuum line that runs from the EGR valve to the control solenoid
  • Replace an EGR temperature sensor (or clean any carbon on it) if you find that it is not properly registering the temperature change. 
  • Clear any blockages by cleaning the carbon out of the EGR tubes to the intake manifold.

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