Trouble Codes

P0401 Exhaust gas recirculation system – insufficient flow detected

błąd p0401 code

OBD2 error P0401 possible causes

The reasons that may lead to the establishment of code P0401 may be as follows:

  • EGR channel clogging
  • Defective EGR vacuum modulator valve
  • Defective EGR valve
  • The electrovalve beam of the EGR system is open or closed
  • EGR solenoid valve circuit weak electrical connection
  • Weak battery
  • Defective EGR position sensor
  • Exhaust gas leaks
    a faulty ECM controller should be remembered that this is a rare event and the fault should be looked for elsewhere before replacing the control module

Technical notes

A malfunction in the EGR flow can be caused by a clogged EGR valve or EGR pipe. Try to clean the valve, pipe and EGR channels before replacing any parts.


When will the code be detected?

A low exhaust gas flow in the EGR valve was detected

P0401 Description

Exhaust gas recirculation (EGR) components include an EGR valve and an engine controlled valve (ECΜ) with an adjustable vacuum valve or an EGR electrovalve and an EGR vacuum modulator. Depending on the engine and driving conditions, the ECΜ will control the EGR solenoid valve, which will control the EGR vacuum modulator to regulate the opening and closing of the EGR valve. The EGR system in new vehicles uses a stepper motor to control the EGR flow rate from the exhaust manifold. This engine has four operating phases. It operates according to the ECΜ pulse output signal. The two windings are switched on and off in turn. Each time an ON pulse is generated, the valve opens or closes, changing the flow rate. When no change in flow rate is required, the ECΜ does not give a pulse signal. Α a specific voltage signal is given so that the valve remains in that particular position.

What are the symptoms of code P0401?
Some typical symptoms of code P0401 may include:

  • A stored fault code and possibly an illuminated warning light
  • Depending on the type of EGR valve installed in the application, there may be additional codes with P0401
  • Some applications may show a deep “knock” when accelerating
  • In some applications, there may not be any symptoms other than the stored code and warning light.
  • Fuel consumption may increase in some applications
  • The vehicle may fail the emission test because of high levels of nitric oxide in the exhaust gas

What are typical solutions for P0401 code?
The most common solutions for P0401 may include:

  • Replacing clogged EGR valves
  • Checking and repairing faulty cabling
  • Inspection and repair of vacuum control systems
  • Removing clogged EGR channels in the manifold and sometimes in the cylinder heads

How serious is code P0401?
Code P0401 should be considered serious because the combination of high combustion and pre-ignition temperatures (knocking or pinging – if any) can cause serious damage to pistons and valves over an extended period of time. The code should therefore be resolved on time.