P0401 - EXHAUST GAS RECIRCULATION FLOW INSUFFICIENT DETECTED

The EGR (Exhaust Gas Recirculation Valve) is part of the vehicle emissions system. Its function is to reduce the combustion temperature, as well as the pressure to control the NO (Nitrogen Oxides).

In general, this system has three parts which are: The EGR valve, a solenoid drive and a Differential Pressure Feedback Sensor (DPEF). All these components work together to deliver the amount of recirculation that is needed. This delivery is based on the temperature and the load of the motor. When the fault code P0401 OBD2 is established, it indicates that the amount of recirculation has been detected to be insufficient.

• Check Engine service light turns on.
• The engine may hit when you accelerate.

The problems that can lead to the establishment of P0401 code can be:

• The DPEF sensor (Differential Pressure Feedback Sensor) may be defective.
• Perhaps an EGR system pipe is clogged by carbon buildup and, therefore, does not allow the necessary flow of exhaust gases into the manifold.
• EGR valve may not open due to lack of vacuum.
• It is possible that the Exhaust Gas Recirculation Valve is defective.

• In general, the solution to this diagnostic code is the replacement of the EGR valve, but it must be taken into account that there are times when this is not the main culprit when establishing this DTC code. So before making the change of this valve you can do the following:
• With the help of a vacuum pump, pull the Exhaust Gas Recirculation Valve (EGR) and observe the engine RPM as well as the DPEF sensor voltage (Differential Pressure Feedback Sensor). There must be a difference between the RPM with respect to the EGR valve when it is open.
• You can clean the Exhaust Gas Recirculation (EGR) valve and even your pipes.
• Check the voltage of the Differential Pressure Feedback Sensor (DPEF) and compare it with the factory specifications. You can replace it if you notice any inconsistency.