(Updated on April 20, 2020)
Every vehicle with an internal combustion engine contains an exhaust gas recirculation system, also known as an EGR system. The purpose of this system is to reduce the level of nitrogen oxide emissions which get produced during the combustion process of a gasoline engine or diesel engine.
Basically, when exhaust gas comes out of the engine after the combustion process, the EGR system will recirculate some of those gasses back into the cylinders of the engine. It is almost like recycling the gasses by reusing them for the next combustion.
If there is a problem with your EGR system, a mechanic can find out by scanning your power control module to see the exact issue that is going on with it.
If the computer tells the scanning tool that the issue pertains to trouble code P0401, this means the recirculation flow of your exhaust gas has been detected as being insufficient.
Hopefully, you are driving a car that will automatically give you this trouble code on your dashboard. If not, then you need to hire a mechanic to scan for the trouble code with their scanning tool.
Common Causes of a P0401 Trouble Code
Whether you drive a truck, sports utility vehicle, or a regular car, the EGR valve is eventually going to stick and get clogged. Other areas of the EGR system that may get clogged are its ports and passages too.
If these areas remain restricted, then gasses will not be able to flow properly. This would certainly cause the P0401 trouble code to be generated as a sign of this recirculation problem.
Other possible causes for this trouble code to occur include a faulty DPFE sensor, a catalytic converter that is clogged, EGR valve control circuit electrical issues, or a malfunctioning engine control unit.
Common Symptoms of a P0401 Trouble Code
If the flow of the exhaust gases cannot recirculate back into the engine’s cylinders adequately, then you will experience a variety of different symptoms that will impact your driving.
One of the worst symptoms is engine surging, which is when the RPM speed will fluctuate rapidly between the low hundreds and the low thousands.
Meanwhile, you may experience stalling, rough idle, or hear pinging noises or engine knocking. Weak engine performance is certainly something to be worried about in this situation. Your fuel economy will suffer as well, forcing you to spend more money at the gas pump.