What does code P0401 mean? Find the reasons for this and find out how to fix this engine test code from a mechanic who has done this countless times.
This DTC “insufficient EGR flow” indicates that there is not enough exhaust gas returning back to the engine air. EGR means “exhaust gas recirculation.” The exhaust gas recirculation system consists of three parts: the exhaust gas recirculation valve, DPFE (EGR differential pressure sensor) and the actuator solenoid valve.
Automakers have created this system so that already burnt exhaust gas can flow back into the engine (when the EGR valve is open) and lower the combustion temperature. This helps reduce emissions.
This OBD code basically means that the car computer tried to open the exhaust gas recirculation valve, but it could not get enough exhaust gas into the engine. Exhaust gas recirculation systems were controlled by engine vacuum through hoses and valves. Now most of them are driven by electric solenoids.
• Exhaust Gas Recirculation Valve
• Locked EGR passages
• EGR control (No or Low Vacuum)
• Faulty solenoid or wiring
Less common causes
• Cars Computer
• DPFE valve (pressure feedback check valve)
• Modulator valve
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How to fix engine code P0401
Each car manufacturer has its own design of the exhaust gas recirculation system, but the most likely two reasons for this code are the valve itself or the passages (in many cases the intake manifold will have very small passages that are clogged with soot) through which the exhaust gases pass.
In many cases, this code is caused by clogged EGR channels, and sometimes removing the sensor will give you access to clogged EGR channels.
Another thing you can do yourself is check all the vacuum hoses and all the wiring going to the EGR valve. You could find a hose with a hole in it, or you could find a connector that is not fully seated, or some wiring that has been rubbed.
This trouble code is more difficult to diagnose mechanics if you do not have good experience and special tools. Many times this code will disappear if you replace the exhaust gas recirculation valve (but not always). If you do not have the skills or patience to diagnose this problem, you can try to do this and simply replace the exhaust gas recirculation valve.
If you have any unsolved problems with the car or questions, you can contact an auto mechanic online. For expert answers regarding the make and model of your car, I recommend JustAnswer Car. They have a large pool of certified mechanics to answer your questions for a small fee, and you can also view their answers to other users for free.
