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The Powertrain Control Module (PCM) monitors the Exhaust Gas Recirculation (EGR) valve pintle position input to ensure that the valve responds properly to commands from the PCM. When the ignition switch is turned ON, the PCM learns the EGR learned minimum position. The PCM compares the EGR learned minimum position to the EGR position sensor when the EGR valve is commanded closed. If the EGR position sensor indicates that the EGR valve is still open when the PCM is commanding the EGR valve closed, this DTC will set.
A scan tool that is capable of commanding the EGR circuits on and off is required to verify EGR performance and sensor feedback voltages at the PCM. However, this code is USUALLY caused by carbon getting stuck in the EGR pintle and holding it open. A good cleaning is usually all that is required to fix this.
You will need an EGR gasket. Remove the EGR valve and inspect the ports for heavy carbon deposits. These deposits can usually be cleaned out using screwdrivers and a piece of mechanics wire to break the carbon loose and some carb and choke cleaner to finish the clean-up. A wire brush and some carb cleaner usually works for the EGR valve itself. Once the ports and the valve are clean, re-install the valve using the new gasket. Clear the codes and drive the vehicle to see if the problem is fixed. Please note that the EGR monitor runs at speeds over 50 Mph. during deceleration, so you need to get the vehicle on the highway for a valid test of the EGR system.
If the Check Engine light does not come on during the road test, Connect a code reader and check the OBD readiness monitors. If the EGR monitor says "complete" and there are no codes in the computer, then you have done a successful repair.
Exhaust gas recirculation - when your car is at running temperature it runs lean. A lean running engine has very hot ignition temperatures. This not only risks burning the valves but it also creates the ideal conditions for nitrogen to combine with oxygen; nitrous oxides are harmful emissions and are to be avoided. The EGR valve recirculates a metered amount of inert exhaust gas back into the inlet mix and artificially enriching the mix by effectively reducing the amount of oxygen. The engine ignition runs much cooler as a result, cool enough to avoid oxides of nitrogen from forming.
The EGR valve sits between the inlet and exhaust manifolds. The EGR valve is most often opened electrically by the ECU when the engine is above idle at about 3000 rpm. The operation of the EGR is monitored by a DPFE sensor which measures pressure variation brought about by the opening of the EGR valve.
The EGR valve is bolted on with two bolts and has an electrical connection to the top of it. Dismantle the EGR valve taking car not to damage the gasket as you can reuse it. Use plenty of WD40 or carburettor cleaner and clean the EGR pintle valve until like new and has full freedom of movement. Make sure the ports are clean before reassembly. That should be it unless the solenoid mechanism within the valve has burnt out in which case it will need replacing.
P0401: Isufficient Flow Detected in EGR system.
-clean the EGR port with the carburetor cleaner.
-clean the EGR passage inside the EGR valve with the caburetor cleaner.
Reset the light, if the light still coming back, then replace the EGR valve.
EGR stands for Exhaust Gas Recirculation. It is part of the vehicle emmissions system, and is used to reduce combustion temperature and pressure to control Oxides of Nitrogen. There are generally three parts to the EGR system: the EGR valve, an actuator solenoid, and a differential pressure sensor EGR (DPFE). These things work together to deliver the correct amount of recirculation based on engine temperature, load, etc. The P0401 code means that OBD detected an insufficient amount of EGR.
You may notice drivability problems such as pinging (a.k.a. pre-ignition knock) when the engine is under load or the vehicle is at higher speeds. There may also be other symptoms. Causes
A code P0401 most likely means one or more of the following has happened:
* The DPFE (differential pressure feedback EGR) sensor is faulty and needs to be replaced * There is a blockage in the EGR (tube), most likely carbon buildup * The EGR valve is faulty * The EGR valve may not be opening due to a lack of vaccuum
Possible Solutions
In fixing this code, it is quite common for people to just replace the EGR valve only to have the OBD code return. The EGR valve is not always the culprit.
* Use a vacuum pump and pull the EGR valve open while monitoring engine RPM's & DPFE voltage. There should be a noticable difference in RPM's with the EGR open * Clean out the EGR valve and/or tubing to remove deposits * Check the voltage at the DPFE, compare to specified values (refer to a repair manual for your specific model) * Replace the DPFE sensor (with a good quality / OEM one) * Replace the EGR valve
Yes, take it back. The might of replaced the Egr valve to turn off the light. Don't let them charge you for retesting it, that's why you took it in in the first place.
Your EGR valve shouldn't open up during idle or the engine will run rough and may even stall. Remove it and clean the plunger and port with a wire brush and some carb cleaner. Test the diaphragm with a vacuum pump. If it doesn't work after cleaning, or the diaphragm is bad, buy a new EGR valve.
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