Question about 2002 Honda Accord
Insufficient EGR Flow
What does that mean?
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.
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
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
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Posted on Sep 07, 2010
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Posted on Jan 02, 2017
The DPFE is located near the EGR valve, it has 2 very thick silicone rubber hoses connected to it that come off the exhaust. It is rectangular and about 1/2 the size of a pack of smokes
Posted on Nov 12, 2008
Does the egr vavle open ? You will need to use a scanner to test the dpfe voltage when the egr valve is energized you should read around 3.5 4.00 volts. Also you could remove the vacume line from the egr valve and with the engine running you should see around 100 rpm drop in engine rpm at least this would indicate the egr valve is capable of flowing egr gases through the system to the cylinders.
Posted on May 30, 2010
DPFE is a reasonable concern. There is also a very thin tube from the EGR to the DPFE that plugs up with carbon. Check the tube prior to the DPFE.
Posted on Feb 24, 2010
when you maunally open the egr valve does the engine run rough? it should. if it does not then you need to clean out the EGR passages. You have replaced a lot of parts that were good.
Posted on Sep 01, 2011
Tips for a great answer:
Nov 04, 2012 | 2003 Hyundai Santa Fe
Jul 11, 2012 | 2001 Ford Windstar
Feb 25, 2012 | 2002 Ford Focus
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
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