trouble code P0401 EGR flow insufficiant?
- Thread starter motoloco
- Start date
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thanks
That is the most common CEL code and there are lots of threads discussing it. In general, it is not a considered to be a serious code but your CEL light will keep comming on and some day it may be something more serious and you will think that it is just the P0401. Your gas mileage will most likely drop 1 or 2 mpg. Also, if your EGR modulator is bad, there is a chance that you will leak carbon into your intake and fowl things up. For starters pop the top off the EGR modulator and see if the white filter thing is black. If so, your modulator is most likely bad and you are leaking carbon. If you do the work yourself, you can most likely fix it for under $100. With the price of gas, it will pay for itself. From my research of this issue, most cases point to either a bad modulator or a VSV that is stuck open. You may want to check the simple thigs first like leaking or plugged vacuum lines, ports that are plugged etc.
I just checked my modulator, and it's not black, but it's grayish, I have a picture, it's underneath the shadow of my hood, and it's taken with a cell phone camera, but is it possible I need a new one?
Here's a link to the picture of mine. Right hurr.
http://i68.photobucket.com/albums/i5/screamingorangejuice/Photo0293.jpg
Here's a link to the picture of mine. Right hurr.
http://i68.photobucket.com/albums/i5/screamingorangejuice/Photo0293.jpg
Here is a thread with a picture of a bad and leaking modulator. Even if it is clean, it may still be bad. The FSM has a prodedure for testing it.
https://forum.ih8mud.com/showthread.php?t=12498
Below, is a thread that shows some VSV troubleshooting. The third to the last picture shows the vacuum line going from the EGR valve to the manifold. This is connected to the VSV on the other side of the manifold. The VSV closes causing the vacuum to open the EGR valve which causes exhaust gas to flow. Here is what I did to troubleshoot mine. Get the engine hot. Feel the metal tube on the bortom of the EGR valve. This is where the exhaust gas enters into the system. It should be slightly warm if exhaust gas is not flowing, otherwise it will be really hot, so touch with caution. Pull the vacuum line off T connector on the EGR valve on the side that goes down to the manilfold in the picture reffered to above. Plug the Open end of the T connector with your finger. This is the same as the VSV closing and should cause the EGR to flow. With the T connector plugged, Rev the engine for about 10-20 seconds. Feel the metal tube again. If it is a lot hotter, the chances are that your VSV is stuck open. If that is the case, the VSV is about $75. The good news is that it is easy to replace without removing the intake plenum. There are theads showing the use of a 3' extension to remove the bolt.
https://forum.ih8mud.com/showthread.php?t=111750
https://forum.ih8mud.com/showthread.php?t=12498
Below, is a thread that shows some VSV troubleshooting. The third to the last picture shows the vacuum line going from the EGR valve to the manifold. This is connected to the VSV on the other side of the manifold. The VSV closes causing the vacuum to open the EGR valve which causes exhaust gas to flow. Here is what I did to troubleshoot mine. Get the engine hot. Feel the metal tube on the bortom of the EGR valve. This is where the exhaust gas enters into the system. It should be slightly warm if exhaust gas is not flowing, otherwise it will be really hot, so touch with caution. Pull the vacuum line off T connector on the EGR valve on the side that goes down to the manilfold in the picture reffered to above. Plug the Open end of the T connector with your finger. This is the same as the VSV closing and should cause the EGR to flow. With the T connector plugged, Rev the engine for about 10-20 seconds. Feel the metal tube again. If it is a lot hotter, the chances are that your VSV is stuck open. If that is the case, the VSV is about $75. The good news is that it is easy to replace without removing the intake plenum. There are theads showing the use of a 3' extension to remove the bolt.
https://forum.ih8mud.com/showthread.php?t=111750