DTC P0401 – How To Clean your Honda Accord EGR

The Exhaust Gas Recirculation system is a vital part of how your vehicle controls emissions, by recirculating some of the fuel and exhaust gases back into your engine. This is done through a EGR port and panel, that has openings or provisions in each port for each runner in your Accord intake manifold.

As your drive your Honda, this EGR system located on top of your intake manifold runners is always in action. By taking excess exhaust and unburnt fuel as well as other gasses created during the combustion cycle and re-routing them from your intake manifold back into your engine, you decrease your tailpipe emissions.

When your EGR valve, or the ports in your intake manifold that connect your 2.3 liter F23 Honda engine to the EGR system get clogged up or fail to open, your Honda ECU will trigger a P0401 error code. The specific wording for this OBDII diagnostic code is P0401 Insufficient EGR Flow. This is a sign that your intake manifold or your EGR panel or EGR valve has become clogged or is not working correctly.

Today we’ll be showing you how to clean your Honda Accord EGR system, and eliminate your OBDII DTC of P0401 in a 1998 Honda Accord. This vehicle is equipped with the F23 engine, although fixing this problem in a SOHC Accord is very similar across the board. The replacement EGR valve for your Honda Accord is Honda part number 18011-PAA-A00, and you can also find this unit under a Isuzu brand as 5862060090.

Typically there’s three kinds of conditions that can affect your Honda Accord EGR Valve. Any one of these issues will make your Accord ECU turn on the Check Engine Light or CEL and signify that your EGR has a problem with a P0401 code.

1. Accord EGR stuck open : When your EGR valve becomes stuck open, it’s either from EGR valve failure or contamination causing the valve to seat incorrectly. When this happens the EGR cannot regulate the gases re-entering your engine, and you can feel this in your vehicle pretty easily. Hesitation, surging or bucking under throttle are some very common issues.

Q – Why does my Accord surge or buck when I give it gas?

A – Because your EGR valve cannot seat and seal, it will adversely affect the engine as unburnt fuel and air can mix with your incoming air charge. This will result in a lack of clean burnable air that your engine can struggle to ignite.

2. Accord EGR stuck closed : Common when there’s an issue with your EGR wiring or the EGR valve just plain fails. This is a dangerous condition that will not only make your Accord run rough, but can potentially break or destroy your engine. Because the EGR valve is not opening, there’s an excess of combustion chamber blowby and your exhaust gas temperatures can rise.

This can cause your SOHC Accord engine to run extremely hot, and can cause pre-ignition or detonation. Failure to repair this condition can cause serious engine damage.

Luckily for you, both of these problems are easy to fix in your Honda Accord. The EGR valve is located in the image above, directly in front of your throttle body. Disconnect the EGR plug and undo the two nuts that secure the EGR valve to the intake manifold. Slide the EGR valve off cleanly and carefully, chances are your EGR valve gasket is completely wasted, so don’t bother trying to save it.

When you have remove and replace the EGR valve only, make sure to clean the surface of your intake manifold carefully. Provide a clean surface for your new EGR valve and Honda EGR valve gasket to mount to. A dirty or contaminated mounting surface could complicate matters further, and make you do the job over.

There does come times when you replace your Honda Accord EGR but the OBDII DTC P0401 doesn’t go away. This is when our how to clean your Honda Accord EGR DIY guide can help you fix the P0401 trouble code.

EGR Valve or passages clogged : The third condition for EGR valve failure, the process behind our DIY guide on how to clean your Honda Accord EGR, is not hard but time consuming. The EGR valve uses a plate and a built in passage system to deliver the combustion gases to the valve from the intake manifold runners. Over time and because of contaminants and carbon buildup, these passages can become clogged or even close completely.

Before you begin our how to clean your Honda Accord EGR DIY guide, it’s a good idea to disconnect the negative post on your battery. This will prevent any accidental electrical issues from arising when you are working on the car, as well as lessen the chance of any sparks that could ignite because your fuel rail must be removed.

If you are going to be cleaning the EGR plate and the passages in your intake manifold, you will need to locate your fuel pump relay or fuel pump fuse. Open your Honda Accord fusebox and remove the FUEL fuse, and then attempt to start your Honda Accord again. Your Accord should start and then promptly shut off.

This is because your fuel pump is no longer receiving power, and it’s an easy way to remove the existing fuel pressure in your F23 fuel rail.

Locate your PCV valve and gently unplug it from your Honda Accord valve cover. This connects to a PCV valve that must later be unplugged in our guide.

Once you have this PCV valve removed, unplug the solenoid and begin to unclip your fuel injector harnesses.

Now it’s time to undo the main fuel pressure damper, which is the oblong plastic covered unit shown above. Undo the fuel pressure damper, and carefully unscrew the damper. Make sure not to lose any of the gaskets or washers, or forget the orientation or how they mount onto your fuel rail.

Slide off the banjo fuel pressure line, and set to the side. Not to state the obvious but you shouldn’t be smoking right now, and your battery should be disconnected.

Next is the fuel pressure regulator, which is at the end of your Honda Accord fuel rail. There’s two 10mm bolts that hold this regulator in place, undo these bolts and carefully remove the fuel pressure regulator. Take a moment to locate your fuel pressure regulator o-ring, which is either stuck on your Honda Accord fuel rail, or still inside the fuel pressure regulator itself.

Now remove the three 10mm nuts that hold the fuel rail in place, because your fuel pressure lines and PCV lines have all been removed, your fuel rail should be able to lift up and out. If your throttle cables are getting in the way, don’t disconnect them from your throttle body, rather remove the 10mm bolts that hold the throttle cable bracket to your intake manifold.

Pull off your fuel rail and undo the 10mm bolts that hold the EGR plate in place. Carefully remove with your EGR valve as a complete assembly. Using brake cleaner or acetone, scrub the plate cleanly to remove all the extra carbon and deposits that have built up over the years.

Scrub the face of this EGR plate cleanly to ensure that your EGR valve receives the airflow it needs to operate correctly. The last leg of our how to clean your Honda Accord EGR will involve the use of a Shop Vac, and a pick to clean the EGR ports of your intake manifold.

There’s no real easy way to go about this procedure, unless you are willing to remove the intake manifold completely. Try to use your pick to break through the EGR ports which are probably clogged up pretty good. Once you have an opening, use your shop vac to try and suck up as much material and carbon as possible.

As stated previously, there’s no real way to avoid carbon from falling into your combustion chamber, but if you take it nice and slow you should have clean EGR ports to remount your SOHC Honda EGR plate and valve to.

Once you have cleaned all the necessary EGR parts, go ahead and reinstall to complete our how to clean your Honda Accord EGR guide. Use a scan tool or a device like the HKS OB Link to clear your OBDII trouble code, and you are good to go!

Have any questions about our how to clean your Honda Accord EGR guide? Leave them for us below!