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Old 06-04-2011, 10:53 AM   #1
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Join Date: May 2011
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Location: Charlotte, NC
What I Drive: 2003, green, Focus ZTW

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Solving the P0401 OBD Trouble Code

EGR Insufficient flow - or better known as the P0401 code - the code from hell! Just what is it and how can you fix it? It seems that this trouble code gives more headaches than anything else! Here is what I did and solved the problem:

2.0L 2003 ZTW, 118,000 miles, no major issues.....well, until this OBD code broke my dream! When this code strikes you, you might as well change everything that can be changed. Sometimes spending a few bucks will save you LOTS of headaches!

1. EGR Valve (~$50.)
2. DPFE Sensor (~27.)
3. Solenoid (~30.)
4. Replace all vacuum hoses (~$5.) for 10 feet of vacuum line - can also use it for you wiper lines.
5. get another EGR valve gasket (~$2.) trust me - you will need it.
6. Can spray carb cleaner (~$3.)
7. Toothbrush
8. A long flexible brush - WalMart ~$5. In the houseware section, and is used to clean bathroom drains. Yes, that's right!
9. A can of Deep Creep to clean the throttle body (~$8.)
10. A can of MAF spray cleaner (Mass Air Flow) (~$8.)
11. A can of spray QD Electronic Cleaner (~$7.)

I removed the old EGR valve and tossed it. Some say that the EGR rarely goes bad, but I think that you might as well replace if you can and avoid headaches. That valve gets alot of carbon built up and you just can't clean it good enough. The DPFE Sensor tends to get filled with water from condensation over time. R & R and that is that. The sensor next to it gets problematic as well, and it is not very expensive either. Replace the vacuum hoses form the DPFE sensor (2) that go to the EGR tube assembly. Doing that will close the possibility of crackes or holes in the vaccuum line for that area. While everything is open, replace the vacuum lines that go from the egr valve to the solenoid and trace the other line to the side of the engine and make sure that there are no breaks, cuts, or tears in the line, and that connectrions are solid. If so, replace the lines. You do not need to go to Ford for that thin plastic-like line assembly either, as you can keep the old assembly and cut a piece of vacuum hose and fit and connect the two pieces of cut plastic like line with a piece of vacuum hose. Works like a charm, and restores any lost vacuum. Use a little olive oil on the plastic hose ends and feed them into the new vacuum line.

Next, you will need to clean out the EGR tube that runs from the EGR valve you removed to the throttle body entrance. This is where you will pop the code because the carbon in the tube causes the insufficient flow. Take the carb cleaner and spray the tube form the valve side. Take that long brush and feed it in the tube - don't worry, it wont come apart in the tube - and push it in and out to clean the tube. Spray it again and leave it sit overnight. Take the Deep Creep spray and spray inside the throttle body and use the toothbrush to scrub. Please DO NOT let go of the toothbrush! You will be able to retrieve it, but it will be a hassle for ya! About 4" into the throttle body, the EGR Tube enters. Scrub that area as well to get the carbon buildup broken apart. The deep creep will do a good job here. Make sure that you also place a clean shop rag over the throttle body entrance as well. The next day you can spray more cleaner and do more scrubbing. It won't hurt. When you eventually do start the car, expect white smoke as the deep creep burns off - it won't hurt.

Another thing to expect is a good amount of Carb Cleaner to be collected on the throttle body floor - quite a bit. What I did was to use a clean old T-shirt cut into a long strip and feed it into the throttle body using a long thin screwdriver to soak up the excess cleaner. Take your time doing this, so you do not leave any material behind.

Now, clean the MAF Sensor using the spray. You can take it apart easily from the air intake duct by removing the 2 screws after you disconnect the airflow sensor wiring plug. DO NOT TOUCH the filament as it is very fragile. Use the MAF spray cleaner and spray the bejeses out of it and let it dry. That is pretty much all you have to do to it. After it is dry, replace it. And while you are there, use the QD Electronic Cleaner to clean your electrical connection plugs. It's great stuff, and dries quickly. Before you plug connections together, use a bit of dielectric grease on the plugs to improve connectivity.

When you are finished, replace the gasket for the EGR valve (use a bit of Anti-sieze on it) and secure the EGR valve - BUT FIRST make sure that you attach and secure the connection to the bottom of the EGR valve to the tube. Hey, people forget this and the problem code will persist! Secure all of your connections, and clean all tools from the engine compartment.

You will not have to reset the computer, as it will do it itself after 2 drive cycles. Drive the car ~60 miles, let it cool overnight and drive it again. The check engine ligt will (should) go off, or already be off.

The whole issue here is the carbon buildup that happens over time. So, clean the carbon deposits, and say good-bye to the P-code!

Now, find your friends, your girlfriend, go out, listen to the , drink some , and party - you deserve it! Oh, and don't drive that want to stay alive to enjoy the car after all of that hard work!

Best to all....DDay7
I am learning how to post photos, and will add to this as soon as I have a handle on that!

Last edited by DDay7; 06-04-2011 at 11:02 AM. Reason: additions
DDay7 is offline  
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