Intermittent P0401 EGR Code

So my 2010 Jetta Sedan is throwing a p0401 code every so often. It comes on for a few hundred miles, then at a restart may go off for a few hundred, then come on again during driving. I've pulled the EGR Valve (between the TB and the head) and cleaned it, it was a little gunky but not too bad. CEL came back on and has behaved with the same intermittent behavior.

So I thought I was pretty clever pulling and cleaning the EGR, but no dice.... anyone have some suggestions. If you can explain how the EGR works and the components that would be great too. Is there a filter?

Thanks!

so I found a little info on the forums.... I think I cleaned the high pressure EGR valve.... Is it possible that the other EGR valve or the EGR cooler is clogged up?

Replace dpf and egr filter common problem covered under warrenty.

Can someone point out where each of these valves is located? A few pics would be great, but a general description will do.

86K miles, not under warranty. How do I know the DPF is the problem? Where is the EGR filter - I don't see the filter on the schematic....?

I've had the "check engine" light come on a few times. At the third time, a friend of mine pulled the code, and it was the infamous P0401 code. The fourth time occurred just recently -- the time in between has become shorter -- and it started to bother me.

So, I took my car in today to the dealer. A little irritated that it was going to be initially $125 out of pocket for diagnosis if the repair wasn't covered under warranty. After a few hours, they said that they are going to replace the DPF and EGR intercooler and clean the valve.

They have my car now. This is the second major warranty repair, as I also had the HPFP fail on me.

I guess it might not be the EGR itself. I have heard that the DPF failing may cause everything to be clogged.

I was advised not to continue driving the car as a fire may be possible -- don't know if that's true. But, something to consider, as it is a big safety issue. I will probably contact the NHSTA lawyer who I spoke with regarding my HPFP.

So a lot of people get this problem and I'm wondering does anyone sell an EGR delete?

I'm guessing this would be a blockoff plate(s) and you'd need to tweak the ECU. Can VCDS access this part of the ECU? I have not invested in one, but if it can toggle these parameters, I'd buy one....

98mkiv said:

so I found a little info on the forums.... I think I cleaned the high pressure EGR valve.... Is it possible that the other EGR valve or the EGR cooler is clogged up?

Click to expand...

I have had the "EGR Filter" replaced sevral times in my own Chronic P0401 problems. It appears that there are seperate valves for the High and low pressure EGR systems. Does this mean they each have their own filter, or is it only in the low pressure system after the cooler? If there are 2 filters it would explain a lot of my questions about why VW has changed so many of my filters...

I had this same code about two months ago, Exhaust Flap Motor turned out to be the culprit


Sent from my iPhone 4S using Tapatalk

I'm having the same issue. Mine turned on after an oil change, but then eventually went off, after the next oil change, lights back on again.

I've pulled out my EGR and and cleaned it as well. One thing that I did was take the EGR apart (just a cover that covers the motor/gears as its not a vacuum one).. and I tried to open/close the valve. It opened and closed with no problems by hand by twisting the gears. Did not notice any resistance (Other than the spring that pulls it back to place).

I then decided to plug it in and use my VCDS to do an EGR test. It seems as it would only open a little bit. Not quite the amount i was able to open by turning the gears myself. I cleaned it up and put it back in.. MIL light is intermittant.

Unfortunately, I don't have a warranty on my car as its from the US and its now registered in Canada. Has anyone else tried to do the EGR test using VCDS and see that it doesn't or does open all the way?

Isn't this part of the new extended waranty?

I think all these threads on this form concerning frequent intermittent P0401 proves that the EGR system in the biggest engineering debacle in the CJAA 140 CR TDI, and VW should feel shameful for putting such crappy systems in their cars. I think most folks who run into this problem who don't have to worry about emissions will delete the system entirely.

v1k1ng01 said:

I have had the "EGR Filter" replaced sevral times in my own Chronic P0401 problems. It appears that there are seperate valves for the High and low pressure EGR systems. Does this mean they each have their own filter, or is it only in the low pressure system after the cooler? If there are 2 filters it would explain a lot of my questions about why VW has changed so many of my filters...

Click to expand...

So I'm pretty sure there is no such thing as an EGR filter. I'm interested to know where it is if there is one and a pic would be great. I think the EGR cooler could be confused for an EGR filter as it does clog up..... Anyone with a definitive answer?

v1k1ng01 said:

I think all these threads on this form concerning frequent intermittent P0401 proves that the EGR system in the biggest engineering debacle in the CJAA 140 CR TDI, and VW should feel shameful for putting such crappy systems in their cars. I think most folks who run into this problem who don't have to worry about emissions will delete the system entirely.

Click to expand...

I'm the first in line to delete the EGR - I have no need to pump exhaust gas back thru my intake. Getting 40 MPG is my service to the damn environment, I don't need to put **** thru my motor on top of that IMO.... So my biggest question is, does anyone know if you can use VCDS to disable the DPF and EGR systems because I will delete both mechanically if I can defeat them thru the ECU software.

There is definitely an egr filter ... Search and read ... If the dpf is flawed or cracked , which has happened to a few people here on the forums it allows soot through and clogs the filter in the low pressure egr circuit... Here is a picture of the filter

And here is a link explaining the emissions system.
http://www.myturbodiesel.com/1000q/DPF-Adblue-FAQ-VW-Audi.htm

awesome, thanks for the link. reading now.....

98mkiv said:

So I'm pretty sure there is no such thing as an EGR filter. I'm interested to know where it is if there is one and a pic would be great. I think the EGR cooler could be confused for an EGR filter as it does clog up..... Anyone with a definitive answer?



I'm the first in line to delete the EGR - I have no need to pump exhaust gas back thru my intake. Getting 40 MPG is my service to the damn environment, I don't need to put **** thru my motor on top of that IMO.... So my biggest question is, does anyone know if you can use VCDS to disable the DPF and EGR systems because I will delete both mechanically if I can defeat them thru the ECU software.

Click to expand...

I can definitivly say there is a Filter in the Low Pressure EGR. VW has replaced that part in my car 3 times, and it's getting replaced again tomorrow. I'm can post a copy of the work order I have with part numbers if you like.

You can mechanically delete the DPF with a straght pipe, and pipass the EGR by blocking the valve. You can VCDS the codes away but your car wont run correctly without new tuning. Stage 2 Malone includes a DPF and EGR delete, and it the best way to go from what I have read. That said it's not street legal as EPA regulation requires you to have these componets on your diesel car. If you have to do emissions testing you will not pass with these kinds of modifications.

98mkiv said:

awesome, thanks for the link. reading now.....

Click to expand...

See if Reflex tuning on 28 Bypass would be able to hook you up with a emissions mod. That's my plan when P401 shows up.

My 2010 has 78K and still going strong, minus exhaust flap valve recently replaced, knock on wood!

740GLE said:

See if Reflex tuning on 28 Bypass would be able to hook you up with a emissions mod. That's my plan when P401 shows up.

My 2010 has 78K and still going strong, minus exhaust flap valve recently replaced, knock on wood!

Click to expand...

740GLE, your plan is the number one fix for the issue! Number two is stage 2 Malone, and Three is let the Stealer fix it...

Ok, great.

So I have a few questions:

1. can the EGR filter be removed and cleaned? What's in it?
2. I know where the EGR valve is that is between the throttle body and the head, where is the other EGR valve?

Thanks!

Softrockrenegade said:

There is definitely an egr filter ... Search and read ... If the dpf is flawed or cracked , which has happened to a few people here on the forums it allows soot through and clogs the filter in the low pressure egr circuit... Here is a picture of the filter

And here is a link explaining the emissions system.
http://www.myturbodiesel.com/1000q/DPF-Adblue-FAQ-VW-Audi.htm

Click to expand...

^ +1 for awesome picture of EGR Filter!

98mkiv said:

Ok, great.

So I have a few questions:

1. can the EGR filter be removed and cleaned? What's in it?
2. I know where the EGR valve is that is between the throttle body and the head, where is the other EGR valve?

Thanks!

Click to expand...

There's like 3-4 EGR valves that need to work properly for the EGR system to work.

I don't think the EGR filter can be cleaned. Most of the times a P401 code has come up a dealers answer is to replace the entire emissions/egr system DPF parts included. Not cheap.

Few here have replaced just the EGR filter to solve the P401 code, only to have it come back a few 1000 miles or so. People were guessing the DPF might be shredding parts into the EGR filter causing it to clog.

740GLE said:

There's like 3-4 EGR valves that need to work properly for the EGR system to work.

I don't think the EGR filter can be cleaned. Most of the times a P401 code has come up a dealers answer is to replace the entire emissions/egr system DPF parts included. Not cheap.

Few here have replaced just the EGR filter to solve the P401 code, only to have it come back a few 1000 miles or so. People were guessing the DPF might be shredding parts into the EGR filter causing it to clog.

Click to expand...

That's an accurate description of what been happening to my car. I have had 8k euro ($11k) worth of work done one my car because P0401, which would have made me broke if it hadn't all been covered under warranty.

98mkiv said:

Ok, great.

So I have a few questions:

1. can the EGR filter be removed and cleaned? What's in it?
2. I know where the EGR valve is that is between the throttle body and the head, where is the other EGR valve?

Thanks!

Click to expand...

Yes, the EGR filter can be cleaned, soot is flammable. You will need to remove the part. Then use a propane torch and air hose to ignite the soot. A barbecue grill is a good container. Though, I warn you that this is usually just a temporary fix. A delete or new exhaust plumbing is more permanent.

Depending on your situation, you may be able to drive the car for a while with the p0401 code. I'm now over 13k with the same code. Sure many others member have more miles than me. Going for a delete once the system fails.

As an observation by me and other members, would also like to add that the p0401 code usually trigger's in warm conditions (above 45f). For this reason, most of us who have a flawed/out of specs EGR flow will not see the CEL so much in the cold climates.

It could also be a possibility that VW programmed our ECU's with a very sensitive parameter for EGR flow. I've heard of no way to adjust this with VAGCOM (don't think you can). Wish I knew more on how to check the limitations and OEM flow specs guidelines. Just like to see how far off the flow pressure is.

chadwick1979 said:

As an observation by me and other members, would also like to add that the p0401 code usually trigger's in warm conditions (above 45f). For this reason, most of us who have a flawed/out of specs EGR flow will not see the CEL so much in the cold climates.

It could also be a possibility that VW programmed our ECU's with a very sensitive parameter for EGR flow. I've heard of no way to adjust this with VAGCOM (don't think you can). Wish I knew more on how to check the limitations and OEM flow specs guidelines. Just like to see how far off the flow pressure is.

Click to expand...

P0401 is insufficient EGR Flow..... looking at the schematic the only sensor for airflow seems to be the MAF. How does the system detect EGR flow? The cold temps leading to fewer EGR problems may be indicative that the density of the air is causing enough of a signal offset that the system reports low EGR flow... meaning this sucker is very sensitive. Perhaps a dirty sensor might trigger this as well... so to diagnose it would be helpful if someone could point out the location of all the sensors the EGR system references.

chadwick1979 said:

Yes, the EGR filter can be cleaned, soot is flammable. You will need to remove the part. Then use a propane torch and air hose to ignite the soot. A barbecue grill is a good container. Though, I warn you that this is usually just a temporary fix. A delete or new exhaust plumbing is more permanent.

Depending on your situation, you may be able to drive the car for a while with the p0401 code. I'm now over 13k with the same code. Sure many others member have more miles than me. Going for a delete once the system fails.

Click to expand...

Ok, good to know. I will remove it and inspect, maybe snap some pics.

v1k1ng01 said:

That's an accurate description of what been happening to my car. I have had 8k euro ($11k) worth of work done one my car because P0401, which would have made me broke if it hadn't all been covered under warranty.

Click to expand...

Thanks for the heads up, I've got specific questions and this didn't answer them.

740GLE said:

There's like 3-4 EGR valves that need to work properly for the EGR system to work.

I don't think the EGR filter can be cleaned. Most of the times a P401 code has come up a dealers answer is to replace the entire emissions/egr system DPF parts included. Not cheap.

Few here have replaced just the EGR filter to solve the P401 code, only to have it come back a few 1000 miles or so. People were guessing the DPF might be shredding parts into the EGR filter causing it to clog.

Click to expand...

Looking at the schematic I see two EGR valves and one sensor. I know there are more sensors, but I don't think there are more valves. Can you share pictures of these other valves....

At this point, I have cleaned the high pressure egr valve (up by the throttle body) but I will now clean the filter and the low pressure valve. I know where the filter is.... can someone please snap a pic or tell me where the low pressure valve is located?

I want to get to the bottom of this - many people have this and replacing an entire system sounds wrong - a single component ($100's) is at fault here - not a whole system ($1000's).

I've also experienced this issue on my 2012 TDI Golf. 3 MIL in April. First two times the dealer cleaned something (not sure) and reset the light and said it would be fine. By third time they got to what is hopefully the root cause - the exhaust flap valve - and replaced it under warranty.

That was yesterday so I hope this is not a continuing saga.

A thought occurred to me while going through this - there is no good reason why VW or other manufacturers do not display MIL codes on the instrument cluster screen for customers.


Sent from my iPad using Tapatalk HD

so I haven't had a chance to get under the car, but in order to systematically diagnose this issue I'm going to do the following....

clean the TB/EGR valve at the front of the motor (already did this, not the problem)
clean the MAF
check the exhaust flap valve
clean the EGR at the back side of the motor
clean the EGR filter
then last look at the DPF...

But there is one thing I noticed tonight when I was checking my oil. When I did my DSG service I accidently left a large diameter flex hose loose. The flex connects the airbox to an aluminum cast pipe at the back of the motor. No idea what this does, it reminds me quite a bit of a intake pre-heater from the old days - pulling heat from the exhaust manifold. It was disconnected at the airbox end, completely loose, just hanging there. Wonder if this might be enough of an offset to make the MAF think something is wrong..... I reconnected it so I guess I'll find out. Wouldn't that be funny if that was the case.

Unfortunately, that hose is probably not the case of your CEL, mine was disconnected too. Still have the same code appearing. In my case, I also changed the air filter and fixed a turbo oil leak. The only thing that took that code off for a little while (2-3k) was cleaning the EGR filter.

so what is that hose for?

That is a feed hose for the cold air intake bypass. It's there just in case the cold air intake ever gets blocked/clogged.