P401 egr insufficient flow

[Nasif Khan]

Hi all.
I have a P0401 egr insufficient flow error code come up.

I have cleaned the existing egr and the light came back. Bought one from a breaker and light came back.

I have been reading this thread from 2011 as well as others. Thought I'd create new thread rather than resurrect an old one.
2.0 TDi EGR flow - Page 2 (http://www.vwaudiforum.co.uk/forum/showthread.php/117549-2-0-TDi-EGR-flow/page2)

According to the replies and solution it seems that it could be the egr solenoid.

Where is this located on my car. I have a 2.0tdi Bluemotion B6 passat with cbdc engine code.

[grant19841]

I got this pic from another thread, 29566

Sent from my SM-A300FU using Tapatalk

[grant19841]

I got that pic from eBay but that's is the egr solenoid for the vacum pipe

Sent from my SM-A300FU using Tapatalk

[Nasif Khan]

Thanks. Where is it located?

[DMitch16]

There are a few valves and potentiometers in the EGR circuit on a Common Rail engine. The EGR system that regulates the re-burning of exhaust gases has High and Low pressure circuits depending on engine load etc.

Read this as it will be relevant to your engine and may help you understand the EGR system in more detail. It is from VW America however who have lower diesel emissions limits than Europe but had nice software installed to meet them!! :biglaugh:

http://www.natef.org/NATEF/media/NATEFMedia/VW%20Files/2-0-TDI-SSP.pdf

[Nasif Khan]

Thanks for the replies.
I'll definitely have a look at that.

With the whole emissions thing...VW wrote to me saying my car is affected by the dodgy software.

I have read somewhere that if it is a EGR cooler issue then there would be coolant loss. Is this correct? Because I don't get any coolant leak.

Any suggestions?

[DMitch16]

For the dodgy software VW will just book you in and update to remove the hidden code. For the EGR problem the coolant loss is connected to another issue and not really to the gas flow. On odd occasions the EGR cooler will corrode on the inside allowing coolant to seep into the gas flow tubes. This causes problematic running and white smoke from the exhaust. Coolant levels drop without any visual leaks. If your coolant level is fine this will not be the problem affecting your car. Sometimes the aluminium EGR pipe from the back of the engine soots up and reduces gas flow but a serious restriction because of this is very rare. Often it is because the turbo seals on the exhaust side of the turbo have failed and oil vapourises into the EGR pipe along with sooty gas - not a nice mixture. It then gums up your main EGR valve and anti shudder flap at the intake manifold end as the already contaminated sooty gas mixes with more oily gas from the intercooler (which over time condenses oil from the crankcase vent pipe that shoves oil vapour into the pre turbo intake pipe - what a great system!).

[Nasif Khan]

Thanks mad mitch for the reply.
Not sure if this helps....I did have a turbo underboost issue. Got the actuator repair kit fitted and it back to normal. The EML was on during this whole time. Since having the actuator repair the EML light comes on for around 100 miles and also goes off after about 100 miles.

[DMitch16]

EML light? Engine shaped one is Emissions Warning and the yellow curl is the engine fault warning light (and in normal circumstances ALSO the Glow Plug preheat light).

If the engine shaped one keeps coming on there is an issue with the combustion and the gas flow pressure out through the exhaust / DPF which is measured by sensors.

[Nasif Khan]

It's the engine one. For thr past 100 miles it's been off but could come on.
When you say measured by sensors...do you think it could be a faulty sensor?

The glow plug one would come on for the turbo underboost.

Sorry I didn't make it clear.

[DMitch16]

The glow plug light comes on for most non serious engine faults and will say via the dash MFD "Engine Fault - Go To Workshop" or something similar (the most serious ones are when you hear a massive bang and hear metal bits clanking around but if nothing mechanical drastically fails the car for more potentially damaging faults usually screams at you and the dash MFD tells you to STOP!).

The emissions warning one (engine shaped on a VW TDI) usually reacts to inconsistent readings from the DPF pressure difference sensor at the top of the engine (it has an electrical connector and 2 rubber hoses connected to it that are in turn connected to narrow metal pipes bolted to the DPF that read the pressure before and after the DPF filter can. This is so the ECU can determine the gas flow pressure through it. The ECU then uses these readings to make small adjustments to the running or to invoke a regeneration should the soot index level of the DPF be high at this time and other regeneration conditions are met. If it doesn't like the reading being returned it may illuminate the emissions fault light on the dash. Mine has in the past come on and after a few trips and gone off again but it should not be a regular recurrence which would indicate some sort of problem still.

There is of course much, much more monitoring and adjusting going on other than this in the ECU and across the engine systems so this is just to give you an idea.

[Nasif Khan]

Thank you for your detailed reply.
Can that sensor you mention be at fault?

[martin1810]

P401 egr insufficient flow usually means what it says and the egr valve isn't opening and closing properly. The normal thing to do is replace the egr with a new one.

[Nasif Khan]

Replace the whole egr system or just the valve?

[Nasif Khan]

Can a blockage in the silver pipe that leads up to the egr/throttle body cause this code to come up?

[Nasif Khan]

Bump

[DMitch16]

Just the EGR valve. Make sure all vacuum lines have been inspected / tested. It is possible that the EGR pipe itself is restricted but usually unlikely. A build up of soot coating the inside of the pipe is likely but not to the point that it becomes too narrow to allow sufficient flow. The smaller vacuum solenoid valve nearer the EGR cooler could be faulty however not allowing full travel when needed. If in doubt remove the pipe and use a flexible pipe brush to clean inside. That would be the cheapest option and one thing ruled out if the problem still persists. Then move onto the cooler flow solenoid valve, check and or replace. Finally if the problem is still there replace the EGR valve itself which will be the most expensive part at around £150 (if electric type) or £55 (if pneumatic vacuum type).

[Nasif Khan]

Sorry to resurrect old post.
I've changed the egr valve with a brand new one....reset the MIL light and after 90 miles the MIL light came back on.

You have mentioned the solenoid valves...where csn I find these?

Not sure if this helps...The MIL light does go off itself every 80 to 100 miles.

[DMitch16]

Read this from Ross-Tech but note near the bottom that some CR Tdis have an EGR filter fitted somewhere in the circuit which can become blocked.

16785/P0401/001025 - Ross-Tech Wiki (http://wiki.ross-tech.com/wiki/index.php/16785/P0401/001025)

I have just worked on a friend's CBDC engine so I will take a look at his. Some non VW cars have had a similar issue with the Exhaust Gas Pressure sensor across the DPF being at fault (one guy even put in a needle valve between the high and low pressure sides to balance the pressure so the code went away - not sure that is the right way to solve the problem and whether long term damage would happen as a result). The sensor is easy to replace but the 2 pipes must be connected the right way around.

[Nasif Khan]

Funny you mention the pressure sensor. I replaced 2 on the DPF. I believe from memory it was before and after the DPF or before and on the DPF. It's one or the other. However, this didn't cause the MIL light...The flashing glow plug came on.

I'll await a response once you've had a look. I'm able to do basic things but am no mechanic.

[DMitch16]

If the emissions warning light (engine shaped) still comes on I would change the pressure difference sensor. It is the plastic sensor with the 2 rubber hoses connected to it. For your car the part number is 076906051A or 076906051B (chassis number dependent).

It is number 20 on the diagram below.

http://www.jimellisvwparts.com/showAssembly.aspx?ukey_assembly=744173

Often one hose is wider than the other making it easy to put on the right way.

[Nasif Khan]

Chassis is WVWZZZ3CZAP00XXX
I've had a look at the part number and searched on ebay. They vary from £10 - £50
Will any do or is it better to get a brand one like Bosch?

[RichardSEL]

Better get the correct one from your VIN from VW dealer spares. Often dealer spares are only a few quid more than aftermarket parts shops which might be selling you an older version -- or one with rice.
At least you'll get the most up to date part number there (revision letter on the end) Mine even gives me a print out of the ETKA diagram -- whether I buy or not.

[DMitch16]

Chassis is WVWZZZ3CZAP00XXX
I've had a look at the part number and searched on ebay. They vary from £10 - £50
Will any do or is it better to get a brand one like Bosch?

A version is for the following chassis numbers
F >> 3C-9E079 136 F >> 3C-9G005 641* F >> 3C-9P044 380*

B version is for following chassis numbers
F 3C-9E079 137>> F 3C-9G005 642>>* F 3C-9P044 381>>*

I would get genuine version or if a bit steep one from a reputable source such as ECP, GSF, Mister-Auto etc. Ebay is a lottery and full of cheap copies (and no free fortune cookie).

[Nasif Khan]

Thanks for that. So which is the one ill need? I'm not sure how to match those numbers to the chassis.

[DMitch16]

Your chassis number is WVWZZZ3CZAP00XXX which is older than the last chassis number for the A version 3C P044 380* so an A version is your part. You can also tell by looking at the existing sensor if it still has the sticker on it but although some parts are superceded with upgraded versions it is not always the highest version letter that would be applicable to your vehicle. As RichardSEL says ask VW which one you should put on.

[Nasif Khan]

Thanks for that mad mitch. I'll be on the phone to them tomorrow.

[Nasif Khan]

VW were not being helpful and didn't want to disclose the part number I needed. Went to ECP and they gave me a bosch DPS with a part number 0281002710.
Will have it fitted tomorrow and hoping it is the right one.

[RichardSEL]

So, what price did VW give you?
Did they ask for your VIN?

[Nasif Khan]

Vw said 60 something. They took reg plate

[Nasif Khan]

The part ECP gave was wrong. Had a look at the one on my car and it's 076906051B. Will have to order that

http://uploads.tapatalk-cdn.com/20160512/7ab11a22175e85718fc6f53c81f373ab.jpg

[/IMG]http://uploads.tapatalk-cdn.com/20160512/279c835f83ad02fef3b95ba58a1dad7c.jpg

[DMitch16]

Bosch make one too as an aftermarket part. Probably the same part as Bosch make some of the B6 electrical stuff for VW (along with Valeo and a few others - basically VW commissioned parts for the B6 from anywhere and everywhere!!!)

Piece of cake to change.

[Nasif Khan]

Definately easy to change but the part looked different.
Had 1 screw hole on the side and 1 at the top whereas the one from the car has 2 holes on the side and straight from the top.
The 2 pipes were the same size. I have ordered a replacement, so hopefully will receive it today.

[DMitch16]

The actual part on your car only has one bolt hole the rest is a bracket that it is clipped into and bolted to the engine. You'll see this when you undo the top bolt (the bottom bolt just holds the pipe clip in position).

[Nasif Khan]

Lol. Didn't take it apart myself. ..just had a look and it looked different. Maybe it was the right part. I wonder what part they have ordered

http://uploads.tapatalk-cdn.com/20160513/28a37789ccbde10b1c4615e8d9594164.jpg

http://uploads.tapatalk-cdn.com/20160513/0556eec44f6f2085f265b127df357d55.jpg

Pics from eBay

[DMitch16]

That's definitely the wrong Bosch one - Bosch do an OE equivalent that looks like the first picture.

[Nasif Khan]

Yea. I've given it back...gave the part number so hopefully should get it today.

Sent from my SM-G900F using Tapatalk

[Nasif Khan]

http://uploads.tapatalk-cdn.com/20160519/0cc21996756d44d6bda6c5a0ef10f2e7.jpg

Finally got the right one. Will put it in today and see if it gets rid of the annoying engine management light

update....changed it over...reset the light. Will have to see if it comes on again

[Nasif Khan]

Light has come back on after 40 miles of driving.
So far I've changed the egr valve and the DPS.
Any ideas what else can be the issue?

[DMitch16]

A couple of things left to check. A restriction in the metal EGR pipe from the manifold around to the EGR valve itself (excess carbon build up) or a lack of vacuum to open the EGR properly. The latter one involves inspecting all vacuum pipes from the EGR back to the main solenoid valve (N75) and if all good testing the vacuum pressure of the system at various points to see if enough vacuum is present. Have you rescanned to see if the fault code is there and is still the same fault?

[Nasif Khan]

Rescanned and same error code.
Will have to check the metal pipe next and then vacuum test.
The EML does go off every now and then itself.

[DMitch16]

If you have VCDS monitor the engine blocks that have the EGR cycle shown. Start from cold and record the EGR percentages as the valve opens and closes until the engine is up to temperature. It should be closed at startup as its main purpose is to lower combustion temperature which it won't do when the engine is cold. Once the engine is hot the valve should be opening. If the valve readings seem very slow to react or it does not react at all it will usually point to an EGR issue or if the EGR is new, to a vacuum pressure issue.

[Nasif Khan]

Been using a friends VCDS. I'll give the engine blocks a go.
Do I have to drive around or do this while the car is stationary?

[martin1810]

You cannot test any air supply or fuel supply with car stationary

[Nasif Khan]

Ok thanks
I'll give it a go

[DMitch16]

Also have a look at blocks 068 and 075 as they usually provide the load state of your DPF. Pay particular attention to the Carbon Mass Index which is in grams. Readings over 45g means that your DPF is reaching or has reached its full ASH load capacity (not to be confused with the SOOT load percentage which when it hits 45% invokes a regeneration to burn the soot into ash).

[Nasif Khan]

group 68 does not give any reading and group 75 shows 4.00, -7.00, -1.00
am i doing it right?
under the installed tab, clicked on ENGINE, then clicked on MEAS. BLOCKS

[DMitch16]

Right area but mine is a PD, yours a CR so the block numbers for CR engines should be 099 and 108 (also try 241, 242 and 243).

[Nasif Khan]

Didn't get a reading on 99.
108 shows 168ml oil ash, 10.5 carbon mass spec, 15.9 carbon mass actual

[Nasif Khan]

Didn't get a reading on 99.
108 shows 168ml oil ash, 10.5 carbon mass spec, 15.9 carbon mass actual
How do i check the egr blocks?

[DMitch16]

Decent and not excessive as yet.

EGR will be shown under the early engine blocks starting at 001. Have a look at each one in turn on the first line and get used to what they relate to.

[Nasif Khan]

If you have VCDS monitor the engine blocks that have the EGR cycle shown. Start from cold and record the EGR percentages as the valve opens and closes until the engine is up to temperature. It should be closed at startup as its main purpose is to lower combustion temperature which it won't do when the engine is cold. Once the engine is hot the valve should be opening. If the valve readings seem very slow to react or it does not react at all it will usually point to an EGR issue or if the EGR is new, to a vacuum pressure issue.
How do i do this on VCDS?

[Nasif Khan]

anyone?

[RichardSEL]

Search results for "egr" - Ross-Tech Wiki (http://wiki.ross-tech.com/wiki/index.php/Special:Search?search=egr)

[Nasif Khan]

I think i have managed to do it. A point I would like to make...when I started the car, the EML went off by itself however the code is still stored.

File converted to XLS and graph added in 2nd workbook:
EGR cold start - data and graph.xlsx - Google Drive (https://drive.google.com/open?id=0B0DB1605b4lpak1JcldwYTRDd1E)

The CSV File:
LOG-01-003-EGR cold start.csv - Google Drive (https://drive.google.com/open?id=0B0DB1605b4lpTzh6cXJRUndTTms)

Freeze Frame:
https://drive.google.com/open?id=0B0DB1605b4lpOUYxN1ItZWY5N2M

doesn't make much sense to me but I hope it does to you.

[Nasif Khan]

Anyone help?

[Johnny14]

This is the common problems with VW engine. Simply egr problem. This usually don't need to be replaced if you have a clue with the cars. To replace EGR will cost a lot. So do as follows. 1. Go and buy tunap Egr cleaner. 2. Remove the pipe from egr to intake system. 3. Fill up a lot of the egr cleaner in the hole which goes to Egr (below the turbo charger) 4. Wait 15 minutes and start the engine and accelerate to 2500rpm and the thing that Block egr valve will be blown from the hole. 5. Stopp the engine and procedd like this 4 times and your egr will be fine. Make sure you dont run the engine too long. Surely you will have trouble codes ib ECU, you can easily delete with vag com.
Brief explanation on EGR. This is made to reduce Nitrogen oxide from exhaust. Deisel engine needs more temperature than petrol engine. Egr is to bring back the cooler Co to intake. The cooler Co bring less Nox.
Goodluck😊😊

[Nasif Khan]

Thanks for the reply. I've already changed the egr valve but still have the same code after deleting it.

[Johnny14]

You got vagcom; check readiness. Make sure oxygen sensor is ok.

[Nasif Khan]

These are the results with the EML on

LOG-01-003-8.6.16.xlsx - Google Drive (https://drive.google.com/open?id=0B0DB1605b4lpbDk3QklhbG9PLU0)

please can you advise what needs to be done.

[Nasif Khan]

You got vagcom; check readiness. Make sure oxygen sensor is ok.

oxygen sensor is ok.

[Johnny14]

First sorry that I didn't read your former post. And I'm mot english so it may be difficult to understand me. But I'm just here to help some when I got time.
I see that you have changed some parts already by suspecting them. You have problem with EGR now. That what you have to consider. Your EGR 99% got fault becoz of unclean fuel. So whenever you change your Egr you should clean cooler metal pipe from EGR to intake. This pipe usually got blocked. Don't go and buy anything before you are 100% sure. Go and make sure your EGR is properly installed and check the cooler and the pipe is totally cleaned.
Last question, was the former EGR opened? Did you check it?

As a car mechanic, whenever I have this issue, I usually check every air flow system and clean them. Like intake, egr cooler, pipe before new egr.

Goodluck 😊

[DMitch16]

Can a blockage in the silver pipe that leads up to the egr/throttle body cause this code to come up?

My answer was in the first page and second page of this thread. The silver pipe CAN get restricted and although a blockage is rare you should still clean the pipe to rule it out. There is also a smaller flow valve at the back of the engine next to the cooler which should also be checked to make sure it opens and closes under vacuum otherwise the flow with be wrong under certain conditions like you will get maximum cooling when the flow is slower and not enough cooling when the flow is faster.

[genghis]

Did this problem ever get sorted?

I have 2010 passat CC 105kw TDI - with P0401, originally had a lambda sensor issue, changed the sensor, then got the EGR P0401 error, changed the EGR without Checking anything, Lambda sensor code came back. Had the auto elec check done on the lambda sensor, found that the new one was spurious. Replaced that. Then everything went fine for a week. 100miles later, i have P0401 error on again.

So by reading this forum. Seems like i need to check the EGR selenoid, check inlet flows on the metal pipe from DPF?

I do not have access to a vagcom.

[Nasif Khan]

No. Never got it sorted. Best to blank off the EGR and have the car remapped and this code taken out.

[genghis]

Does this actually work?

[genghis]

No. Never got it sorted. Best to blank off the EGR and have the car remapped and this code taken out.

Does this actually work?

This is my second Passat CC that is dying on me, my first one was 2009, 170 TDI with 200,000 miles on the clock that had a fuel pressure issue, that no one could resolve...