16785/P0401/001025 Fault CR TDI Discussion

Ok, so this topic has been beaten to death with a lot of answers that shoot from the holster at the DPF being cracked and needing to be replaced. As a Professional Service Manager at an automotive shop; I see the good, bad, and the ugly of diagnostics. With that being said, I know there are a lot of very intelligent minds out there, as well as a lot of people with experience working on this car. (I say this car, because this is IMO not really a MKV or an MKVI vehicle. It has the CBEA common rail engine, so not a MKV TDI. Yet it shares a similar engine setup to the MKVI TDI on MKV electronics. God Bless Us, those that own these beasts, for VW made this car in spite of VW techs and mechanics everywhere.)

So the history on this for me is I bought the car with 143,000 and change on her. Fortunately, I was able to get my hands on the Dealer's bill for the last service done before I bought it. They replaced the Vacuum Sensor (076906051A), Sensor/Convertor (1K0906627A), the Intake Manifold (03L129711E), Turbo Wastegaste Actuator Kit (03L198716A), an Intercooler Hose (1K0145828) (I have since replaced both because they were leaking oil and I thought the clamps were old, had I looked at this invoice further I would have seen one had been done, but no harm no foul.), a parking brake cable, and a battery. They also did an oil change on it, but get this, they used 5w-40 synthetic oil. (Great job, who knows what that did to her.)

Well, 500 miles after I drove her off the lot, the check engine light came on. I took it to the VW dealer for diagnostic because I knew they had VCDS and could see if there were any underlying codes. There were, but it was for the things the shop had replaced right before I bought it and an EGT sensor which the dealership wanted 164.07 for the part and something ridiculous for the labor, in three moves I've misplaced the written estimate of time. Anyway, I paid 148.03 with shipping for the part and 299.02 with shipping for the tool set from snap on and it took me maybe 30 minutes to get the new part on and torqued down. Definitely a frustrating 30 mins due to the space allowed in this engine bay, but worth it.

Later on my adventures began to become fun with this car as I now have a persistent P0401 or 01025 code for EGR Insufficient Flow. I have done a timing belt, water pump, 3 idler pulleys, and a tensioner replacement (roughly at 157K miles) and the serpentine belt twice. (Once before the TB and then luckily the kit came with a new one, because a stone got lodged in my crank pulley and ripped through the one rib on the belt I had just put on 1,000 miles ago.) I also did the thermostat at that time, can I be the first one to say, get the special tools to put your front bumper in service position, because otherwise you better have a lot of patience and tools that can get those two bolts at the verizon symbol angle.

Sorry if this gets long, but this is a detailed and aggravating situation that I need to figure out.

After the timing belt I replaced the Vacuum hose from the air filter box (03L131055E), made sure the vacuum lines from the pressure convertor were directed correctly, put the 1K0198803B Cold Region Intercooler Update Kit in, started using the cold weather air filter with the prefilter on it, changed oil and fuel filters multiple times (about every 5k on the oil, about every 10k on the fuel), put in a new pcv heater intake adapter with the updated valve cover hose, put a new valve cover gasket in with a new intake manifold gasket and cleaned both out, I have the p2015 metalnerd fix on the intake manifold so that doesn't become an issue, new seals on the injectors with new tensioning plates, a new fuel line (03L201360G) because the old rubber connections on that were wearing not to my liking, a new fuel line protective strip (03L130380) because it wasn't there, an updated oil pump hex shaft so I don't have to deal with the shaft shearing, the oil pan sealant (which by all means screw that! I miss the prefab oil pan gaskets), a new hot air intake pipe 1K0129565AA, a new EGR Filter 1K0253120 with new gaskets, clamps, and bolts/nuts, both cooling fans, and then the whopper - a new EGR Valve 03L131501K, a new throttle body 03G128063T, and a new mass air flow sensor 03G906461C. Among other things, but I'm trying to keep this Engine related.

I did check timing before (1 tooth off), during (adjusted twice to get it correct), and after TB replacement. I did adapt the throttle body and egr valve after replacement. I did use brand new coolant in a 60/40 mix with distilled water when I replaced the TB and water pump. The EGT sensor took care of that code at the time and I did go back and make sure the code I had was for that sensor. When I replaced the EGR filter, the main body was sitting on the bottom pipe because it had separated because it was missing the top nut. I did, positively torque every bolt/nut to spec, I promise. (I am super super anal about that, because it takes all doubt out of doing your own repairs.) I used the special tools to line up the TB and HPFP. Speaking of HPFP, I do not have any sort of flakes in the fuel filter housing and I have used VAS5226 to remove water from the system every time. I also replaced the EGR connecting pipe gasket each time I removed it from the EGR Valve. I know they say to replace that as well, but I just didn't see that it was necessary as I don't have a lot of soot built up in it. Also when I replaced the EGR Filter, I had about 1 mm of soot, but no more. I figured the DPF was ok because of this. I do have small amounts of soot that get on my candy white tailgate and bumper, but the tail pipes don't have a lot of build up. (It's a 173,000 mile car now, it going to have some there.)

A side note that may be of help, I don't know - The return line gasket from the turbo is leaking lightly at the turbo, I don't know that it means anything, but I do plan on replacing that gasket. (I have the part already.) I also have some oil flowing through the intake system. Now, I've seen a number of threads on that, from what I gather I really shouldn't worry about that. I guess it's pretty normal. I haven't checked for build up on the EGR Valve since I replaced it about a week ago, but I will say that when I did the valve cover and intake manifold gaskets, I removed a bunch of build up on that plunger. About 1,000 miles later when I replaced the EGR Valve nothing had build back up on the plunger inside the valve.

I don't have any major leaks, just some seepage from the oil pan gasket that I plan on redoing (my first time doing a sealant gasket like that, so sue me...don't really, I currently have very little money due to this car) and from the oil return line on the turbo. Since I did the valve cover gasket and PCV heater, I have had little to no additional oil build up on the valve cover. (I did have some on there before, but really couldn't hammer down where it was coming from.) I did make sure not to switch the injectors, cleaned them well with a brass brush (I thought steel might be a little much on them, brass seemed to do well with the little amount of build up on them, basically small spots of oil I suppose, without scratching them.

I do want to check the VNT adjustment, but I'm not sure that has anything to do with it. Also once I changed the throttle body/charge air pressure regulator and EGR valve, I have boost to no end.

While watch VCDS, I do have some lag between specified and actual boost values at idle, but my mass air flow values are back in check (were only slightly off, but I figured it couldn't hurt). My calculated oil ash sits at 180ml and hasn't moved since I bought my schwaben (foxwell) scanner.

I am curious that I don't have particulate filter carbon mass values in live data, so I wonder if this is normal for the CBEA. If not, I'd like to know what sensor that data comes from.

Also, if anyone knows how to find which sensor detects a generic code like this p0401, please let me know. I don't have VCDS in the Ross Tech sense, but I have VAG COM on the foxwell scanner and I can usually get very close to VCDS information. Also, I started to notice that this code always seems to show around 5 degrees BTDC. I have no idea if that's correlated, but I don't think it would be since this code was coming up before I did the TB. I usually extract my oil, but I did the last oil change from the bottom because I was doing the hex shaft replacement and oil pan gasket obviously. The oil left in the pan didn't have a ton of metal shavings or any build up in it either.

Anyone with experience, advice, things to check, please be my guest. Calling all who KNOW about the CBEA and possibly CJAA engine. This engine is vastly different from the BRM and slightly different from the CJAA. Yes, it runs on MKV electronics, but aside from that and the aesthetic appearance, she's really not a MKV IMO. Please help, I don't want this to cost me a DPF or turbo if that's not the issue.

Also, please back up your suggestions with ideas of how to test these things. I just updated the scanner, so my live data is gone. I have pics of the EGR Valve when I was cleaning it out. She's also not eating coolant or oil and neither looks contaminated with the other. Anymore info needed, please don't hesitate to ask.

Thanks for getting through this initial post and helping! Don't forget I have access to TSBs, Mitchell ProDemand and Identifix in case that helps! (For all you public users, there are a lot of TSBs logged in Mitchell that aren't available to the public...smh dirty secrets are no fun.)

CRWalker

With all the work you have done on the car, why have you not purchased a VCDS cable?

pretty sure we will be headed past you on the way to Ski Roundtop in the next few weeks, I would be happy to meet you someplace and bring my lapop and cable. I will send you a PM

Assume you have seen my thread about the sooty exhaust, and associated readings and errors.

http://forums.tdiclub.com/showthread.php?t=445921 I updated the first post recently.

Basic settings are written into the ECU to help isolate problems.

you may want to run Basic Settings 3, 67, and 78. best if the car is at operating temp when running these checks.

can you access the saved freeze-frame data from the P0401 error?

from my observations, the P0401 error comes from a check that is run once in a while after start-up, and is closely correlated with the checks run for Basic settings 078. so temperature of the LP EGR, differential pressure across the LP EGR (not the DPF pressure), and engine RPM information are sourced by whatever self-check program is run. since LP EGR flow depends on the exhaust flap, it is a good guess that at least the position of the exhaust flap, and probably the high and low pressure egr valve are also used by the program that reports the error.

There are a couple measuring blocks regarding soot levels reported that do not report any values

MB 240 and 241 are good on my car, MB 240 include fuel, miles, and time since last DPf regeneration, and MB 241 includes oil ash volume, and the calulated and measured soot.

the SSP for the 2.0 (our engine) http://www.natef.org/NATEF/media/NATEFMedia/VW Files/2-0-TDI-SSP.pdf

includes a good discussion on page 62 (66 of 90) on the models used to calculate the two soot load figures, and which sensors are used to feed the computer program that comes up with the numbers.

meerschm said:

With all the work you have done on the car, why have you not purchased a VCDS?

Click to expand...

I bought the Schwaben (Foxwell) Scanner for $199 or so...and then found out about the Ross Tech VCDS cable. However, I do work as a PSM, so any ol' Dub/Audi that rolls in, I can pull VAG specific codes/run basic settings with vin specific blocks. I would've had to buy the cable with the most vin uses...basically I bought a Windows 97 before finding out about Windows 2000. And now that I have it and it's pretty functional...I guess I'm starting to see the benefits of VCDS, I just haven't had the cash to buy it yet. (I also bought a Blackberry Z10, awesome phone, same problem...not enough users to make the benefits benefit my purchase.)

I appreciate the input about the code itself...after doing all this work and seeing the code back, my heart sank thinking it may be a problem with the LP Valve. I just was taking obvious signs to be the culprit. I.e. Charge Pressure valve internal resistance being way out of whack, LP filter sitting on itself, oil leaking from the EGR Valve before the manifold. I also know the Exhaust Control Valve in the exhaust itself works, because running basic settings, I can feel when it closes and opens under idle.

If you can run basic settings, when you have the chance, perhaps you can share values for a couple Basic SettingsFor Basic Settings 3 and 67, the values will change back and forth as the valves are operated. they will bounce around a bit, but you can provide an eyeball average.

for Basic Settings 078, idle speed is increased, and the pressure across the low pressure EGR path is measured (you will see some instrument panel lights and beeping, but that is normal)

also normal to have to exit and start from scratch after a single Basic Settings operation.

http://forums.tdiclub.com/showpost.php?p=4895896&postcount=64
Matt posted a couple helpful checksheets with should-be numbers

Question... When run Basic Settings, the car goes through the steps by itself. Is that normal? It's a question I've had for quite some time now, because the scanner help section indicates that I should initiate the on/off, but every time I attempt to do that it stops and one block will read error.

Thanks,
CRWalker

VCDS has an on/off/next to operate.

http://www.ross-tech.com/vcds/tour/b-settings.php



it may be that your tool initiates the test on it's own.

the basic settings each have prerequisites. (mostly engine running, car stopped, park if a DSG)

they do seem to want to stop easy (for unexpected user input), and then you have to back out and come back into the basic settings part of the program.

meerschm said:

If you can run basic settings, when you have the chance, perhaps you can share values for a couple Basic Settings

Basic settings 003 High pressure EGR Valve:
EGR Spec OFF/99% duty cycle/EGR (actual): [value in mg/str]
EGR Spec ON/60% duty cycle/EGR (actual): [value in mg/str]
OFF - On: [difference in mg/str]

Basic settings 067 Low pressure EGR valve:
On/40%: [value in mg/str]
Off/100%: [value in mg/str]
Off - On : [difference in mg/str]

Basic settings 078 (low pressure EGR) as the others, press on/off/next and note increased RPM
78-1 mbar:
78-2 %?:
78-3 mbar(offset):
78-4 Degrees C:

​

For Basic Settings 3 and 67, the values will change back and forth as the valves are operated. they will bounce around a bit, but you can provide an eyeball average.

for Basic Settings 078, idle speed is increased, and the pressure across the low pressure EGR path is measured (you will see some instrument panel lights and beeping, but that is normal)

also normal to have to exit and start from scratch after a single Basic Settings operation.

http://forums.tdiclub.com/showpost.php?p=4895896&postcount=64
Matt posted a couple helpful checksheets with should-be numbers

Click to expand...

Ok, so running basic settings:

Basic settings 003 High pressure EGR Valve:
EGR Spec OFF/99% duty cycle/EGR (actual): 99.4 (485)
EGR Spec ON/60% duty cycle/EGR (actual): 60.2 (350)
OFF - On: [difference in mg/str] 135

Basic settings 067 Low pressure EGR valve:
On/40%: 40.2 (486)
Off/100%: 99.4 (460)
Off - On : 26

If that means what I think it does...yay $500 Egr cooler!

If I can I'll try to figure out how to post the video for the 78.

What were the readings for Basic Settings 78? (while the engine speed is increased by the ECU)

For comparison, I ran these on my car after a ten mile drive (and DPF regeneration) this morning. I logged the values and used excel to average the on/off values

Basic settings 003 High pressure EGR Valve:
EGR Spec OFF/99% duty cycle/EGR (actual): [value in mg/str] 583
EGR Spec ON/60% duty cycle/EGR (actual): [value in mg/str] 416
OFF - On: [difference in mg/str] 167

Basic settings 067 Low pressure EGR valve:
On/40%: [value in mg/str] 354
Off/100%: [value in mg/str] 556
Off - On : [difference in mg/str] 202

Basic settings 078 (low pressure EGR) as the others, press on/off/next and note increased RPM
78-1 mbar: 100
78-2 %?: 51
78-3 mbar(offset): -3
78-4 Degrees C: 276

Note that the LP EGR temp in my BS 78 reads a bit high, due to just finishing a DPF regeneration a couple minutes before.

Your difference numbers seem a bit low, both the high and low pressure valve values do not change as much as the check sheet suggests.

did you have the car at operating temperature?

meerschm said:

For comparison, I ran these on my car after a ten mile drive (and DPF regeneration) this morning. I logged the values and used excel to average the on/off values

Basic settings 003 High pressure EGR Valve:
EGR Spec OFF/99% duty cycle/EGR (actual): [value in mg/str] 583
EGR Spec ON/60% duty cycle/EGR (actual): [value in mg/str] 416
OFF - On: [difference in mg/str] 167

Basic settings 067 Low pressure EGR valve:
On/40%: [value in mg/str] 354
Off/100%: [value in mg/str] 556
Off - On : [difference in mg/str] 202

Basic settings 078 (low pressure EGR) as the others, press on/off/next and note increased RPM
78-1 mbar: 100
78-2 %?: 51
78-3 mbar(offset): -3
78-4 Degrees C: 276

Note that the LP EGR temp in my BS 78 reads a bit high, due to just finishing a DPF regeneration a couple minutes before.

Your difference numbers seem a bit low, both the high and low pressure valve values do not change as much as the check sheet suggests.

did you have the car at operating temperature?

Click to expand...

Basic settings 078 (low pressure EGR) as the others, press on/off/next and note increased RPM
78-1 mbar: 169
78-2 %?: flipping between 71.40 and 76.50 (literally no other values at all)
78-3 mbar(offset): -3
78-4 Degrees C: between 132 and 138 (it was about 39 F Ambient Air Temp when I was doing this)

Sorry couldn't figure out the video sharing. The ol girl was at operating temperature, just had driven about 30 mins mostly doing 50mph after a two min. warmup before shifting to first and hitting the road. (I do that to get oil flowing in the winter, not long enough to let oil start getting stripped off cylinder walls...noticed that also makes the engine seems to warm more linearly than cold forever and a giant jump. If you don't agree sue me lol, just spent too much time trying to under stand turbo engineering and this engine to do otherwise when it's cold outside.)

Also the check sheet I see is blank in the blocks, where do you see values to check against?

http://forums.tdiclub.com/showpost.php?p=4865545&postcount=1

Those values for the Basic settings 78 are well on the side of a blocked up low pressure EGR filter. The highest ever shared with me.

I would expect an increasing frequency noted in the freeze frame data associated with the P0401 code. can you see this data with your tool?

I will not make any judgements on letting the car wake up before hitting the road. it is not like you are idling for 20 minutes to let the defroster work before driving a mile to work.

the check sheets have numbered text paragraphs between the blocks. I will paraphrase here:Here is an image of the check sheet:

Your difference readings for the valves are both low, but I suspect some common issue. at least they change. both read from the MAF.

Solved During Emissions Modification

The end solution for anyone reading this thread was the DPF was cracked and was replaced during the emissions modification. (That one then cracked 10k later and was replaced under warranty, we’ll see if this one lasts)