Audi A6 2006 with EVAP problem (P2404)

Repair manual.......?
www.erwin.audi.com

Did you try to verify the LDP for crimp tests to isolate function and leaks or gas cap?
N80 status?

Jack@European_Parts said:

Repair manual.......?
www.erwin.audi.com

Did you try to verify the LDP for crimp tests to isolate function and leaks or gas cap?
N80 status?

Click to expand...

FYI @David Hoerl. Mr Jack is always right. I remembered these 06 AUDI's LDP issues back in 2011. we are always fixing them if the TSB criteria fit the car by installing new software updates and brand new LDP... and I think you car might I am not saying this is the case but FYI... this is the TSB.in pics below. important pics 3 Where are you located beyond that check wiring harness?

Now Back to Mr. Jack Shapiro. hey, this TSB (Using ODIS ) recommend to check LDP resistant (640 to 720 ohms resistance) which is always OK, that's what leads the tech to shot software... How would you do it using VCDS?. for instance measuring LDP vacuum and resistant's. perhaps using FTP variations and MVB fileds that retrieve resistant??? .I know there are PIDs or MVB to check HO2 resistant that save us a lot of time. is it possible to do the same for LDP? I know evap test is there and the evap test always come back small leaks and trigger this DTC P2404. but I want to learn a less invasive way to go than checking using the DMO or vacuum pumps. thanks again.



pcis 2


pics 3 Where are you located?

FYI @David Hoerl. Mr Jack is always right. I remembered these 06 AUDI's LDP issues back in 2011. we are always fixing them if the TSB criteria fit the car by installing new software updates and brand new LDP... and I think you car might I am not saying this is the case but FYI... this is the TSB.in pics below. important pics 3 Where are you located beyond that check wiring harness?

Now Back to Mr. Jack Shapiro. hey, this TSB (Using ODIS ) recommend to check LDP resistant (640 to 720 ohms resistance) which is always OK, that's what leads the tech to shot software... How would you do it using VCDS?. for instance measuring LDP vacuum and resistant's. perhaps using FTP variations and MVB fileds that retrieve resistant??? .I know there are PIDs or MVB to check HO2 resistant that save us a lot of time. is it possible to do the same for LDP? I know evap test is there and the evap test always come back small leaks and trigger this DTC P2404. but I want to learn a less invasive way to go than checking using the DMO or vacuum pumps. thanks again.

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Very good Victor...... I see your heart is pure.
I am not always right either .......I make many mistakes.

Basics should never be circumvented before an update.
Updates/TSB should be referenced with a tool such as VCDS as well as block values.
I held my tongue due to no full auto-scan posted, nor valid references to things in the repair manual.
That is either poster.......

Later cars are incorporating a second control unit to watchdog the PSI in the tanks.
You can also be sure that they fail just as an N80 does........ repeating havoc.

There is no substitute for doing the vacuum/crimp tests I always aforementioned.

This is the biggest reason people change an LDP and it doesn't need it.....99% of the time its a small leak or gas cap.
The vacuum pump with isolating zones will find the leak and give the ability to test valves ability to hold.
These basics tests are fast tracked when using VCDS in the 070/071 tests.
This is done to verify the zones by reading said switched vacuum PSI held, or created, and seeing noid release based on that block value......... + physical verification on the gage.
Visual inspection is always recommended!
I have seen deleted LDP and EVAP systems physical or from FOD ECU tuner tampering, that even the tuner or customer were not aware of it made a DTC, however, they thought the system was shut down.

Always verify......... never short cut, or you are just a hero in your own mind for flat rate times.

The J757 relay is located in a compartment held together with 4 or 5 Torx screws - just in front of the driver in the chamber under the removable cover. Its easier to get at if you first loosen the shield that goes around the windshield wiper arms. Its a PITA to get the relay out and in. When I ordered mine they sent me two in the box, so I replaced both relays. No change whatsoever.

First, a couple of comments.

victor35ma: thanks so much for the info on the updated firmware, and in the end I may go to the "stealer" to get it done - if all else failed.

jack: thanks for suggestions on using VCDS group 2 070/071. My problem is there isn't a d*mn thing written about this in the manual. What I saw **implies** that you would do these with the engine off, but in that case the LDP cannot run - it won't have vacuum. What I would have hoped to have found is a detailed procedure of how to run the test, what I should do step by step, and what result I should see back. I am very nervous about using VCDS actively with my car running. I used it the other day to force the rear electrical parking break to go out, then in, then train, while replacing my back brakes - and my hands were virtually shaking!


This is my wife's car, and the CEL is driving her mad (and thus she is making my life miserable). Since she went on a two week trip, I put her car on jacks, and have pulled the whole EVAP system apart, and I'm testing each component. To do this you need a vac pump, voltmeter, low pressure gauge (so you can see fractions of a PSI), lots of extra stuff.

I'm not doing this for just myself. I'm taking lots of photos, and have already written up a detailed procedure on how to test each and every component, including verifying that your LDP works (you use a MityVac and the 12V power from the battery, add a small plugged hose to the discharge side, and you can see that it builds pressure then holds it). I will be posting this as Tech article on Audiworld, to join another one I did a few years ago on the Jet Pump. I'll post a link here when its done and up on that site.

Anyway, there is good news and bad news. Every d*mn thing looks good. The vacuum line to the LDP hold vacuum. Running the LDP as mentioned above shows it will build pressure and hold it. The canister line to both the PVC and the gas tank hold pressure. The EVAP canister itself will hold a big pressure - 10 PSI or so.

There are three wires to the LDP, and the power line shows full voltage (but have not tested it under load yet, that is, after connecting it to the pump and then activating the valve (ground one wire). Looking with a volt meter back to the ECU, the one line used to activate the pump has a 50-100K resistance to ground, as does the "signal" line connected to the reed switch. The resistances of the LDP are correct (and as I mentioned before, I can show its working to some degree).

My next step is to put the LDP back in, and perhaps run a separate wire into the car so I can observe the actual voltages while driving (well, my wife would monitor them - I'm driving). I will verify that with all hoses reconnected, that the EVAP system will still hold 1 PSI of pressure (from what I read, gas caps should normally open around 2 PSI or so - I could never find anything definitive on this.

I also plan to tee the low pressure gauge into the purge valve hose, so I can tell whether there is actually a time when it has 0.25 PSI or so. probably I could do this with the motor running and using VCDS, but for the life of me I cannot figure out how to do this (noobie, remember).

Right now, I guess its possible that a ECU firmware update will fix the problem. Perhaps the cost would be the same to just replace the thing, as others have claimed they did to fix P2404 on the various Audi forums.

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Lastly, there is ONE odd thing I am seeing. When I begin to pressurize the EVAP canister line going to the gas tank, even pumping it up slowly (with bike pump), it POPs! Even with really really low pressure - like 0.05 PSI. It pops as soon as you start pressurizing it, and keeps popping as you increase pressure to say 0.5 PSI. The noise is similar to the pop your mouth can make - purse lips, open mouth quickly, make that POP sound that we grandparents use to amuse grandchildren. This to me seems really odd, and now I'm wondering if the line is clogged with carbon bits from the canister or some other bizarre thing. I let the pressure out by opening the gas cap, and even with no pressure there, you can clearly hear popping continue as the pressure decreases for several seconds - maybe longer (didn't time them). This really makes me wonder if something is amiss, but I have nothing to compare it to.

The other idea I had is to build a small circuit I can attach to the LDP with the engine running (vacuum), disconnect the purge valve power, and run the LDP myself. Again, VCDS probably can do it. If so, why isn't there a procedure showing exactly how to do it here or elsewhere? I have two Audis, work on them when I must, I'm not a pro.

victor35ma, what really sucks is that the car was registered in NY from purchase until I got it 4 years ago. Looking at the full scan I posted here on page 2, the version is 0040 - so the update was never applied.

That said, the car is 9 years old, and has about 115K miles on it - and that CEL never came on until a few months ago. What happened is that the little hard vacuum tube that connects to the front of the engine intake, and leads to the LDP - cracked. It was almost impossible to see. The car started generating a slew of errors, and another thread pointed me to the fix (remove the cracked/broken section). Doing that, all other codes went away never to be seen again - except P2404. No matter how many times I clear it, it will always return - like the proverbial bad penny!

Do I need a dealer to get it flashed? The car is now registered in NJ. Jack is a bit over an hour's drive away...

I have posted several times on the web how to do these tests.

These tests are done two ways...... at idle, and at steady part throttle during drive of steady speed or RPM.
What you need to pay attention to is the check valve, specifically the open close function to see release of the LDP solenoid........ when in test of basic settings via VCDS 0x01-04-071

Question? Does 0x01-04-070 pass........ engine running while at idle.

Don't be afraid to run tests at idle that are supposed to be done this way engine running.

You could always drive up for update drop off and have me look at the system.

dhoerl said:

victor35ma, the car is 9 years old, and has about 115K miles on it - and that CEL never came on until a few months ago. What happened is that the little hard vacuum tube that connects to the front of the engine intake, and leads to the LDP - cracked. It was almost impossible to see. The car started generating a slew of errors, and another thread pointed me to the fix (remove the cracked/broken section). Doing that, all other codes went away never to be seen again - except P2404
...

Click to expand...

Hi, glad you are having progress... what I can tell about this is: and please you need to understand that I am not VW expert...but we fix GM Ford and VW among others in the same way, I Know people here will disagree in this but.... anyway, and Within DTC nomenclature you can have the same DTC with a different symptom for instance:
P0204-XXX where the symptom is XXX, because of the symptom, you have to approach the car in an entire different manner. and because I saw; P2404 - 006 - Implausible Signal - MIL ON most of the time symptom - 006 along with software version lead us to Updates.

it will be a completely different approach if your soft version was higher than 050. that's what I like about VCDS it gives you the symptom part of the DTC code where we can look up in our local information system to build up a test plan. GM tech school have trained us to fix car that way and it is a very effective one. remember Auto tech can't afford more than 1.5 hours of diagnostic time so, for us time really matters. ... and even when things seen to be ok, we always recommend re-flash controllers as soon the version is available.... we call it the Dodge situation (Wi-Tech dodge OE diagnostic tool) can't work if it sees out of date controllers. so be it. but that's dodge

dhoerl said:

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Do I need a dealer to get it flashed? ...

Click to expand...

...you do. we use VW OE scan tool for that purpose only, since it is so expensive license tool to have, we go in a 3 days subscription when required. but on daily basis we love VCDS.

I ran the VCDS tests (my first such usage, was a bit confusing) 0x01-04-070 and 0x01-04-071. Not sure what the former does, that latter actuates the LDP and does the full Leak Detection test. I'm adding this to my article - as a noobie it was a bit scary, but here it is in a nutshell:

- plug in the VCDS
- turn ignition on, and start car (car MUST be running to get both 12V power and vacuum to the LDP
- navigate to 0x01-04-071 (see note at end) and start test ASAP, as the car will also try to perform it
- tap GO (think test is running now - NOPE! This took me a while to figure out...but as I said, I was a noobie...)
- tap the "ON/OFF/NEXT" button upper right to start the test
- wait a second or two, the test starts

You cannot run the test twice. Navigate back to the first VCDS screen, then stop and restart car, renavigate, to run the test again.

I got mixed results with the 71 test. I think I know the problem, and will post here later today.

Oh, another poor sole struggling with long standing P2404 on Audiworld site (thread I am active on there).

I now proclaim myself the world's expert on the Audi 2006 EVAP System [Well, I can claim the title!] The proof will be in my opus: "The Audi 2006 EVAP System: understanding it and diagnosing problems"

NOTE: This means open the VCDS program, click Select, click Engine (01) button, then Basic Settings button (04), then input block # 071

I ran the VCDS tests (my first such usage, was a bit confusing) 0x01-04-070 and 0x01-04-071. Not sure what the former does, that latter actuates the LDP and does the full Leak Detection test. I'm adding this to my article - as a noobie it was a bit scary, but here it is in a nutshell:

- plug in the VCDS
- turn ignition on, and start car (car MUST be running to get both 12V power and vacuum to the LDP
- navigate to 0x01-04-071 (see note at end) and start test ASAP, as the car will also try to perform it
- tap GO (think test is running now - NOPE! This took me a while to figure out...but as I said, I was a noobie...)
- tap the "ON/OFF/NEXT" button upper right to start the test
- wait a second or two, the test starts

You cannot run the test twice. Navigate back to the first VCDS screen, then stop and restart car, renavigate, to run the test again.

I got mixed results with the 71 test. I think I know the problem, and will post here later today.

Oh, another poor sole struggling with long standing P2404 on Audiworld site (thread I am active on there).

I now proclaim myself the world's expert on the Audi 2006 EVAP System [Well, I can claim the title!] The proof will be in my opus: "The Audi 2006 EVAP System: understanding it and diagnosing problems"

NOTE: This means open the VCDS program, click Select, click Engine (01) button, then Basic Settings button (04), then input block # 071

Click to expand...

I now proclaim myself the world's expert on the Audi 2006 EVAP System

Click to expand...

Love it !

You cannot run the test twice.

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Incorrect!



The reason you can't run the test a second time after doing it is that you have successfully pumped the tank with air.
In order to run the test again in same session ...........you must relieve it by opening the gas cap, and then the reed valve on LDP combination noid will disengage.
This is why 3 wire power and ground to pulse and position! See that in WD?

It is maybe best to study how the system operates before writing an article, but specific questions I can help if asked one by one.

Jack, tell you what - I'll post the article first on a public site (my dropbox account). You be the judge of it first.

I will gladly add you as a second author, given all your help here, along with a link to your company.

I was unaware that depressurizing would let me run it again - will try that shortly.

I'm just about there on this - by tonight for sure (wife returns tomorrow, car has to be at least back together by noon tomorrow!)

Just email me a PDF and I will help you tweak the technical and you can handle the grammar which I lack so I don't get grammar slammed.

Well, in the end, I think I found the problem. I'm 99% sure its the PV. But, you ask, why didn't you change it. Well, when I first saw this code LAST year - one year ago - I did. Problem went away, came back when I tripped on the broken vacuum line, then stayed around. So I'm 100% sure it cannot be the PV. I did a quick pressure test on the inlet side - it held pressure just fine.

What really got me looking at the PV was when I was using VCDS to run EVAP test 071, and it would pass a few times, then fail a few times. So I tee'd in my low pressure gauge into the system, right at the PV inlet side, and wow - the gauge was oscillating hugely while the test ran (at least in one test that failed). No wonder the error code is "Implausible Signal" - the ECU must be reading the reed switch as almost random values. Once I changed the PV, the gauge behavior exhibited virtually no oscillation.

Since my EVAP tome is going to take me a while to finish, I knocked out a quick and dirty test you can use to test your PV. The other thing you can do, with virtually no effort, is to remove the hose from the PV inlet, plug it, then plug the PV inlet. You could reset your error code, then drive around for a few days and see if it comes back or not. If not, its got to be the PV. Or, run the VCDS test several times with the hose plugged, and see if it passes each time (as Jack said, remove the gas cap to vent the tank before running subsequent tests).

I posted a PDF of the PV article on Dropbox:

Testing an Audi Purge Valve

The PDF has links to two ".mov" movies (QuickTime), of the Leak Test 071 with a new and old PV.

You could reset your error code, then drive around for a few days and see if it comes back or not

Click to expand...

Ahhh no way man!....... I want to know now and with VCDS and crimp tests for N80 and LDP I know in minutes.

Never did get an email of a PDF and I don't use drop box.

N80 is separate zone to LDP.......however, must be crimp isolated to verify not stuck open for loss of vacuum...... to achieve LDP pump up of tank PSI.

https://youtu.be/T_tTrZFj-_I?t=334

Jack, the link is the blue text in the post. I didn't send you a PDF as this is a real simple Purge Valve test. I have a like 20 page article on the whole EVAP system in process, but its going to take a while to finish. This was in response to finding my (grrrrrr) purge value had gone bad after a year (or perhaps sooner, who knows).

This is the link I posted: https://www.dropbox.com/s/hmwng8wu0glzro7/PV.pdf?dl=0

Some people don't own VCDS and even if they do (like me) are not fluent with it, as they only use it sparsely when they encounter a problem. I hope to bridge that gap, but really, look at the PDF. The Purge Valve is fragile (in my humble opinion, IMHO). It it leaks even slightly, the EVAP test will fail. The PV has -10 PSI on one side (the outlet side), and 0 to 0.25 on the inlet side, powered by the tiny little LDP. Even a slight leak will wreck havoc - forget stuck open.

I tested 071 multiple times - the first few passed, later on I got a small leak, then a big leak. I monitored several places with a low pressure gauge. VCDS alone will not indicate the problem, only the pass or fail. It does not have access to values we can obtain using external pressure or vacuum gauges.

In my situation - the 071 passed several times. Then failed several times. VCDS will not tell me who is at fault. By measuring pressure and vacuum, we can eventually track it down. Its a painful process, and in the end I surprise the following:

- LDP failure likelyhood -> Very Small (I see no one reports that this component failed hard, and that replacing it fixes their problem)
- Evap Canister failure -> Medium (people who over fill their gas tanks by hand, can soak the canister, and this can cause problems
- Gas Cap failure -> medium (some do it yourselfers report this fixes things)
- Purge Valve -> Highly Likely (this component has to maintain a near-perfect seal so that the EVAP system does not leak into the engine manifold, even when there is a 10 PSI difference.

Everything else is a hard route to somewhere else - hose, metal pipe, etc. Yeah, if you run the car over open ground, then something might smash a line. Normal driving, the above is it.

Some people don't own VCDS and even if they do (like me) are not fluent with it, as they only use it sparsely when they encounter a problem. I hope to bridge that gap, but really, look at the PDF. The Purge Valve is fragile (in my humble opinion, IMHO). It it leaks even slightly, the EVAP test will fail. The PV has -10 PSI on one side (the outlet side), and 0 to 0.25 on the inlet side, powered by the tiny little LDP. Even a slight leak will wreck havoc - forget stuck open.

Click to expand...

Incorrect.......most cars will still pass stuck open and if a gas cap is removed because the systems are separate.

I tested 071 multiple times - the first few passed, later on I got a small leak, then a big leak. I monitored several places with a low pressure gauge. VCDS alone will not indicate the problem, only the pass or fail. It does not have access to values we can obtain using external pressure or vacuum gauges.

Click to expand...

At idle or at offset?

In my situation - the 071 passed several times. Then failed several times. VCDS will not tell me who is at fault. By measuring pressure and vacuum, we can eventually track it down. Its a painful process, and in the end I surprise the following:

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Exactly :

This car should only be tested during road test and at idle is normal to get the leaks when running multiple tests.

LDP pumps hardly ever fail........ they most likely get diagnosed incorrectly.

Gas cap most of the time due to its always touched or people fill while engine running.
Purge valve only sees vapors and many times it could be a second bad OXS or vacuum leak causing an evap code too.
Trims will show this though when observed properly.

For anyone who has seen the "Maltese Falcon" - near the movie end, they get what they believe to be the real Maltese Falcon. However, a quick test with a knife shows that its a fake. The Fat Man grumbles, then says, well, it must be in Istanbul - we'll go there and chase it down. The hunt continues!

Well, same with me. After replacing the Purge Valve, we had a week of no CEL - then - YIKES - its back!!! My wife is asking me, "What kind of half baked mechanic are you - lets go buy a new car."

The CEL came on while she was motoring along at about 40 MPH. I looked at the fault with VCDS, and again, the one oddity is that the temperature in the fault report is shown as 93% C - googling for P2404 and looking at other failure reports, the temperature is always something sane.

That said, its time to run 071 with the car in motion (as Jack had asked me to do earlier). With my wife gone, I had the ability to rip the EVAP system apart. With her back, I now have someone to drive the car while I run 071 tests.

PS: I am still working on my articles. The first one is a detailed description from the perspective of someone trying to find faults. When that's done I'll put one together for running the VCDS tests (with screen shots), and finally the whole - how do I pull the whole EVAP system apart and test each piece (which I photographed and wrote copies notes on).

PSS: The dealer said the 0040 updates is not marked as current, and Audi claims my 0030 release is the official release for my car (even though the dealer claimed NJ follows CA's emission standards, and 0040 was targeted at CA among other states). The cost to update it anyway would be 1 hour of time (more or less - probably $150 in NJ). If the whole ECU is defective, well, that's several thousand dollars!

You might want to consider a temp test overlay of all 3 wires to the LDP......... to rule out connectivity on all tracks.

Interesting that you mention connectivity. I was really p*ssed off when I pulled the wheel well shroud off, and found that the wiring harness was dangling inside - it has a plastic cap attached to the harness, which is suppose to get pressed onto a stud. In fact the pump itself was not properly seated into its frame - two of the rubber standoffs were not properly pressed into the frame. I'm not sure if this is original, or someone else (like an Audi dealer) was poking around the pump. I should have asked the sales manager if it had been replaced in the past or not (and I guess I can still do this, I have his email).

So I was really concerned about potential wiring issues early on.

However, I used an ohm meter to monitor the resistance on each wire separately, and while doing this moved and wiggled the harness all over the place - not even a tiny discontinuity. Also turned on ignition and monitored the power line while wiggling and moving the harness, all was fine.

Interesting that you mention connectivity. I was really p*ssed off when I pulled the wheel well shroud off, and found that the wiring harness was dangling inside - it has a plastic cap attached to the harness, which is suppose to get pressed onto a stud. In fact the pump itself was not properly seated into its frame - two of the rubber standoffs were not properly pressed into the frame. I'm not sure if this is original, or someone else (like an Audi dealer) was poking around the pump. I should have asked the sales manager if it had been replaced in the past or not (and I guess I can still do this, I have his email).

So I was really concerned about potential wiring issues early on.

However, I used an ohm meter to monitor the resistance on each wire separately, and while doing this moved and wiggled the harness all over the place - not even a tiny discontinuity. Also turned on ignition and monitored the power line while wiggling and moving the harness, all was fine.

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You monitored the resistance..........? Ahh nope doubt it during operation.
Did you verify the ability to carry current?

Three wires overlay direct to each destination track/PIN and verify ........how hard can it be?

Many times I have seen this and it is the power supply relay, wiring or connector............ hence why diagnostics report it as such and referenced on wiki.

Firmware update also addresses this issue so get it done!