surender kumar

hi , pls check this link , might help you,,

carlzimmerman

After replacing ECU (after replacing literally everything else in EVAP system) 3.5k miles later I am still enjoying a blissful check engine light free dashboard.

Audi did determine (as per prior post) that it was an overheating issue, it was probably just a fan within the ECU that was faulty. The overheating issue was throwing people off because you would drive for a short distance and then it would come on so we thought it was mechanical. Can you fix the fan in ECU? No idea.

Just wanted to give everyone an update that unfortunately it is probably your ECU, which will run around $1,700, but if you take care of your car like I have, it will be well worth it. It's a love hate relationship with the 3.2l

Just let go of your doubts.. it's the ECU. I struggled with this for four long years - the stress and anxiety is not worth it!

ILLusive

+1

If you've done a smoke test and haven't found any leaks, its your ECU. I have not had the CEL come on since I replaced mine last year. Bite the bullet and fix the issue once and for all.

A6Gary

Thanks for the updates. I'm still having the dreaded DTC pop up at various times, but have yet to replace or repair the ECM. However, I just ordered the ECM connector screws so I can R&R it later. After chasing this problem for ~2 years as well as your results, I know I will need to bite the bullet and do this expensive repair. Right now, my current repair task is R&R the rear adaptive air shock absorbers. Later this summer, I will tackle the ECM issue.

4Driver4

I'm going to try to cheat mine through emissions. If you can get the car to pass, just drive it, I figure. My plan is to toss the ECU in the freezer overnight, then hook it up fire up the car, and run the readiness test on evap as soon as possible. If it passes, I'll just let the car fully warm up each time I start it until it goes to emissions.

I think it's due this fall, so we'll see how it goes...

dhoerl

I've been struggling with this issue for 2 years, think I'm finally done with it (at least for now). You can read my story of woe here: Audi A6 2006 with EVAP problem (P2404) - Page 12

Anyway, what I believe happened to me is:

- the hard pipe to the vacuum line cracked right around the dipstick, depriving the LDP of good vacuum
- had 2404 along with other errors
- I let it go for a month, finally tracked it down to a cracked pipe (runs along dipstick) and repaired pipe [common problem!]
- 2404 error stayed - it never went away for more than a day or two

What I surmise happened (and Jack on thread, professional, says its reasonable theory):

- no vacuum caused ECU to run LDP test over and over and over, day after day
- excessive testing most likely overheated an electronics part in the ECU, a solder joint, or the circuit card - damaging it somewhat but not completely

At that point, there is nothing you can do besides repair/replace the ECU to address faulty electronics. I found one company that said they could repair the unit, but no online reviews of them so no idea if they can or cannot do this: SIA Electronics | ECU Repair for all Makes and Models

I got a recycled unit (matched both codes on top of ECU), and sent old unit and new unit to European Parts Emporium to have the old cloned to new unit. It wasn't cheap but the total cost of unit + recoding was half a new unit from Audi.

If you have a VCDS you may be able to tell if you have bad electronics. I posted two videos to the RossTech URL above - old unit and new unit running test 071. In the old one you would see the REED switch toggle CLOSED to OPEN. With the new unit it stays OPEN for virtually the whole test.

Note:
- I replaced my LDP assembly ($217 on eBay) in case it was responsible for damaging the LDP - did this precautionary so as to 100% avoid damaging the new ECU
- getting ECU out is a nightmare - plan on several hours with a Dremel and cutting disks to slot security screws. I replaced same with metric bolts from Ace Hardware

4Driver4

I'm not buying the theory that repeated testing ruined the ECU. If you told me that repeated testing ruined the pump, I'd be on board. Solid state electronics don't fail from overuse. It's a design defect and/or component failure. There are plenty of others in this boat that never had a leak.

dhoerl

Hate to pop your bubble, but I'm an electrical engineer who has worked both as a repair technician as well as a circuit design engineer.

I've had both my 1999 ABS units rebuilt because Audi (well BOSCH) saved a few pennies per car by using "drivers" with marginal current capacity that often fail 10 years into service, per rebuilder in Idaho.

The heat can also exacerbate soldered connections - see my thread on the 1999 Audi cruise control problem caused by a manufacturing defect not accounting for thermal problems: https://www.audiworld.com/forums/a6-...-16-a-1728645/

My BOSCH dishwasher failed two weeks after the warranty expired - crappy solder joints on a power relay (http://zo-d.com/stuff/how-do-i/bosch...s-running.html). I resoldered but after a few years it got flaky again, so I soldered a wire from pin to pin to avoid the circuit board all together (fixing the problem for good).

Jack on the other forum just posted he just had another ECU fail due to an improperly installed LDP. Apparently the same issue - ECU driving LDP excessively overheats, fails, then has to be replaced. Note that the link to SIU (repair ECUs) explicitly told me they repair ECUs with bad LDP drivers.

PS: I've saved my old LDP in case someone offers to test it in their car - or seriously analyze it. Will ship for free!

A6Gary

As a mechanical engineer (which also includes thermodynamics and heat transfer training/analysis), I agree that heat can cause problems with solid state electronics. That's why some of the supercomputers have their circuit boards submerged in coolant. This LDP problem is clearly due to a failure in the ECM circuitry. In my case, I can run the LDP 071 test when I first start the car (engine must be cold), and the system passes. But if I don't run the test and just drive the car, the ECM fails to activate the LDP, and will illuminate the CEL with DTC 009220/P2404. I am planning on having my ECM repaired rather than replaced with a new unit to fix this problem. Good to know that SIA Electronics informed you that they have repaired ECMs w/ bad LDP drivers.

BTW, the Bosch ABS module failure you mentioned was the result of Bosch buying the Japanese company that made the modules. So it wasn't really a Bosch design failure, although they should have fix the problem they inherited. And my Bosch dishwasher that is 11 years old is still running strong, no repairs (knock on wood!).

dhoerl

You're having the exact same symptoms as I did in the past: test would pass always when car started and idling, then fail after 10 min or so when the ECU ran the test again while car in motion.

In my case this issue first appeared after a prolonged period of time with a cracked vacuum line and many faults.

Did your failure just start happening or was there a precipitating event?

PS: I added the link to the Bosch dishwasher problem - scroll to bottom to see eroded solder joint.