frankinstyn

Hello all,


So I've had this P2404 problem for quite some time ( about 2 years now ). I replace many components and am down to replacing the ecm. A reputable shop smoke tested my system for a week and couldn't find any leaks. They recommended a used ecm if I could found one for a decent price.


That brings me to my problem. I did find the correct ECM. It is off of an 2006 Audi A6 with the same engine (3.2)

http://www.ebay.com/itm/351287928492?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
The part number matches but I can't seem to get it to work.

1) The car runs fine on the ecm in it. I've swapped it in and out several times while trying to get the new one to work with no problem.

2) The new ecm will fire for less than a second when I turn the car over but will stop immediately. If I try to start it up again it will just turn over for about 45 seconds and then pop the check engine light. If I wait a minute and try to start it, it will do exactly the same thing over again.

3) I've tried resetting the engine codes with a generic code reader with the same results. I then unplugged the computer for a few minutes but still had the same results.


I'm currently back on the old computer and the car runs as it always did. I left my vag-com cable at work and will try recoding the ECU tomorrow but I was under the impression that I shouldn't need to as it's from a car with the same engine.



Here are the procedures I'll be following.

DIY: How to Recode an ECU to use in your car - AudiForums.com



Has anyone done this without having the dealer reprogram it? I'm just not up for that expense. Please Help!

IknowHuhA6

ECM's are not plug and play. They are typically coded to each specific car. Even my previous car that wasn't loaded with so many electronic gizmo's would not work unless the ECM was flashed with correct VIN number stored in other car's components.

Since you already bought it, I suggest reaching out to Audi performance shops that provide ecm flashing to see if they can flash it to work on your car. If not, other option may be to buy flashed ecm (if available) from the aftermarket place itself.
Then there's the obvious super expensive dealer route If you can't get it to work.

But good luck with the VagCom, sounds like it should work.

frankinstyn

The dealer told me the vin number is not coded to the engine computer and other a security measure I cannot see a reason it would be. It doesn't seem like this is a security measure though as all I have to do take make it fire up for a second is wait a few seconds between tries. So weird.

Has no one swapped an ecu before?

IknowHuhA6

My apologies then if I miss informed. However I would not believe everything dealer says either since they are looking to get you to spend money. It is a business collecting premium prices after all.
Granted my experience is mostly with ECM's (AKA PCM's) are on American GM cars not German. Still learning these platforms but the business and marketing strategies aren't very different regardless of what they try to sell consumers. I will be looking to swap ECM soon but not in time to solve your problem. Hope someone can help. Good luck.

Trekie

IknowHuhA6 is on the right track here. The ECU is coded each car. The dealer will have to do this for you. I don't know if they will do this for a used ECU or make you buy one from them. Some years back the ECU and the instrument cluster had to be coded together. On these newer cars it may have to be coded to several computers in the car and not just the instrument cluster.

Prospeeder

Usually immobilizer system is tied in with the engine computer, at least on other models, VW and Audi, the ECU and Instrument cluster have a shared password with the 7 digit pin code, and they must match for the engine to start. Putting a different ECU in should trigger the immobilizer and do exactly what your describing, start then die, start then die. To make this happen without going to the dealer, you need and instrument cluster and ecu from the same car. The matched pair will go right in your car no conflict. Although, some control modules, like the Bose amp, have "Component Protection" and have the VIN of the car stored, and if it doesnt match everyone else it doesnt work. Just had to throw that in there, I have no idea if Instrument cluster or ECU have Component Protection.

So as far as the code your getting, You replaced the leak detection pump? You check continuity and resistance from its connector directly to the ECU plug using a Digital volt ohm meter? Does this code instantly come back or come on after several drive cycles? I would be very very skeptical that the ecu will be what fixes your problem.

frankinstyn

Well I passed emissions so I'm not going to change anything now but my problem started with that P2404 code about 2 months after I bought it.

I started with replacing the n80 valve
Then I replaced the gas cap.
Then I pulled and replaced all the evap lines throughout the car and did the vacuum lines while I was in there.
Then I replaced all the evap check valves and vacuum system check valves.
Then I replaced the evac leak detection pump with an audi brand new one.
Then I replaced the charcoal canister (but that was necessary because it was hard to fill the car...the old one was clogged).

I then took it in for a smoke test. They had it for four days and couldn't find anything wrong.
I then bought this stupid computer and tried swapping it.

I did some more research and found there is a four digit code or a 7 digit SKU ( you mentioned this on) that would let me go on with replacing it but didn't pony up the money to buy the program that could pull that code for me.

Instead I bought a factory audi n80 valve, popped it in, cleared the engine codes and drove a hundred miles followed immediately by the emissions test.

I passed! This clearing the code and driving a hundred miles will be my process every time I need emissions if this code comes back.....which I am sure it will.


THANK YOU ALL for the input and pushing me in the right direction. Below are the instructions on how to swap the computer if you don't want to pay the dealer to do it.

Immobilizer III ECU Swapping - Ross-Tech Wiki


Here are the instructions on how to get the pin for you car. Once you do have it (if you can) keep that thing safe. It can do all sorts of things that you probably shouldn't...like change and update you cluster, mileage....

I've found my SKC with Vagtacho. | Audi-Sport.net



I've basically found that there a few ways to get it but they are not easy and there is no nice walkthrough. You can do all these functions with the dealer but they will not be able to see the code much less give it to you so you will have to continue to go to them if you want to do more with your car.

It's interesting to me that no one really tries to get into this.

richard-tx

I believe you are barking up the wrong tree. P2404 is an evap fault. Not an ECU fault.

frankinstyn

That was 7 years ago…

A6Gary

And the P2404 DTC can be caused by a defect in the ECM (ask me how I know!).