captainbilly

I helped a friend do an ECU swap yesterday on a 2001, immobilizer, A6 and here is the real story on what is involved. Just for some background info, the ECU is the computer that controls the fuel injection, turbochargers, ignition timing, etc. The immobilizer is the software in the instrument cluster that, among other things, checks the code on your key to make sure that it is really the correct key. On new A6s the immobilizer also checks to make sure that all/some of the other computers on the car are coded correctly, so that you can not, for example, steal an ECU from your neighbors car and use it on yours.

The code that is required to be set into the ECU must match, through some security algorithm, the immobilizer ID in the instrument cluster and it is only available through AOA/dealer network. Unlike the radio code, you do not have this code on anything that was given to you when you bought the car. The dealers are apparently told not to give this code out to the customer although some are willing to do so. The dealer can not look this code up on his computer system, they have to actually call AOA and ask for it by giving them your VIN and the immobilizer ID that they get when they check the instrument cluster (17) with the VAcomputer. It seems that AOA wants to keep very tight tabs on the immobilizer code and ,other possibilities aside, it makes some sense if the theft/stripping prevention aspect of the system.

So, how do you do the ECU swap.
1. connect a VAG-COM to the car and find the immobilizer ID on the instrument cluster (#17) screen.
2. Find a dealer who is willing to give you the four digit immobilizer "secret" code. They will need the immobilizer ID to get the secret code.
3. Install the new ECU then go to the Engine (#1) screen on your VAG-COM and go to adaptation. Set the block to 50 then enter the immobilizer code with a leading 0 added in the space below the place where you set bolck 50. Click on test to see if your code will work, if it works you will see your VIN appear in the empty spaces at the top of the screen. Click on save, turn off the ignition then turn it back on (but don't start the car) wait for a few minutes for the throttle adaptation then start the car.

If you did everything correctly the car will start and run, if you didn't the car will start and stall. You will not have to repeat this again if you put the original ECU back in or if you put the spare back after that, this should be a one time only opperation. Of course you always have to do the throttle adaptation, which just requires turning on the ignition for a couple of minutes before starting the engine each time you swap ECUs.

I believe that these instructions are available from RossTech (the guy that makes the VAG-COM) and APR has this info also.

I have heard other explainations of how to do the ECU swap but I tried some of them and they don't work on a late 2000 build 2001 2.7t.

TXurS6

You say that RossTech and APR has this info but everyone will not remember this after this thread is long gone. Could you make a FAQ out of this and post it here on AW?

Jim

absentme

2001 A6 2.7T
6 spd.
V1
Forge

timcar

Very valuable! Would you consider making this a FAQ?