The main obstacle to continuing the work has not yet been resolved. After powering on the BCM, including the ignition, the buttons did not respond. The first logical step was to read the errors in the block, and one error was present: external antenna malfunction. I also saw the adaptation called "Garage door opener, programming antenna," but I was not able to read the current value because ODIS requested the login. I tried every login (login-code) I found on forums, but none of them worked. ODIS says that the authorization was successful, but after that, it asked for login again. 

Also, the BCM had an error regarding the CP (component protection). It was a problem, too, because the CP can block the working of the lot of functions to make your life harder and force you to remove the CP. It can be done only with ODIS online, and it requires to send all the identification information about your block to the VAG servers to check if the block is clean (e.g. not stollen, etc..). To remove the component protection, each block has its own guided function in ODIS and, of course, requires two other blocks: the gateway and the immobilizer. 

On the B9 platform, the immobilizer is located in BCM2; also, it is responsible for access authorization and ignition (KL15). So, after contacting the seller who sold me the BCM, I was waiting for the 2 other blocks: 4M1907468D and 8W0907064EC. The original key fob has been ordered together with an antenna and start-stop button. All these components were from the same car. Unfortunately, the gateway was melted. So, I got only two BCMs from one car and "accessories" for them: a key, an antenna, and a button. The gateway was exchanged from another car. It broke the whole idea and added another issue - 100% component protection in all blocks, because the master block that checks component protection is exactly the gateway.

Another issue was with the BCM2 connection. By default, it has only 3 KL30 inputs:

• Connector A:
  • pin 16
  • pin 17
• Connector C:
  • pin 16

The wiring diagram says that pin 17 is responsible for the keyless access and authorization. So, only that pin was connected to the power supply. And BCM2 starts to respond to ODIS. But the start stop button did not do anything, like the key was not recognized. A lot of checks by ODIS, measurements, etc. AND NOTHING. The remote buttons work. Diagnosis works. But the key has not been recognized after start-stop button clicks. The problem was with CP, too, because the key is required to remove CP.

A big thanks to my friend, who gifted me his smashed taillight from an A4. It will save me a lot of time. I decided to check the taillight's reaction to the key buttons. I connected the left taillight and provided the power supply to both pin 16. I was frustrated after clicking on the start-stop button, but now it is working!

Interesting fact here - if the 2 fuses responsible for the taillights have been removed, the car would never start the ignition!

Ignition solved. But the buttons are not working anyway.

During the investigation of the ignition issue, I accidentally tested different guided functions. I found the functions to adapt and replace the Homelink module. And I decided to run them. The replacement is just a bit longer version that includes the adaptation function. Somehow, after running that function, I decided to try to read the adaptation that was just written. And what a miracle, ODIS read it without requesting the login. Looks like the guided function did the authorization in the background, and ODIS is keeping that authorization during the session. Theoretically, the login can be extracted using a CAN sniffer. Now, we can change the adaptation that interests us. And it was successful. The error becomes inactive and can be deleted. A bit later, I double-checked my theory with guided function, and it was confirmed.

So, now we have the following conditions:

• The ignition is on
• No errors in the memory (regarding Homelink)
• Component protection

Another thanks to the store that sold the parts to me. They left the first BCM that was melted they left it to me, and I got the 2 BCMs, one totally workable and one with the results of water inside. But that BCM is working somehow, and the most important thing - it has no component protection error! And unfortunately, it also was not working.