Good day. I decided to spend more time for my car, and get into the tuning process =)

History of my ECU is unclear, the previous owner said he has chipped the car, I chipped the car at unnamed car service (it was just a chip, no tests before/after etc). So I decided to start from a clean state.

My car is New Beetle 2003, 1.8t, Mexico. I have Immo III. My ECU was 06A906032KQ (this is what ECU returned, I haven't look on the ECU in real). I couldn't find an original firmware exactly for my ECU, but using the analogs thread, I found an original firmware for similar ECU: 06A906032FD.

Yesterday, I flashed it with MPPS via OBD, and the car stopped to start. Although it starts but stops in a second later. I get a single DTC error:

17978 engine start blocked by Immobilizer

I wonder why it stopped working since my EEPROM ImmoID and SKC remain the same. The immo light is blinking on the dash.

I started to move forward: I got to recover the SKC key.
I dumped my EEPROM with me7_95040 and found my SKC. I'm able to login to the Immo with that code (17-Instrumental), but not to ECU (01-Engine): it disconnects no matter how many times I tried (yes, I did 2-3 minutes intervals).

Currently, I can't flash any other firmware with MPPS via OBD, it returns an error. My guess is because of the immo.

Here are screenshots from VCDS, the strange things that ECU knows nothing about the immo. Weird things: there is nothing at 081 group of ECU, it looks like it doesn't recognize the immo. The other weird thing is that the immo block has Starting permitted 0, so the immo doesn't like something as well. And the main question: why ECU doesn't accept my SKC from its EEPROM?

I know, I can disable immo in EEPROM and flash it in boot mode, but that's more educational post: why does it happen? Isn't ECU happy with the previous EEPROM?

Got my ECU to a bench. It's really KQ.

Flashed disabled immo EEPROM (switched 01's to 02's). The car started with no problems. There is no 091 group available for ECU, and Immo says "Start permitted 1" and "Engine responds 0". There is still no info about immo in the ECU.

You might say that my problem is solved, but still, I'd like to have the immo working, and get know, why doesn't it work by default

P.S. Going to flash another ori firmware I have, for GB. It's might be just an incompatible firmware with immo 3 or so

I was glad too soon. Even if a new firmware allowed me to login, it couldn't make the adaptation. It says: System Not Ok.
I tried 06A 906 032 LP (it's from Golf IV). I thought, it's likely because Golf has a different immo than my New Beetle, so I tried 1C0 906 032 firmware, but it didn't work as well.

So, after a number of attempts, I had to disable immo. It seems like firmware expects different immo modules, and for some reason, the adaptation can't be done.