Engine Control Unit (ECU) Connection Problem

Hello.
Good day to everyone. I'm new to this forum.
I've owned VCDS for several years and also have the latest version, 12.12.0.
So far, everything has always worked perfectly.
I've had a Golf 1 Cabrio with a 16V engine conversion for a year now, and I bought it already with the conversion done.
Now, to my problem.
I've been trying to connect to the engine control unit for several days now, but unfortunately without success. According to the previous owner, he had the diagnostic data read out at a Bosch service center.
It always says "(Control unit not responding)".
Engine control unit (ECU) (part number 8A0 907 404 CC) from a Passat 16V engine (type 9A), manufactured in 1992.
I checked the wiring and everything is okay.

"I installed a different control unit, connected the control unit according to the wiring diagram while it was disconnected, but nothing worked."
I've already read through all the forums discussing different protocol settings, and I've measured the K-line voltage, which is 12.94V when the interface is connected.
When dialing "01 MSG", the voltage drops to 1V.

Now I've also read that the voltage must only drop to half its original value.
If I'm not mistaken.
Well, I'm definitely at my wit's end.
It would be great if you could help me.
Thank you in advance.

Hello,

according to http://www.corradotechnik.de/index.php/Steuergeräte_Corrado
Is the engine control unit a KE-Motronic?

This device cannot be used for actual diagnostics based on any specific diagnostic protocols; it can only output error codes via blinking lights.
Do the error codes from the Audi 100 Motronic system match? It might be worth trying.
http://www.audi100-online.de/Technik/Einspritzung/einspritzung.html

Best regards, Rainer.

Hello Rainer,

Thank you for the quick response.

But, as I've read in many forums, it's possible to establish a connection to the MSG.
I also have an original VAG repair manual, which also describes how to use a diagnostic tool to read error codes and make adjustments.
There has to be a way to make this work.

Best regards, Mario.

Hello,

Actually, there is even a label file available for part number 8A0 907 404, and apparently there are control units that provide measurement block 0.

Are you sure this applies to your 8A0 907 404 CC as well, and not just to the 8A0 907 404 K or with index L?

With older components, it sometimes happens that both the K-line and the L-line are necessary to establish a connection.

-> Check the wiring/schematic diagram, see also the pin configuration of the connectors below:
/viewtopic.php?t=3089&highlight=diagnoseadapter

Here's another tip: If the "wrong" software (i.e., bad chip tuning or incompatible software) is installed in the engine control unit (ECU), it often malfunctions in older ECUs. This can lead to certain functions, such as diagnostics, not working properly, or other strange issues may arise (for example, with a 1Z engine, the ambient air pressure might read 900 mbar instead of 1000 mbar).

Best regards, Rainer.

Hello Rainer,

The repair manual only mentions the MSG with the part number 8A0 907 404.
They are installed starting from a price of €10.90, and the index is not a factor in that.
"Already checked the wiring, and I've even connected it directly."

Best regards, Mario.

Hello,

better late than never.

Have you ever set the initial baud rate to 4800?

Best regards,

Thank you for the tip.
I've already done that.
Best regards,