Audi A4: Immobilizer Bypass / Disable

I'm having a problem with the immobilizer.
My friend's Audi A4 19 TDI 110 HP, engine code 0281001425/426, manufactured in 1996, always stalls when starting. It starts briefly, the engine check light illuminates, and then it immediately stalls again. There are no error codes registered. We have already tried using the spare key (transponder), but the problem is the same. Last week, we replaced the immobilizer control unit, but it didn't help either. It seems like the problem could be with the engine control unit or the reader. Since my friend is on a tight budget, I was wondering if it would be possible to disable the immobilizer? What else can I do?
I would be very grateful for any help.
best regards
flo

Hello,

Are you sure it's the immobilizer?
How long does it take from the engine starting to the engine stopping?
Does it always happen, or only sometimes?
What does relay 109 do?
Is the connector on the ESP, as well as the cable and plug connecting to the ESP, in good condition?

Best regards, Rainer.

Hello.
The engine starts briefly but then immediately dies. This doesn't always happen. Where is the relay 109 located?
best regards
flo

flo 1 wrote:

Last week, we replaced the immobilizer control unit, but unfortunately, it didn't help either.

It can probably only be the engine control unit or the diagnostic tool. }
Hi,

After replacing the WFS (Water Pump Frequency Sensor) or the engine control unit (ECU), the two units must be "married" to each other using a diagnostic tool/VAGCOM, otherwise the WFS will repeatedly shut down the engine.
Feature: The engine starts, runs for approximately 1 second (always exactly the same amount of time!), and then shuts off without any sputtering or other issues, as if the key were turned back.

If he is behaving differently, the problem is likely not with the WFS.

hi,
If the immobilizer is replaced and no adjustment is made afterwards,
Then the engine control unit (ECU) will be locked, and it will remain locked until a correct adjustment is made.
If an error is made during the adaptation process, it can result in a permanent lock of the engine control unit (ECU), which will require replacement.
greetings

"Hi, I've had the same problem. Here's what you can do: You can read the WFS (Vehicle Functional Status) data, but only when the error is occurring, for example, when you start the engine, it starts, runs for 3 seconds, and then shuts off. Don't turn off the ignition, otherwise the error will be erased from the WFS control unit. Leave the ignition on, connect the diagnostic tool, and read the WFS control unit data, then see what the control unit says about the WFS. As others have mentioned, the two control units absolutely must be linked together, and the key must be present, otherwise it won't work even remotely. Best regards, Bernd. For further questions, call 01702305097."