Passat B4 1.9 TDI: Error 00546 Troubleshooting

Best regards from the Sauerland region.
My Passat B4, manufactured in 1995, with a 1.9 TDI engine, is currently leaving me quite puzzled, but since there's a wealth of expertise here, I'm optimistic... it can't be that difficult.

Background;
Driving the scooter around with a good mood, the dashboard lights flicker briefly, there's a slight smell of electricity, but the scooter keeps running. Pulled over to the right, the scooter is making a knocking sound and struggling to accelerate.

Diagnosis.
Cable fire, short circuit in the supply line to the nozzle adjuster (short circuit to ground), resulting in the pump running at maximum speed with the earliest possible injection timing.

Action;
Harness cut, wires checked, replaced, everything put back together.

Success.
When I turn the ignition key, the horn starts honking, the preheating indicator doesn't turn off, and the engine doesn't start.

Diagnosis.
The shut-off valve is not receiving power, but there is a connection to the control unit. When 12V is manually applied to the shut-off valve, the engine runs with approximately 50 horsepower, and everything seems fine (the horn is currently not fuse-protected).
The error code 00546 (data line interrupted) is appearing in the diagnostic memory, which likely indicates an issue with the immobilizer system (I couldn't find any specific immobilizer components).
The WFS control unit appears normal, just like the 109. Power supply is present.
The friendly person didn't seem particularly interested in the problem, but they bombarded me with circuit diagrams. Unfortunately, I can't find any diagrams for the WFS anywhere, while there are several diagrams available for the DWA.
Does the MSG have a hand in this, or perhaps there's no connection to the WFS after all?
Am I completely wrong?
I would really like to shut down this stupid WFS system.

Who knows more?
The Heiopei from Sauerland.