AUDI A4 2.5 TDI AKE VP44 Problem Please for advice or help

dear Dieselschrauber community,

I have a huge problem with my
Audi A4 2,5 TDI
model year 2003
Motor: AKE

it started with a defective diesel pump control unit.

so I ordered a used complete diesel pump from the internet.
afterwards, however, I only replaced the control unit. Then I read out the errors and three errors came up:

01318 - Control unit for injection pump (J399)
03-00 - no signal
01318 - Control unit for injection pump (J399)
49-00 - no communication
+
ERROR WFS


Since the activation of the immobilizer with the existing login code did not work,
I decided to deactivate the immobilizer.
The immobilizer is currently deactivated and the error of the immobilizer
has also disappeared, but the start still does not work.


therefore I got another control unit
and installed it. The errors, or rather the two errors no signal and no communication, remained. However, I can hear that the flow distributor is permanently
activated.
I still cannot connect to the diesel pump.
I have checked pins six and seven from the motor cable harness; on both pins there is 12 V once and ground once. If I remove the plug from the control unit, the buzzing also stops.

I have tested fuse 28 and there is only voltage while trying to start the engine. However, unsuccessfully. I must add that the currently installed control unit comes from an AKN motor. But only the control unit.
I would be very grateful if you could help me.

Unfortunately, I cannot add a vehicle scan as it apparently does not work for some reason.
What I can say, and which is also very mysterious to me, is that the fuel gauge does not work and I am 100% sure that the tank was filled up and I also saw the full indicator before the vehicle could no longer be started.

POSTSCRIPT LT VCDS I HAVE NO VOLTAGE AT THE DIESELPUMP

thank you very much for your help