AKN Injection Pump Fault

Hello everyone, I was here before but unfortunately I don't have my account + email anymore...

Okay, now let's get to the topic.

I just bought an A6 Avant (99) with an automatic transmission from a well-known dealer. According to Audi, the fuel pump should be defective, but after some tests, the error "quantity control unit defective" appeared statically.
Subsequently, I replaced the timing belt (which was overdue) and the ESP.
I have disassembled and adjusted everything using original VAG tools.

after I had bled everything, the engine still wouldn't start, and the error message "injector pump control unit J399 defective" appeared. it's static, and I can't clear it...
Furthermore, after turning on the pump, I hear a humming or rapid ticking sound coming from the pump. This was definitely not the case with the old pump. The humming sound is also audible for about 10 minutes after turning off the ignition or locking the vehicle.

I am currently not sure whether the problem lies in the electrical system or in the new Bosch replacement pump. Therefore, I am asking for experiences. Perhaps someone has already experienced similar symptoms.

A clarifying question: when I unpacked the new pump, it wasn't locked, so I could freely rotate the pump handle. While the guide pin only fits in one position, is it relevant if the pump can be rotated 360 degrees? With a rotation of the pump, all 6 cylinders should be supplied with fuel...

I'm looking forward to any help.

Cable fault or pump malfunction. You can rotate them however you like, but that wouldn't cause any error from the control unit. Rotating by 180 degrees also fits perfectly, immediately, because there's no hole...

hey and thanks for your reply.
That's exactly what I meant: you can't rotate the pump because at 180 degrees there's no flow, and after 360 degrees it's essentially back to zero.

Can you say something about the humming of the pump? The old one didn't make that noise either. I'm getting the old pump back today in the afternoon and will check if it makes the same noise. If not, then the new pump is probably defective...