Control Unit Failure (VAG): No Power & Clicking Noise

Hello,

I've read a lot here, but I haven't found anything that fits my needs.

My car is a Volkswagen Golf 3 TDI with the 1Z engine, producing 90 horsepower, manufactured in 1994.

The problem is: the car has absolutely no power anymore.
When the engine is properly warmed up, it starts to make a clicking noise at around 2000 RPM.

Error message with VAG: Control unit defective.

I installed a new one today, but it didn't fix anything. It's the same error (655 35 00-00--).

I am grateful for any advice.

Best regards, Christian .

Read and work through articles on systematic troubleshooting.