AFN Issues: Huge Problems & Troubleshooting

'Hi, I'm new to the forum and I own a 1998 Passat TDI (AFN, 110 hp). I'm having a major problem. The engine has no power, and the error code indicates that the mass airflow sensor (MAF), the turbo control valve, and the exhaust system are defective, or that the wiring to these components has a short circuit or is broken. The valves and MAF sensor are fine, but after checking the wiring, I found a fault and fixed it, but the error codes still appear. Yesterday, I replaced the entire engine wiring harness with a lot of hope, but nothing changed. Today, I took the car back to the workshop to have the error codes read again. After that, the engine was running extremely rough, very loud, and annoying. Another scan revealed a severely misadjusted injection timing. Now, the car is in the workshop, and I'm starting to get frustrated. Tomorrow, the expert from the training course will come and take a look, and I hope it helps.'

Does anyone have any idea why these errors are occurring even though everything has been replaced?
How the injection timing can be easily changed and/or what might be broken. .

Thank you for your help.

Greetings from the Harz region.

Is the control unit defective? Are the valves defective?

Best regards, WarLord.

Hi,
Could it be that you fixed the wiring harness issue, but someone forgot to check the fuse for those devices? According to my wiring diagram, it should be fuse S102 with a rating of 15 amps.
Have you checked if there is power supplied to the valves and mass airflow sensor?

Best, Andy.

All the actuators you mentioned are connected to relay 109 via a single fuse.
also the injection molding machine.

Do all the valves also receive a 12V power supply?
Was wäre, wenn das der Fehler wäre, den du gefunden hast?

CU Gremlin.

'How many kilometers does the car have? Approximately 90,000 km.'
At what RPM (revolutions per minute) do you experience a significant drop in performance, approximately 2500 RPM?


If so, then the mass airflow sensor (MAF) is likely defective.
At VW, the issue is a known problem.
If it's the first one, then the LMM only costs 80 euros + 19% VAT instead of 250 euros.

It was also defective for me, but then it started working again.
and don't rely on the error messages from the control unit, as they are not always accurate.



See you, Marco.

@ Marco

Daring, daring.

Not everything that stops performing above 2500 RPM has a faulty mass airflow sensor!

And 88 euros is still too much if they were useless.

I would prefer to see a log file from the Large Language Model (LLM) sometime, as that would allow us to understand and justify its statements.

m;

Thanks for your tips and suggestions. I'll start by hearing what the workshop says tomorrow, and then I'll see what needs to happen next.

I'll post an update on the current state of knowledge tomorrow evening.

Greetings from the Harz region .

If there is no more power output above 2500 RPM, the recirculated air pressure sensor might be malfunctioning.
Then the boost pressure and fuel flow are adjusted because the control system believes the vehicle is at a higher altitude, specifically 1500 meters. This is done to prevent the turbocharger from over-revving due to the thinner air, and a limit is imposed.
If a defect causes the control system to incorrectly indicate an altitude of 1500 meters...

Best regards,
Jürgen