Multiple temperature sensor failures, resulting in a short circuit to ground.

Hello,

In a friend's Audi 80 B4 TDI (1Z) from 1994, the following problem occurs:
The car no longer has any power and only accelerates up to approximately 100 km/h. I have already carried out some troubleshooting and tested the throttle position sensor (see a few threads further down). The effect was that the car simply wouldn't start .
Now, a friend has cleared the error codes, and at least the engine is starting again . However, there are still many entries with errors:
Fuel, intake air, and coolant temperature to any freezing temperature and short circuit due to ground fault. Similarly to airflow meters -> Short circuit to ground

I was trying to read and delete the memory, but unfortunately I wasn't able to do that, so I can't provide more details. However, has anyone else experienced all of these errors at the same time? It sounds a bit like a break in a common ground wire... Unfortunately, the mechanic is also struggling with Latin at the end...

However, it could also be a faulty engine control unit. Is there a way to test it somewhere (e.g., at a Bosch service) or, if necessary, have it repaired? I'm actually not really keen on the garage replacing the MSG on suspicion, especially if they come up with some false excuses (which would definitely be very expensive).

Thank you & Best regards - Stefan

Upon request, deleted.

Hello,

First of all, thank you to 'diesel.gustav'!
I'm planning to get a multimeter soon and start checking the wires and measuring them. Two mechanics have already tried this (with a wiring diagram), and if I understand correctly, they consistently measured 5 volts on various sensors. This indicates that the power supply from the control unit is functioning. remains the only remaining possible source of error, namely the common ground connection to pin 33.
I really hope that there isn't a defect in the control unit itself. If there isn't a clearly visible cold solder joint, I can't even tell what needs to be repaired

Should I arrive at a solution, I will certainly post it.

Thank you & Best regards - Stefan

[Translating...]

Hi,

mein 1Z hatte das auch mal.
Durch ein druchgescheuertes Kabel im Kabelbaum war eine Masseleiterbahn im STG abgeraucht --- geiler Fehler.