Hi Shogun,

thanks for your reply. I honestly don't know if my car even has a DWA since it has a very basic extra equipment (Executive Ausstattung). I did, however, find the little blue crash sensor (German = Stoßschalter) which was hidden quite well under the left rear seat. Is there any way to check if that crash sensor is still working properly? It rattles when you shake it - but I guess that's how it is supposed to be.

A few days ago I found the leak where the water was getting inside the war. There were two quite large rustholes (both ca. 5 cm2 in size) in the drivers footwell, right beneath the location where the loudspeaker is mounted. Thanks to my dad's remarkable welding-skills, these holes were fixed quickly.
After I sealed the welding properly, I'll finally be able to assemble most of the interior back together so that I can drive the car again.

I was also thinking about the wiring loom that leats to the trunk hatch. I read that these wires break quite frequently and since I've had problems with the central locking at the trunk-lock for ages, maybe that's the culprit.
Maybe the GM somehow notices that there's a short in the trunk-wiring-loom and registers this as a possible break-in-attempt, so it sends this information to the EWS which blocks the starter? That's why the car starts fine without the GM...?

I'll report back on monday.
Until then best regards from Germany.