Have a 1980 300D, just got engine and transmission out of engine bay.

Thought I carefully removed each connected wire.

Have a single green wire about 18 guage (pretty small) coming
out of the transmission tunnel, almost up at the firewall,
on the passenger side.

What is odd is that it is not part of a harness, thought it was aftermarket,
but it has a manufacturers grommet at the opening and black casing.

I looked carefully at the engine to see if something came disconnected,
not much on the passenger side. The trans doen't seem to have anything
here either.

Keep in mind though I have to spray away 10 years worth of built up crud to
see anything. I'll pressure wash it all tomorrow.