Doing a belt change on a friends 87’ S4 and when I removed the belly pan, this wire was dangling. The car runs fine, no notable issues, except tach doesn’t work. What does this connect to/come off of?

Black wire that comes down by the filter.

Inside of the cap, small round female plug.

 

Looks like one of the connectors for the oil pressure sender

 

Oil level sensor on the top of the oil pan under the crank pulley.
Stole this picture. :-)

 

Looks like the connector that goes on the oil level switch.

 

Appreciate the quick response, gents, thank you!

Found it.

Re-attached