Hello folks! I have been mooching about my bis and there has been a cable dangling at the back of the car ever since I bought the car. Looking at the wiring diagram I think its the cable to the oil pressure sensor, but my problem is WHERE is this sensor(I know it somewhere on the engine but like I say WHERE)

. Iv'e looked in the manuals and can't find it(I am blind as a bat). Someone must have had a problem with it before me and just thought stuffit and cut it off.
Any idea's? Yes I'm thick!

and havn't got a clue.