That is the auto-timed self destruct plug. If you EVER give it a currant (bun not electrical) it will trigger "mother" into destruct mode due to her thinking an alien (the horrible ********, not the silly ones with the odd heads) is on board your car, probably in the spare wheel well or the glovebox. You can try driving at speed and open the rear quarter window to try and create a vaccum and suck it (the alien) out. Failing that "mother" will blow herself (your car) up and you may get arrested due to the authorities thinking it was a terrorist incident...Remember, in your Audi nobody can hear you scream (especially if you have the windows up and your stereo on). You have been warned...........