'90 Jetta Carat Wolfsburg Edetion Sensor?

Anybody out there know what sensor or sending unit is bolted to the side of the block just behind the radiatur hose. It looks to be foil wrapped and has a 2 prong connector?

Come On some of you auto techs have to have some Idea what that sending unit is for and it's importance.

It's the Knock sensor. It feeds information to the engine computer and is rather important to the proper operation of the engine. They're about the most expensive sensor on the car, $45 or so online. They are easily damaged, so be careful how much you tighten it.

Thanks for the info, I will get one tomorrow.

If the knock sensor died, I would just run higher octane gas until I got it fixed.