Check this DIY at BW, if you can't find it with this I don't know what to say. It is a tight fit but it's blind work on the E-class as well. Once you put your hand down there you can't see the CPS anymore.

Oh, I assume you mean CRANK position sensor. If not post back.

http://www.benzworld.org/forums/w210-e-class/1380045-hood-opening-location-cps-sensor-pre.html