It is at the end of the Valvetronic ecentric shaft
-it is located under the valve cover
-it tells the ECU what position the shaft is in, barely rotated for idle, fully rotated for full power
If the valvetronic mechanism controls the 'throttling' of the engine just as a throttle body and butterfly would, then the eccentric shaft sensor is the equivalent to the throttle position sensor.
This sensor tells the computer how much the eccentric shaft has rotated, it gives feedback to the computer as to how much 'valve lift/throttling' the engine gets.
The valve cover is removed and the VCG is replaced when re-attaching the valve cover.
2008 328xi E90|N51|monaco blue|premium|sports|cold weather|logic 7|ipod|BMW Assist|xenon|sunshade|HD radio