Most M57 information shows the crank sensor should not be inside the bell housing....
It should be on the left side of the block, towards the rear (B6203)...
And yeah, this looks to be below the starter motor...
But when you look at the part fiche for the later M57TU engine, it seems to be mounted on the rear oil seal frame...
This M57TU oil seal TIS shows it better...
https://www.newtis.info/tisv2/a/en/e...covers/BvmiMs4
Although even this TIS uses mixed images!
vs
Might have to come up from underneath - maybe pull the plastic transmission shield off - easy to do - as this will give you a better view/access.
Here's what you're looking for...
BMW # 13627809334