About once a month, I get this warning. I saw a message a few days ago saying it is located on the head, drivers side. (Why would an oil sensor be located on the head anyway?) I think I located it, but how in the hell do you get to it? It looks like you have to remove the coolant resovoir or take the FI off the car. Any suggestions? Auto Zone sells the part for $11.99. Will that work or do I need a BMW sensor?