how many crank sensors on car

This CPS (crankshaft position sensor) is the heartbeat of the E320. These are also a big problem area. I am on my second W210 and have had 2 fail, one without a check engine light and one with. Usually the car will not restart up after being driven and getting the engine compartment hot. The lack of cool air over the sensor causes them to fail enough to cause either a long crank time to start the engine or no start at all. These are an easy fix. The part is @ 135.00 at Mercedes and an aftermarket one usually doesn't work. At the back of the engine on the drivers side (after removing to plastic engine cover) you can follow the wiring down to the sensor. It is only one small bolt and must be done by feel, but is easy to change.