'97 SL500. This sensor has a single electric connector at the end. It is right above the oil pan held by a C clip to the engine block. It is located on the passenger side, very close to the oil filter canister. It is not oil pressure sensor switch which is much bigger. This one is about 1.5" long with thickness like an index finger.

I notice a little oil leak around this sensor. I tried to remove it from the engine block without success. I can move it in and out slighter with hand so it is not firmly pressed to the block but I can't pry it out any further with a screw driver. I took the photo showing to a local dealer but no one can tell me what this is.