Hi, It is on the back of the engine block bellow the starter motor. There is one ribe bolt holding it on and there is a rubber 'o' ring around the sensor.
You can see it here on the photo of my old engine upside down
At the top of the photo is the RPM/TDC sensor. In the middle with no wire is the oil pressure sensor. At the bottom of the photo with a wire is the knock sensor.